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Title: The Earth as Modified by Human Action
Author: George P. Marsh
Release Date: July, 2004 [EBook #6019] [Yes, we are more than one year ahead of schedule] [This file was first posted on October 18, 2002]
Edition: 10
Language: English
THE EARTH AS MODIFIED BY HUMAN ACTION.
A NEW EDITION OF MAN AND NATURE.
BY
GEORGE P. MARSH.
"Not all the winds, and storms, and earthquakes, and seas, and seasons of the world, have done so much to revolutionize the earth as MAN, the power of an endless life, has done since the day he came forth upon it, and received dominion over it."—H. Bushnell, Sermon on the Power of an Endless Life.
1874.
PREFACE TO THE FIRST EDITION.
The object of the present volume is: to indicate the character and, approximately, the extent of the changes produced by human action in the physical conditions of the globe we inhabit; to point out the dangers of imprudence and the necessity of caution in all operations which, on a large scale, interfere with the spontaneous arrangements of the organic or the inorganic world; to suggest the possibility and the importance of the restoration of disturbed harmonies and the material improvement of waste and exhausted regions; and, incidentally, to illustrate the doctrine that man is, in both kind and degree, a power of a higher order than any of the other forms of animated life, which, like him, are nourished at the table of bounteous nature.
In the rudest stages of life, man depends upon spontaneous animal and vegetable growth for food and clothing, and his consumption of such products consequently diminishes the numerical abundance of the species which serve his uses. At more advanced periods, he protects and propagates certain esculent vegetables and certain fowls and quadrupeds, and, at the same time, wars upon rival organisms which prey upon these objects of his care or obstruct the increase of their numbers. Hence the action of man upon the organic world tends to derange its original balances, and while it reduces the numbers of some species, or even extirpates them altogether, it multiplies other forms of animal and vegetable life.
The extension of agricultural and pastoral industry involves an enlargement of the sphere of man's domain, by encroachment upon the forests which once covered the greater part of the earth's surface otherwise adapted to his occupation. The felling of the woods has been attended with momentous consequences to the drainage of the soil, to the external configuration of its surface, and probably, also, to local climate; and the importance of human life as a transforming power is, perhaps, more clearly demonstrable in the influence man has thus exerted upon superficial geography than in any other result of his material effort.
Lands won from the woods must be both drained and irrigated; river-banks and maritime coasts must be secured by means of artificial bulwarks against inundation by inland and by ocean floods; and the needs of commerce require the improvement of natural and the construction of artificial channels of navigation. Thus man is compelled to extend over the unstable waters the empire he had already founded upon the solid land.
The upheaval of the bed of seas and the movements of water and of wind expose vast deposits of sand, which occupy space required for the convenience of man, and often, by the drifting of their particles, overwhelm the fields of human industry with invasions as disastrous as the incursions of the ocean. On the other hand, on many coasts, sand-hills both protect the shores from erosion by the waves and currents, and shelter valuable grounds from blasting sea-winds. Man, therefore, must sometimes resist, sometimes promote, the formation and growth of dunes, and subject the barren and flying sands to the same obedience to his will to which he has reduced other forms of terrestrial surface.
Besides these old and comparatively familiar methods of material improvement, modern ambition aspires to yet grander achievements in the conquest of physical nature, and projects are meditated which quite eclipse the boldest enterprises hitherto undertaken for the modification of geographical surface.
The natural character of the various fields where human industry has effected revolutions so important, and where the multiplying population and the impoverished resources of the globe demand new triumphs of mind over matter, suggests a corresponding division of the general subject, and I have conformed the distribution of the several topics to the chronological succession in which man must be supposed to have extended his sway over the different provinces of his material kingdom. I have, then, in the introductory chapter, stated, in a comprehensive way, the general effects and the prospective consequences of human action upon the earth's surface and the life which peoples it. This chapter is followed by four others in which I have traced the history of man's industry as exerted upon Animal and Vegetable Life, upon the Woods, upon the Waters, and upon the Sands; and to these I have added a concluding chapter upon Man.
It is perhaps superfluous to add, what indeed sufficiently appears upon every page of the volume, that I address myself not to professed physicists, but to the general intelligence of observing and thinking men; and that my purpose is rather to make practical suggestions than to indulge in theoretical speculations more properly suited to a different class from that for which I write.
GEORGE P. MARSH.
December 1, 1868.
PREFACE TO THE PRESENT EDITION.
In preparing for the press an Italian translation of this work, published at Florence in 1870, I made numerous corrections in the statement of both facts and opinions; I incorporated into the text and introduced in notes a large amount of new data and other illustrative matter; I attempted to improve the method by differently arranging many of the minor subdivisions of the chapters; and I suppressed a few passages which teemed to me superfluous. In the present edition, which is based on the Italian translation, I have made many further corrections and changes of arrangement of the original matter; I have rewritten a considerable portion of the work, and have made, in the text and in notes, numerous and important additions, founded partly on observations of my own, partly on those of other students of Physical Geography, and though my general conclusions remain substantially the same as those I first announced, yet I think I may claim to have given greater completeness and a more consequent and logical form to the whole argument
Since the publication of the original edition, Mr. Elisee Reclus, in the second volume of his admirable work, La Terre (Paris, 1868), lately made accessible to English-reading students, has treated, in a general way, the subject I have undertaken to discuss. He has, however, occupied himself with the conservative and restorative, rather than with the destructive, effects of human industry, and he has drawn an attractive and encouraging picture of the ameliorating influences of the action of man, and of the compensations by which he, consciously or unconsciously, makes amends for the deterioration which he has produced in the medium he inhabits. The labors of Mr. Reclus, therefore, though aiming at a much higher and wider scope than I have had in view, are, in this particular point, a complement to my own. I earnestly recommend the work of this able writer to the attention of my readers.
George P. Marsh
Rome, May 1, 1878.
BIBLIOGRAPHICAL LIST OF WORKS CONSULTED IN THE PREPARATION OF THIS VOLUME.
Amersfoordt, J.P. Het Haarlemmermeer, Oorsprong, Geschiedenis,
Droogmaking. Haarlem, 1857. 8vo.
Andresen, C.C. Om Klitformationen og Klittens Behandling og Bestyrelse.
Kjobenhavn, 1861. 8vo.
Annali di Agricoltura, Industria e Commercio. Pubblicati per cura del Ministero d'Agricoltura, Industria e Commercio. Faso i-v. Torino, 1862-'3. 8vo.
Arago, F. Extracts from, in Becquerel, Des Climate.
Arriani, Opera. Lipsiae, 1856. 2 vols. 12mo.
Asbjornen, P.Chr. Om Skoveno og om et ordnet Skovbrug i Norge.
Christiania, 1855. 12mo.
Aus der Natur. Die neuesten Entdeckungen auf dem Gebiete der
Naturwissenschaften. Leipzig, various years. 20 vols. 8vo.
Ave-Lallemant, K.C.B. Die Benutzung der Palmen am Amazonenstrom in der
Oekonomie der Indier. Hamburg, 1861. 18mo.
Babinet. Etudes et Lectures sur les Sciences d'Obsorvation. Paris, 1855- 1863. 7 vols. 18mo.
Baer, von. Kaspische Studien. St. Petersburg, 1855-1859. 8vo.
Barth, Heinrich. Wanderungen durch die Kustenlander des Mittelmeeres.
V.1. Berlin, 1849. 8vo.
Barth, J.B. Om Skovene i deres Forhold til Nationaloeconomien.
Christiania, 1857. 8vo.
Baude, J.J. Les Cotes de la Manche, Revue des Deux Mondes, 15 Janvier, 1859.
Baumgarten. Notice sur les Rivieres de la Lombardie; in Annales des
Ponts et Chaussees, 1847, 1er semestre, pp. 129-199.
Beckwith, Lieut. Report in Pacific Railroad Report, vol. Ii.
Becquerel. Des Climats et de l'Influence qu'exercent les Sols bolses et non-boises. Paris, 1858. 8vo.
——Elements de Physique Terrestre et de Meteorologie. Paris, 1847. 8vo.
Belgrand. De l'Influence des Forets sur l'ecoulement des Eaux Pluviales; in Annales des Ponts et Chaussees, 1854, ler semestre, pp. 1, 27.
Berg, Edmund von. Das Verdrangen der Laubwalder im Nordlichen
Deutschlande durch die Fichte und die Kiefer. Darmstadt, 1844. 8vo.
Bergsoe, A.F. Greve Ch. Ditlev Frederik Reventlovs Virksomhed som
Kongens Embedsmand og Statens Borger. Kjobenhavn, 1837. 2 vols. 8vo.
Berlepsch, H. Die Alpen in Natur-und Lebensbildern. Leipzig, 1862. 8vo.
Bianchi, Celestino. Compendio di Geografia Fisica Speciale d'Italia.
Appendice alla traduzione Italiana della Geog.-Fisica di Maria
Somerville. Firenze, 1861. (2d vol. of translation.)
Bigelow, John. Les Etats Unis d'Amerique en 1868. Paris, 1868. 8vo.
Blake, Wm. P. Reports in Pacific Railroad Report, vols. ii and v.
Blanqui. Memoire sur les Populations des Hautes Alpes; in Memoires de l'Academie del Sciences Morales et Politiques, 1843.
——Voyage en Bulgarie. Paris, 1843. 12mo.
——Precis Elementaire d'Economie Politique, suivi du Resume de l'Histoire du Commerce et de l'Industrie. Paris, 1857. 12mo.
Boitel, Amedee. Mise en valeur des Terres pauvres par le Pin Maritime. 2d edition. Paris, 1857. 8vo.
Bonnemere, Eugene. Histoire des Paysons depuis la fin du Moyen Age jusqu'a nos jours. Paris, 1856. 2 vols. 8vo.
Bottger, C. Das Mittelmeer. Leipzig, 1859.
Boussingault, J.B. Economie Rurale consideree dans ses Rapports avec la Chimie, la Physique, et la Meteorologie. 2d edition. Paris, 1851. 2 vols. 8vo.
Bremontier, N.T. Memoire sur les Dunes; in Annales des Ponts et
Chaussees, 1833, ler semestre, pp. 145, 228.
Brincken, J. von den. Ausichten uber die Bewaldung der Steppen des
Europaeischen Russland. Braunschweig, 1854. 4to.
Buttner, J.G. Zur Physikalischen Geographie; in Berghaus, Geographisches
Jabrbuch, No. iv, 1852, pp. 9-19.
Caimi, Pietro. Conni sulla Importanza e Coltura del Boschi. Milano, 1857. 8vo.
Cantegril, and others. Extracts in Comptes Rendus a l'Academie des
Sciences. Paris, 1861.
Castellani. Dell' immediata influenza delle Selve sul corso delle acqua.
Torino, 1818, 1819. 2 vols. 4to.
Census of the United States for 1860. Preliminary Report on, Washington, 1862. 8vo.
Cerini, Giuseppe. Dell' Impianto e Conservazione dei Boschi. Milano, 1844. 8vo.
Champion, Maurice. Les Inondations en France depuis le VIme Siecle jusqu'a nos jours. Paris, 1858, 1862. Vols. i-iv, 8vo.
Chateauvieux, F. Lullin de. Lettres sur l'Italie. Seconde edition,
Geneve, 1834. 8vo.
Chevandier. Extracts in Comptes Rendus a l'Academie des Sciences.
Juillet-Decembre, 1844. Paris.
Clave, Jules. Etudes sur l'Economie Forestiere. Paris, 1862. 12mo.—-La
Foret de Fontainebleau; Revue des Deux Mondes, 1 Mai, 1868.
Cooper, J. G. The Forests and Trees of Northern America; in Report of the Commissioner of Patents for the year 1860, pp. 416, 445.
Cotta, Bernhard. Deutschlands Boden. Leipzig, 1858. 2 vols. 8vo.—-Vorwort zu Paramelle's Quellenkunde. See Paramelle.—-Die Alpen. Leipzig, 1851. 8vo.
Coultas, Harland. What may be Learned from a Tree. New York, 1860. 8vo.
Courier, Paul-Louis. Oeuvres Completes. Bruxelles, 1838. 8vo.
Dana, James D. Manual of Geology. Philadelphia, 1863. 8vo.
Delamarre, L. G. Historique de la Creation d'une Richesse Millionaire par la culture des Pins. Paris, 1827. 8vo. D. Hericourt, A. F. Les Inondations et le livre de M. Valles; Annales Forestieres, December, 1857, pp. 310, 321. Paris.
Diggelen, B. P. G. van. Gruote Werken in Nederland. Zwolle, 1855. 8vo.
Dumas, M. J. La Science des Fontaines. 2me edition, Paris, 1857. 8vo.
Dumont, Aristide. Des Travaux Publics dans leurs Rapports avec l'Agriculture. Paris, 1847. 8vo.
Dwight, Timothy. Travels in New England and New York. New Haven, 1821. 4 vols. 8vo.
Emerson, George B. A Report on the Trees and Shrubs growing naturally in
Massachusetts. Boston, 1850. 8vo.
Emory, Wm. H., Col. Report of Commissioners of the United States and
Mexican Boundary Survey, vol. i, 1857.
Escourrou-Miliago, A. L'Italie a propos de l'Exposition Universelle de
Paris. Paris, 1856. 8vo.
Evelyn, John. Silva; or, a Discourse of Forest Trees. With Notes by A.
Hunter. York, 1786. 2 vols. 4to.
——Terra, a Philosophical Discourse of Earth. York, 1786. 4to. in vol. ii of Silva.
Feraud-Giraud. L. J. D. Police des Bois, Defrichements et Reboisements. Commentaire pratique sur les lois promulguees en 1859 et 1860. Paris, 1861. 8vo.
Ferrara, Francesco. Descrizione dell' Etna. Palermo, 1818. 8vo.
Feuillide, C. de. L'Algerie Francaise. Paris, 1856. 8vo.
Figuier, Louis. L'Annee Scientifique et Industrielle. Paris, 1862-'3. 12mo.
Finnboga Saga hins rama. Kaupmannahofn, 1812. 4to.
Foissac, P. Meteorologie mit Ruoksicht auf die Lehre vom Kosmos, Deutsch von A. H. Emsmann. Leipzig, 1859. 8vo.
Forchhammer, G. Geognostische Studien am Meeres-Ufer; in Leonhard und
Bronn's Neues Jabrbuch fur Mineralogie, Geognosie, Geologie, etc.
Jahrgang, 1841, pp. 1-38.
Fossombroni, Vittorio. Memorie Idraulico-Storiche sopra la
Val-di-Ohiana. Montepulciano, Sza edizione, 1835. 8vo.
Fraas, C. Klima und Pflanzenwelt in der Zeit. Landshut, 1847. 8vo.
Frisi, Paolo. Del Modo di regolare i Fiumi e i Torrenti. Lucca, 1762. 4to.
Fuller, Thomas. The History of the Worthies of England. London, 1662.
Folio.
Gilliss, J. M., Capt. United States Naval Astronomical Expedition to the
Southern Hemisphere. Washington, 1855. 2 vols. 4to.
Giorgini. Paper by; in Salvagnoli-Marchetti, Rapporto sul Bouificamento delle Maremme, App. v.
Girard et Parent-Duchatelet. Rapport sur les Puits fores dits Artesiens;
Annales des Ponts et Chaussees, 1833, 2me semestre, 818-844.
Graham, J. D., Lieut.-Col. A Lunar Tidal Wave in the North American
Lakes demonstrated. Cambridge, 1861. 8vo. pamphlet. Also in vol. xiv,
Proc. Am. Ass. for Adv. of Science for 1860.
Hakluyt, Richard. The Principal Navigations, Voyages, &c., of the
English Nation. London, 1598-'9. 8 vols. folio.
Harrison, W. An Historicall Description of the Iland of Britaine; in
Holinshed's Chronicles. Reprint of 1807, vol, i.
Hartwig, G. Dus Leben des Meeres. Frankfurt,1857. 8vo.
Haxthausen, August von. Transkaukasia. Leipzig, 1856. 2 vols. 8vo.
Henry, Prof. Joseph. Paper on Meteorology in its connection with Agriculture; in United States Patent Office Report for 1857, pp. 419-550.
Herschel, Sir J. F. W. Physical Geography. Edinburgh, 1861. 12mo.
Heyer, Gustav. Das Verhalten der Waldbuume gegen Licht und Schatten.
Erlangen, 1852. 8vo.
Hohenstein, Adolph. Der Wald sammt dessen wichtigem Einfluss auf das
Klima, &c. Wien, 1860. 8vo.
Humbolt, Alexander von. Ansichten der Natur. Dritte Ausgabe, Stuttgart und Tubingen, 1849. 2 vols. 12mo.
Hummel, Karl. Physische Geographie. Grax, 1835. 8vo.
Hunter, A. Notes to Evelyn, Silva, and Terra. York, 1786. See Evelyn.
Jacini, Stefano. La Proprieta Fondiaria e le Popolazioni agrioole in
Lombardia. Milano e Verona, 1857. 8vo.
Joinville. Histoire de Saint-Louis. Nouvelle Collection des Memoires pour servir a l'Histoire de France, par Michaud et Poujoulat. Tome i. Paris, 1836. 8vo.
Josselyn, John. New England Rarities. London, 1672. 12mo.
Knorr, E. A. Studien uber die Buchen-Wirthschaft. Nordhausen, 1863. 8vo.
Kohl, J. G. Alpenreisen. Dresden und Leipzig, 1849. 8 vols. 8vo.
——Die Marschen und Inseln der Herzogthumer Schleswig und Holstein.
Dresden und Leipzig, 1846. 3 vols. 8vo.
Kramer, Gustav. Der Fuciner-See. Berlin, 1839. 4to.
Krause, G. C. A. Der Dunenbau auf den Ostsee-Kusten West-Preussens. 1850. 8vo.
Kremer, Alfred von. AEgypten, Forschungen uber Land und Volk. Leipzig, 1863. 2 vols. 8vo.
Kriegk, G. L. Schriften zur allgemeinen Erdkunde. Leipzig, 1840. 8vo.
Ladoucette, J. C. F. Histoire, Topographie, Antiquites, Usages,
Dialectes des Hautes Alpes. Seconde edition, 1834. 1 vol. 8vo. and
Atlas.
Laestadius, Lars Levi. Om Mojligheten och Fordelen af allmanna
Uppodlingar i Lappmarken. Stockholm, 1824. 12mo.
Laestadius, Petrus. Journal for forsta aret af hans Tjenstgoring sasom
Missionaire i Lappmarken. Stockholm, 1831. 8vo.
——Fortsattning af Journalen ofver Missions-Resor i Lappmarken.
Stockholm, 1833. 8vo.
Lampridius. Vita Elagabali in Script. Hist., August.
Landgrebe, Georg. Naturgeschichte der Vulcane. Gotha, 1855. 2vols. 8vo.
Laurent, Ch. Memoires sur le Sahara Oriental au point de vue des Puits
Artesiens. Paris, 1859. 8vo. pamphlet. Also, in Mein de la Soc. des
Ingenieurs Civils, and the Bulletin de la Soc. Geologique de France.
Laval. Memoire sur les Dunes da Golfe de Gascogno; in Annales des Ponts et Ohaussees, 1847, 2mo semestre, pp. 218-268.
Lavergne, M. L. de. Economie Rurale de la France, depuis 1789. 2me edition, Paris, 1861. 12mo.
Le Alpi che cingono l'Italia. Parte 1er, vol. 1er. Torino, 1845. 8vo.
Lefort. Notice sur les travaux de Fixation des Dunes; in Annales des
Ponts et Ohaussecs, 1831, 2me semestre, pp. 320-382
Lenormant. Note relative a l'Execution d'un Puits Artesien en Egypte sous la XVIIIeme Dynastie; Academie des Inscriptions et Belles-Lettres, 12 Novembre, 1852.
Liber Albus: The White Book of the City of London. London, 1861. 4to.
Loftus, W. K. Travels and Researches in Chaldaea and Susiana. New York, 1867. 8vo.
Lombardini. Cenni Idrografi sulla Lombardia; Intorno al Sistema
Idraulico del Po; epitomized by Baumgarten in Annales des Ponts et
Chaussees, 1847, 1er semestre, pp. 129, 199; and in Dumont, Des Travaux
Publics, pp. 268, 335.
——Sui progetti intesi ad estendere l'irrigazione della Pianura del Po.
Politecnico. Gennajo, 1863, pp. 5-50.
Lorentz. Cours Elementaire de Culture des Bois, complete et publie par
A. Parade, 4me edition. Paris et Nancy, 1860. 8vo.
Lyell, Sir Charles. The Geological Evidence of the Antiquity of Man.
London, 1863. 8vo. Principles of Geology. New York, 1862. 8vo.
Mardigny, M de. Memoire sur les Inondations des Rivieres de l'Ardeche.
Paris, 1860. 8vo.
Marschand, A. Ueber die Entwaldung der Gebirge. Bern, 1840. 12mo. pamphlet.
Martineau. Endeavors after the Christian Life. Boston, 1858.
Martins. Revue des Deux Mondes, Avril, 1863.
Maury, M. F. The Physical Geography of the Sea. Tenth edition. London, 1861. 8vo.
Medlicott, Dr. Observations of, quoted from London Athenaeum, 1868.
Meguscher, Francesco. Memorie sulla migliore maniera per rimettere i
Boschi della Lombardia, etc. Milano, 1859. 8vo.
Mejdell, Th. Om Foranstaltninger til Behandling af Norges Skove.
Christiania, 1868. 8vo.
Mella. Delle Inondazioni del Mella nella notte del 14 al 15 Agosto, 1850. Brescia, 1851. 8vo. Meyer, J. Physik der Schweiz. Leipzig, 1854. 8vo.
Michelet, J. L'Insecte, 4me edition. Paris, 1860. 12mo.
——L'Oiseau, 7me edition. Paris, 1861. 12mo.
Monestier-Savignat, A. Etude sur les Phenomenes, l'Amenagement et la
Legislation des Eaux au point de vue des Inondations. Paris, 1858. 8vo.
Montluisant. Note sur les Dessechements, les Endiguements et les Irrigations; in Annales des Ponts et Chaussees, 1833, 2me semestre, pp. 281-294.
Morozzi, Ferdinando. Dello Stato Antico e Moderno del Fiume Arno.
Firenze, 1762. 4to.
Muller, K. Das Buch der Pflanzenwelt. Leipzig, 1857. 2 vols 12mo.
Nangis, Guillaume de. Extracts from, in Nouvelle Collection des Memoires pour servir par Michaud et Poujoulat. Vol. i. Paris, 1836.
Nanquette, Henri. Cours d'Amenagement des Forets. Paris et Nancy, 1860. 8vo.
Newberry, Dr. Report in Pacific Railroad Report, vol. vi.
Niebelunge-Lied, Der. Abdruck der Handschrift von Joseph von Lassburg.
Leipzig, 1840. Folio.
Niel. L'Agriculture des Etats Sardes. Turin, 1857. 8vo.
Pacific Railroad Report. Reports of Explorations and Surveys for a
Railroad Route to the Pacific. Washington, various years. 12 vols. 4to.
Palissy, Bernard, Oeuvres Completes, avec des Notes, etc., par Paul-
Antoine Cap. Paris, 1844. 12mo.
Parade, A. See Lorentz.
Paramelle, Abbe. Quellenkunde, Lehre von der Bildung und Auffindung der
Quellen; mit einem Vorwort von B. Cotta. Leipzig, 1856. 12mo.
Parish, Dr. Life of Dr. Eleazer Wheelock. 8vo. Parry, C.C. Report in
United States and Mexican Boundary Survey, vol.i.
Parthey, G. Wanderungen durch Sicilien und die Levante. Berlin, 1834. 2 vols. 12mo.
Piper, R.U. The Trees of America. Boston, 1858, Nos. i-iv. 4to.
Plini, Historia Naturalis, ed. Hardouin. Paris, 1729. 8 vols. folio.
Ponz, Antonio, Viage de Espana. Madrid, 1788, etc. 18 vols. 12mo.
Quatrefages, A. de. Souvenirs d'un Naturaliste. Paris, 1834. 2 vols. 12mo.
Reclus, Elisee. Le Littoral de la France; Revue des Deux Mondes, 15
Decembre, 1862.
Rentzsch, Hermann. Der Wald im Haushalt der Natur und der
Volkswirtschaft. Leipzig, 1862. 8vo.
Ribbe, Charles de. La Provence au point de vue des Bois, des Torrents et des Inondations. Paris, 1857. 8vo.
Ridolfi, Cosimo. Lezioni Orali. Firenze, 1862. 2 vols. 8vo.
Ritter, Carl. Einleitung zur allgemeinen vergleichenden Geographie.
Berlin, 1852. 8vo.
——Die Erdkunde im Verhaltnisa zur Natur und zur Geschichte des
Menschen. Berlin, various years. 19 vols. 8vo.
Rosa, G. Le Condizioni de' boschi, de' fiumi e de' torronti nella provincia di Bergamo. Politecnico, Dicembre, 1861, pp. 606, 621.
-Studii sui Boschi. Politecnico, Maggio, 1862, pp. 232, 238.
Rossmassler, C. A. Der Wald. Leipzig und Heidelberg, 1863. 8vo.
Roth, J. Der Vesuv and die Umgebung von Neapel. Berlin, 1857. 8vo.
Rozet, M. Moyens de forcer les Torrents des Montagnes de rendre une partie du sol qu'ils ravagent. Paria, 1856. 8vo. pamphlet.
Salvagnoli-Marchetti, Antonio. Memorio Economico-Statistiche sulle
Maremme Toscane. Firenze, 1846. 8vo.
——Raccolta di Documenti sul Bonificamento delle Moremme Toscane.
Firenze, 1861. 8vo.
——Rapporto sul Bonficamento delle Maremme Toscane. Firenze, 1859. 8vo.
——Rapporto sulle Operazioni Idrauliche ed Economiche eseguite nel 1859-'60 nelle Maremme Toscane. Firenze, 1860. 8vo.
Sandys, George. A Relation of a Journey begun An. Dom. 1610. London, 1627. Folio.
Schacht, H. Les Arbres, Etudes sur leur Structure et leur Vegetation, traduit par E. Morreu. Bruxelles et Leipzig, 1862. 8vo.
Schleiden, M. J. Die Landenge von Sues. Leipzig, 1858. 8vo.
——Die Pflanze und ihr Leben. Leipzig, 1848. 8vo.
Schubert, W. von. Resa genom Sverige, Norrige, Lappland, etc. Stockholm, 1828. 8 vols. 8vo.
Seneca, L. A. Opera Omnia quae supersont, ex rec. Ruhkopf. Aug.
Taurinorum, 1831. 6 vols. 8vo.
Simonde, J. E. L. Tableau de l'Agriculture Toscane. Geneve, 1801. 8vo.
Smith, Dr. William. A Dictionary of the Bible. London, 1860. 8 vols. 8vo.
——A. Dictionary of Greek and Roman Geography. London, 1854, 1857. 2 vols. 8vo.
Smith, John. Historie of Virginia. London, 1624. Folio.
Somerville, Mary. Physical Geography. Fifth edition. London, 1862. 12mo.
Springer, John S. Forest-Life and Forest-Trees. New York, 1851. 12mo.
Stanley, Dr. Lectures on the History of the Jewish Church. London, 1863. 8vo.
Staring, W. H. De Bodem van Nederland. Haarlem, 1856. 2 vols. 8vo.
——Voormaals en Thans. Haarlem, 1858. 8vo.
Stevens, Gov. Report in Pacific Railroad Report, vol. xii.
Strain, Lieut. I.C. Darien Exploring Expedition, by J.T. Headley, in
Harper's Magazine. New York, March, April, and May, 1855.
Streffleur, V. Ueber die Natur und die Wirkungen der Wildbuche. Sitz. Ber. der M.N.W. Classe der Kaiserl. Akad. der Wis. February, 1852, viii, p. 248.
Strom, Ier. Om Skogarnas Vard och Skotsel. Upsala, 1853. Pamphlet.
Surell, Alexandre. Etude sur les Torrents des Hautes Alpes. Paris, 1844. 4to.
Tartini, Ferdinando. Memorio sul Bonificamento delle Maremme Toscane. Firenze, 1888. Folio. Thomas and Baldwin. Gazetteer. Philadelphia, 1855. 1 vol. 8vo.
Thompson, Z. History of Vermont, Natural, Civil, and Statistical.
Burlington, 1842. 8vo.
——Appendix to History of Vermont. Burlington, 1853. 8vo.
Titcomb, Timothy. Lessons in Life. New York, 1861. 12mo.
Treadwell, Dr. Observations of, quoted from Report of Commissioner of
Patents.
Trey, Paul. Etude sur le Reboisement des Montagnes. Paris et Toulouse, 1861. 8vo. pamphlet.
Tschudi, Friedrich von. Ueber die Landwirthschaftliche Bedeutung der
Vogel. St. Gallen, 1854. 12mo.
Tschudi, J.J. von. Travels in Peru. New York, 1848. 8vo.
Valles, M.F. Etudes sur les Inondations, leurs causes et leurs effets.
Paris, 1857. 8vo.
Valvasor, Johann Weichard. Die Ehre des Herzogthums Crain. Laybach,
1689. 4 vols. folio.
Van Lennep. Extracts from Journal of, in the Missionary Herald.
Vaupell, Chr. Bogene Indvandring i de Danske Skove. Kjobenhavn, 1857. 8vo.
——De Nordsjaellandake Skovmoser. Kjobenhavn, 1851. 4to, pamphlet.
Venema, G.A. Over het Dalen van de Noordelijke Kuststreken van ons Land.
Groningen, 1854. 8vo.
Villa, Antonio Giovanni Batt. Necessita dei Boschi nella Lombardia.
Milano, 1850. 4to.
Viollet, J.B. Theorie des Puits Artesiens. Paris, 1840. 8vo.
Waltershausen, W. Sartorius von. Ueber den Sicilianischen Ackerbau
Gottingen, 1863.
Webster, Noah. A Collection of Papers on Political, Literary, and Moral
Subjects. New York, 1843. 8vo.
Wessely, Joseph. Die Oesterreichischen Alpenlander und ihre Forste.
Wien, 1853. 2 vols. 8vo.
Wetzstein, J.G. Reisebericht uber Hanran und die Trachonen. Berlin,
1860. 8vo.
Wild, Albert. Die Niederlande. Leipzig, 1862. 2 vols. 8vo.
Wilhelm, Gustav. Der Boden und das Wasser. Wien, 1861. 8vo.
Williams, Dr. History of Vermont. 2 vols. 8vo.
Wittwer, W.C. Die Physikalische Geographie. Leipzig, 1855. 8vo.
Young, Arthur. Voyages en France, pendant les annees 1787, 1788, 1789, procedee d'une introduction par Lavergne. Paris, 1860. 2 vols. 12mo.
——Voyages en Italie et en Espagne, pendant les annees 1787, 1789.
Paris, 1860. 1 vol. 12mo.
TABLE OF CONTENTS
CHAPTER I.
INTRODUCTORY
Natural Advantages of the Territory of the Roman Empire—Physical Decay of that Territory—Causes of the Decay—Reaction of Man on Nature—Observation of Nature—Uncertainty of Our Historical Knowledge of Ancient Climates—Uncertainty of Modern Meteorology—Stability of Nature—Formation of Bogs—Natural Conditions Favorable to Geographical Change—Destructiveness of Man—Human and Brute Action Compared—Limits of Human Power—Importance of Physical Conservation and Restoration—Uncertainty as to Effects of Human Action
CHAPTER II.
TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES.
Modern Geography takes Account of Organic Life—Geographical Importance
of Plants—Origin of Domestic Vegetables—Transfer of Vegetable
Life—Objects of Modern Commerce—Foreign Plants, how
Introduced—Vegetable Power of Accommodation—Agricultural Products of
the United States—Useful American Plants Grown in Europe—Extirpation
of Vegetables—Animal Life as a Geological and Geographical
Agency—Origin and Transfer of Domestic Quadrupeds—Extirpation of Wild
Quadrupeds—Large Marine Animals Relatively Unimportant in
Geography—Introduction and Breeding of Fish—Destruction of
Fish—Geographical Importance of Birds—Introduction of
Birds—Destruction of Birds—Utility and Destruction of
Reptiles—Utility of Insects and Worms—Injury to the Forest by
Insects—Introduction of Insects—Destruction of Insects—Minute
Organisms
CHAPTER III.
THE WOODS.
The Habitable Earth Originally Wooded—General Meteorological Influence
of the Forest—Electrical Action of Trees—Chemical Influence of
Woods—Trees as Protection against Malaria—Trees as Shelter to Ground
to the Leeward—Influence of the Forest as Inorganic on
Temperature—Thermometrical Action of Trees as Organic—Total Influence
of the Forest on Temperature—Influence of Forests as Inorganic on
Humidity of Air and Earth—Influence as Organic—Balance of Conflicting
Influences—Influence of Woods on Precipitation—Total Climatic Action
of the Forest—Influence of the Forest on Humidity of Soil—The Forest
in Winter—Summer Rain, Importance of—Influence of the Forest on the
Flow of Springs—Influence of the Forest on Inundations and
Torrents—Destructive Action of Torrents—Floods of the
Ardeche—Excavation by Torrents—Extinction of Torrents—Crushing Force
of Torrents—Transporting Power of Water—The Po and its
Deposits—Mountain Slides—Forest as Protection against
Avalanches—Minor Uses of the Forest—Small Forest Plants and Vitality
of Seeds—Locusts do not Breed in Forests—General Functions of
Forest—General Consequences of Destruction of—Due Proportion of
Woodland—Proportion of Woodland in European Countries—Forests of Great
Britain—Forests of France—Forests of Italy—Forests of
Germany—Forests of United States—American Forest Trees—European and
American Forest Trees Compared—The Forest does not furnish Food for
Man—First Removal of the Forest—Principal Causes of Destruction of
Forest—Destruction and Protection of Forests by Governments—Royal
Forests and Game-laws—Effects of the French Revolution—Increased
Demand for Lumber—Effects of Burning Forest—Floating of
Timber—Restoration of the Forest—Economy of the Forest—Forest
Legislation—Plantation of Forests In America—Financial Results of
Forest Plantations—Instability of American Life
CHAPTER IV.
THE WATERS.
Land Artificially Won from the Waters—Great Works of Material
Improvement—Draining of Lincolnshire Fens—Incursions of the Sea in the
Netherlands—Origin of Sea-dikes—Gain and Loss of Land in the
Netherlands—Marine Deposits on the Coast of Netherlands—Draining of
Lake of Haarlem—Draining of the Zuiderzee—Geographical Effects
of—Improvements in the Netherlands—Ancient Hydraulic Works—Draining
of Lake Celano by Prince Torlonia—Incidental Consequences of Draining
Lakes—Draining of Marshes—Agricultural Draining—Meteorological
Effects of Draining—Geographical Effects of Draining—Geographical
Effects of Aqueducts and Canals—Antiquity of Irrigation—Irrigation in
Palestine, India, and Egypt—Irrigation in Europe—Meteorological
Effects of Irrigation—Water withdrawn from Rivers for
Irrigation—Injurious Effects of Rice-culture—Salts Deposited by Water
of Irrigation—Subterranean Waters—Artesian Wells—Artificial
Springs—Economizing Precipitation—Inundations in France—Basins of
Reception—Diversion of Rivers—Glacier Lakes—River Embankments—Other
Remedies against Inundations—Dikes of the Nile—Deposits of Tuscan
Rivers—Improvements in Tuscan Maremma—Improvements in Val di
Chiana—Coast of the Netherlands
CHAPTER V.
THE SANDS.
Origin of Sand—Sand now Carried to the Sea—Beach Sands of Northern
Africa—Sands of Egypt—Sand Dunes and Sand Plains—Coast Dunes—Sand
Banks—Character of Dune Sand—Interior Structure of Dunes—Geological
Importance of Dunes—Dunes on American Coasts—Dunes of Western
Europe—Age, Character, and Permanence of Dunes—Dunes as a Barrier
against the Sea—Encroachments of the Sea—Liimfjord—Coasts of
Schleswig-Holstein, Netherlands, and France—Movement of Dunes—Control
of Dunes by Man—Inland Dunes—Inland Sand Plains
CHAPTER VI.
GREAT PROJECTS OF PHYSICAL CHANGE ACCOMPLISHED OR PROPOSED BY MAN.
Cutting of Isthmuses—Canal of Suez—Maritime Canals in Greece—Canals
to Dead Sea—Canals to Libyan Desert—Maritime Canals in Europe—Cape
Cod Canal—Changes in Caspian—Diversion of the Nile—Diversion of the
Rhine—Improvements in North American Hydrography—Soil below
Rock—Covering Rock with Earth—Desert Valleys—Effects of
Mining—Duponchel's Plans of Improvement—Action of Man on the
Weather—Resistance to Great Natural Forces—Incidental Effects of Human
Action—Nothing Small In Nature
THE EARTH AS MODIFIED BY HUMAN ACTION.
CHAPTER 1.
INTRODUCTORY.
Natural Advantages of the Territory of the Roman Empire.—Physical Decay
of that Territory.—Causes of the Decay.—Reaction of Man on Nature.—
Observation of Nature.—Uncertainty of Our Historical Knowledge of
Ancient Climates.—Uncertainty of Modern Meteorology.—Stability of
Nature.—Formation of Bogs—Natural Conditions Favorable to Geographical
Change.—Destructiveness of Man—Human and Brute Action
Compared.—Limits of Human Power.—Importance of Physical Conservation
and Restoration—Uncertainty as to Effects of Human Action.
Natural Advantages of the Territory of the Roman Empire.
The Roman Empire, at the period of its greatest expansion, comprised the regions of the earth most distinguished by a happy combination of physical conditions. The provinces bordering on the principal and the secondary basins of the Mediterranean enjoyed in healthfulness and equability of climate, in fertility of soil, in variety of vegetable and mineral products, and in natural facilities for the transportation and distribution of exchangeable commodities, advantages which have not been possessed in any equal degree by any territory of like extent in the Old World or the New. The abundance of the land and of the waters adequately supplied every material want, ministered liberally to every sensuous enjoyment. Gold and silver, indeed, were not found in the profusion which has proved so baneful to the industry of lands richer in veins of the precious metals; but mines and river beds yielded them in the spare measure most favorable to stability of value in the medium of exchange, and, consequently, to the regularity of commercial transactions. The ornaments of the barbaric pride of the East, the pearl, the ruby, the sapphire, and the diamond—though not unknown to the luxury of a people whose conquests and whose wealth commanded whatever the habitable world could contribute to augment the material splendor of their social life—were scarcely native to the territory of the empire; but the comparative rarity of these gems in Europe, at somewhat earlier periods, was, perhaps, the very circumstance that led the cunning artists of classic antiquity to enrich softer stones with engravings, which invest the common onyx and cornelian with a worth surpassing, in cultivated eyes, the lustre of the most brilliant oriental jewels.
Of these manifold blessings the temperature of the air, the distribution of the rains, the relative disposition of land and water, the plenty of the sea, the composition of the soil, and the raw material of the primitive arts, were wholly gratuitous gifts. Yet the spontaneous nature of Europe, of Western Asia, of Libya, neither fed nor clothed the civilized inhabitants of those provinces. The luxuriant harvests of cereals that waved on every field from the shores of the Rhine to the banks of the Nile, the vines that festooned the hillsides of Syria, of Italy and of Greece, the olives of Spain, the fruits of the gardens of the Hesperides, the domestic quadrupeds and fowls known in ancient rural husbandry—all these were original products of foreign climes, naturalized in new homes, and gradually ennobled by the art of man, while centuries of persevering labor were expelling the wild vegetation, and fitting the earth for the production of more generous growths. Every loaf was eaten in the sweat of the brow. All must be earned by toil. But toil was nowhere else rewarded by so generous wages; for nowhere would a given amount of intelligent labor produce so abundant, and, at the same time, so varied returns of the good things of material existence.
Physical Decay of the Territory of the Roman Empire.
If we compare the present physical condition of the countries of which I am speaking, with the descriptions that ancient historians and geographers have given of their fertility and general capability of ministering to human uses, we shall find that more than one-half their whole extent—not excluding the provinces most celebrated for the profusion and variety of their spontaneous and their cultivated products, and for the wealth and social advancement of their inhabitants—is either deserted by civilized man and surrendored to hopeless desolation, or at least greatly reduced in both productiveness and population. Vast forests have disappeared from mountain spurs and ridges; the vegetable earth accumulated beneath the trees by the decay of leaves and fallen trunks, the soil of the alpine pastures which skirted and indented the woods, and the mould of the upland fields, are washed away; meadows, once fertilized by irrigation, are waste and unproductive because the cisterns and reservoirs that supplied the ancient canals are broken, or the springs that fed them dried up; rivers famous in history and song have shrunk to humble brooklets; the willows that ornamented and protected the banks of the lesser watercourses are gone, and the rivulets have ceased to exist as perennial currents, because the little water that finds its way into their old channels is evaporated by the droughts of summer, or absorbed by the parched earth before it reaches the lowlands; the beds of the brooks have widened into broad expanses of pebbles and gravel, over which, though in the hot season passed dryshod, in winter sealike torrents thunder; the entrances of navigable streams are obstructed by sandbars; and harbors, once marts of an extensive commerce, are shoaled by the deposits of the rivers at whose mouths they lie; the elevation of the beds of estuaries, and the consequently diminished velocity and increased lateral spread of the streams which flow into them, have converted thousands of leagues of shallow sea and fertile lowland into unproductive and miasmatic morasses.
Besides the direct testimony of history to the ancient fertility of the now exhausted regions to which I refer—Northern Africa, the greater Arabian peninsula, Syria, Mesopotamia, Armenia and many other provinces of Asia Minor, Greece, Sicily, and parts of even Italy and Spain—the multitude and extent of yet remaining architectural ruins, and of decayed works of internal improvement, show that at former epochs a dense population inhabited those now lonely districts. Such a population could have been sustained only by a productiveness of soil of which we at present discover but slender traces; and the abundance derived from that fertility serves to explain how large armies, like those of the ancient Persians, and of the Crusaders and the Tartars in later ages, could, without an organized commissariat, secure adequate supplies in long marches through territories which, in our times, would scarcely afford forage for a single regiment.
It appears then, that the fairest and fruitfulest provinces of the Roman Empire, precisely that portion of terrestrial surface, in short, which, about the commencement of the Christian era, was endowed with the greatest superiority of soil, climate, and position, which had been carried to the highest pitch of physical improvement, and which thus combined the natural and artificial conditions best fitting it for the habitation and enjoyment of a dense and highly refined and cultivated population, are now completely exhausted of their fertility, or so diminished in productiveness, as, with the exception of a few favored oases that have escaped the general ruin, to be no longer capable of affording sustenance to civilized man. If to this realm of desolation we add the now wasted and solitary soils of Persia and the remoter East that once fed their millions with milk and honey, we shall see that a territory larger than all Europe, the abundance of which sustained in bygone centuries a population scarcely inferior to that of the whole Christian world at the present day, has been entirely withdrawn from human use, or, at best, is thinly inhabited by tribes too few in numbers, too poor in superfluous products, and too little advanced in culture and the social arts, to contribute anything to the general moral or material interests of the great commonwealth of man.
Causes of this Decay.
The decay of these once flourishing countries is partly due, no doubt, to that class of geological causes whose action we can neither resist nor guide, and partly also to the direct violence of hostile human force; but it is, in a far greater proportion, either the result of man's ignorant disregard of the laws of nature, or an incidental consequence of war and of civil and ecclesiastical tyranny and misrule. Next to ignorance of these laws, the primitive source, the causa causarum, of the acts and neglects which have blasted with sterility and physical decrepitude the noblest half of the empire of the Caesars, is, first, the brutal and exhausting despotism which Rome herself exercised over her conquered kingdoms, and even over her Italian territory; then, the host of temporal and spiritual tyrannies which she left as her dying curse to all her wide dominion, and which, in some form of violence or of fraud, still brood over almost every soil subdued by the Roman legions. [Footnote: In the Middle Ages, feudalism, and a nominal Christianity, whose corruptions had converted the most beneficent of religions into the most baneful of superstitions, perpetuated every abuse of Roman tyranny, and added new oppressions and new methods of extortion to those invented by older despotisms. The burdens in question fell most heavily on the provinces that had been longest colonized by the Latin race, and those are the portions of Europe which have suffered the greatest physical degradation. "Feudalism," says Blanqui, "was a concentration of scourges. The peasant, stripped of the inheritance of his fathers, became the property of inflexible, ignorant, indolent masters; he was obliged to travel fifty leagues with their carts whenever they required it; he labored for them three days in the week, and surrendered to them half the product of his earnings during the other three; without their consent he could not change his residence, or marry. And why, indeed, should he wish to marry, when he could scarcely save enough to maintain himself The Abbot Alcuin had twenty thousand slaves, called SERFS, who were forever attached to the soil. This is the great cauue of the rapid depopulation observed in the Middle Ages, and of the prodigious multitude of monasteries which sprang up on every side. It was doubtless a relief to such miserable men to find in the cloisters a retreat from oppression; but the human race never suffered a more cruel outrage, industry never received a wound better calculated to plunge the world again into the darkness of the rudest antiquity. It suffices to say that the prediction of the approaching end of the world, industriously spread by the rapacious monks at this time, was received without terror."—Resume de l'Histoire du Commerce, p. 156.] Man cannot struggle at once against human oppression and the destructive forces of inorganic nature. "When both are combined against him, he succumbs after a shorter or longer struggle, and the fields he has won from the primeval wood relapse into their original state of wild and luxuriant, but unprofitable forest growth, or fall into that of a dry and barren wilderness. The abbey of Saint-Germain-des-Pres, which, in the time of Charlemagne, had possessed a million of acres, was, down to the Revolution, still so wealthy, that the personal income of the abbot was 300,000 livres. Theabbey of Saint-Denis was nearly as rich as that of Saint-Germain-des-Pres.—Lavergne, Economie Rurale de la France, p. 104.
Paul Louis Courier quotes from La Bruyere the following striking picture of the condition of the French peasantry in his time: "One sees certain dark, livid, naked, sunburnt, wild animals, male and female, scattered over the country and attached to the soil, which they root and turn over with indomitable perseverance. They have, as it were, an articulate voice, and when they rise to their feet, they show a human face. They are, in fact, men; they creep at night into dens, where they live on black bread, water, and roots. They spare other men the labor of ploughing, Bowing, and harvesting, and therefore deserve some small share of the bread they have grown." "These are his own words," adds Courier, "and he is speaking of the fortunate peasants, of those who had work and bread, and they were then the few."—Petition a la Chambre des Deputes pour les Villageois l'en empeche ce danser.
Arthur Young, who travelled in France from 1787 to 1789, gives, in the twenty-first chapter of his Travels, a frightful account of the burdens of the rural population even at that late period. Besides the regular governmental taxes, and a multitude of heavy fines imposed for trifling offense, he enumerates about thirty seignorial rights, the very origin and nature of some of which are now unknown, while those of some others are as repulsive to humanity and morality, as the worst abuses ever practised by heathen despotism. But Young underrates the number of these oppressive impositions. Moreau de Jonnes, a higher authority, asserts that in a brief examination he had discovered upwards of three hundred distinct lights of the feudatory over the person or the property of his vassal. See Etat Economique et Social de la France, Paris, 1890, p. 389. Most of these, indeed, had been commuted for money payments, and were levied on the peasantry as pecuniary imposts for the benefit of prelates and lay lords, who, by virtue of their nobility, were exempt from taxation. The collection of the taxes was enforced with unrelenting severity. On one occasion, in the reign of Louis XIV., the troops sent out against the recreant peasants made more than 3,000 prisoners, of whom 400 were condemned to the galleys for life, and a number so large that the government did not dare to disclose it, were hung on trees or broken on the wheel.—Moreau de Jonnes, Etat Economique et Social de la France, p. 420. Who can wonder at the hostility of the French plebeian classes towards the aristocracy in the days of the Revolution?
Rome imposed on the products of agricultural labor in the rural districts taxes which the sale of the entire harvest would scarcely discharge; she drained them of their population by military conscription; she impoverished the peasantry by forced and unpaid labor on public works; she hampered industry and both foreign and internal commerce by absurd restrictions and unwise regulations. [Footnote: Commerce, in common with all gainful occupations except agriculture, was despised by the Romans, and the exercise of it was forbidden to the higher ranks. Cicero, however, admits that though retail trade, which could only prosper by lying and knavery, was contemptible, yet wholesale commerce was not altogether to be condemned, and might even be laudable, provided the merchant retired early from trade and invested his gaits in farm lands.—De Officiis, lib. i.,42.] Hence, large tracts of land were left uncultivated, or altogether deserted, and exposed to all the destructive forces which act with such energy on the surface of the earth when it is deprived of those protections by which nature originally guarded it, and for which, in well-ordered husbandry, human ingenuity has contrived more or less efficient substitutes. [Footnote: The temporary depopulation of an exhausted soil may be, in some cases, a physical, though, like fallows in agriculture, a dear-bought advantage. Under favorable circumstances, the withdrawal of man and his flocks allows the earth to clothe itself again with forests, and in a few generations to recover its ancient productiveness. In the Middle Ages, worn-out fields were depopulated, in many parts of the Continent, by civil and ecclesiastical tyrannies, which insisted on the surrender of the half of a loaf already too small to sustain its producer. Thus abandoned, these lands often relapsed into the forest state, and, some centuries later, were again brought under cultivation with renovated fertility.] Similar abuses have tended to perpetuate and extend these evils in later ages, and it is but recently that, even in the most populous parts of Europe, public attention has been half awakened to the necessity of restoring the disturbed harmonies of nature, whose well-balanced influences are so propitious to all her organic offspring, and of repaying to our great mother the debt which the prodigality and the thriftlessness of former generations have imposed upon their successors—thus fulfilling the command of religion and of practical wisdom, to use this world as not abusing it.
Reaction of Man on Nature.
The revolutions of the seasons, with their alternations of temperature and of length of day and night, the climates of different zones, and the general conditions and movements of the atmosphere and the seas, depend upon causes for the most part cosmical, and, of course, wholly beyond our control. The elevation, configuration, and composition of the great masses of terrestrial surface, and the relative extent and distribution of land and water, are determined by geological influences equally remote from our jurisdiction. It would hence seem that the physical adaptation of different portions of the earth to the use and enjoyment of man is a matter so strictly belonging to mightier than human powers, that we can only accept geographical nature as we find her, and be content with such soils and such skies as she spontaneously offers.
But it is certain that man has reacted upon organized and inorganic nature, and thereby modified, if not determined, the material structure of his earthly home. The measure of that reaction manifestly constitutes a very important element in the appreciation of the relations between mind and matter, as well as in the discussion of many purely physical problems. But though the subject has been incidentally touched upon by many geographers, and treated with much fulness of detail in regard to certain limited fields of human effort and to certain specific effects of human action, it has not, as a whole, so tar as I know, been made matter of special observation, or of historical research, by any scientific inquirer. Indeed, until the influence of geographical conditions upon human life was recognized as a distinct branch of philosophical investigation, there was no motive for the pursuit of such speculations; and it was desirable to inquire how far we have, or can, become the architects of our own abiding place, only when it was known how the mode of our physical, moral, and intellectual being is affected by the character of the home which Providence has appointed, and we have fashioned, for our material habitation. [Footnote:Gods Almagt wenkte van den troon, En schiep elk volk een land ter woon: Hier vestte Zij een grondgebied, Dat Zij ona zelven scheppon llet.] It is still too early to attempt scientific method in discussing this problem, nor is our present store of the necessary facts by any means complete enough to warrant me in promising any approach to fulness of statement respecting them. Systematic observation in relation to this subject has hardly yet begun, and the scattered data which have chanced to be recorded have never been collected. It has now no place in the general scheme of physical science, and is matter of suggestion and speculation only, not of established and positive conclusion. At present, then, all that I can hope is to excite an interest in a topic of much economical importance, by pointing out the directions and illustrating the modes in which human action has been, or may be, most injurious or most beneficial in its influence upon the physical conditions of the earth we inhabit We cannot always distinguish between the results of man's action and the effects of purely geological or cosmical causes. The destruction of the forests, the drainage of lakes and marshes, and the operations of rural husbandry and industrial art have unquestionably tended to produce great changes in the hygrometric, thermometric, electric, and chemical condition of the atmosphere, though we are not yet able to measure the force of the different elements of disturbance, or to say how far they have been neutralised by each other, or by still obscurer influences; and it is equally certain that the myriad forms of animal and vegetable life, which covered the earth when man first entered upon the theatre of a nature whose harmonies he was destined to derange, have been, through his interference, greatly changed in numerical proportion, sometimes much modified in form and product, and sometimes entirely extirpated. [Footnote: Man has not only subverted the natural numerical relations of wild as well as domestic quadrupeds, fish, birds, reptile, insect, and common plants, and even of still humbler tribes of animal and vegetable life, but he has effected in the forms, habits, nutriment and products of the organisms which minister to his wants and his pleasures, changes which, more than any other manifestaion of human energy, resemble the exercise of a creative power. Even wild animals have been compelled by him, through the destruction of plants and insects which furnished their proper aliment, to resort to food belonging to a different kingdom of nature. Thus a New Zealand bird, originally granivorous and insectivorous, has become carnivorous, from the want of its natural supplies, and now tears the fleeces from the backs of the sheep, in order to feed on their living flesh. All these changes have exercised more or less direct or indirect action on the inorganic surface of the globe; and the history of the geographical revolutions thus produced would furnish ample material for a volume.
The modification of organic species by domestication is a branch of philosophic inquiry which we may almost say has been created by Darwin; but the geographical results of these modifications do not appear to have yet been made a subject of scientific investigation.
I do not know that the following passage from Pliny has ever been cited in connection with the Darwinian theories but it is worth a reference:
"But behold a very strange and new fashion of them [cucumbers] in Campane, for there you shall have abundance of them come up in forme of a Quince. And as I heare say, one of the channced so to grow first at a very venture; but afterwards from the seed of it came a whole race and progenie of the like, which therefore they call Melonopopones, as a man would say, the Quince-pompions or cucumbers"—Pliny, Nat. Hist., Holland's translation, book xix, c.5
The word cucumis used in the original of this passage embraces many of the cucurbitaceae, but the context shows that here means the cucumber.
The physical revolutions thus wrought by man have not indeed all been destructive to human interests, and the heaviest blows he has inflicted upon nature have not been wholly without their compensations. Soils to which no nutritious vegetable was indigenous, countries which once brought forth but the fewest products suited for the sustenance and comfort of man—while the severity of their climates created and stimulated the greatest number and the most imperious urgency of physical wants—surfaces the most rugged and intractable, and least blessed with natural facilities of communication, have been brought in modern times to yield and distribute all that supplies the material necessities, all that contributes to the sensuous enjoyments and conveniences of civilized life. The Scythia, the Thule, the Britain, the Germany, and the Gaul which the Roman writers describe in such forbidding terms, have been brought almost to rival the native luxuriance and easily won plenty of Southern Italy; and, while the fountains of oil and wine that refreshed old Greece and Syria and Northern Africa have almost ceased to flow, and the soils of those fair lands are turned to thirsty and inhospitable deserts, the hyperborean regions of Europe have learnod to conquer, or rather compensate, the rigors of climate, and have attained to a material wealth and variety of product that, with all their natural advantages, the granaries of the ancient world can hardly be said to have enjoyed.
Observation of Nature.
In these pages it is my aim to stimulate, not to satisfy, curiosity, and it is no part of my object to save my readers the labor of observation or of thought. For labor is life, and Death lives where power lives unused. [Footnote: Verses addressed by G. C. to Sir Walter Raleigh.—Haklutt, i., p. 608.]
Self is the schoolmaster whose lessons are best worth his wages; and since the subject I am considering has not yet become a branch of formal instruction, those whom it may interest can, fortunately, have no pedagogue but themselves. To the natural philosopher, the descriptive poet, the painter, the sculptor, and indeed every earnest observer, the power most important to cultivate, and, at the same time, hardest to acquire, is that of seeing what is before him. Sight is a faculty; seeing, an art. The eye is a physical but not a self-acting apparatus, and in general it sees only what it seeks. Like a mirror, it reflects objects presented to it; but it may be as insensible as a mirror, and not consciously perceive what it reflects. [Footnote: —I troer, at Synets Sands er lagt i Oiet, Mens dette kun er Redskab. Synet strommer Fra Sjaelens Dyb, og Oiets fine Nerver Gaae ud fra Hjernens hemmelige Vaerksted. Henrik Hertz, Kong Rene's Datter, sc. ii.
In the material eye, you think, sight lodgeth! The EYE is but an organ.
SEEING streameth from the soul's inmost depths. The fine perceptive
Nerve springeth from the brain's mysterious workshop.]
It has been maintained by high authority, that the natural acuteness of our sensuous faculties cannot be heightened by use, and hence, that the minutest details of the image formed on the retina are as perfect in the most untrained as in the most thoroughly disciplined organ. This may be questioned, and it is agreed on all hands that the power of multifarious perception and rapid discrimination may be immensely increased by well-directed practice. [Footnote: Skill in marksmanship, whether with firearms or with other projectile weapons, depends more upon the training of the eye than is generally supposed, and I have often found particularly good shots to possess an almost telescopic vision. In the ordinary use of the rifle, the barrel is guided by the eye, but there are sportemen who fire with the butt of the gun at the hip. In this case, as in the use of the sling, the lasso, and the bolas, in hurling the knife (see Babinet, Lectures, vii., p. 84), in throwing the boomerang, the javelin, or a stone, and in the employment of the blowpipe and the bow, the movements of the hand and arm are guided by that mysterious sympathy which exists between the eye and the unseeing organs of the body. "Some men wonder whye, in casting a man's eye at the marke, the hand should go streighte. Surely if he considered the nature of a man's eye he would not wonder at it: for this I am certaine of, that no servaunt to his maister, no childe to his father, is so obedient, as every joynte and peece of the bodye is to do whatsover the eye biddes."—Roger Ascham, Taxophilus, Book ii.
In shooting the tortoises of the Amazon and its tributaries, the Indians use an arrow with a long twine and a float attached to it. Ave-Lallemant (Die Benutzung der Palmen am Amazonenstrom, p. 32) thus describes their mode of aiming: "As the arrow, if aimed directly at the floating tortoise, would strike it at a small angle and glance from its fiat and wet shell, the archers have a peculiar method of shooting. They are able to calculate exactly their own muscular effort, the velocity of the stream, the distance and size of the tortoise, and they shoot the arrow directly up into the air, so that it falls almost vertically upon the shell of the tortoise, and sticks in it." Analogous calculations—if such physico-mental operations can property be so called—are made in the use of other missiles; for no projectile flies in a right line to its mark. But the exact training of the eye lies at the bottom of them all, and marksmanship depends almost wholly upon the power of that organ, whose directions the blind muscles implicitly follow. Savages accustomed only to the use of the bow become good shots with firearms after very little practice. It is perhaps not out of place to observe here that our English word aim comes from the Latin aestimo, I calculate or estimate. See Wedgwood's Dictionary of English Etymology, and the note to the American edition, under Aim.
Another proof of the control of the limbs by the eye has been observed in deaf-and-dumb schools, and others where pupils are first taught to write on large slates or blackboards. The writing is in large characters, the small letters being an inch or more high. They are formed with chalk or a slate pencil firmly grasped in the fingers, and by appropriate motions of the wrist, elbow, and shoulder, not of the finger joints. Nevertheless, when a pen is put into the hand of a pupil thus taught, his handwriting, though produced by a totally different set of muscles and muscular movements, is identical in character with that which he has practised on the blackboard. For a very remarkable account of the restoration of vision impaired from age, by judicious training, see Lessons in Life, by Timothy Titcomb, lesson xi. It has been much doubted whether the artists of the classic ages possessed a more perfect light than those of modern times, or whether, in executing their minute mosaics and gem engravings, they need magnifiers. Glasses ground convex have been found at Pompeii, but they are too rudely fashioned and too imperfectly polished to have been of any practical use for optical purposes. But though the ancient artists may have had a microscopic vision, their astronomers cannot have had a telescopic power of sight; for they did not discover the satellites of Jupiter, which are often seen with the naked eye at Oormeeah, in Persia, and sometimes, as I can testify by personal observation, at Cairo.]
This exercise of the eye I desire to promote, and, next to moral and religious doctrine, I know no more important practical lessons in this earthly life of ours—which, to the wise man, is a school from the cradle to the grave—than those relating to the employment of the sense of vision in the study of nature.
The pursuit of physical geography, embracing actual observation of terrestrial surface, affords to the eye the best general training that is accessible to all. The majority of even cultivated men have not the time and means of acquiring anything beyond a very superficial acquaintance with any branch of physical knowledge.
Natural science has become so vastly extended, its recorded facts and its unanswered questions so immensely multiplied, that every strictly scientific man must be a specialist, and confine the researches of a whole life within a comparatively narrow circle. The study I am recommending, in the view I propose to take of it, is yet in that imperfectly developed state which allows its votaries to occupy themselves with broad and general views attainable by every person of culture, and it does not now require a knowledge of special details which only years of application can master. It may be profitably pursued by all; and every traveller, every lover of rural scenery, every agriculturist, who will wisely use the gift of sight, may add valuable contributions to the common stock of knowledge on a subject which, as I hope to convince my readers, though long neglected, and now inartificially presented, is not only a very important but a very interesting field of inquiry.
Measurement of Man's Influence.
The exact measurement of the geographical and climatic changes hitherto effected by man is impracticable, and we possess, in relation to them, the means of only qualitative, not quantitative analysis. The fact of such revolutions is established partly by historical evidence, partly by analogical deduction from effects produced, in our own time, by operations similar in character to those which must have taken place in more or less remote ages of human action. Both sources of information are alike defective in precision; the latter, for general reasons too obvious to require specification; the former, because the facts to which it bears testimony occurred before the habit or the means of rigorously scientific observation upon any branch of physical research, and especially upon climatic changes, existed.
UNCERTAINTY OF OUR HISTORICAL CONCLUSIONS ON ANCIENT CLIMATES.
The invention of measures of heat and of atmospheric moisture, pressure, and precipitation, is extremely recent. Hence, ancient physicists have left us no thermometric or barometric records, no tables of the fall, evaporation, and flow of waters, and even no accurate maps of coast lines and the course of rivers. Their notices of these phenomena are almost wholly confined to excessive and exceptional instances of high or of low temperatures, extraordinary falls of rain and snow, and unusual floods or droughts. Our knowledge of the meteorological condition of the earth, at any period more than two centuries before our own time, is derived from these imperfect details, from the vague statements of ancient historians and geographers in regard to the volume of rivers and the relative extent of forest and cultivated land, from the indications furnished by the history of the agriculture and rural economy of past generations, and from other almost purely casual sources of information. [Footnote: The subject of climatic change, with and without reference to human action as a cause, has been much discussed by Moreau de Jonnes, Dureau de la Malle, Arago, Humboldt, Fuster, Gasparin, Becquerel, Schleiden, and many other writers in Europe, and by Noah Webster, Forry, Drake, and others in America. Fraas has endeavored to show, by the history of vegetation in Greece, not merely that clearing and cultivation have affected climate, but that change of climate has essentially modified the character of vegetable life. See his Klima und Pflansenwelt in der Zeit.]
Among these latter we must rank certain newly laid open fields of investigation, from which facts bearing on the point now under consideration have been gathered. I allude to the discovery of artificial objects in geological formations older than any hitherto recognized as exhibiting traces of the existence of man; to the ancient lacustrine habitations of Switzerland and of the terremare of Italy, [Footnote: See two learned articles by Pigorini, in the Nuova Antologia for January and October, 1870.] containing the implements of the occupants, remains of their food, and other relics of human life; to the curious revelations of the Kjokkenmoddinger, or heaps of kitchen refuse, in Denmark and elsewhere, and of the peat mosses in the same and other northern countries; to the dwellings and other evidences of the industry of man in remote ages sometimes laid bare by the movement of sand dunes on the coasts of France and of the North Sea; and to the facts disclosed on the tide-washed flats of the latter shores by excavations in Halligs or inhabited mounds which were probably raised before the era of the Roman Empire. [Footnote: For a very picturesque description of the Halligs, see Pliny, N.H., Book xvi, c. 1.] These remains are memorials of races which have left no written records, which perished at a period beyond the reach of even historical tradition. The plants and animals that furnished the relics found in the deposits were certainly contemporaneous with man; for they are associated with his works, and have evidently served his uses. In some cases, the animals belonged to species well ascertained to be now altogether extinct; in some others, both the animals and the vegetables, though extant elsewhere, have ceased to inhabit the regions where their remains are discovered. From the character of the artificial objects, as compared with others belonging to known dates, or at least to known periods of civilization, ingenious inferences have been drawn as to their age; and from the vegetable remains which accompany them, as to the climates of Central and Northern Europe at the time of their production.
There are, however, sources of error which have not always been sufficiently guarded against in making these estimates. When a boat, composed of several pieces of wood fastened together by pins of the same material, is dug out of a bog, it is inferred that the vessel, and the skeletons and implements found with it, belong to an age when the use of iron was not known to the builders. But this conclusion is not warranted by the simple fact that metals were not employed in its construction; for the Nubians at this day build boats large enough to carry half a dozen persons across the Nile, out of small pieces of acacia wood pinned together entirely with wooden bolts, and large vessels of similar construction are used by the islanders of the Malay archipelago. Nor is the occurrence of flint arrow heads and knives, in conjunction with other evidences of human life, conclusive proof as to the antiquity of the latter. Lyell informs us that some Oriental tribes still continue to use the same stone implements as their ancestors, "after that mighty empires, where the use of metals in the arts was well known, had flourished for three thousand years in their neighborhood;" [Footnote: Antiquity of Man, p. 377.] and the North American Indians now manufacture weapons of stone, and even of glass, chipping them in the latter case out of the bottoms of thick bottles, with great facility. [Footnote: "One of the Indians seated himself near me, and made from a fragment of quartz, with a simple piece of round bone, one end of which was hemispherical, with a small crease in it (as if worn by a thread) the sixteenth of an inch deep, an arrow head which was very sharp and piercing, and such as they use on all their arrows. The skill and rapidity with which it was made, without a blow, but by simply breaking the sharp edges with the creased bone by the strength of his hands—for the crease merely served to prevent the instrument from slipping, affording no leverage—was remarkable."—Reports of Explorations and Surveys for Pacific Railroad, vol. ii., 1855, Lieut. Beckwith'S Report, p. 43. See also American Naturalist for May, 1870, and especially Stevens, Flint Chips, London, 1870, pp. 77 et seq.
Mariette Bey lately saw an Egyptian barber shave the head of an Arab with a flint razor.]
We may also be misled by our ignorance of the commercial relations existing between savage tribes. Extremely rude nations, in spite of their jealousies and their perpetual wars, sometimes contrive to exchange the products of provinces very widely separated from each other. The mounds of Ohio contain pearls, thought to be marine, which must have come from the Gulf of Mexico, or perhaps even from California, and the knives and pipes found in the same graves are often formed of far-fetched material, that was naturally paid for by some home product exported to the locality whence the material was derived. The art of preserving fish, flesh, and fowl by drying and smoking is widely diffused, and of great antiquity. The Indians of Long Island Sound are said to have carried on a trade in dried shell fish with tribes residing very far inland. From the earliest ages, the inhabitants of the Faroe and Orkney Islands, and of the opposite mainland coasts, have smoked wild fowl and other flesh. Hence it is possible that the animal and the vegetable food, the remains of which are found in the ancient deposits I am speaking of, may sometimes have been brought from climates remote from that where it was consumed.
The most important, as well as the most trustworthy conclusions with respect to the climate of ancient Europe and Asia, are those drawn from the accounts given by the classical writers of the growth of cultivated plants; but these are by no means free from uncertainty, because we can seldom be sure of an identity of species, almost never of an identity of race or variety, between vegetables known to the agriculturists of Greece and Rome and those of modern times which are thought most nearly to resemble them. Besides this, there is always room for doubt whether the habits of plants long grown in different countries may not have been so changed by domestication or by natural selection, that the conditions of temperature and humidity which they required twenty centuries ago were different from those at present demanded for their advantageous cultivation. [Footnote: Probably no cultivated vegetable affords so good an opportunity of studying the law of acclimation of plants as maize or Indian corn. Maize is grown from the tropics to at least lat. 47 degrees in Northeastern America, and farther north in Europe. Every two or three degrees of latitude brings you to a new variety with new climatic adaptations, and the capacity of the plant to accommodate itself to new conditions of temperature and season seems almost unlimited.
Many persons now living remember that, when the common tomato was first introduced into Northern New England, it often failed to ripen; but, in the course of a very few years, it completely adapted itself to the climate, and now not only matures both its fruit and its seeds with as much certainty as any cultivated vegetable, but regularly propagates itself by self-sown seed. Meteorological observations, however, do not show any amelioration of the summer climate in those States within that period.
It may be said that these cases—and indeed all cases of a supposed acclimation consisting in physiological changes—are instances of the origination of new varieties by natural selection, the hardier maize, tomato, and other vegetables of the North, being the progeny of seeds of individuals endowed, exceptionally, with greater power of resisting cold than belongs in general to the species which produced them. But, so far as the evidence of change of climate, from a difference in vegetable growth, is concerned, it is immaterial whether we adopt this view or maintain the older and more familiar doctrine of a local modification of character in the plants in question.
Maize and the tomato, if not new to human use, have not been long known to civilization, and were, very probably, reclaimed and domesticated at a much more recent period than the plants which form the great staples of agricultural husbandry in Europe and Asia. Is the great power of accommodation to climate possessed by them due to this circumstance There is some reason to suppose that the character of maize has been sensibly changed by cultivation in South America; for, according to Tschudi, the ears of this grain found in old Peruvian tombs belong to varieties not now known in Peru.—Travels in Peru, chap. vii. See important observations in Schubeler, Die Pflanzenwelt Norwegans (Allgemeiner Theil), Christinania, 1873, 77 and following pp.] Even if we suppose an identity of species, of race, and of habit to be established between a given ancient and modern plant, the negative fact that the latter will not grow now where it flourished two thousand years ago does not in all cases prove a change of climate. The same result might follow from the exhaustion of the soil, [Footnote: The cultivation of madder is said to have been introduced into Europe by an Oriental in the year 1765, and it was first planted in the neighborhood of Avignon. Of course, it has been grown in that district for less than a century; but upon soils where it has been a frequent crop, it is already losing much of its coloring properties.—Lavergne, Economic Rurale de la France, pp. 250-201.
I believe there is no doubt that the cultivation of madder in the vicinity of Avignon is of recent introduction; but it is certain that it was grown by the ancient Romans, and throughout nearly all Europe in the middle ages. The madder brought from Persia to France, may belong to a different species, or at least variety.] or from a change in the quantity of moisture it habitually contains. After a district of country has been completely or even partially cleared of its forest growth, and brought under cultivation, the drying of the soil, under favorable circumstances, goes on for generations, perhaps for ages. [Footnote: In many parts of New England there are tracts, many square miles in extent and presenting all varieties of surface and exposure, which were partially cleared sixty or seventy years ago, and where little or no change in the proportion of cultivated ground, pasturage, and woodland has taken place since. In some cases, these tracts compose basins apparently scarcely at all exposed to any local influence in the way of percolation or infiltration of water towards or from neighboring valleys. But in such situations, apart from accidental disturbances, the ground is growing drier and drier from year to year, springs are still disappearing, and rivulets still diminishing in their summer supply of water. A probable explanation of this is to be found in the rapid drainage of the surface of cleared ground, which prevents the subterranean natural reservoirs, whether cavities or merely strata of bibulous earth, from filling up. How long this process is to last before an equilibrium is reached, none can say. It may be, for years; it may be, for centuries.
Livingstone states facts which strongly favor the supposition that a secular desiccation is still going on in central Africa, and there is reason to suspect that a like change is taking place in California. When the regions where the earth is growing drier were cleared of wood, or, indeed, whether forests ever grew there, we are unable to say, but the change appears to have been long in progress. A similar revolution appears to have occurred in Arabia Petraea. In many of the wadis, and particularly in the gorges between Wadi Feiran and Wadi Esh Sheikh, there are water-worn banks showing that, at no very remote period, the winter floods must have risen fifty feet in channels where the growth of acacias and tamarisks and the testimony of the Arabs concur to prove that they have not risen six feet within the memory or tradition of the present inhabitants. Recent travellers have discovered traces of extensive ancient cultivation, and of the former existence of large towns in the Tih desert, in localities where all agriculture is now impossible for want of water. Is this drought due to the destruction of ancient forests or to some other cause?
For important observations on supposed changes of climate in our Western prairie region, from cultivation of the soil and the introduction of domestic cattle, see Bryant's valuable Forest Trees, 1871, chapter v., and Hayden, Preliminary Report on Survey of Wyoming, p. 455. Some physicists believe that the waters of our earth are, from chemical of other less known causes, diminishing by entering into new inorganic combinations, and that this element will finally disappear from the globe.]
In other cases, from injudicioua husbandry, or the diversion or choking up of natural water-courses, it may become more highly charged with humidity. An increase or diminution of the moisture of a soil almost necessarily supposes an elevation or a depression of its winter or its summer heat, and of its extreme if not of its mean annual temperature, though such elevation or depression may be so slight as not sensibly to raise or lower the mercury in a thermometer exposed to the open air. Any of these causes, more or less humidity, or more or less warmth of soil, would affect the growth both of wild and of cultivated vegetation, and consequently, without any appreciable change in atmospheric temperature, precipitation, or evaporation, plants of a particular species might cease to be advantageously cultivated where they had once been easily reared. [Footnote: The soil of newly subdued countries is generally highly favorable to the growth of the fruits of the garden and the orchard, but usually becomes much less so in a very few years. Plums, of many varieties, were formerly grown, in great perfection and abundance, in many parts of New England where at present they can scarcely be reared at all; and the peach, which, a generation or two ago, succeeded admirably in the southern portion of the same States, has almost ceased to be cultivated there. The disappearance of these fruits is partly due to the ravages of insects, which have in later years attacked them; but this is evidently by no means the sole, or even the principal cause of their decay. In these cases, it is not to the exhaustion of the particular acres on which the fruit trees have grown that we are to ascribe their degeneracy, but to a general change in the condition of the soil or the air; for it is equally impossible to rear them successfully on absolutely new land in the neighborhood of grounds where, not long since, they bore the finest fruit.
I remember being told, many years ago, by intelligent early settlers of the State of Ohio, that the apple trees raised there from seed sown soon after the land was cleared, bore fruit in less than half the time required to bring to bearing those reared from seed gown when the ground had been twenty years under cultivation. Analogous changes occur slowly and almost imperceptibly even in spontaneous vegetation. In the peat mosses of Denmark, Scotch firs and other trees not now growing in the same localities, are found in abundance. Every generation of trees leaves the soil in a different state from that in which it found it; every tree that springs up in a group of trees of another species than its own, grows under different influences of light and shade and atmosphere from its predecessors. Hence the succession of crops, which occurs in all natural forests, seems to be due rather to changes of condition than of climate. See chapter iii., post.]
Uncertainty of Modern Meteorology.
We are very imperfectly acquainted with the present mean and extreme temperature, or the precipitation and the evaporation of any extensive region, even in countries most densely peopled and best supplied with instruments and observers. The progress of science is constantly detecting errors of method in older observations, and many laboriously constructed tables of meteorological phenomena are now thrown aside as fallacious, and therefore worse than useless, because some condition necessary to secure accuracy of result was neglected, in obtaining and recording the data on which they were founded.
To take a familiar instance: it is but recently that attention has been drawn to the great influence of slight differences in station upon the results of observations of temperature and precipitation. Two thermometers hung but a few hundred yards from each other differ not unfrequently five, sometimes even ten degrees in their readings; [Footnote: Tyndall, in a lecture on Radiation, expresses the opinion that from ten to fifteen per cent. of the heat radiated from the earth is absorbed by aqueous vapor within ten feet of the earth's surface.—Fragments of Science, 3d edition, London, 1871, p. 203. Thermometers at most meteorological stations, when not suspended at points regulated by the mere personal convenience of the observer, are hung from 20 to 40 feet above the ground. In such positions they are less exposed to disturbance from the action of surrounding bodies than at a lower level, and their indications are consequently more uniform; but according to Tyndall's views they do not mark the temperature of the atmospheric stratum in which nearly all the vegetables useful to man, except forest trees, bud and blossom and ripen, and in which a vast majority of the ordinary operations of material life are performed. They give the rise and fall of the mercury at heights arbitrarily taken, without reference to the relations of temperature to human interests, or to any other scientific consideration than a somewhat less liability to accidental disturbance.] and when we are told that the annual fall of rain on the roof of the observatory at Paris is two inches less than on the ground by the side of it, we may see that the height of the rain-gauge above the earth is a point of much consequence in making estimates from its measurements. [Footnote: Careful observations by the late lamented Dallas Bache appeared to show that there is no such difference in the quantity of precipitation falling at slightly different levels as has been generally supposed. The apparent difference was ascribed by Prof. Bache to the irregular distribution of the drops of rain and flakes of snow, exposed, as they are, to local disturbances by the currents of air around the corners of buildings or other accidents of the surface. This consideration much increases the importance of great care in the selection of positions for rain-gauges. But Mr. Bache's conclusions seem not to be accepted by late experimenters in England. See Quarterly Journal of Science for January, 1871, p. 123.]
The data from which results have been deduced with respect to the hygrometrical and thermometrical conditions, to the climate in short, of different countries, have very often been derived from observations at single points in cities or districts separated by considerable distances. The tendency of errors and accidents to balance each other authorizes us, indeed, to entertain greater confidence than we could otherwise feel in the conclusions drawn from such tables; but it is in the highest degree probable that they would be much modified by more numerous series of observations, at different stations within narrow limits. [Footnote: The nomenclature of meteorology is vague and sometimes equivocal. Not long since, it was suspected that the observers reporting to a scientific institution did not agree in their understanding of the mode of expressing the direction of the wind prescribed by their instructions. It was found, upon inquiry, that very many of them used the names of the compass-points to indicate the quarter FROM which the wind blew, while others employed them to signify the quarter TOWARDS which the atmospheric currents were moving. In some instances, the observers were no longer within the reach of inquiry, and of course their tables of the wind were of no value. "Winds," says Mrs. Somerville, "are named from the points whence they blow, currents exactly the reverse. An easterly wind comes from the east; whereas on easterly current comes from the west, and flows towards the east."—Physical Geography, p. 229.
There is no philological ground for this distinction, and it probably originated in a confusion of the terminations -WARDLY and -ERLY, both of which are modern. The root of the former ending implies the direction TO or TO-WARDS which motion is supposed. It corresponds to, and is probably allied with, the Latin VERSUS. The termination -ERLY is a corruption or softening of -ERNLY, easterly for easternly, and many authors of the nineteenth century so write it. In Haklnyt (i., p. 2), EASTERLY is applied to place, "EASTERLY bounds," and means EASTERN. In a passage in Drayton, "EASTERLY winds" must mean winds FROM the east; but the same author, in speaking of nations, uses NORTHERLY for NORTHERN. Lakewell says: "The sonne cannot goe more SOUTHERNLY from us, nor come more NORTHERNLY towards us." Holland, in his translation of Pliny, referring to the moon, has: "When shee is NORTHERLY," and "shee is gone SOUTHERLY." Richardson, to whom I am indebted for the above citations, quotes a passage from Dampier where WESTERLY is applied to the wind, but the context does not determine the direction. The only example of the termination -WARDLY given by this lexicographer is from Donne, where it means TOWARDS the west.
Shakespeare, in Hamlet(v., ii.), uses NORTHERLY wind for wind FROM the north. Milton does not employ either of these terminations, nor were they known to the Anglo-Saxons, who, however, had adjectives of direction in -AN or -EN, -ern and -weard, the last always meaning the point TOWARDS which motion in supposed, the others that FROM which it proceeds. The vocabulary of science has no specific name for one of the most important phenomena in meteorology—I mean for watery vapor condensed and rendered visible by cold. The Latins expressed this condition of water by the word vapor. For INVISIBLE vapor they had no name, because they did not know that it existed, and Van Helmont was obliged to invent a word, gas, as a generic name for watery and other fluids in the invisible state. The moderns have perverted the meaning of the word vapor, and in science its use is confined to express water in the gaseous and invisible state. When vapor in rendered visible by condensation, we call it fog or mist—between which two words there is no clearly established distinction—if it is lying on or near the surface of the earth or of water; when it floats in the air we call it cloud. But these words express the form and position of the humid aggregation, not the condition of the water-globules which compose it. The breath from our mouths, the steam from an engine, thrown out into cold air, become visible, and consist of water in the same state as in fog or cloud; but we do not apply those terms to these phenomena. It would be an improvement in meteorological nomenclature to restore vapor to its original meaning, and to employ a new word, such for example as hydrogas, to explain the new scientific idea of water in the invisible state.]
There is one branch of research which is of the utmost importance in reference to these questions, but which, from the great difficulty of direct observation upon it, has been less successfully studied than almost any other problem of physical science. I refer to the proportions between precipitation, superficial drainage, absorption, and evaporation. Precise actual measurement of these quantities upon even a single acre of ground is impossible; and in all cabinet experiments on the subject, the conditions of the surface observed are so different from those which occur in nature, that we cannot safely reason from one case to the other. In nature, the inclination and exposure of the ground, the degree of freedom or obstruction of the flow of water over the surface, the composition and density of the soil, the presence or absence of perforations by worms and small burrowing quadrupeds—upon which the permeability of the ground by water and its power of absorbing and retaining or transmitting moisture depend—its temperature, the dryness or saturation of the subsoil, vary at comparatively short distances; and though the precipitation upon very small geographical basins and the superficial flow from them may be estimated with an approach to precision, yet even here we have no present means of knowing how much of the water absorbed by the earth is restored to the atmosphere by evaporation, and how much carried off by infiltration or other modes of underground discharge. When, therefore, we attempt to use the phenomena observed on a few square or cubic yards of earth, as a basis of reasoning upon the meteorology of a province, it is evident that our data must be insufficient to warrant positive general conclusions. In discussing the climatology of whole countries, or even of comparatively small local divisions, we may safely say that none can tell what percentage of the water they receive from the atmosphere is evaporated; what absorbed by the ground and conveyed off by subterranean conduits; what carried down to the sea by superficial channels; what drawn from the earth or the air by a given extent of forest, of short pasture vegetation, or of tall meadow-grass; what given out again by surfaces so covered, or by bare ground of various textures and composition, under different conditions of atmospheric temperature, pressure, and humidity; or what is the amount of evaporation from water, ice, or snow, under the varying exposures to which, in actual nature, they are constantly subjected. If, then, we are so ignorant of all these climatic phenomena in the best-known regions inhabited by man, it is evident that we can rely little upon theoretical deductions applied to the former more natural state of the same regions—less still to such as are adopted with respect to distant, strange, and primitive countries.
STABILITY OF NATURE.
Nature, left undisturbed, so fashions her territory as to give it almost unchanging permanence of form, outline, and proportion, except when shattered by geologic convulsions; and in these comparatively rare cases of derangement, she sets herself at once to repair the superficial damage, and to restore, as nearly as practicable, the former aspect of her dominion. In new countries, the natural inclination of the ground, the self-formed slopes and levels, are generally such as best secure the stability of the soil. They have been graded and lowered or elevated by frost and chemical forces and gravitation and the flow of water and vegetable deposit and the action of the winds, until, by a general compensation of conflicting forces, a condition of equilibrium has been readied which, without the action of main, would remain, with little fluctuation, for countless ages. We need not go far back to reach a period when, in all that portion of the North American continent which has been occupied by British colonization, the geographical elements very nearly balanced and compensated each other. At the commencement of the seventeenth century, the soil, with insignificant exceptions, was covered with forests; [Footnote: I do not here speak of the vast prairie region of the Mississippi valley, which cannot properly said ever to have been a field of British colonization; but of the original colonies, and their dependencies in the territory of the present United States, and in Canada. It is, however, equally true of the Western prairies as of the Eastern forest land, that they had arrived at a state of equilibrium, though under very different conditions.] and whenever the Indian, in consequence of war or the exhaustion of the beasts of the chase, abandoned the narrow fields he had planted and the woods he had burned over, they speedily returned, by a succession of herbaceous, arborescent, and arboreal growths, to their original state. Even a single generation sufficed to restore them almost to their primitive luxuriance of forest vegetation. [Footnote: The great fire of Miramichi in 1825, probably the most extensive and terrific conflagration recorded in authentic history, spread its ravages over nearly six thousand square miles, chiefly of woodland, and was of such intensity that it seemed to consume the very soil itself. But so great are the recuperative powers of nature, that, in twenty-five years, the ground was thickly covered again with tree of fair dimensions, except where cultivation and pasturage kept down the forest growth.]
The unbroken forests had attained to their maximum density and strength of growth, and, as the older trees decayed and fell, they were succeeded by new shoots or seedlings, so that from century to century no perceptible change seems to have occurred in the wood, except the slow, spontaneous succession of crops. This succession involved no interruption of growth, and but little break in the "boundless contiguity of shade;" for, in the husbandry of nature, there are no fallows. Trees fall singly, not by square roods, and the tall pine is hardly prostrate, before the light and heat, admitted to the ground by the removal of the dense crown of foliage which had shut them out, stimulate the germination of the seeds of broad-leaved trees that had lain, waiting this kindly influence, perhaps for centuries.
FORMATION OF BOGS.
Two natural causes, destructive in character, were, indeed, in operation in the primitive American forests, though, in the Northern colonies, at least, there were sufficient compensations; for we do not discover that any considerable permanent change was produced by them. I refer to the action of beavers and of fallen trees in producing bogs, [Footnote: The English nomenclature of this geographical feature does not seem well settled. We have bog, swamp, marsh, morass, moor, fen, turf-moss, peat-moss, quagmire, all of which, though sometimes more or less accurately discriminated, are often used interchangeably, or are perhaps employed, each exclusively, in a particular district. In Sweden, where, especially in the Lappish provinces, this terr-aqueous formation is very extensive and important, the names of its different kinds are more specific in their application. The general designation of all soils permanently pervaded with water is Karr. The elder Laestadius divides the Karr into two genera: Myror (sing. myra), and Mossar (sing. mosse). "The former," he observes, "are grass-grown, and overflowed with water through almost the whole summer; the latter are covered with mosses and always moist, but very seldom overflowed." He enumerates the following species of Myra, the character of which will perhaps be sufficiently understood by the Latin terms into which he translates the vernacular names, for the benefit of strangers not altogether familiar with the language and the subject: 1. Homyror, paludes graminosae. 2. Dy, paludes profundae. 3. Flarkmyror, or proper karr, paludes limosae. 4. Fjalimyror, paludes uliginosae. 5. Tufmyror, paludes caespitosae. 6. Rismyror, paludes virgatae. 7. Starrangar, prata irrigata, with their subdivisions, dry starrungar or risangar, wet starrangar and frakengropar. 8. Polar, lacunae. 9. Golar, fossae inundatae. The Mossar, paludes turfosae, which are of great extent, have but two species: 1. Torfmossar, called also Mossmyror and Snottermyror, and, 2. Bjornmossar.
The accumulations of stagnant or stagnating water originating in bogs are distinguished into Trask, stagna, and Tjernar or Tjarnar (sing. Tjern or Tjarn), stagnatiles. Trask are pools fed by bogs, or water emanating from them, and their bottoms are slimy; Tjernar are small Trask situated within the limits of Mossar.—L.L. Laestadius, om Mojligheten af Uppodlingar i Lappmarken, pp. 23, 24.
Although the quantity of bog land in New England is less than in many other regions of equal area, yet there is a considerable extent of this formation in some of the Northeastern States. Dana (Manual of Geology, p. 614) states that the quantity of peat in Massachusetts is estimated at 120,000,000 cords, or nearly 569,000,000 cubic yards, but he does not give either the area or the depth of the deposits. In any event, however, bogs cover but a small percentage of the territory in any of the Northern States, while it is said that one tenth of the whole surface of Ireland is composed of bogs, and there are still extensive tracts of undrained marsh in England. The amount of this formation in Great Britain is estimated at 6,000,000 acres, with an average depth of twelve feet, which would yield 21,600,000 tons of air-dried peat.—Asbjornsen, Tore og Torodrift, Christiania, 1868, p. 6. Peat beds have sometimes a thickness of ten or twelve yards, or even more. A depth of ten yards would give 48,000 cubic yards to the acre. The greatest quantity of firewood yielded by the forests of New England to the acre is 100 cords solid measure, or 474 cubic yards; but this comprises only the trunks and larger branches. If we add the small branches and twigs, it is possible that 600 cubic yards might, in some cases, be cut on an acre. This is only one eightieth part of the quantity of peat sometimes found on the same area. It is true that a yard of peat and a yard of wood are not the equivalents of each other, but the fuel on an acre of deep peat is worth much more than that on an acre of the best woodland. Besides this, wood is perishable, and the quantity of an acre cannot be increased beyond the amount just stated; peat is indestructible, and the beds are always growing. See post, Chap. IV. Cold favors the conversion of aquatic vegetables into peat. Asbjornsen says some of the best peat he has met with is from a bog which is frozen for forty weeks in the year.
The Greeks and Romans were not acquainted with the employment of peat as fuel, but it appears from a curious passage which I have already cited from Pliny, N. H., book xvi., chap. 1, that the inhabitants of the North Sea coast used what is called kneaded turf in his time. This is the finer and more thoroughly decomposed matter lying at the bottom of the peat, kneaded by the hands, formed into small blocks and dried. It is still prepared in precisely the same way by the poorer inhabitants of those shores.
But though the Low German tribes, including probably the Anglo-Saxons, have used peat as fuel from time immemorial, it appears not to have been known to the High Germans until a recent period. At least, I can find neither in Old nor in Middle High German lexicons and glossaries any word signifying peat. Zurb indeed is found in Graff as an Old High German word, but only in the sense of grass-turf, or greensward. Peat bogs of vast extent occur in many High German localities, but the former abundance of wood in the same regions rendered the use of peat unnecessary.] and of smaller animals, insects, and birds, in destroying the woods. [Footnote: See Chapter II., post.]
Bogs generally originate in the checking of watercourses by the falling of timber or of earth and rocks, or by artificial obstructions across their channels. If the impediment is sufficient to retain a permanent accumulation of water behind it, the trees whose roots are overflowed soon perish, and then by their fall increase the obstruction, and, of course, occasion a still wider spread of the stagnating stream. This process goes on until the water finds a new outlet, at a higher level, not liable to similar interruption. The fallen trees not completely covered by water are soon overgrown with mosses; aquatic and semiaquatic plants propagate themselves, and spread until they more or less completely fill up the space occupied by the water, and the surface is gradually converted from a pond to a quaking morass. The morass is slowly solidified by vegetable production and deposit, then very often restored to the forest condition by the growth of black ashes, cedars, or, in southern latitudes, cypresses, and other trees suited to such a soil, and thus the interrupted harmony of nature is at last reestablished. [Footnote: "Aquatic plants have a utility in raising the level of marshy grounds, which renders them very valuable, and may well be called a geological function. The engineer drains ponds at a great expense by lowering the surface of the water; nature attains the same end, gratuitously, by raising the level of the soil without depressing that of the water; but she proceeds more slowly. There are, in the Landes, marshes where this natural filling has a thickness of four metres, and some of them, at first lower than the sea, have been thus raised and drained so as to grow summer crops, such, for example, as maize."—Boitel, Mise en valeur des Terres pauvres, p. 227.
The bogs of Denmark—the examination of which by Steenstrap and Vaupell has presented such curious results with respect to the natural succession of forest trees—appear to have gone through this gradual process of drying, and the birch, which grow freely in very wet soils, has contributed very effectually by its annual deposits to raise the surface above the water level, and thus to prepare the ground for the oak.—Vaupell, Bogens Indvandring, pp. 39, 40.
The growth of the peat not unfrequently raises the surface of bogs considerably above the level of the surrounding country, and they sometimes burst and overflow lower grounds with a torrent of mud and water as destructive as a current of lava.]
In countries somewhat further advanced in civilization than those occupied by the North American Indians, as in mediaeval Ireland, the formation of bogs may be commenced by the neglect of man to remove, from the natural channels of superficial drainage, the tops and branches of trees felled for the various purposes to which wood is applicable in his rude industry; and, when the flow of the water is thus checked, nature goes on with the processes I have already described. In such half-civilized regions, too, windfalls are more frequent than in those where the forest is unbroken, because, when openings have been made in it for agricultural or other purposes, the entrance thus afforded to the wind occasions the sudden overthrow of hundreds of trees which might otherwise have stood for generations and have fallen to the ground, only one by one, as natural decay brought them down. [Footnote: Careful examination of the peat mosses in North Sjaelland—which are so abundant in fossil wood that, within thirty years, they have yielded above a million of trees—shows that the trees have generally fallen from age and not from wind. They are found in depressions on the declivities of which they grew, and they lie with the top lowest, always falling towards the bottom of the valley.—Vaupell, Bogens Indvandring i de Danske Skove, pp. 10,14.] Besides this, the flocks bred by man in the pastoral state keep down the incipient growth of trees on the half-dried bogs, and prevent them from recovering their primitive condition. Young trees in the native forest are sometimes girdled and killed by the smaller rodent quadrupeds, and their growth is checked by birds which feed on the terminal bud; but these animals, as we shall see, are generally found on the skirts of the wood only, not in its deeper recesses, and hence the mischief they do is not extensive.
In fine, in countries untrodden by man, the proportions and relative positions of land and water, the atmospheric precipitation and evaporation, the thermometric mean, and the distribution of vegetable and animal life, are maintained by natural compensations, in a state of approximate equilibrium, and are subject to appreciable change only from geological influences so slow in their operation that the geographical conditions may be regarded as substantially constant and immutable.
NATURAL CONDITIONS FAVORABLE TO GEOGRAPHICAL CHANGE.
There are, nevertheless, certain climatic conditions and certain forms and formations of terrestrial surface, which tend respectively to impede and to facilitate the physical degradation both of new countries and of old. If the precipitation, whether great or small in amount, be equally distributed through the seasons, so that there are neither torrential rains nor parching droughts, and if, further, the general inclination of ground be moderate, so that the superficial waters are carried off without destructive rapidity of flow, and without sudden accumulation in the channels of natural drainage, there is little danger of the degradation of the soil in consequence of the removal of forest or other vegetable covering, and the natural face of the earth may be considered as virtually permanent. These conditions are well exemplified in Ireland, in a great part of England, in extensive districts in Germany and France, and, fortunately, in an immense proportion of the valley of the Mississippi and the basin of the great American lakes, as well as in many parts of the continents of South America and of Africa, and it is partly, though by no means entirely, owing to topographical and climatic causes that the blight, which has smitten the fairest and most fertile provinces of Imperial Rome, has spared Britannia, Germania, Pannonia, and Moesia, the comparatively inhospitable homes of barbarous races, who, in the days of the Caesars, were too little advanced in civilized life to possess either the power or the will to wage that war against the order of nature which seems, hitherto, an almost inseparable condition precedent of high social culture, and of great progress in fine and mechanical art. Destructive changes are most frequent in countries of irregular and mountainous surface, and in climates where the precipitation is confined chiefly to a single season, and where, of course, the year is divided into a wet and a dry period, as is the case throughout a great part of the Ottoman empire, and, indeed, in a large proportion of the whole Mediterranean basin. In mountainous countries various causes combine to expose the soil to constant dangers. The rain and snow usually fall in greater quantity, and with much inequality of distribution; the snow on the summits accumulates for many months in succession, and then is not unfrequently almost wholly dissolved in a single thaw, so that the entire precipitation of months is in a few hours hurried down the flanks of the mountains, and through the ravines that furrow them; the natural inclination of the surface promotes the swiftness of the gathering currents of diluvial rain and of melting snow, which soon acquire an almost irresistible force and power of removal and transportation; the soil itself is less compact and tenacious than that of the plains, and if the sheltering forest has been destroyed, it is contined by few of the threads and ligaments by which nature had bound it together, and attached it to the rocky groundwork. Hence every considerable shower lays bare its roods of rock, and the torrents sent down by the thaws of spring, and by occasional heavy discharges of the summer and autumnal rains, are seas of mud and rolling stones that sometimes lay waste and bury beneath them acres, and even miles, of pasture and field and vineyard. [Footnote: The character of geological formation is an element of very great importance in determining the amount of erosion produced by running water, and, of course, in measuring the consequences of clearing off the forests. The soil of the French Alps yields very readily to the force of currents, and the declivities of the northern Apennines, as well as of many minor mountain ridges in Tuscany and other parts or Italy, are covered with earth which becomes itself almost a fluid when saturated with water. Hence the erosion of such surfaces is vastly greater than on many other mountains of equal steepness of inclination. The traveller who passes over the route between Bologna and Florence, and the Perugia and the Siena roads from the latter city to Rome, will have many opportunities of observing such localities.]
Destructiveness of Man.
Man has too long forgotten that the earth was given to him for usufruct alone, not for consumption, still less for profligate waste. Nature has provided against the absolute destruction of any of her elementary matter, the raw material of her works; the thunderbolt and the tornado, the most convulsive throes of even the volcano and the earthquake, being only phenomena of decomposition and recomposition. But she has left it within the power of man irreparably to derange the combinations of inorganic matter and of organic life, which through the night of aeons she had been proportioning and balancing, to prepare the earth for his habitation, when in the fulness of time his Creator should call him forth to enter into its possession.
Apart from the hostile influence of man, the organic and the inorganic world are, as I have remarked, bound together by such mutual relations and adaptations as secure, if not the absolute permanence and equilibrium of both, a long continuance of the established conditions of each at any given time and place, or at least, a very slow and gradual succession of changes in those conditions. But man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords. The proportions and accommodations which insured the stability of existing arrangements are overthrown. Indigenous vegetable and animal species are extirpated, and supplanted by others of foreign origin, spontaneous production is forbidden or restricted, and the face of the earth is either laid bare or covered with a new and reluctant growth of vegetable forms, and with alien tribes of animal life. These intentional changes and substitutions constitute, indeed, great revolutions; but vast as is their magnitude and importance, they are, as we shall see, insignificant in comparison with the contingent and unsought results which have flowed from them.
The fact that, of all organic beings, man alone is to be regarded as essentially a destructive power, and that he wields energies to resist which Nature—that nature whom all material life and all inorganic substance obey—is wholly impotent, tends to prove that, though living in physical nature, he is not of her, that he is of more exalted parentage, and belongs to a higher order of existences, than those which are born of her womb and live in blind submission to her dictates.
There are, indeed, brute destroyers, beasts and birds and insects of prey—all animal life feeds upon, and, of course, destroys other life,—but this destruction is balanced by compensations. It is, in fact, the very means by which the existence of one tribe of animals or of vegetables is secured against being smothered by the encroachments of another; and the reproductive powers of species, which serve as the food of others, are always proportioned to the demand they are destined to supply. Man pursues his victims with reckless destructiveness; and, while the sacrifice of life by the lower animals is limited by the cravings of appetite, he unsparingly persecutes, even to extirpation, thousands of organic forms which he cannot consume. [Footnote: The terrible destructiveness of man is remarkably exemplified in the chase of large mammalia and birds for single products, attended with the entire waste of enormous quantities of flesh, and of other parts of the animal which are capable of valuable uses. The wild cattle of South America are slaughtered by millions for their hides and hairs; the buffalo of North America for his skin or his tongue; the elephant, the walrus, and the narwhal for their tusks; the cetacen, and some other marine animals, for their whalebone and oil; the ostrich and other large birds, for their plumage. Within a few years, sheep have been killed in New England, by whole flocks, for their pelts and suet alone, the flesh being thrown away; and it is even said that the bodies of the same quadrupeds have been used in Australia as fuel for limekilns. What a vast amount of human nutriment, of bone, and of other animal products valuable in the arts, is thus recklessly squandered! In nearly all these cases, the part which constitutes the motive for this wholesale destruction, and is alone saved, is essentially of insignificant value as compared with what is thrown away. The horns and hide of an ox are not economically worth a tenth part as much as the entire carcass. During the present year, large quantities of Indian corn have been used as domestic fuel, and even for burning lime, in Iowa and other Western States. Corn at from fifteen to eighteen cents per bushel is found cheaper than wood at from five to seven dollars per cord, or coal at six or seven dollars per ton.-Rep. Agric. Dept., Nov. and Dec., 1872, p. 487.
One of the greatest benefits to be expected from the improvement civilization is, that increased facilities of communication will render it possible to transport to places of consumption much valuable material that is now wasted because the price at the nearest market will not pay freight. The cattle slaughtered in South America for their hides would feed millions of the starving population of the Old World, if their flesh could be economically preserved and transported across the ocean. This, indeed, is already done, but on a scale which, though absolutely considerable, is relatively insignificant. South America sends to Europe a certain quantity of nutriment in the form of meat extracts, Liebig's and others; and preserved flesh from Australia is beginning to figure in the English market. We are beginning to learn a better economy in dealing with the inorganic world. The utilization—or, as the Germans more happily call it, the Verwerthung, the BEWORTHING—of waste from metallurgical, chemical, and manufacturing establishments, is among the most important results of the application of science to industrial purposes. The incidental products from the laboratories of manufacturing chemists often become more valuable than those for the preparation of which they were erected. The slags front silver refineries, and even from smelting houses of the coarser metals, have not unfrequently yielded to a second operator a better return than the first had derived from dealing with the natural ore; and the saving of lead carried off in the smoke of furnaces has, of itself, given a large profit on the capital invested in the works. According to Ure's Dictionary of Arts, see vol. ii., p. 832, an English miner has constructed flues five miles in length for the condensation of the smoke from his lead-works, and makes thereby an annual saving of metal to the value of ten thousand pounds sterling. A few years ago, an officer of an American mint was charged with embezzling gold committed to him for coinage. He insisted, in his defence, that much of the metal was volatilized and lost in refining and melting, and upon scraping the chimneys of the melting furnaces and the roofs of the adjacent houses, gold enough was found in the soot to account for no small part of the deficiency.
The substitution of expensive machinery for manual labor, even in agriculture—not to speak of older and more familiar applications—besides being highly remunerative, has better secured the harvests, and it is computed that the 230,000 threshing machines used in the United States in 1870 obtained five per cent. more grain from the sheaves which passed through them than could have been secured by the use of the flail.
The cotton growing States in America produce annually nearly three million tons of cotton seed. This, until very recently, has been thrown away as a useless incumbrance, but it is now valued at ten or twelve dollars per ton for the cotton fibre which adheres to it, for the oil extracted from it, and for the feed which the refuse furnishes to cattle. The oil—which may be described as neutral—is used very largely for mixing with other oils, many of which bear a large proportion of it without injury to their special properties.
There are still, however, cases of enormous waste in many mineral and mechanical industries. Thus, while in many European countries common salt is a government monopoly, and consequently so dear that the poor do not use as much or it as health requires, in others, as in Transylvania, where it is quarried like stone, the large blocks only are saved, the fragments, to the amount of millions of hundred weights, being thrown away.—Bonar, Transylvania, p. 455, 6.
One of the most interesting and important branches of economy at the present day is the recovery of agents such as ammonia and ethers which had been utilized in chemical manufactures, and re-employing them indefinitely afterwards in repeating the same process.
Among the supplemental exhibitions which will be formed in connection with the Vienna Universal Exhibition is to be one showing what steps have been taken since 1851 (the date of the first London Exhibition) in the utilization of substances previously regarded as waste. On the one hand will be shown the waste products in all the industrial processes included in the forthcoming Exhibition; on the other hand, the useful products which have been obtained from such wastes since 1851. This is intended to serve as an incentive to further researches in the same important direction.]
The earth was not, in its natural condition, completely adapted to the use of man, but only to the sustenance of wild animals and wild vegetation. These live, multiply their kind in just proportion, and attain their perfect measure of strength and beauty, without producing or requiring any important change in the natural arrangements of surface, or in each other's spontaneous tendencies, except such mutual repression of excessive increase as may prevent the extirpation of one species by the encroachments of another. In short, without man, lower animal and spontaneous vegetable life would have been practically constant in type, distribution, and proportion, and the physical geography of the earth would have remained undisturbed for indefinite periods, and been subject to revolution only from slow development, from possible, unknown cosmical causes, or from geological action.
But man, the domestic animals that serve him, the field and garden plants the products of which supply him with food and clothing, cannot subsist and rise to the full development of their higher properties, unless brute and unconscious nature be effectually combated, and, in a great degree, vanquished by human art. Hence, a certain measure of transformation of terrestrial surface, of suppression of natural, and stimulation of artificially modified productivity becomes necessary. This measure man has unfortunately exceeded. He has felled the forests whose network of fibrous roots bound the mould to the rocky skeleton of the earth; but had he allowed here and there a belt of woodland to reproduce itself by spontaneous propagation, most of the mischiefs which his reckless destruction of the natural protection of the soil has occasioned would have been averted. He has broken up the mountain reservoirs, the percolation of whose waters through unseen channels supplied the fountains that refreshed his cattle and fertilized his fields; but he has neglected to maintain the cisterns and the canals of irrigation which a wise antiquity had constructed to neutralize the consequences of its own imprudence. While he has torn the thin glebe which confined the light earth of extensive plains, and has destroyed the fringe of semi-aquatic plants which skirted the coast and checked the drifting of the sea sand, he has failed to prevent the spreading of the dunes by clothing them with artificially propagated vegetation. He has ruthlessly warred on all the tribes of animated nature whose spoil he could convert to his own uses, and he has not protected the birds which prey on the insects most destructive to his own harvests.
Purely untutored humanity, it is true, interferes comparatively little with the arrangements of nature, [Footnote: It is an interesting and not hitherto sufficiently noticed fact, that the domestication of the organic world, so far as it has yet been achieved, belongs, not indeed to the savage state, but to the earliest dawn of civilization, the conquest of inorganic nature almost as exclusively to the most advanced stages of artificial culture. Civilization has added little to the number of vegetable or animal species grown in our fields or bred in our folds—the cranberry and the wild grape being almost the only plants which the Anglo-American has reclaimed out of our most native flora and added to his harvests—while, on the contrary, the subjugation of the inorganic forces, and the consequent extension of man's sway over, not the annual products of the earth only, but her substance and her springs of action, is almost entirely the work of highly refined and cultivated ages. The employment of the elasticity of wood and of horn, as a projectile power in the bow, is nearly universal among the rudest savages. The application of compressed air to the same purpose, in the blowpipe, is more restricted, and the use of the mechanical powers, the inclined plane, the wheel and axle, and even the wedge and lever, seems almost unknown except to civilized man. I have myself seen European peasants to whom one of the simplest applications of this latter power was a revelation.
It is familiarly known to all who have occupied themselves with the psychology and habits of the ruder races, and of persons with imperfectly developed intellects in civilized life, that although these humble tribes and individuals sacrifice, without scruple, the lives of the lower animals to the gratification of their appetites and the supply of their other physical wants, yet they nevertheless seem to cherish with brutes, and even with vegetable life, sympathies which are much more feebly felt by civilized men. The popular traditions of the simpler peoples recognize a certain community of nature between man, brute animals, and even plants; and this serves to explain why the apologue or fable, which ascribes the power of speech and the faculty of reason to birds, quadrupeds, insects, flowers, and trees, is one of the earliest forms of literary composition.
In almost every wild tribe, some particular quadruped or bird, though persecuted as a destroyer of other animals more useful to man, or hunted for food, is regarded with peculiar respect, one might almost say, affection. Some of the North American aboriginal nations celebrate a propitiatory feast to the manes of the intended victim before they commence a bear hunt; and the Norwegian peasantry have not only retained an old proverb which ascribes to the same animal "ti Maends Styrke og tolo Maends Vid," ten men's strength and twelve men's cunning, but they still pay to him something of the reverence with which ancient superstition invested him. The student of Icelandic literature will find in the saga of Finnbogi hinn rami a curious illustration of this feeling, in an account of a dialogue between a Norwegian bear and an Icelandic champion—dumb show on the part of Bruin, and chivalric words on that of Finnbogi—followed by a duel, in which the latter, who had thrown away his arms and armor in order that the combatants might meet on equal terms, was victorious. See also Friis, Lappisk Mythologi, Christiania, 1871, section 37, and the earlier authors there cited. Drummond Hay's very interesting work on Morocco contains many amusing notices of a similar feeling entertained by the Moors towards the redoubtable enemy of their flocks—the lion.
This sympathy helps us to understand how it is that most if not all the domestic animals—if indeed they ever existed in a wild state—were appropriated, reclaimed and trained before men had been gathered into organized and fixed communities, that almost every known esculent plant had acquired substantially its present artificial character, and that the properties of nearly all vegetable drugs and poisons were known at the remotest period to which historical records reach. Did nature bestow upon primitive man some instinct akin to that by which she has been supposed to teach the brute to select the nutritious and to reject the noxious vegetables indiscriminately mixed in forest and pasture?
This instinct, it must be admitted, is far from infallible, and, as has been hundreds of times remarked by naturalists, it is in many cases not an original faculty but an acquired and transmitted habit. It is a fact familiar to persons engaged in sheep husbandry in New England—and I have seen it confirmed by personal observation—that sheep bred where the common laurel, as it is called, Kalmia angustifolia, abounds, almost always avoid browsing upon the leaves of that plant, while those brought from districts where laurel is unknown, and turned into pastures where it grows, very often feed upon it and are poisoned by it. A curious acquired and hereditary instinct, of a different character, may not improperly be noticed here. I refer to that by which horses bred in provinces where quicksands are common avoid their dangers or extricate themsleves from them. See Bremontier, Memoire sur les Dunes, Annales des Ponts et Chaussees, 1833; premier semestre, pp. 155-157.
It is commonly said in New England, and I believe with reason, that the crows of this generation are wiser than their ancestors. Scarecrows which were effectual fifty yeara ago are no longer respected by the plunderers of the cornfield, and new terrors must from time to time be invented for its protection.
Schroeder van der Kolk, in Het Verschil tusschen den Psychischen, Aanleg van het Dier en van den Mensch, cites many interesting facts respecting instincts lost, or newly developed and become hereditary, in the lower animals, and he quotes Aristotle and Pliny as evidence that the common quadrupeds and fowls of our fields and our poultry yards were much less perfectly domesticated in their times than long, long ages of servitude have now made them.
Among other inntances of obliterated instincts, this author states that in Holland, where, for centuries, the young of the cow has been usually taken from the dam at birth and fed by hand, calves, even if left with the mother, make no attempt to suck; while in England, where calves are not weaned until several weeks old, they resort to the udder as naturally as the young of wild quadrupeds.-Ziel en Ligchaam, p. 128. n.
Perhaps the half-wild character ascribed by P. Laestadius and other Swedish writers to the reindeer of Lapland, may be in some degree due to the comparative shortness of the period during which he has been partially tamed. The domestic swine bred in the woods of Hungary and the buffalo of Southern Italy are so wild and savage as to be very dangerous to all but their keepers. The former have relapsed into their original condition, the latter, perhaps, have never been fully reclaimed from it.] and the destructive agency of man becomes more and more energetic and unsparing as he advances in civilization, until the impoverishment with which his exhaustion of the natural resources of the soil is threatening him, at last awakens him to the necessity of preserving what is left, if not of restoring what has been wantonly wasted. The wandering savage grows no cultivated vegetable, fells no forest, and extirpates no useful plant, no noxious weed. If his skill in the chase enables him to entrap numbers of the animals on which he feeds, he compensates this loss by destroying also the lion, the tiger, the wolf, the otter, the seal, and the eagle, thus indirectly protecting the feebler quadrupeds and fish and fowls, which would otherwise become the booty of beasts and birds of prey. But with stationary life, or at latest with the pastoral state, man at once commences an almost indiscriminate warfare upon all the forms of animal and vegetable existence around him, and as he advances in civilization, he gradually eradicates or transforms every spontaneous product of the soil he occupies. [Footnote: The difference between the relations of savage life, and of incipient civilization, to nature, is well seen in that part of the valley of the Mississippi which was once occupied by the mound builders and afterwards by the far less developed Indian tribes. When the tillers of the fields, which must have been cultivated to sustain the large population that once inhabited those regions, perished, or were driven out, the soil fell back to the normal forest state, and the savages who succeeded the more advanced race interfered very little, if at all, with the ordinary course of spontaneous nature.]
Human and Brute Action Compared.
It is maintained by authorities as high as any known to modern science, that the action of man upon nature, though greater in DEGREE, does not differ in KIND from that of wild animals. It is perhaps impossible to establish a radical distinction in genere between the two classes of effects, but there is an essential difference between the motive of action which calls out the energies of civilized man and the mere appetite which controls the life of the beast. The action of man, indeed, is frequently followed by unforeseen and undesired results, yet it is nevertheless guided by a self-conscious will aiming as often at secondary and remote as at immediate objects. The wild animal, on the other hand, acts instinctively, and, so far as we are able to perceive, always with a view to single and direct purposes. The backwoodsman and the beaver alike fell trees; the man that he may convert the forest into an olive grove that will mature its fruit only for a succeeding generation, the beaver that he may feed upon the bark of the trees or use them in the construction of his habitation. The action of brutes upon the material world is slow and gradual, and usually limited, in any given case, to a narrow extent of territory. Nature is allowed time and opportunity to set her restorative powers at work, and the destructive animal has hardly retired from the field of his ravages before nature has repaired the damages occasioned by his operations. In fact, he is expelled from the scene by the very efforts which she makes for the restoration of her dominion. Man, on the contrary, extends his action over vast spaces, his revolutions are swift and radical, and his devastations are, for an almost incalculable time after he has withdrawn the arm that gave the blow, irreparable. The form of geographical surface, and very probably the climate of a given country, depend much on the character of the vegetable life belonging to it. Man has, by domestication, greatly changed the habits and properties of the plants he rears; he has, by voluntary selection, immensely modified the forms and qualities of the animated creatures that serve him; and he has, at the same time, completely rooted out many forms of animal if not of vegetable being. [Footnote: Whatever may be thought of the modification of organic species by natural selection, there is certainly no evidence that animals have exerted upon any form of life an influence analogous to that of domestication upon plants, quadrupeds, and birds reared artificially by man; and this is as true of unforeseen as of purposely effected improvements accomplished by voluntary selection of breeding animals.
It is true that nature employs birds and quadrupeds for the dissemination of vegetable and even of animal species. But when the bird drops the seed of a fruit it has swallowed, and when the sheep transports in its fleece the seed-vessel of a burdock from the plain to the mountain, its action is purely mechanical and unconscious, and does not differ from that of the wind in producing the same effect.] What is there, in the influence of brute life, that corresponds to this We have no reason to believe that, in that portion of the American continent which, though peopled by many tribes of quadruped and fowl, remained uninhabited by man or only thinly occupied by purely, savage tribes, any sensible geographical change had occurred within twenty centuries before the epoch of discovery and colonization, while, during the same period, man had changed millions of square miles, in the fairest and most fertile regions of the Old World, into the barrenest deserts. The ravages committed by man subvert the relations and destroy the balance which nature had established between her organized and her inorganic creations, and she avenges herself upon the intruder, by letting loose upon her defaced provinces destructive energies hitherto kept in check by organic forces destined to be his best auxiliaries, but which he has unwisely dispersed and driven from the field of action. When the forest is gone, the great reservoir of moisture stored up in its vegetable mould is evaporated, and returns only in deluges of rain to wash away the parched dust into which that mould has been converted. The well-wooded and humid hills are turned to ridges of dry rock, which encumbers the low grounds and chokes the watercourses with its debris, and—except in countries favored with an equable distribution of rain through the seasons, and a moderate and regular inclination of surface—the whole earth, unless rescued by human art from the physical degradation to which it tends, becomes an assemblage of bald mountains, of barren, turfless hills, and of swampy and malarious plains. There are parts of Asia Minor, of Northern Africa, of Greece, and even of Alpine Europe, where the operation of causes set in action by man has brought the face of the earth to a desolation almost as complete as that of the moon; and though, within that brief space of time which we call "the historical period," they are known to have been covered with luxuriant woods, verdant pastures, and fertile meadows, they are now too far deteriorated to be reclaimable by man, nor can they become again fitted for human use, except through great geological changes, or other mysterious influences or agencies of which we have no present knowledge, and over which we have no prospective control. The earth is fast becoming an unfit home for its noblest inhabitant, and another era of equal human crime and human improvidence, and of like duration with that through which traces of that crime and that improvidence extend, would reduce it to such a condition of impoverished productiveness, of shattered surface, of climatic excess, as to threaten the depravation, barbarism, and perhaps even extinction of the species. [Footnote: —-"And it may be remarked that, as the world has passed through these several stages of strife to produce a Christendom, so by relaxing in the enterprises it has learnt, does it tend downwards, through inverted steps, to wildness and the waste again. Let a people give up their contest with moral evil; disregard the injustice, the ignorance, the greediness, that may prevail among them, and part more and more with the Christian element of their civilization; and in declining this battle with sin, they will inevitably get embroiled with men. Threats of war and revolution punish their unfaithfulness; and if then, instead of retracing their steps, they yield again, and are driven before the storm, the very arts they had created, the structures they had raised, the usages they had established, are swept away; 'in that very day their thoughts perish.' The portion they had reclaimed from the young earth's ruggedness is lost; and failing to stand fast against man, they finally get embroiled with nature, and are thrust down beneath her ever-living hand .-Martineau's Sermon, "The Good Soldier of Jesus Christ."]
Physical Improvement.
True, there is a partial reverse to this picture. On narrow theatres, new forests have been planted; inundations of flowing streams restrained by heavy walls of masonry and other constructions; torrents compelled to aid, by depositing the slime with which they are charged, in filling up lowlands, and raising the level of morasses which their own overflows had created; ground submerged by the encroachments of the ocean, or exposed to be covered by its tides, has been rescued from its dominion by diking; swamps and even lakes have been drained, and their beds brought within the domain of agricultural industry; drifting coast dunes have been checked and made productive by plantation; seas and inland waters have been repeopled with fish, and even the sands of the Sahara have been fertilized by artesian fountains. These achievements are more glorious than the proudest triumphs of war, but, thus far, they give but faint hope that we shall yet make full atonement for our spendthrift waste of the bounties of nature. [Footnote: The wonderful success which has attended the measures for subduing torrents and preventing inundations employed in Southern France since 1863 and described in Chapter III., post, ought to be here noticed as a splendid and most encouraging example of well-directed effort in the way of physical restoration.]
Limits Of Human Power.
It is on the one hand, rash and unphilosophical to attempt to set limits to the ultimate power of man over inorganic nature, and it is unprofitable, on the other, to speculate on what may be accomplished by the discovery of now unknown and unimagined natural forces, or even by the invention of new arts and new processes. But since we have seen aerostation, the motive power of elastic vapors, the wonders of modern telegraphy, the destructive explosiveness of gunpowder, of nitro-glycerine, and even of a substance so harmless, unresisting, and inert as cotton, there is little in the way of mechanical achievement which seems hopelessly impossible, and it is hard to restrain the imagination from wandering forward a couple of generations to an epoch when our descendants shall have advanced as far beyond us in physical conquest, as we have marched beyond the trophies erected by our grandfathers. There are, nevertheless, in actual practice, limits to the efficiency of the forces which we are now able to bring into the field, and we must admit that, for the present, the agencies known to man and controlled by him are inadequate to the reducing of great Alpine precipices to such slopes as would enable them to support a vegetable clothing, or to the covering of large extents of denuded rock with earth, and planting upon them a forest growth. Yet among the mysteries which science is hereafter to reveal, there may be still undiscovered methods of accomplishing even grander wonders than these. Mechanical philosophers have suggested the possibility of accumulating and treasuring up for human use some of the greater natural forces, which the action of the elements puts forth with such astonishing energy. Could we gather, and bind, and make subservient to our control, the power which a West Indian hurricane exerts through a small area in one continuous blast, or the momentum expended by the waves in a tempestuous winter, upon the breakwater at Cherbourg, [Footnote: In heavy storms, the force of the waves as they strike against a sea-wall is from one and a half to two tons to the square foot, and Stevenson, in one instance at Skerryvore and in another at the Bell Rock lighthouse, found this force equal to nearly three tons per foot. The seaward front of the breakwater at Cherbourg exposes a surface about 2,500,000 square feet. In rough weather the waves beat against this whole face, though at the depth of twenty-two yards, which is the height of the breakwater, they exert a very much less violent motive force than at and near the surface of the sea, because this force diminishes in geometrical, and the distance below the surface increases in arithmetical, proportion. The shock of the waves is received several thousand times in the course of twenty four hours, and hence the sum of impulse which the breakwater resists in one stormy day amounts to many thousands of millions of tons. The breakwater is entirely an artificial construction. If then man could accumulate and control the forces which he is able effectually to resist, he might be said to be physically speaking, omnipotent.] or the lifting power of the tide, for a month, at the head of the Bay of Fundy, or the pressure of a square mile of sea water at the depth of five thousand fathoms, or a moment of the might of an earthquake or a volcano, our age—which moves no mountains and casts them into the sea by faith alone—might hope to scarp the ragged walls of the Alps and Pyrenees and Mount Taurus, robe them once more in a vegetation as rich as that of their pristine woods, and turn their wasting torrents into refreshing streams. [Footnote: Some well-known experiments show that it is quite possible to accumulate the solar heat by a simple apparatus, and thus to obtain a temperature which might be economically important even in the climate of Switzerland. Saussure, by receiving the sun's rays in a nest of boxes blackened within and covered with glass, raised a thermometer enclosed in the inner box to the boiling point; and under the more powerful sun of the Cape of Good Hope, Sir John Hershel cooked the materials for a family dinner by a similar process, using however, but at single box, surrounded with dry sand and covered with two glasses. Why should not so easy a method of economizing fuel be resorted to in Italy, in Spain, and even in more northerly climate The unfortunate John Davidson records in his journal that he saved fuel in Morocco by exposing his teakettle to the sun on the roof of his house, where the water rose to the temperature of one hundred and forty degrees, and, of course, needed little fire to bring it to boil. But this was the direct and simple, not the concentrated or accumulated heat of the sun.
On the utilizing of the solar heat, simply as heat, see the work of Mouchot, La Chaleur solaire et ses applications industrielles. Paris, 1860.
The reciprocal convertibility of the natural forces has suggested the possibility of advantageously converting the heat of the sun into mechanical power. Ericsson calculates that in all latitudes between the equator and 45 degrees, a hundred square feet of surface exposed to the solar rays develop continuously, for nine hours a day on an average, eight and one fifth horse-power.
I do not know that any attempts have been made to accumulate and store up, for use at pleasure, force derived from this powerful source.] Could this old world, which man has overthrown, be rebuilded, could human cunning rescue its wasted hillsides and its deserted plains from solitude or mere nomade occupation, from barrenness, from nakedness, and from insalubrity, and restore the ancient fertility and healthfulness of the Etruscan sea coast, the Campagna and the Pontine marshes, of Calabria, of Sicily, of the Peloponnesus and insular and continental Greece, of Asia Minor, of the slopes of Lebanon and Hermon, of Palestine, of the Syrian desert, of Mesopotamia and the delta of the Euphrates, of the Cyrenaica, of Africa proper, Numidia, and Mauritania, the thronging millions of Europe might still find room on the Eastern continent, and the main current of emigration be turned towards the rising instead of the setting sun.
But changes like these must await not only great political and moral revolutions in the governments and peoples by whom these regions are now possessed, but, especially, a command of pecuniary and of mechanical means not at present enjoyed by these nations, and a more advanced and generally diffused knowledge of the processes by which the amelioration of soil and climate is possible than now anywhere exists. Until such circumstances shall conspire to favor the work of geographical regeneration, the countries I have mentioned, with here and there a local exception, will continue to sink into yet deeper desolation, and in the meantime the American continent, Southern Africa, Australia, New Zealand, and the smaller oceanic islands, will be almost the only theatres where man is engaged, on a great scale, in transforming the face of nature.
IMPORTANCE OF PHYSICAL CONSERVATION, AND RESTORATION.
Comparatively short as is the period through which the colonization of foreign lands by European emigrants extends, great and, it is to be feared, sometimes irreparable injury has already been done in the various processes by which man seeks to subjugate the virgin earth; and many provinces, first trodden by the homo sapiens Europae within the last two centuries, begin to show signs of that melancholy dilapidation which is now driving so many of the peasantry of Europe from their native hearths. It is evidently a matter of great moment, not only to the population of the states where these symptoms are manifesting themselves, but to the general interests of humanity, that this decay should be arrested, and that the future operations of rural husbandry and of forest industry, in districts yet remaining substantially in their native condition, should be so conducted as to prevent the widespread mischiefs which have been elsewhere produced by thoughtless or wanton destruction of the natural safeguards of the soil. This can be done only by the diffusion of knowledge on this subject among the classes that, in earlier days, subdued and tilled ground in which they had no vested rights, but who, in our time, own their woods, their pastures, and their ploughlands as a perpetual possession for them and theirs, and have, therefore, a strong interest in the protection of their domain against deterioration.
PHYSICAL RESTORATION.
Many circumstances conspire to invest with great present interest the questions: how far man can permanently modify and ameliorate those physical conditions of terrestrial surface and climate on which his material welfare depends; how far he can compensate, arrest, or retard the deterioration which many of his agricultural and industrial processes tend to produce; and how far he can restore fertility and salubrity to soil which his follies or his crimes have made barren or pestilential. Among these circumstances, the most prominent, perhaps, is the necessity of providing new homes for a European population which is increasing more rapidly than its means of subsistence, new physical comforts for classes of the people that have now become too much enlightened and have imbibed too much culture to submit to a longer deprivation of a share in the material enjoyments which the privileged ranks have hitherto monopolized.
To supply new hives for the emigrant swarms, there are, first, the vast unoccupied prairies and forests of America, of Australia, and of many other great oceanic islands, the sparsely inhabited and still unexhausted soils of Southern and even Central Africa, and, finally, the impoverished and half-depopulated shores of the Mediterranean, and the interior of Asia Minor and the farther East. To furnish to those who shall remain after emigration shall have conveniently reduced the too dense population of many European states, those means of sensuous and of intellectual well-being which are styled "artificial wants" when demanded by the humble and the poor, but are admitted to be "necessaries" when claimed by the noble and the rich, the soil must be stimulated to its highest powers of production, and man's utmost ingenuity and energy must be tasked to renovate a nature drained, by his improvidence, of fountains which a wise economy would have made plenteous and perennial sources of beauty, health, and wealth.
In those yet virgin lands which the progress of modern discovery in both hemispheres has brought and is still bringing to the knowledge and control of civilized man, not much improvement of great physical conditions is to be looked for. The proportion of forest is indeed to be considerably reduced, superfluous waters to be drawn off, and routes of internal communication to be constructed; but the primitive geographical and climatic features of these countries ought to be, as far as possible, retained.
In reclaiming and reoccupying lands laid waste by human improvidence or malice, and abandoned by man, or occupied only by a nomade or thinly scattered population, the task of the pioneer settler is of a very different character. He is to become a co-worker with nature in the reconstruction of the damaged fabric which the negligence or the wantonness of former lodgers has rendered untenantable. He must aid her in reclothing the mountain slopes with forests and vegetable mould, thereby restoring the fountains which she provided to water them; in checking the devastating fury of torrents, and bringing back the surface drainage to its primitive narrow channels; and in drying deadly morasses by opening the natural sluices which have been choked up, and cutting new canals for drawing off their stagnant waters. He must thus, on the one hand, create new reservoirs, and, on the other, remove mischievous accumulations of moisture, thereby equalizing and regulating the sources of atmospheric humidity and of flowing water, both which are so essential to all vegetable growth, and, of course, to human and lower animal life.
I have remarked that the effects of human action on the forms of the earth's surface could not always be distinguished from those resulting from geological causes, and there is also much uncertainty in respect to the precise influence of the clearing and cultivating of the ground, and of other rural operations, upon climate. It is disputed whether either the mean or the extremes of temperature, the periods of the seasons, or the amount or distribution of precipitation and of evaporation, in any country whose annals are known, have undergone any change during the historical period. It is, indeed, as has been already observed, impossible to doubt that many of the operations of the pioneer settler TEND to produce great modifications in atmospheric humidity, temperature, and electricity; but we are at present unable to determine how far one set of effects is neutralized by another, or compensated by unknown agencies. This question scientific research is inadequate to solve, for want of the necessary data; but well conducted observation, in regions now first brought under the occupation of man, combined with such historical evidence as still exists, may be expected at no distant period to throw much light on this subject.
Australia and New Zealand are, perhaps, the countries from which we have a right to expect the fullest elucidation of these difficult and disputable problems. Their colonization did not commence until the physical sciences had become matter of utmost universal attention, and is, indeed, so recent that the memory of living men embraces the principal epochs of their history; the peculiarities of their fauna, their flora, and their geology are such as to have excited for them the liveliest interest of the votaries of natural science; their mines have given their people the necessary wealth for procuring the means of instrumental observation, and the leisure required for the pursuit of scientific research; and large tracts of virgin forest and natural meadows are rapidly passing under the control of civilized man. Here, then, exist greater facilities and stronger motives for the careful study of the topics in question than have ever been found combined in any other theatre of European colonization.
In North America, the change from the natural to the artificial condition of terrestrial surface began about the period when the most important instruments of meteorological observation were invented. The first settlers in the territory now constituting the United States and the British American provinces had other things to do than to tabulate barometrical and thermometrical readings, but there remain some interesting physical records from the early days of the colonies, [Footnote: The Travels of Dr. Dwight, president of Yale College, which embody the results of his personal observations, and of his inquiries among the early settlers, in his vacation excursions in the Northern States of the American Union, though presenting few instrumental measurements or tabulated results, are of value for the powers of observation they exhibit, and for the sound common sense with which many natural phenomena, such for instance as the formation of the river meadows, called "intervales," in New England, are explained. They present a true and interesting picture of physical conditions, many of which have long ceased to exist in the theatre of his researches, and of which few other records are extant.] and there is still an immense extent of North American soil where the industry and the folly of man have as yet produced little appreciable change. Here, too, with the present increased facilities for scientific observation, the future effects, direct a contingent, of man's labors, can be measured, and such precautions taken in those rural processes which we call improvements, as to mitigate evils, perhaps, in some degree, inseparable from every attempt to control the action of natural laws.
In order to arrive at safe conclusions, we must first obtain a more exact knowledge of the topography, and of the present superficial and climatic condition of countries where the natural surface is as yet more or less unbroken. This can only be accomplished by accurate surveys, and by a great mutiplication of the points of meteorological registry, [Footnote: The general law of tempeture is that it decreases as we ascend. But in hilly areas the law is reversed in cold, still weather, the cold air descending, by reason of its greater gravity, into the valleys. If there be wind enough however, to produce a disturbance and intermixture of higher and lower atmospheric strata, this exception to the general law does not take place. These facts have long been familiar to the common people of Switzerland and of New England, but their importance has not been sufficiently taken into account in the discussion of meterological observations. The descent of the cold air and the rise of the warm effect the relative temperatures of hills and valleys to a much greater extent that has been usually supposed. A gentleman well known to me kept a thermometrical record for nearly a half century in a New England county town, at an elevation of at least 1,5000 feet above the sea. During these years his thermometer never fell lower that 26 degrees Farrenheit, while at the shire town of the county, situated in a basin thousand feet lower, and only tem miles distant, as well as at other points in similar positions, the mercury froze several times in the same period] already so numerous; and as, moreover, considerable changes in the proportion of forest and of cultivated land, or of dry and wholly or partially submerged surface, will often take place within brief periods, it is highly desirable that the attention of observers, in whose neighborhood the clearing of the soil, of the drainage of lakes and swamps, or other great works of rural improvement, are going on or meditated, should be especially drawn not only to revolutions in atmospheric tempeture and precipitation, but to the more easily ascertained and perhaps more important local changes produced by these operations in the temperature and the hygrometric state of the superficial strata of the earth, and in its spontaneous vegetable and animal products.
The rapid extension of railroads, which now everywhere keep pace with, and sometimes even precede, the occupation of new soil for agricultural purposes, furnishes great facilities for enlarging our knowledge of the topography of the territory they traverse, because their cuttings reveal the composition and general structure of surface, and the inclination and elevation of their lines constitute known hypsometrical sections, which give numerous points of departure for the measurement of higher and lower stations, and of course for determining the relief and depression of surface, the slope of the beds of watercourses, and many other not less important questions. [Footnote: Railroad surveys must be received with great caution where any motive exists for COOKING them. Capitalists are shy of investments in roads with steep grades, and of course it is important to make a fair show of facilities in obtaining funds for new routes. Joint-stock companies have no souls; their managers, in general, no consciences. Cases can be cited where engineers and directors of railroads, with long grades above one hundred foot to the mile, have regularly sworn in their annual reports, for years in succession, that there were no grades upon their routes exceeding half that elevation. In fact, every person conversant with the history of these enterprises knows that in their public statements falsehood is the rule, truth the exception.
What I am about to remark is not exactly relevant to my subject; but it is hard to "get the floor" in the world's great debating society, and when a speaker who has anything to say once finds access to the public ear, he must make the must of his opportunity, without inquiring too nicely whether his observations are "in order." I shall harm no honest man by endeavoring, as I have often done elsewhere, to excite the attention of thinking and conscientious men to the dangers which threaten the great moral and even political interests of Christendom, from the unscrupulousness of the private associations that now control the monetary affairs, and regulate the transit of persons and property, in almost every civilized country. More than one American State is literally governed by unprincipled corporations, which not only defy the legislative power, but have, too often, corrupted even the administration of justice. The tremendous power of these associations is due not merely to pecuniary corruption, but partly to an old legal superstition—fostered by the decision of the Supreme Court of the United States in the famous Dartmouth College case—in regard to the sacredness of corporate prerogatives. There is no good reason why private rights derived from God and the very constitution of society should be less respected than privileges granted by legislatures. It should never be forgotten that no privilege can be a right, and legislative bodies ought never to make a grant to a corporation, without express reservation of what many sound jurists now hold to be involved in the very nature of such grants, the power of revocation. Similar evils have become almost equally rife in England, and on the Continent; and I believe the decay of commercial morality, and of the sense of all higher obligations than those of a pecuniary nature, on both sides of the Atlantic, is to be ascribed more to the influence of joint-stock banks and manufacturing and railway companies, to the workings, in short, of what is called the principle of "associate action," than to any other one cause of demoralization.
The apophthegm, "the world is governed too much," though unhappily too truly spoken of many countries—and perhaps, in some aspects, true of all—has done much mischief whenever it has been too unconditionally accepted as a political axiom. The popular apprehension of being over-governed, and, I am afraid, more emphatically the fear of being over-taxed, has had much to do with the general abandonment of certain governmental duties by the ruling powers of most modern states. It is theoretically the duty of government to provide all those public facilities of intercommunication and commerce, which are essential to the prosperity of civilized commonwealths, but which individual means are inadequate to furnish, and for the due administration of which individual guarantees are insufficient. Hence public roads, canals, railroads, postal communications, the circulating medium of exchange whether metallic or representative, armies, navies, being all matters in which the nation at large has a vastly deeper interest than any private association can have, ought legitimately to be constructed and provided only by that which is the visible personification and embodiment of the nation, namely, its legislative head. No doubt the organization and management of those insitutions by government are liable, as are all things human, to great abuses. The multiplication of public placeholders, which they imply, is a serious evil. But the corruption thus engendered, foul as it is, does not strike so deep as the rottenness of private corporations; and official rank, position, and duty have, in practice, proved better securities for fidelity and pecuniary integrity in the conduct of the interests in question, than the suretyships of private corporate agents, whose bondsmen so often fail or abscond before their principal is detected. Many theoretical statesmen have thought that voluntary associations for strictly pecuniary and industrial purposes, and for the construction and control of public works, might furnish, in democratic countries, a compensation for the small and doubtful advantages, and at the same time secure an exemption from the great and certain evils, of aristocratic institutions. The example of the American States shows that private corporations—whose rule of action is the interest of the association, not the conscience of the individual—though composed of ultra-democratic elements, may become most dangerous enemies to rational liberty, to the moral interests of the commonwealth, to the purity of legislation and of judicial action, and to the sacredness of private rights.]
The geological, hydrographical, and topographical surveys, which almost every general and even local government of the civilized world is carrying on, are making yet more important contributions to our stock of geographical and general physical knowledge, and, within a comparatively short space, there will be an accumulation of well established constant and historical facts, from which we can safely reason upon all the relations of action and reaction between man and external nature.
But we are, even now, breaking up the floor and wainscoting and doors and window frames of our dwelling, for fuel to warm our bodies and to seethe our pottage, and the world cannot afford to wait till the slow and sure progress of exact science has taught it a better economy. Many practical lessons have been learned by the common observation of unschooled men; and the teachings of simple experience, on topics where natural philosophy has scarcely yet spoken, are not to be despised.
In these humble pages, which do not in the least aspire to rank among scientific expositions of the laws of nature, I shall attempt to give the most important practical conclusions suggested by the history of man's efforts to replenish the earth and subdue it; and I shall aim to support those conclusions by such facts and illustrations only as address themselves to the understanding of every intelligent reader, and as are to be found recorded in works capable of profitable perusal, or at least consultation, by persons who have not enjoyed a special scientific training.
CHAPTER II.
TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES.
Modern geography takes account of organic life—Geographical importance of plants—Origin of domestic vegetables-Transfer of vegetable life—Objects of modern commerce-Foreign plants, how introduced—Vegetable power of accommodation—Agricultural products of the United States—Useful American plants grown in Europe—Extirpation of vegetables—Animal life as a geological and geographical agency—Origin and transfer of domestic quadrupeds—Extirpation of wild quadrupeds—Large marine animals relatively unimportant in geography—Introduction and breeding of fish—Destruction of fish—Geographical importance of birds—Introduction of birds—Destruction of birds—Utility and destruction of reptiles—Utility of insects and worms—Injury to the forest by insects—Introduction of insects—Destruction of insects—Minute organisms.
MODERN GEOGRAPHY EMBRACES ORGANIC LIFE.
It was a narrow view of geography which confined that science to delineation of terrestrial surface and outline, and to description of the relative position and magnitude of land and water. In its improved form it embraces not only the globe itself and the atmosphere which bathes it, but the living things which vegetate or move upon it, the varied influences they exert upon each other, the reciprocal action and reaction between them and the earth they inhabit. Even if the end of geographical studies were only to obtain a knowledge of the external forms of the mineral and fluid masses which constitute the globe, it would still be necessary to take into account the element of life; for every plant, every animal, is a geographical agency, man a destructive, vegetables, and in some cases even wild beasts, restorative powers. The rushing waters sweep down earth from the uplands; in the first moment of repose, vegetation seeks to reestablish itself on the bared surface, and, by the slow deposit of its decaying products, to raise again the soil which the torrent lhad lowered. So important an element of reconstruction in this, that it has been seriously questioned whether, upon the whole, vegetation does not contribute as much to elevate, as the waters to depress, the level of the surface.
Whenever man has transported a plant from its native habitat to a new soil, he has introduced a new geographical force to act upon it, and this generally at the expense of some indigenous growth which the foreign vegetable has supplanted. The new and the old plants are rarely the equivalents of each other, and the substitution of an exotic for a native tree, shrub, or grass, increases or diminishes the relative importance of the vegetable element in thegeography of the country to which it is removed. Further, man sows that he may reap. The products of agricultural industry are not suffered to rot upon the ground, and thus raise it by an annual stratum of new mould. They are gathered, transported to greater or less distances, and after they have served their uses in human economy, they enter, on the final decomposition of their elements, into new combinations, and are only in smnall proportion returned to the soil on which they grew. The roots of the grasses, and of many other cultivated plants, however, usually remain and decay in the earth, and contribute to raise its surface, though certainly not in the same degree as the forest.
The smaller vegetables which have taken the place of trees unquestionably perform many of the same functions. They radiate heat, they absorb gases, and exhale uncombined gases and watery vapor, and consequently act upon the chemical constitution and hygrometrical condition of the air, their roots penetrate the earth to greater depths than is commonly supposed, and form an inextricable labyrinth of filaments which bind the soil together and prevent its erosion by water. The broad-leaved annuals and perennials, too, shade the ground, and prevent the evaporation of moisture from its surface by wind and sun. [Footnote: It is impossible to say how far the abstraction of water from the earth by broad-leaved field and garden plants—such as maize, the gourd family, the cabbage, &c.—is compensated by the condensation of dew, which sometimes pours from them in a stream, by the exhalation of aqueous vapor from their leaves, which is directly absorbed by the ground, and by the shelter they afford the soil from sun and wind, thus preventing evaporation. American farmers often say that after the leaves of Indian corn are large enough to "shade the ground," there is little danger that the plants will suffer from drought; but it is probable that the comparative security of the fields from this evil is in port due to the fact that, at thin period of growth, the roots penetrate down to a permanently humid stratum of soil, and draw from it the moisture they require. Stirring the ground between the rows of maize with a light harrow or cultivator, in very dry seasons, is often recommended as a preventive of injury by drought. It would seem, indeed, that loosening and turning over the surface earth might aggravate the evil by promoting the evaporation of the little remaining moisture; but the practice is founded partly on the belief that the hygroscopicity of the soil is increased by it to such a degree that it gains more by absorption than it loses by evaporation, and partly on the doctrine that to admit air to the rootlets, or at least to the earth near them, is to supply directly elements of vegetable growth.] At a certain stage of growth, grass land is probably a more energetic evaporator and refrigerator than even the forest, but this powerful action is exerted, in its full intensity, for a comparatively short time only, while trees continue such functions, with unabated vigor, for many months in succession. Upon the whole, it seems quite certain, that no cultivated ground is as efficient in tempering climatic extremes, or in conservation of geographical surface and outline, as is the soil which nature herself has planted.
ORIGIN OF DOMESTIC PLANTS.
One of the most important questions connected with our subject is: how far we are to regard our cereal grains, our esculent bulbs and roots, and the multiplied tree fruits of our gardens, as artificially modified and improved forms of wild, self-propagating vegetation. The narratives of botanical travellers have often announced the discovery of the original form and habitat of domesticated plants, and scientific journals have described the experiments by which the identity of particular wild and cultivated vegetables has been thought to be established. It is confidently affirmed that maize and the potato—which we must suppose to have been first cultivated at a much later period than the breadstuffs and most other esculent vegetables of Europe and the East—are found wild and self-propagating in Spanish America, though in forms not recognizable by the common observer as identical with the familiar corn and tuber of modern agriculture. It was lately asserted, upon what seemed very strong evidence, that the Aegilops ovata, a plant growing wild in Southern France, had been actually converted into common wheat; but, upon a repetition of the experiments, later observers have declared that the apparent change was only a case of temporary hybridation or fecundation by the pollen of true wheat, and that the grass alleged to be transformed into wheat could not be perpetuated as such from its own seed.
The very great modifications which cultivated plants are constantly undergoing under our eyes, and the numerous varieties and races which spring up among them, certainly countenance the doctrine, that every domesticated vegetable, however dependent upon human care for growth and propagation in its present form, may have been really derived, by a long Succession of changes, from some wild plant not now perhaps much resembling it. [Footnote: What is the possible limit of such changes, we do not know, but they may doubtless be carriad vastly beyond what experience has yet shown to be practicable. Civilized man has experimented little on wild plants, and especially on forest trees. He has indeed improved the fruit, and developed new varieties, of the chestnut, by cultivation, and it is observed that our American forest-tree nuts and berries, such as the butternut and thewild mulberry, become larger and better flavored in a single generation by planting and training. (Bryant, Forest Trees, 1871, pp. 99, 115.) Why should not the industry and ingenuity which have wrought such wonders in our horticulture produce analogous results when applied to the cultivation and amelioration of larger vegetables Might not, for instance, the ivory nut, the fruit of the Phytelephas macrocarpa, possibly be so increased in size as to serve nearly all the purposes of animal ivory now becoming so scarce Might not the various milk-producing trees become, by cultivation, a really important source of nutriment to the inhabitants of warm climates In short, there is room to hope incalculable advantage from the exercise of human skill in the improvement of yet untamed forms of vegetable life.] But it is, in every case, a question of evidence.
The only satisfactory proof that a given wild plant is identical with a given garden or field vegetable, is the test of experiment, the actual growing of the one from the seed of the other, or the conversion of the one into the other by transplantation and change of conditions. [Footnote: The poisonous wild parsnip of New England has been often asserted to be convertible into the common garden parsnip by cultivation, or rather to be the same vegetable growing under different conditions, and it is said to be deprived of its deleterious qualities simply by an increased luxuriance of growth in rich, tilled earth. Wild medicinal plants, so important in the rustic materia medica of New England—such as pennyroyal, for example—are generally much less aromatic and powerful when cultivated in gardens than when self-sown on meagre soils. On the other hand, the cinchona, lately introduced from South America into British India and carefully cultivated there, is found to be richer in quinine than the American tree.]
It is hardly contended that any of the cereals or other plants important as human aliment, or as objects of agricultural industry, exist and propagate themselves uncultivated in the same form and with the same properties as when sown and reared by human art. [Footnote: Some recent observations of Wetzatein are worthy of special notice. "The soil of the Hauran," he remarks, "produces, in its primitive condition, much wild rye, which is not known as a cultivated plant in Syria, and much wild barley and oats. These cereals precisely resemble the corresponding cultivated plants in leaf, ear, size, and height of straw, but their grains are sensibly flatter and poorer in flour."—Reisebericht uber Hauran und die Trachenen, p. 40.
Some of the cereals are, to a certain extent, self-propagating in the soil and climate of California. "VOLUNTEER crops are grown from the seed which falls out in harvesting. Barley has been known to volunteer five crops in succession."—Prayer-Frowd, Six Months in California, p. 189.] In fact, the cases are rare where the identity of a wild with a domesticated plant is considered by the best authorities as conclusively established, and we are warranted in affirming of but few of the latter, as a historically known or experimentally proved fact, that they ever did exist, or could exist, independently of man. [Footnote: This remark is much less applicable to fruit trees than to garden vegetables and the cerealia. The wild orange of Florida, though once considered indigenous, is now generally thought by botanists to be descended from the European orange introduced by the early colonists. On the wild apple trees of Massachusetts see an interesting chapter in Thoreau, Excursions. The fig and the olive are found growing wild in every country where those trees are cultivated The wild fig differs from the domesticated in its habits, its season of fructification, and its insect population, but is, I believe, not specifically distinguishable from the garden fig, though I do not know that it is reclaimable by cultivation. The wild olive, which is so abundant in the Tuscan Maremma, produces good fruit without further care, when thinned out and freed from the shade of other trees, and is particularly suited for grafting. See Salvagnoli, Memorie sulle Maremme, pp. 63-73. The olive is indigenous in Syria and in the Punjaub, and forms vast forests in the Himalayas at from 1,400 to 2,100 feet above the level of the sea.—Cleghorn, Memoir on the Timber procured from the Indus, etc., pp. 8-15. Fraas, Klima und Pfanzenwelt in der Zeit, pp. 35-38, gives, upon the authority of Link and other botanical writers, a lift of the native habitats of most cereals and of many fruits, or at least of localities where those plants are said to be now found wild; but the data do not appear to rest, in general, upon very trustworthy evidence. Theoretically, there can be little doubt that all our cultivated plants are modified forms of spontaneous vegetation, though the connection is not historically shown, nor are we able to say that the originals of some domesticated vegetables may not be now extinct and unrepresented in the existing wild flora. See, on this subject, Humboldt, Ansichten der Natur, i., pp. 208, 209.
The Adams of modern botany and zoology have been put to hard shifts in finding names for the multiplied organisms which the Creator has brought before them, "to see what they would call them;" and naturalists and philosophers have shown much moral courage in setting at naught the law of philology in the coinage of uncouth words to express scientific Ideas. It is much to be wished that some bold neologist would devise English technical equivalents for the German verwildert, run-wild, and veredelt, improved by cultivation.]
Transfer of Vegetable Life.
It belongs to vegetable and animal geography, which are almost sciences of themselves, to point out in detail what man has done to change the distribution of plants and of animated life and to revolutionize the aspect of organic nature; but some of the more important facts bearing on the first branch of this subject may pertinently be introduced here. Most of the cereal grains, the pulse, the edible roots, the tree fruits, and other important forms of esculent vegetation grown in Europe and the United States are believed, and—if the testimony of Pliny and other ancient naturalists is to be depended upon—many of them are historically known, to have originated in the temperate climates of Asia. The agriculture of even so old a country as Egypt has been almost completely revolutionized by the introduction of foreign plants, within the historical period. "With the exception of wheat," says Hehn, "the Nile valley now yields only new products, cotton, rice, sugar, indigo, sorghum, dates," being all unknown to its most ancient rural husbandry. [Footnote: On these points see the learned work of Hehn, Kultur. Pflanzen und Thiere in ihrem Uebergang aus Asien, 1870. On the migration of plants generally, see Lyell, Principles of Geology, 10th ed., vol. ii., c.] The wine grape has been thought to be truly indigenous only in the regions bordering on the eastern end of the Black Sea, where it now, particularly on the banks of the Rion, the ancient Phasis, propagates itself spontaneously, and grows with unexampled luxuriance. [Footnote: The vine-wood planks of the ancient great door of the cathedral at Ravenna, which measured thirteen feet in length by a foot and a quarter in width, are traditionally said to have boon brought from the Black Sea, by way of Constantinople, about the eleventh or twelfth century. Vines of such dimension are now very rarely found in any other part of the East, and, though I have taken some pains on the subject, I never found in Syria or in Turkey a vine stock exceeding six inches in diameter, bark excluded. Schulz, however, saw at Beitschin, near Ptolemais, a vine measuring eighteen inches in diameter. Strabo speaks of vine-stocks in Margiana (Khorasan) of such dimension that two men, with outstretched arms, could scarcely embrace them. See Strabo, ed. Casaubon, pp. 78, 516, 826. Statues of vine wood are mentioned by ancient writers. Very large vine-stems are not common in Italy, but the vine-wood panels of the door of the chapter-hall of the church of St. John at Saluzzo are not less than ten inches in width, and I observed not long since, in a garden at Pie di Mulera, a vine stock with a circumference of thirty inches.] But some species of the vine seem native to Europe, and many varieties of grape have been too long known as common to every part of the United States to admit of the supposition that they were introduced by European colonists. [Footnote: The Northmen who—as I think it has been indisputably established by Professor Rafn of Copenhagen—visited the coast of Massachusetts about theyear 1000, found grapes growing there in profusion, and the wild vine still flourishes in great variety and abundance in the southeastern counties of that State. The townships in the vicinity of the Dighton rock, supposed by many—with whom, however, I am sorry I cannot agree—to bear a Scandinavian inscription, abound in wild vines. According to Laudonniere, Histoire Notable de la Florida, reprint, Paris, 1853, p 5, the French navigators in 1562 found in that peninsula "wild vines which climb the trees and produce good grapes."]
OBJECTS OF MODERN COMMERCE.
It is an interesting fact that the commerce—or at least the maritime carrying trade—and the agricultural and mechanical industry of the world are, in very large proportion, dependent on vegetable and animal products little or not at all known to ancient Greek, Roman, and Jewish civilization. In many instances, the chief supply of these articles comes from countries to which they are probably indigenous, and where they are still almost exclusively grown; but in most cases, the plants or animals from which they are derived have been introduced by man into regions now remarkable for their successful cultivation, and that, too, in comparatively recent times, or, in other words, within two or three centuries.
Something of detail on this subject cannot, I think, fail to prove interesting. Pliny mentions about thirty or forty oils as known to the ancients, of which only olive, sesame, rape seed and walnut oil—for except in one or two doubtful passages I find in this author no notice of linseed oil—appear to have been used in such quantities as to have had any serious importance in the carrying trade. At the present time, the new oils, linseed oil, the oil of the whale and other largeo marine animals, petroleum—of which the total consumption of the world in 1871 is estimated at 6,000,000 barrels, the port of Philadelphia alone exporting 56,000,000 gallons in that year—palm-oil recently introduced into commerce, and now imported into England from the coast of Africa at the rate of forty or fifty thousand tuns a year, these alone undoubtedly give employment to more shipping than the whole commerce of Italy—with the exception of wheat—at the most flourishing period of the Roman empire. [Footnote: A very few years since, the United States had more than six hundred large ships engaged in the whale fishery, and the number of American whalers, in spite of the introduction of many now sources of oils, still amounts to two hundred and fifty.
The city of Rome imported from Sicily, from Africa, and from the Levant, enormous quantities of grain for gratuitous distribution among the lower classes of the capital. The pecuniary value of the gems, the spices, the unguents, the perfumes, the cosmetics and the tissues, which came principally from the East, was great, but these articles were neither heavy nor bulky and their transportation required but a small amount of shipping. The marbles, the obelisks, the statuary and other objects of art plundered in conquered provinces by Roman generals and governors, the wild animals, such as elephants, rhinoceroses, hippopotami, camelopards and the larger beasts of prey imported for slaughter at the public games, and the prisoners captured in foreign wars and brought to Italy for sale as slaves or butchery as gladiators, furnished employment for much more tonnage than all the legitimate commerce of the empire, with the possible exception of wheat. Independently of the direct testimony of Latin authors, the Greek statuary, the Egyptian obelisks, and the vast quantities of foreign marbles, granite, parphyry, basalt, and other stones used in sculpture and in architecture, which have been found in the remains of ancient Rome, show that the Imperial capital must have employed an immense amount of tonnage in the importation of heavy articles for which there could have been no return freight, unless in the way of military transportation. Some of the Egyptian obelisks at Rome weigh upwards of four hundred tons, and many of the red granite columns from the same country must have exceeded one hundred tons. Greek and African marbles were largely used not only for columns, contablatures, and solid walls, but for casing the exterior and veneering the interior of public and private buildings. Scaurus imported, for the scene alone of a temporary theatre designed to stand scarcely for a month, three hundred and sixty columns, which were disposed in three tiers, the lower range being forty-two feet in height—See Pliny, Nat. Hist., Lib. xxxvi. Italy produced very little for export, and her importations, when not consisting of booty, were chiefly paid for in coin which was principally either the spoil of war or the fruit of official extortion.]
England imports annually about 600,000 tons of sugar, 100,000 tons of jute, and about the same quantity of esparto, six million tons of cotton, of which the value of $30,000,000 is exported again in the form of manufactured, goods—including, by a strange industrial revolution, a large amount of cotton yarn and cotton tissues sent to India and directly or indirectly paid for by raw cotton to be manufactured in England—30,000 tons of tobacco, from 100,000 to 350,000 tons of guano, hundreds of thousands of tons of tea, coffee, cacao, caoutchone, gutta-percha and numerous other important articles of trade wholly unknown, as objects of commerce, to the ancient European world; and this immense importation is balanced by a corresponding amount of exportation, not consisting, however, by any means, exclusively of articles new to commerce. [Footnote: Many of these articles would undoubtedly have been made known to the Greeks and Romans and have figured in their commerce, but for the slowness and costliness of ancient navigation, which, in the seas familiar to them, was suspended for a full third of the year from the inability of their vessels to cope with winter weather. The present speed and economy of transportation have wrought and are still working strange commercial and industrial revolutions. Algeria now supplies Northern Germany with fresh cauliflowers, and in the early spring the market-gardeners of Naples find it more profitable to send their first fruits to St. Petersburg than to furnish them to Florence and Rome.]
FOREIGN PLANTS, HOW INTRODUCED.
Besides the vegetables I have mentioned, we know that many plants of smaller economical value have been the subjects of international exchange in very recent times. Busbequius, Austrian ambassador at Constantinople about the middle of the sixteenth century—whose letters contain one of the best accounts of Turkish life which have appeared down to the present day—brought home from the Ottoman capital the lilac and the tulip. The Belgian Clusius about the same time introduced from the East the horse chestnut, which has since wandered to America. The weeping willows of Europe and the United States are said to have sprung from a slip received from Smyrna by the poet Pope; and planted by him in an English garden; Drouyn de l'IIuys, in a discourse delivered before the French Societe d'Acclimatation, in 1860, claims for Rabelais the introduction of the melon, the artichoke and the Alexandria pink into France; and the Portuguese declare that the progenitor of all the European and American oranges was an Oriental tree transplanted to Lisbon, and still living in the last generation. [Footnote: The name portogallo, so generally applied to the orange in Italy, seems to favor this claim. The orange, however, was known in Europe before the discovery of the Cape of Good Hope, and therefore, before the establishment of direct relations between Portugal and the East.—See Amari, Storia del Musulmani in Sicilia, vol ii., p. 445.
The date-palms of eastern and southern Spain were certainly introduced by the Moors. Leo Von Rozmital, who visited Barcelona in 1476, says that the date-tree grew in great abundance in the environs of that city and ripened its fruit well. It is now scarcely cultivated further north than Valencia. It is singular that Ritter in his very full monograph on the palm does not mention those of Spain.
On the introduction of conifera into England see an interesting article in the Edinburgh Review of October, 1864.
Muller, Das Buch der Pfianzenrodt, p. 86, asserts that in 1802 the ancestor of all the mulberries in France, planted in 1500, was still standing in a garden in the village of Allan-Montelimart.] The present favorite flowers of the parterres of Europe have been imported from America, Japan and other remote Oriental countries, within a century and a half, and, in fine, there are few vegetables of any agricultural importance, few ornamental trees or decorative plants, which are not now common to the three civilized continents.
The statistics of vegetable emigration exhibit numerical results quite surprising to those not familiar with the subject. The lonely island of St. Helena is described as producing, at the time of its discovery in the year 1501, about sixty vegetable species, including some three or four known to grow elsewhere also. [Footnote: It may be considered very highly probable, if not certain, that the undiscriminating herbalists of the sixteenth century must have overlooked many plants native to this island. An English botanist, in an hour's visit to Aden, discovered several species of plants on rocks always reported, even by scientific travellers, as absolutely barren. But after all, it appears to be well established that the original flora of St. Helena was extremely limited, though now counting hundreds of species.] At the present time its flora numbers seven hundred and fifty species—a natural result of the position of the island as the half-way house on the great ocean highway between Europe and the East. Humboldt and Bonpland found, among the unquestionably indigenous plants of tropical America, monocotyledons only, all the dicotyledons of those extensive regions having been probably introduced after the colonization of the New World by Spain.
The seven hundred new species which have found their way to St. Helena within three centuries and a half, were certainly not all, or ever in the largest proportion, designedly planted there by human art, and if we were well acquainted with vegetable emigration, we should probably be able to show that man has intentionally transferred fewer plants than he has accidentally introduced into countries foreign to them. After the wheat, follow the tares that infest it. The woods that grow among the cereal grains, the pests of the kitchen garden, are the same in America as in Europe. [Footnote: Some years ago I made a collection of weeds in the wheatfields of Upper Egypt, and another in the gardens on the Bosphorus. Nearly all the plants were identical with those which grow under the same conditions in New England. I do not remember to have seen in America the scarlet wild poppy so common in European grainfields. I have heard, however, that it has lately crossed the Atlantic, and I am not sorry for it. With our abundant harvests of wheat, we can well afford to pay now and then a loaf of bread for the cheerful radiance of this brilliant flower.] The overturning of a wagon, or any of the thousand accidents which befall the emigrant in his journey across the Western plains, may scatter upon the ground the seeds he designed for his garden, and the herbs which fill so important a place in the rustic materia medica of the Eastern States, spring up along the prairie paths but just opened by the caravan of the settler. [Footnote: Josselyn, who wrote about fifty years after the foundation of the first British colony in New England, says that the settlers at Plymouth had observed more than twenty English plants springing up spontaneously near their improvements.
Every country has many plants not now, if ever, made use of by man, and therefore not designedly propagated by him, but which cluster around his dwelling, and continue to grow luxuriantly on the ruins of his rural habitation after he has abandoned it. The site of a cottage, the very foundation stones of which have been carried off, may often be recognized, years afterwards, by the rank weeds which cover it, though no others of the same species are found for miles.
"Mediaeval Catholicism," says Vaupell, "brought us the red horsehoof—whose reddish-brown flower buds shoot up from the ground when the snow melts, and are followed by the large leaves—comfrey and snake-root, which grow only where there were convents and other dwellings in the Middle Ages."—Bogens Indvandring & de Daneke Skove, pp. 1, 2. ]
Introduction of Foreign Plants.
"A negro slave of the great Cortez," says Humboldt, "was the first who sowed wheat in New Spain. He found three grains of it among the rice which had been brought from Spain as food for the soldiers."
About twenty years ago, a Japanese forage plant, the Lesperadeza striata, whose seeds had been brought to the United States by some unknown accident made its appearance in one of the Southern States. It spread spontaneously in various directions, and in a few years was widely diffused. It grows upon poor and exhausted soils, where the formation of a turf or sward by the ordinary grasses would be impossible, and where consequently no regular pastures or meadows can exist. It makes excellent fodder for stock, and though its value is contested, it is nevertheless generally thought a very important addition to the agricultural resources of the South. [Footnote: Accidents sometimes limit, as well as promote the propagation of foreign vegetables in countries new to them. The Lombardy poplar is a deciduous tree, and is very easily grown from cuttings. In most of the countries into which it has been introduced the cuttings hare been taken from the male, and as, consequently, males only have grown from them, the poplar does not produce seed in those regions. This is a fortunate circumstance, for otherwise this most worthless and least ornamental of trees would spread with a rapidity that would make it an annoyance to the agriculturist.]
In most of the Southern countries of Europe, the sheep and horned cattle winter on the plains, but in the summer are driven, sometimes many days' journey, to mountain pastures. Their coats and fleeces transport seeds in both directions. Hence we see Alpine plants in champaign districts, the plants of the plains on the borders of the glaciers, though in neither case do these vegetables ripen their seeds and propagate themselves. This explains the occurrence of tufts of common red clover with pallid and sickly flowers, on the flanks of the Alps at heights exceeding seven thousand feet.
The hortus siccus of a botanist may accidentally sow seeds from the foot of the Himalayas on the plains that skirt the Alps; and it is a fact of very familiar observation, that exotics, transplanted to foreign climates suited to their growth, often escape from the flower garden and naturalize themselves among the spontaneous vegetation of the pastures. When the cases containing the artistic treasures of Thorvaldsen wore opened in the court of the museum where they are deposited, the straw and grass employed in packing them were scattered upon the ground, and the next season there sprang up from the seeds no less than twenty-five species of plants belonging to the Roman campagna, some of which were preserved and cultivated as a new tribute to the memory of the great Scandinavian sculptor, and at least four are said to have spontaneously naturalized themselves about Copenhagen. [Footnote: Vaupell, Bogens Indvandring i de Danske Skove, p. 2.]
The Turkish armies, in their incursions into Europe, brought Eastern vegetables in their train, and left the seeds of Oriental wall plants to grow upon the ramparts of Buda and Vienna. [Footnote: I believe it is certain that the Turks introduced tobacco into Hungary, and probable that they in some measure compensated, the injury by introducing maize also, which, as well as tobacco, has been claimed as Hungarian by patriotic Magyars.]
In the campaign of 1814, the Russian troops brought, in the stuffing of their saddles and by other accidental means, seeds from the banks of the Dnieper to the valley of the Rhine, and even introduced the plants of the steppes into the environs of Paris.
The forage imported for the French army in the war of 1870-1871 has introduced numerous plants from Northern Africa and other countries into France, and this vegetable emigration is so extensive and so varied in character, that it will probably have an important botanical, and even economical, effect on the flora of that country. [Footnote: In a communication lately made to the French Academy, M. Vibraye gives numerous interesting details on this subject, and says the appearance of the many new plants observed in France in 1871, "results from forage supplied from abroad, the seeds of which had fallen upon the ground. At the present time, several Mediterranean plants, chiefly Algerian, having braved the cold of an exceptionally severe winter, are being largely propagated, forming extensive meadows, and changing soil that was formerly arid and produced no vegetable of importance into veritable oases." See Nature, Aug. 1, 1872, p. 263. We shall see on a following page that canals are efficient agencies in the unintentional interchange of organic life, vegetable as well as animal, between regions connected by such channels.]
The Canada thistle, Erigeron Canadense, which is said to have accompanied the early French voyagers to Canada from Normandy, is reported to have been introduced into other parts of Europe two hundred years ago by a seed which dropped out of the stuffed skin of an American bird.
VEGETABLE POWER OF ACCOMMODATION.
The vegetables which, so far as we know their history, seem to have been longest objects of human care, can, by painstaking industry, be made to grow under a great variety of circumstances, and some of them prosper nearly equally well when planted and tended on soils of almost any geological character; but the seeds of most of them vegetate only in artificially prepared ground, they have little self-sustaining power, and they soon perish when the nursing hand of man is withdrawn from them.
The vine genus is very catholic and cosmopolite in its habits, but particular varieties are extremely fastidious and exclusive in their requirements as to soil and climate. The stocks of many celebrated vineyards lose their peculiar qualities by transplantation, and the most famous wines are capable of production only in certain well-defined and for the most part narrow districts. The Ionian vine which bears the little stoneless grape known in commerce as the Zante currant, has resisted almost all efforts to naturalize it elsewhere, and is scarcely grown except in two or three of the Ionian islands and in a narrow territory on the northern shores of the Morea.
The attempts to introduce European varieties of the vine into the United States have not been successful except in California, [Footnote: In 1869, a vine of a European variety planted in Sta. Barbara county in 1833 measured a foot in diameter four foot above the ground. Its ramifications covered ten thousand square feet of surface and it annually produces twelve thousand pounds of grapes. The bunches are sixteen or eighteen inches long, and weigh six or seven pounds.-Letter from Commissioner of Land-Office, dated May 13, 1860.] and it may be stated as a general rule that European forest and ornamental trees are not suited to the climate of North America, and that, at the same time, American garden vegetables are less luxuriant, productive and tasteful in Europe than in the United States.
The saline atmosphere of the sea is specially injurious both to seeds and to very many young plants, and it is only recently that the transportation of some very important vegetables across the ocean lines been made practicable, through the invention of Ward's air-tight glass cases. By this means large numbers of the trees which produce the Jesuit's bark were successfully transplanted from America to the British possessions in the East, where this valuable plant may now be said to have become fully naturalized. [Footnote: See Cleghorn, Forests and Gardens of South India, Edinburgh, 1861, and The British Parliamentary return on the Chinchona Plant, 1866. It has been found that the seeds of several species of CINCHONA preserve their vitality long enough to be transported to distant regions. The swiftness of steam navigation render it possible to transport to foreign countries not only seeds but delicate living plants which could not have borne a long voyage by sailing vessels.]
Vegetables, naturalized abroad either by accident or design, sometimes exhibit a greatly increased luxuriance of growth.
The European cardoon, an esculent thistle, has broken out from the gardens of the Spanish colonies on the La Plata, acquired a gigantic stature, and propagated itself, in impenetrable thickets, over hundreds of leagues of the Pampas; and the Anacharis alsinastrum, a water plant not much inclined to spread in its native American habitat, has found its way into English rivers, and extended itself to such a degree as to form a serious obstruction to the flow of the current, and even to navigation.
Not only do many wild plants exhibit a remarkable facility of accommodation, but their seeds usually possess great tenacity of life, and their germinating power resists very severe trials. Hence, while the seeds of many cultivated vegetables lose their vitality in two or three years, and can be transported safely to distant countries only with great precautions, the weeds that infest those vegetables, though not cared for by man, continue to accompany him in his migrations, and find a new home on every soil he colonizes. Nature fights in defence of her free children, but wars upon them when they have deserted her banners and tamely submitted to the domination of man. [Footnote: Tempests, violent enough to destroy all cultivated plants, frequently spare those of spontaneous growth. I have often seen in Northern Italy, vineyards, maize fields, mulberry and fruit trees completely stripped of their foliage by hail, while the forest trees scattered through the meadows, and the shrubs and brambles which sprang up by the wayslde, passed through the ordeal with scarcely the loss of a leaflet.]
Indeed, the faculty of spontaneous reproduction and perpetuation necessarily supposes a greater power of accommodation, within a certain range, than we find in most domesticated plants, for it would rarely happen that the seed of a wild plant would fall into ground as nearly similar, in composition and condition, to that where its parent grew, as the soils of different fields artificially prepared for growing a particular vegetable are to each other. Accordingly, though every wild species affects a habitat of a particular character, it is found that, if accidentally or designedly sown elsewhere, it will grow under conditions extremely unlike those of its birthplace. Cooper says: "We cannot say positively that any plant is uncultivable ANYWHERE until it has been tried;" and this seems to be even more true of wild than of domesticated vegetation.
The wild plant is much hardier than the domesticated vegetable, and the same law prevails in animated brute and even human life. The beasts of the chase are more capable of endurance and privation and more tenacious of life, than the domesticated animals which most nearly resemble them. The savage fights on, after he has received half a dozen mortal wounds, the least of which would have instantly paralyzed the strength of his civilized enemy, and, like the wild boar, he has been known to press forward along the shaft of the spear which was trans-piercing his vitals, and to deal a deathblow on the soldier who wielded it.
True, domesticated plants can be gradually acclimatized to bear a degree of heat or of cold, which, in their wild state, they would not have supported; the trained English racer out-strips the swiftest horse of the pampas or prairies, perhaps even the less systematically educated courser of the Arab; the strength of the European, as tested by the dynamometer, is greater than that of the New Zealander. But all these are instances of excessive development of particular capacities and faculties at the expense of general vital power. Expose untamed and domesticated forms of life, together, to an entire set of physical conditions equally alien to the former habits of both, so that every power of resistance and accommodation shall be called into action, and the wild plant or animal will live, while the domesticated will perish.
AGRICULTURAL PRODUCTS OF THE UNITED STATES.
According to the census of 1870, the United States had, on the first of June in that year, in round numbers, 189,000,000 acres of improved land, the quantity having been increased by 16,000,000 acres within the ten years next preceding. [Footnote: Ninth Census of the United States, 1872, p. 841. By "improved" land, in the reports on the census of the United States, is meant "cleared land" used for grazing, grass, or tillage, or which is now fallow, connected with or belonging to a farm."—Instructions to Marshals and Assistants, Census of 1870.] Not to mention less important crops, this land produced, in the year ending on the day last mentioned, in round numbers, 288,000,000 bushels of wheat, 17,000,000 bushels of rye, 282,000,000 bushels of oats, 6,000,000 bushels of peas and beans, 30,000,000 bushels of barley, orchard fruits to the value of $47,000,000, 640,000 bushels of cloverseed, 580,000 bushels of other grass seed, 13,000 tons of hemp, 27,000,000 pounds of flax, and 1,730,000 bushels of flaxseed. These vegetable growths were familiar to ancient European agriculture, but they were all introduced into North America after the close of the sixteenth century.
Of the fruits of agricultural industry unknown to the Greeks and Romans, or too little employed by them to be of any commercial importance, the United States produced, in the same year, 74,000,000 pounds of rice, 10,000,000 bushels of buckwheat, 3,000,000 bales of cotton, [Footnote: Cotton, though cultivated in Asia from the remotest antiquity, and known as a rare and costly product to the Latins and the Greeks, was not used by them except as an article of luxury, nor did it enter into their commerce to any considerable extent as a regular object of importation. The early voyagers found it in common use in the West Indies and in the provinces first colonized by the Spaniards; but it was introduced into the territory of the United States by European settlers, and did not become of any importance until after the Revolution. Cottonseed was sown in Virginia as early as 1621, but was not cultivated with a view to profit for more than a century afterwards. Sea-island cotton was first grown on the coast of Georgia in 1786, the seed having been brought from the Bahamas, when it had been introduced from Anguilla—BIGELOW, Les Etats-Unis en 1868, p. 370]. 87,000 hogsheads of cane sugar, 6,600,000 gallons of cane molasses, 16,000,000 gallons of sorghum molasses, all yielded by vegetables introduced into that country within two hundred years, and—with the exception of buckwheat, the origin of which is uncertain, and of cotton—all, directly or indirectly, from the East Indies; besides, from indigenous plants unknown to ancient agriculture, 761,000,000 bushels of Indian corn, 263,000,000 pounds of tobacco, 143,000,000 bushels of potatoes, 22,000,000 bushels of sweet potatoes, 28,000,000 pounds of maple sugar, and 925,000 gallons of maple molasses. [Footnote: There is a falling off since 1860 of 11,000,000 pounds in the quantity of maple sugar and of more than a million gallons of maple molasses. The high price of cane sugar during and since the late civil war must have increased the product of maple sugar and molasses beyond what it otherwise would have been, but the domestic warfare on the woods has more than compensated this cause of increase.] To all this we are to add 27,000,000 tons of hay,—produced partly by new, partly by long known, partly by exotic and partly by native herbs and grasses, the value of $21,000,000 in garden vegetables chiefly of European or Asiatic origin, 3,000,000 gallons of wine, and many minor agricultural products. [Footnote: Raenie, Bochmeria tenacissima, a species of Chinese nettle producing a fibre which may be spun and woven, and which unites many of the properties of silk and of linen, has been completely naturalized in the United States, and results important to the industry of the country are expected from it.]
The weight of this harvest of a year would be many times the tonnage of all the shipping of the United States at the close of the year 1870—and, with the exception of the maple sugar, the maple molasses, and the products of the Western prairie lands and of some small Indian clearings, it was all grown upon lands wrested from the forest by the European race within little more than two hundred years. The wants of Europe have introduced into the colonies of tropical America the sugar cane, [Footnote: The sugar cane was introduced by the Arabs into Sicily and Spain as early as the ninth century, and though it is now scarcely grown in those localities, I am not aware of any reason to doubt that its cultivation might be revived with advantage. From Spain it was carried to the West Indies, though different varieties have since been introduced into those Islands from other sources.] the coffee plant, the orange and the lemon, all of Oriental origin, have immensely stimulated the cultivation of the former two in the countries of which they are natives, and, of course, promoted agricultural operations which must have affected the geography of those regions to an extent proportionate to the scale on which they have been pursued.
USEFUL AMERICAN PLANTS GROWN IN EUROPE.
America has partially repaid her debt to the Eastern continent. Maize and the potato are very valuable additions to the field agriculture of Europe and the East, and the tomato is no mean gift to the kitchen gardens of the Old World, though certainly not an adequate return for the multitude of esculent roots and leguminous plants which the European colonists carried with them. [Footnote: John Smith mentions, In his Historie of Virginia, 1624, pease and beans as having been cultivated by the natives before the arrival of the whites, and there is no doubt, I believe, that several common cucurbitaceous plants are of American origin; but most, if not all the varieties of pease, beans, and other pod fruits now grown in American gardens, are from European and other foreign seed.
Cartier, A.D. 1535-'6, mentions "vines, great melons, cucumbers, gourds [courges], pease, beans of various colors, but not like ours," as common among the Indians of the banks of the St. Lawrence—Bref Recit, etc., reprint. Paris, 1863, pp. 13, a; 14, b; 20, b; 31, a.] I wish I could believe, with some, that America is not alone responsible for the introduction of the filthy weed, tobacco, the use of which is the most vulgar and pernicious habit engrafted by the semi-barbarism of modern civilization upon the less multifarious sensualism of ancient life; but the alleged occurrence of pipe-like objects in old Sclavonic, and, it has been said, in Hungarian sepulchres, is hardly sufficient evidence to convict those races of complicity in this grave offence against the temperance and the refinement of modern society.
EXTIRPATION OF VEGETABLES.
Lamentable as are the evils produced by the too general felling of the woods in the Old World, I believe it does not appear that any species of native forest tree has yet been extirpated by man on the Eastern continent. The roots, stumps, trunks, and foliage found in bogs are recognized as belonging to still extant species. Except in some few cases where there is historical evidence that foreign material was employed, the timber of the oldest European buildings, and even of the lacustrine habitations of Switzerland, is evidently the product of trees still common in or near the countries where such architectural remains are found; nor have the Egyptian catacombs themselves revealed to us the former existence of any woods not now familiar to us as the growth of still living trees. [Footnote: Some botanists think that a species of water lily represented in many Egyptian tombs has become extinct, and the papyrus, which must have once been abundant in Egypt, is now found only in a very few localities near the mouth of the Nile. It grows very well and ripens its seeds in the waters of the Anapus near Syracuse, and I have seen it in garden ponds at Messina and in Malta. There is no apparent reason for believing that it could not be easily cultivated in Egypt, to any extent, if there were any special motive for encouraging its growth.
Silphium, a famous medicinal plant of Lybia and of Persia, seems to have disappeared entirely. At any rate there is no proof that it now exists in either of those regions. The Silphium of Greek and Roman commerce appears to have come wholly from Cyrene, that from the Asiatic deserts being generally of less value, or, as Strabo says, perhaps of an inferior variety. The province near Cyrene which produced it was very limited, and according to Strabo (ed. Casaubon, p. 837), it was at one time almost entirely extirpated by the nomade Africans who invaded the province and rooted out the plant.
The vegetable which produced the Balm of Gilead has not been found in modern times, although the localities in which it anciently grew have been carefully explored.] It is, however, said that the yew tree, Taxus baccata, formerly very common in England, Germany, and—as we are authorized to infer from Theophrastus—in Greece, has almost wholly disappeared from the latter country, and seems to be dying out in Germany. The wood of the yew surpasses that of almost any other European tree in closeness and fineness of grain, and it is well known for the elasticity which of old made it so great a favorite with the English archer. It is much in request among wood carvers and turners, and the demand for it explains, in part, its increasing scarcity.
It is also asserted that no insect depends upon it for food or shelter, or aids in its fructification, and birds very rarely feed upon its berries: these are circumstances of no small importance, because the tree hence wants means of propagation or diffusion common to so many other plants. But it is alleged that the reproductive power of the yew is exhausted, and that it can no longer be readily propagated by the natural sowing of its seeds, or by artificial methods. If further investigation and careful experiment should establish this fact, it will go far to show that a climatic change, of a character unfavorable to the growth of the yew, has really taken place in Germany, though not yet proved by instrumental observation, and the most probable cause of such change would be found in the diminution of the area covered by the forests. The industry of man is said to have been so successful in the local extirpation of noxious or useless vegetables in China, that, with the exception of a few water plants in the rice grounds, it is sometimes impossible to find a single weed in an extensive district; and the late eminent agriculturist, Mr. Coke, is reported to have offered in vain a considerable reward for the detection of a weed in a large wheatfield on his estate in England. In these cases, however, there is no reason to suppose that diligent husbandry has done more than to eradicate the pests of agriculture within a comparatively limited area, and the cockle and the darnel will probably remain to plague the slovenly cultivator as long as the cereal grains continue to bless him. [Footnote: Although it is not known that man has absolutely extirpated any vegetable, the mysterious diseases which have, for the last twenty years, so injuriously affected the potato, the vine, the orange, the olive, and silk husbandry, are ascribed by some to a climatic deterioration produced by excessive destruction of the woods. As will be seen in the next chapter, a retardation in the period of spring has been observed in numerous localities in Southern Europe, as well as in the United States, and this change has been thought to favor the multiplication of the obscure parasites which causee the injury to the vegetables mentioned. Babinet supposes the parasites which attack the grape and the potato to be animal, not vegetable, and he ascribes their multiplication to excessive manuring and stimulation of the growth of the plants on which they live. They are now generally, it not universally, regarded as vegetable, and if they are so, Babinet's theory would be even more plausible than on his own supposition.—Etudes et lectures, ii, p. 269.
It is a fact of some interest in agricultural economy, that the oidium, which is so destructive to the grape, has produced no pecuniary loss to the proprietors of the vineyards in France. "The price of wine," says Lavergne, "has quintupled, and as the product of the vintage has not diminished in the same proportion, the crisis has been, on the whole, rather advantageous than detrimental to the country."—Economie rurale de la France, pp. 263, 264.
France produces a large surplus of wines for exportation, and the sales to foreign consumers are the principal source of profit to French vinegrowers. In Northern Italy, on the contrary, which exports little wine, there has been no such increase in the price of wine as to compensate the great diminution in the yield of the vines, and the loss of this harvest is severely felt. In Sicily, however, which exports much wine, prices have risen as rapidly as in France. Waltershausen informs us that in the years 1838-'42, the red wine of Mount Etna sold at the rate of one kreuzer and a half, or one cent the bottle, and sometimes even at but two thirds that price, but that at present it commands five or six times as much.
The grape disease has operated severely on small cultivators whose vineyards only furnished a supply for domestic use, but Sicily has received a compensation in the immense increase which it has occasioned in both the product and the profits of the sulphur mines. Flour of sulphur is applied to the vine as a remedy against the disease, and the operation is repeated from two to three or four—and sometimes even eight or ten—times in a season. Hence there is a great demand for sulphur in all the vine-growing countries of Europe, and
Waltershausen estimates the annual consumption of that mineral for this single purpose at 850,000 centner, or more than forty thousand tons. The price of sulphur has risen in about the same proportion as that of the wine.—Waltershausen, Ueber den Sicilianischen Ackerbau, pp. 19, 20.]
All the operations of rural husbandry are destructive to spontaneous vegetation by the voluntary substitution of domestic for wild plants, and, as we have seen, the armies of the colonist are attended by troops of irregular and unrecognized camp-followers, which soon establish and propagate themselves over the new conquests. These unbidden and hungry guests—the gipsies of the vegetable world—often have great aptitude for accommodation and acclimation, and sometimes even crowd out the native growth to make room for themselves. The botanist Latham informs us that indigenous flowering plants, once abundant on the North-Western prairies, have been so nearly extirpated by the inroads of half-wild vegetables which have come in the train of the Eastern immigrant, that there is reason to fear that, in a few years, his herbarium will constitute the only evidence of their former existence. [Footnote: Report of Commissioner of Agriculture of the United States for 1870.]
There are plants—themselves perhaps sometimes stragglers from their proper habitat—which are found only in small numbers and in few localities. These are eagerly sought by the botanist, and some such species are believed to be on the very verge of extinction, from the zeal of collectors.
ANIMAL LIFE AS A GEOLOGICAL AND GEOGRAPHICAL AGENCY.
The quantitative value of animated life, as a geological agency, seems to be inversely as the volume of the individual organism; for nature supplies by numbers what is wanting in the bulk of the animal out of whose remains or structures she forms strata covering whole provinces, and builds up from the depths of the sea large islands, if not continents. There are, it is true, near the mouths of the great Siberian rivers which empty themselves into the Polar Sea, drift islands composed, in an incredibly large proportion, of the bones and tusks of elephants, mastodons, and other huge pachyderms, and many extensive caves in various parts of the world are half filled with the skeletons of quadrupeds, sometimes lying loose in the earth, sometimes cemented together into an osseous breccia by a calcareous deposit or other binding material. These remains of large animals, though found in comparatively late formations, generally belong to extinct species, and their modern congeners or representatives do not exist in sufficient numbers to be of sensible importance in geology or in geography by the mere mass of their skeletons. [Footnote: Could the bones and other relics of the domestic quadrupeds destroyed by disease or slaughtered for human use in civilized countries be collected into large deposits, as obscure causes have gathered together those of extinct animals, they would soon form aggregations which might almost be called mountains. There were in the United States, in 1870, as we shall see hereafter, nearly one hundred millions of horses, black cattle, sheep, and swine. There are great numbers of all the same animals in the British American Provinces and in Mexico, and there are large herds of wild horses on the plains, and of tamed among the independent Indian tribes of North America. It would perhaps not be extravagant to suppose that all these cattle may amount to two thirds as many as those of the United States, and thus we have in North America a total of 160,000,000 domestic quadrupeds belonging to species introduced by European colonization, besides dogs, cats, and other four-footed household pets and pests, also of foreign origin.
If we allow half a solid foot to the skeleton and other slowly destructible parts of each animal, the remains of these herds would form a cubical mass measuring not much short of four hundred and fifty feet to the side, or a pyramid equal in dimensions to that of Cheops, and as the average life of these animals does not exceed six or seven years, the accumulations of their bones, horns, hoofs, and other durable remains would amount to at least fifteen times as great a volume in a single century. It is true that the actual mass of solid matter, left by the decay of dead domestic quadrupeds and permanently added to the crust of the earth, is not so great as this calculation makes it. The greatest proportion of the soft parts of domestic animals, and even of the bones, is soon decomposed, through direct consumption by man and other carnivora, industrial use, and employment as manure, and enters into new combinations in which its animal origin is scarcely traceable; there is, nevertheless, a large annual residuum, which, like decayed vegetable matter, becomes a part of the superficial mould; and in any event, brute life immensely changes the form and character of the superficial strata, if it does not sensibly augment the quantity of the matter composing them. The remains of man, too, add to the earthy coating that covers the face of the globe. The human bodies deposited in the catacombs during the long, long ages of Egyptian history, would perhaps build as large a pile as one generation of the quadrupeds of the United States. In the barbarous days of old Moslem warfare, the conquerors erected large pyramids of human skulls. The soil of cemeteries in the great cities of Europe has sometimes been raised several feet by the deposit of the dead during a few generations. In the East, Turks and Christians alike bury bodies but a cople of feet beneath the sculptures of the ignoble poor, and of those whose monuments time or accident has removed, are opened again and again to receive fresh occupants. Hence the ground in Oriental cemeteries is pervaded with relics of humanity, of not wholly composed of them; and an examination of the soil of the lower part of the Petit Champ des Morts, at Pera, by the naked eye alone, shows the observer that it consists almost exclusively of the comminuted bones of his fellow-man.] But the vegetable products found with them, and, in rare cases, in the stomachs of some of them, are those of yet extant plants; and besides this evidence, the discovery of works of human art, deposited in juxtaposition with fossil bones, and evidently at the same time and by the same agency which buried these latter—not to speak of human bones found in the same strata—proves that the animals whose former existence they testify were contemporaneous with man, and possibly even extirpated by him. [Footnote: The bones of mammoths and mastodons, in many instances, appear to have been grazed or cut by flint arrow-heads or other stone weapons, and the bones of animals now extinct are often wrought into arms and utensils, or split to extract the marrow. These accounts have often been discredited, because it has been assumed that the extinction of these animals was more ancient than the existence of man. Recent discoveries render it certain that this conclusion has been too hastily adopted.
On page 143 of the Antiquity of Man, Lyell remarks that man "no doubt played his part in hastening the era of the extincion" of the large pachyderms and beasts of prey; but, as contemporaneous species of other animals, which man cannot be supposed to have extirpated, have also become extinct, he argues that the disappearance of the quadrupeds in question cannot be ascribed to human action alone.
On this point it may be observed that, as we cannot know what precise physical conditions were necessary to the existence of a given extinct organism, we cannot say how far such conditions may have been modified by the action of man, and he may therefore have influenced the life of such organisms in ways, and to an extent, of which we can form no just idea.] I do not propose to enter upon the thorny question, whether the existing races of man are genealogically connected with these ancient types of humanity, and I advert to these facts only for the sake of the suggestion, that man, in his earliest known stages of existence, was probably a destructive power upon the earth, though perhaps not so emphatically as his present representatives. The larger wild animals are not now numerous enough in any one region to form extensive deposits by their remains; but they have, nevertheless, a certain geographical importance. If the myriads of large browsing and grazing quadrupeds which wander over the plains of Southern Africa—and the slaughter of which by thousands is the source of a ferocious pleasure and a brutal triumph to professedly civilized hunters—if the herds of the American bison, which are numbered by hundreds of thousands, do not produce visible changes in the forms of terrestrial surface, they have at least an immense influence on the growth and distribution of vegetable life, and, of course, indirectly upon all the physical conditions of soil and climate between which and vegetation a mutual interdependence exists. In the preceding chapter I referred to the agency of the beaver in the formation of bogs as producing sensible geographical effects.
I am disposed to think that more bogs in the Northern States owe their origin to beavers than to accidental obstructions of rivulets by wind-fallen or naturally decayed trees; for there are few swamps in those States, at the outlets of which we may not, by careful search, find the remains of a beaver dam. The beaver sometimes inhabits natural lakelets and even large rivers like the Upper Mississippi, when the current is not too rapid, but he prefers to owe his pond to his own ingenuity and toil. The reservoir once constructed, its inhabitants rapidly multiply so long as the trees, and the harvests of pond lilies and other aquatic plants on which this quadruped feeds in winter, suffice for the supply of the growing population. But the extension of the water causes the death of the neighboring trees, and the annual growth of those which could be reached by canals and floated to the pond soon becomes insufficient for the wants of the community, and the beaver metropolis now sends out expeditions of discovery and colonization. The pond gradually fills up, by the operation of the same causes as when it owes its existence to an accidental obstruction, and when, at last, the original settlement is converted into a bog by the usual processes of vegetable life, the remaining inhabitants abandon it and build on some virgin brooklet a new city of the waters. [Footnote: I find confirmation of my own observations on this point (published in 1863) in the North-West Passage by Land of Milton and Cheadle, London, 1865. These travellers observed "a long chain of marshes formed by the damming up of a stream which had now ceased to exist," Chap. X. In Chap. XII, they state that "nearly every stream between the Pembina and the Athabasca—except the large river McLeod—appeared to have been destroyed by the agency of the beaver," and they question whether the vast extent of swampy ground in that region "has not been brought to this condition by the work of beavers who have thus destroyed, by their own labor, the streams necessary to their own existence."
But even here nature provides a remedy, for when the process of "consolidation" referred to in treating of bogs in the first chapter shall have been completed, and the forest re-established upon the marshes, the water now diffused through them will be collected in the lower or more yielding portions, cut new channels for their flow, become running brooks, and thus restore the ancient aspect of the surface.
The authors add the curious observation that the beavers of the present day seem to be a degenerate race, as they neither fell huge trees not construct great dams, while their progenitors cut down trees two feet in diameter and dammed up rivers a hundred feet in width. The change in the habits of the beaver is probably due to the diminution of their numbers since the introduction of fire-arms, and to the tact that their hydraulic operations are more frequently interrupted by the encroachments of man. In the valley of the Yellowstone, which has but lately been much visited by the white man, Hayden saw stumps of trees thirty inches in diameter which had been cut down by beavers. —Geological Survey of Wyoming, p. 135.
The American beaver closely resembles his European congener, and I believe most naturalists now regard them as identical. A difference of speceies has been inferred from a difference in their modes of life, the European animal being solitary and not a builder, the American gregarious and constructive. But late careful researches in Germany have shown the former existence of numerous beaver dams in that country, though the animal, having becaome rare to form colonies, has of course ceased to attempt works which require the co-operation of numerous individuals.—Schleiden, Fur Baum und Wald Leipzig, 1870, p. 68.
On the question of identity and on all others relating to this interesting animal, see L.H. Morgan's important monograph, The American Beaver and his Works, Philadelphia, 1868. Among the many new facts observed by this investigator is the construction of canals by the beaver to float trunks and branches of trees to his ponds. These canals are sometimes 600 to 700 feet long, with a width of two or three feet and a depth of one to one and a half.]
INFLUENCE OF ANIMAL LIFE ON VEGETATION
The influence of wild quadrupeds upon vegetable life have been little studied, and not many facts bearing upon it have been recorded, but, so far as it is known, it appears to be conservative rather than pernicious. Few wild animals depend for their subsistence on vegetable products obtainable only by the destruction of the plant, and they seem to confine their consumption almost exclusively to the annual harvest of leaf or twig, or at least of parts of the vegetable easily reproduced. If there are exceptions to this rule, they are in cases where the numbers of the animal are so proportioned to the abundance of the vegetable that there is no danger of the extermination of the plant from the voracity of the quadruped, or of the extinction of the quadruped from the scarcity of the plant. [Footnote: European foresters speak of the action of the squirrel as injurious to trees. Doubtless this is sometimes true in the case of artificial forests, but in woods of spontaneous growth, ordered and governed by nature, the squirrel does not attack trees, or at least the injury he may do is too trifling to be perceptible, but he is a formidable enemy to the plantation. "The squirrels bite the cones of the pine and consume the seed which might serve to restock the wood; they do still more mischief by gnawing off, near the leading shoot, a strip of bark, and thus often completely girdling the tree. Trees so injured must be felled, as they would never acquire a vigorous growth. The squirrel is especially destructive to the pine in Sologne, where he gnaws the bark of trees twenty or twenty-five years old." But even here, nature sometimes provides a compensation, by making the appetite of this quadruped serve to prevent an excessive production of seed cones, which tends to obstruct the due growth of the leading shoot. "In some of the pineries of Brittany which produce cones so abundantly as to strangle the development of the leading shoot of the maritime pine, it has been observed that the pines are most vigorous where the squirrels are most numerous, a result attributed to the repression of the cones by this rodent."—Boitel, Mise en valeur des Terres pauvres, p. 50.
Very interesting observations, on the agency of the squirrel and other small animals in planting and in destroying nuts and other seeds of trees, may be found in a paper on the Succession of Forests in Thoreau's Excursions, pp. 135 et seqq.
I once saw several quarts of beech-nuts taken from the winter quarters of a family of flying squirrels in a hollow tree. The kernels were neatly stripped of the shells and carefully stored in a dry cavity.] In diet and natural wants the bison resembles the ox, the ibex and the chamois assimilate themselves to the goat and the sheep; but while the wild animal does not appear to be a destructive agency in the garden of nature, his domestic congeners are eminently so. [Footnote: Evelyn thought the depasturing of grass by cattle serviceable to its growth. "The biting of cattle," he remarks, "gives a gentle loosening to the roots of the herbage, and makes it to grow fine and sweet, and their very breath and treading as well as soil, and the comfort of their warm bodies, is wholesome and marvellously cherishing."—Terra, or Philosophical Discourses of Earth, p. 86.
In a note upon this passage, Hunter observes: "Nice farmers consider the lying of a beast upon the ground, for one night only, as a sufficient tilth for the year. The breath of graminivorous quadrupeds does certainly enrich the roots of grass; a circumstance worthy of the attention of the philosophical farmer."—Terra, same page.
The "philosophical farmer" of the present day will not adopt these opinions without some qualification, and they certainly are not sustained by American observation.
The Report of the Department of Agriculture for March and April, 1872, states that the native grasses are disappearing from the prairies of Texas, especially on the bottom-lands, depasturing of cattle being destructive to them.] This is partly from the change of habits resulting from domestication and association with man, partly from the fact that the number of reclaimed animals is not determined by the natural relation of demand and spontaneous supply which regulates the multiplication of wild creatures, but by the convenience of man, who is, in comparatively few things, amenable to the control of the merely physical arrangements of nature. When the domesticated animal escapes from human jurisdiction, as in the case of the ox, the horse, the goat, and perhaps the ass—which, so far as I know, are the only well-authenticated instances of the complete emancipation of household quadrupeds—he becomes again an unresisting subject of nature, and all his economy is governed by the same laws as that of his fellows which have never been enslaved by man; but, so long as he obeys a human lord, he is an auxiliary in the warfare his master is ever waging against all existences except those which he can tame to a willing servitude.
ORIGIN AND TRANSFER OF DOMESTIC QUADRUPEDS.
Civilization is so intimately associated with certain inferior forms of animal life, if not dependent on them, that cultivated man has never failed to accompany himself, in all his migrations, with some of these humble attendants. The ox, the horse, the sheep, and even the comparatively useless dog and cat, as well as several species of poultry, are voluntarily transferred by every emigrant colony, and they soon multiply to numbers far exceeding those of the wild genera most nearly corresponding to them. [Footnote: The rat and the mouse, though not voluntarily transported, are passengers by every ship that sails for a foreign port, and several species of these quadrupeds have, consequently, much extended their range and increased their numbers in modern times. From a story of Heliogabalus related by Lampridius, Hist. Aug. Scriptores, ed. Casaubon, 1690, p. 110, it would seem that mice at least were not very common in ancient Rome. Among the capricious freaks of that emperor, it is said that he undertook to investigate the statistics of the arachnoid population of the capital, and that 10,000 pounds of spiders (or spiders' webs—for aranea is equivocal) were readily collected; but when he got up a mouse-show, he thought ten thousand mice a very fair number. Rats are not less numerous in all great cities; and in Paris, where their skins are used for gloves, and their flesh, it is whispered, in some very complex and equivocal dishes, they are caught by legions. I have read of a manufacturer who contracted to buy of the rat-catchers, at a high price, all the rat-skins they could furnish before a certain date, and failed, within a week, for want of capital, when the stock of peltry had run up to 600,000.
Civilization has not contented itself with the introduction of domestic animals alone. The English sportsman imports foxes from the continent, and Grimalkin-like turns them loose in order that he may have the pleasure of chasing them afterwards.]
Of the origin of our domestic animals, we know historically nothing, because their domestication belongs to the ages which preceded written annals; but though they cannot all be specifically identified with now extant wild animals, it is presumable that they have been reclaimed from an originally wild state. Ancient writers have preserved to us fewer data respecting the introduction of domestic animals into new countries than respecting the transplantation of domestic vegetables. Ritter, in his learned essay on the camel, has shown that this animal was not employed by the Egyptians until a comparatively late period in their history; [Footnote: The horse and the ass were equally unknown to ancient Egypt, and do not appear in the sculptures before the XV. and XVI. dynasties. But even then, the horse was only known as a draught animal, and the only representation of a horseman yet found in the Egyptian tombs is on the blade of a battle axe of uncertain origin and period.] that he was unknown to the Carthaginians until after the downfall of their commonwealth; and that his first appearance in Western Africa is more recent still. The Bactrian camel was certainly brought from Asia Minor to the Northern shores of the Black Sea, by the Goths, in the third or fourth century, and the buffalo first appeared in Italy about A.D. 600, though it is unknown whence or by whom he was introduced. [Footnote: Erdkunde, viii., Asien, 1ste Abtheuung, pp. 660,758. Hehn, Kuttonpflanzen, p. 845.] The Arabian single-humped camel, or dromedary, has been carried to the Canary Islands, partially introduced into Australia, Greece, Spain, and even Tuscany, experimented upon to little purpose in Venezuela, and finally imported by the American Government into Texas and New Mexico, where it finds the climate and the vegetable products best suited to its wants, and promises to become a very useful agent in the promotion of the special civilization for which those regions are adapted.
Quadrupeds, both domestic and wild, bear the privations and discomforts of long voyages better than would be supposed. The elephant, the giraffe, the rhinoceros, and even the hippopotamus, do not seem to suffer much at sea. Some of the camels imported by the U.S. government into Texas from the Crimea and Northern Africa were a whole year on shipboard. On the other hand, George Sand, in Un Hiver au Midi, gives an amusing description of the sea-sickness of swine in the short passage from the Baleares to Barcelona. America had no domestic quadruped but a species of dog, the lama tribe, and, to a certain extent, the bison or buffalo. [Footnote: See Chapter III., post; also Humboldt, Ansichten der Natur, i., p. 71. From the anatomical character of the bones of the urus, or auerochs, found among the relics of the lacustrine population of ancient Switzerland, and from other circumstances, it is inferred that this animal had been domesticated by that people; and it is stated, I know not upon what authority, in Le Alpi che cingono l'Italia, that it had been tamed by the Veneti also. See Lyell, Antiquity of Man, pp. 24, 25, and the last-named work, p. 480. This is a fact of much interest, because it is one of the very few HISTORICALLY known instances of the extinction of a domestic quadruped, and the extreme improbability of such an event gives some countenance to the theory of the identity of the domestic ox with, and its descent from, the urus.]Of course, it owes the horse, the ass, the ox, the sheep, the goat, and the swine, as does also Australia, to European colonization. Modern Europe has, thus far, not accomplished much in the way of importation of new animals, though some interesting essays have been made. The reindeer was successfully introduced into Iceland about a century ago, while similar attempts failed, about the same time, in Scotland. The Cashmere or Thibet goat was brought to France a generation since, and succeeds well. The same or an allied species and the Asiatic buffalo were carried to South Carolina about the year 1850, and the former, at least, is thought likely to prove of permanent value in the United States. [Footnote: The goat introduced into South Carolina was brought from the district of Angora, in Asia Minor, which has long been celebrated for flocks of this valuable animal. It is calculated that more than a million of these goats are raised in that district, and it is commonly believed that the Angora goat and its wool degenerate when transported. Probably this is only an invention of the shepherds to prevent rivals from attempting to interfere with so profitable a monopoly. But if the popular prejudice has any foundation, the degeneracy is doubtless to be attributed to ignorance of the special treatment which long experience has taught the Angora shepherds, and the consequent neglect of such precautions as are necessary to the proper care of the animal. Throughout nearly the whole territory of the United States the success of the Angora goat is perfect, and it would undoubtedly thrive equally well in Italy, though it is very doubtful whether in either country the value of its fleece would compensate the damage it would do to the woods.] The yak, or Tartary ox, seems to thrive in France, and it is hoped that success will attend the present efforts to introduce the South American alpaca into Europe. [Footnote: The reproductive powers of animals, as well as of plants, seem to be sometimes stimulated in an extraordinary way by transfer to a foreign clime. The common warren rabbit introduced by the early colonists into the island of Madeira multiplied to such a degree as to threaten the extirpation of vegetation, and in Australia the same quadruped has become so numerous as to be a very serious evil. The colonists are obliged to employ professional rabbit-hunters, and one planter has enclosed his grounds by four miles of solid wall, at an expense of $6,000, to protect his crops against those ravagers.—Revue des Eaux et Forets, 1870, p. 38.]
According to the census of the United States for 1870, [Footnote: In the enumeration of farm stock, "sucking pigs, spring lambs, and calves," are omitted. I believe they are included in the numbers reported by the census of 1860. Horses and horned cattle in towns and cities were excluded from both enumerations, the law providing for returns on these points from rural districts only. On the whole, there is a diminution in the number of all farm stock, except sheep, since 1860. This is ascribed by the Report to the destruction of domestic quadrupeds during the civil war, but this hardly explains the reduction in the number of swine from 39,000,000 in 1800 to 25,000,000 in 1870.] the total number of horses in all the States of the American Union, was, in round numbers, 7,100,000; of asses and mules, 1,100,000; of the ox tribe, 25,000,000; of sheep, 28,000,000; and of swine, 25,000,000. The only indigenous North American quadruped sufficiently gregarious in habits, and sufficiently multiplied in numbers, to form really large herds, is the bison, or, as he is commonly called in America, the buffalo; and this animal is confined to the prairie region of the Mississippi basin, a small part of British America, and Northern Mexico. The engineers sent out to survey railroad routes to the Pacific estimated the number of a single herd of bisons seen within the last fifteen years on the great plains near the Upper Missouri, at not less than 200,000, and yet the range occupied by this animal is now very much smaller in area than it was when the whites first established themselves on the prairies. [Footnote: "About five miles from camp we ascended to the top of a high hill, and for a great distance ahead every square mile seemed to have a herd of buffalo upon it. Their number was variously estimated by the members of the party; by some as high as half a million. I do not think it any exaggeration to set it down at 200,000." Steven's Narrative and Final Report. Reports of Explorations and Surveys for Railroad to Pacific, vol xii, book i., 1860.
The next day the party fell in with a "buffalo trail," where at least 100,000 were thought to have crossed a slough.
As late as 1868, Sheridan's party estimated the number of bisons seen by them in a single day at 200,000.—Sheridan's Troopers on the Border, 1868, p. 41.] But it must be remarked that the American buffalo is a migratory animal, and that, at the season of his annual journeys, the whole stock of a vast extent of pasture-ground is collected into a single army, which is seen at or very near any one point only for a few days during the entire season. Hence there is risk of great error in estimating the numbers of the bison in a given district from the magnitude of the herds seen at or about the same time at a single place of observation; and, upon the whole, it is neither proved nor probable that the bison was ever, at any one time, as numerous in North America as the domestic bovine species is at present. The elk, the moose, the musk ox, the caribou, and the smaller quadrupeds popularly embraced under the general name of deer, though sufficient for the wants of a sparse savage population, were never numerically very abundant, and the carnivora which fed upon them were still less so. It is almost needless to add that the Rocky Mountain sheep and goat must always have been very rare.
Summing up the whole, then, it is evident that the wild quadrupeds of North America, even when most numerous, were few compared with their domestic successors, that they required a much less supply of vegetable food, and consequently were far less important as geographical elements than the many millions of hoofed and horned cattle now fed by civilized man on the same continent.
EXTIRPATION OF WILD QUADRUPEDS.
Although man never fails greatly to diminish, and is perhaps destined ultimately to exterminate, such of the larger wild quadrupeds as he cannot profitably domesticate, yet their numbers often fluctuate, and oven after they seem almost extinct, they sometimes suddenly increase, without any intentional steps to promote such a result on his part. During the wars which followed the French Revolution, the wolf multiplied in many parts of Europe, partly because the hunters were withdrawn from the woods to chase a nobler game, and partly because the bodies of slain men and horses supplied this voracious quadraped with more abundant food. [Footnote: During the late civil war in America, deer and other animals of the chase multiplied rapidly in the regions of the Southern States which were partly depopulated and deprived of their sportsmen by the military operations of the contest, and the bear is said to have reappeared in districts where he had not been seen in the memory of living man.] The same animal became again more numerous in Poland after the general disarming of the rural population by the Russian Government. On the other hand, when the hunters pursue the wolf, the graminivorous wild quadrupeds increase, and thus in turn promote the multiplication of their great four-footed destroyer by augmenting the supply of his nourishment. So long as the fur of the beaver was extensively employed as a material for hats, it bore a very high price, and the chase of this quadruped was so keen that naturalists feared its speedy extinction. When a Parisian manufacturer invented the silk hat, which soon came into almost universal use, the demand for beavers' fur fell off, and the animal—whose habits are an important agency in the formation of bogs and other modifications of forest nature—immediately began to increase, reappeared in haunts which he had long abandoned, and can no longer be regarded as rare enough to be in immediate danger of extirpation. Thus the convenience or the caprice of Parisian fashion has unconsciously exercised an influence which may sensibly affect the physical geography of a distant continent.
Since the invention of gunpowder, gome quadrupeds have completely disappeared from many European and Asiatic countries where they were formerly numerous. The last wolf was killed in Great Britain two hundred years ago, and the bear was extirpated from that island still earlier. The lion is believed to have inhabited Asia Minor and Syria, and probably Greece and Sicily also, long after the commencement of the historical period, and he is even said to have been not yet extinct in the first-named two of these countries at the time of the first Crusade. [Footnote: In maintaining the recent existence of the lion in the countries named in the text, naturalists have, perhaps, laid. too much weight on the frequent occurrence of representations of this animal in sculptures apparently of a historical character. It will not do to argue, twenty centuries hence, that the lion and the unicorn were common in Great Britain in Queen Victoria's time because they are often seen "fighting for the crown" in the carvings and paintings of that period. Many paleontolgists, however, identify the great cat-like animal, whose skeletons are frequently found in British bone-caves, with the lion of our times.
The leopard (panthera), though already growing scarce, was found in
Cilicia in Cicero's time. See his letter to Coelius, Epist. ad Diversos,
Lib. II., Ep. 11.
The British wild ox is extinct except in a few English and Scottish parks, while in Irish bogs of no great apparent antiquity are found antlers which testify to the former existence of a stag much larger than any extant European species. Two large graminivorous or browsing quadrupeds, the ur and the schelk, once common in Germany, have been utterly extirpated, the eland and the auerochs nearly so. The Nibelungen-Lied, which, in the oldest form preserved to us, dates from about the year 1200, though its original composition no doubt belongs to an earlier period, thus sings:
Then slowe the dowghtie Sigfrid a wisent and an elk, he smote four stoute uroxen and a grim and sturdie schelk. [Footnote: Dar nach sluoger schiere, einen wisent unde elch. Starker ure viere, unt einen grimmen schelch. XVI. Aventiure.
The testimony of the Nibelungen-Lied is not conclusive evidence that these quadrupeds existed in Germany at the time of the composition of that poem. It proves too much; for, a few lines above those just quoted, Sigfrid is said to have killed a lion, an animal which the most patriotic Teuton will hardly claim as a denizen of mediaeval Germany.]
Modern naturalists identify the elk with the eland, the wisent with the auerochs. The period when the ur and the schelk became extinct is not known. The auerochs survived in Prussia until the middle of the last century, but unless it is identical with a similar quadruped said to be found on the Caucasus, it now exists only in the Russian imperial forest of Bialowitz where about a thousand are still preserved, and in some great menageries, as for example that at Schonbrunn, near Vienna, which, in 1852, had four specimens. The eland, which is closely allied to the American wapiti if not specifically the same animal, is still kept in the royal preserves of Prussia, to the number of four or five hundred individuals. The chamois is becoming rare, and the ibex or steinbock, once common in all the high Alps, is now believed to be confined to the Cogne mountains in Piedmont, between the valleys of the Dora Baltea and the Orco, though it is said that a few still linger about the Grandes Jorasses near Cormayeur.
The chase, which in early stages of human life was a necessity, has become with advancing civilization not merely a passion but a dilettanteism, and the cruel records of this pastime are among the most discreditable pages in modern literature. It is true that in India and other tropical countries, the number and ferocity of the wild beasts not only justify but command a war of extermination against them, but the indiscriminate slaughter of many quadrupeds which are favorite objects of the chase can urge no such apology. Late official reports from India state the number of human victims of the tiger, the leopard, the wolf and other beasts of prey, in ten "districts," at more then twelve thousand within three years, and we are informed on like authority that within the last six years more than ten thousand men, women, and children have perished in the same way in the Presidency of Bengal alone. One tiger, we are told, had killed more than a hundred people, and finally stopped the travel on an important road, and another had caused the desertion of thirteen villages and thrown 250 square miles out of cultivation. In such facts we find abundant justification of the slaying of seven thousand tigers, nearly six thousand leopards, and twenty-five hundred other ravenous beasts in the Bengal Presidency, in the space of half a dozen years. But the humane reader will not think the value of the flesh, the skin, and other less important products of inoffensive quadrupeds a satisfactory excuse for the ravages committed upon them by amateur sportsmen as well as by professional hunters. In 1861, it was computed that the supply of the English market with ivory cost the lives of 8,000 elephants. Others make the number much larger and it is said that half as much ivory is consumed in the United States as in Great Britain. In Ceylon, where the elephants are numerous and destructive to the crops, as well as dangerous to travellers, while their tusks are small and of comparatively little value, the government pays a small reward for killing them. According to Sir Emerson Tennant, [Footnote: Natural History of Ceylon, chap. iv.] in three years prior to 1848, the premium was paid for 3,500 elephants in a part of the northern district, and between 1851 and 1856 for 2,000 in the southern district. Major Rogers, famous as an elephant shooter in Ceylon, ceased to count his victims after he had slain 1,300, and Cumming in South Africa sacrificed his hecatombs every month.
In spite of the rarity of the chamois, his cautious shyness, and the comparative inaccessibility of his favorite haunts, Colani of Pontresina, who died in 1837, had killed not less than 2,000 of these animals; Kung, who is still living in the Upper Engadine, 1,500; Hitz, 1,300, and Zwichi an equal number; Soldani shot 1,100 or 1,200 in the mountains which enclose the Val Bregaglia, and there are many living hunters who can boast of having killed from 500 to 800 of these interesting quadrupeds. [Footnote: Although it is only in the severest cold of winter that the chamois descends to the vicinity of grounds occupied by man, its organization does not confine it to the mountains. In the royal park of Racconigi, on the plain a few miles from Turin, at a height of less than 1,000 feet, is kept a herd of thirty or forty chamois, which thrive and breed apparently as well as in the Alps.]
In America, the chase of the larger quadrupeds is not less destructive. In a late number of the American Naturalist, the present annual slaughter of the bison is calculated at the enormous number of 500,000, and the elk, the moose, the caribou, and the more familiar species of deer furnish, perhaps, as many victims. The most fortunate deer-hunter I have personally known in New England had killed but 960; but in the northern part of the State of New York, a single sportsman is said to have shot 1,500, and this number has been doubtless exceeded by zealous Nimrods of the West.
But so far as numbers are concerned, the statistics of the furtrade furnish the most surprising results. Russia sends annually to foreign markets not less than 20,000,000 squirrel skins, Great Britain has sometimes imported from South America 600,000 nutria skins in a year. The Leipzig market receives annually nearly 200,000 ermine, and the Hudson Bay Company is said to have occasionally burnt 20,000 ermine skins in order that the market might not be overstocked. Of course natural reproduction cannot keep pace with this enormous destruction, and many animals of much interest to natural science are in imminent danger of final extirpation. [Footnote: Objectionable as game laws are, they have done something to prevent the extinction of many quadrupeds, which naturalists would be loth to lose, and, as in the case of the British ox, private parks and preserves have saved other species from destruction. Some few wild aminals, such as the American mink, for example, have been protected and bred with profit, and in Pennsylvania an association of gentlemen has set apart, and is about enclosing, a park of 16,000 acres for the breeding of indigenous quadrupeds and fowls.]
LARGE MARINE ANIMALS RELATIVELY UNIMPORTANT IN GEOGRAPHY.
Vast as is the bulk of some of the higher orders of aquatic animals, their remains are generally so perishable that, even where most abundant, they do not appear to be now forming permanent deposits of any considerable magnitude; but it is quite otherwise with shell-fish, and, as we shall see hereafter, with many of the minute limeworkers of the sea. There are, on the southern coast of the United States, beds of shells so extensive that they were formerly supposed to have been naturally accumulated, and were appealed to as proofs of an elevation of the coast by geological causes; but they are now ascertained to have been derived chiefly from oysters and other shell-fish, consumed in the course of long ages by the inhabitants of Indian towns. The planting of a bed of oysters in a new locality might very probably lead, in time, to the formation of a bank, which, in connection with other deposits, might perceptibly affect the line of a coast, or, by changing the course of marine currents, or the outlet of a river, produce geographical changes of no small importance.
INTRODUCTION AND BREEDING OF FISH.
The introduction and successful breeding of fish or foreign species appears to have been long practised in China, and was not unknown to the Greeks and Romans. [Footnote: The observations of COLUMELLA, de Re Rustica, lib. viii., sixteenth and following chapters, on fish-breeding, are interesting. The Romans not only stocked natural but constructed artificial ponds, of both fresh and salt water, and cut off bays of the sea for this purpose. They also naturalized various species of sea-fish in fresh water.] This art has been revived in modern times, but thus far without any important results, economical or physical, though there seems to be good reason to believe it may be employed with advantage on an extended scale. As in the case of plants, man has sometimes undesignedly introduced now species of aquatic animals into countries distant from their birthplace. The accidental escape of the Chinese goldfish from ponds where they were bred as a garden ornament, has peopled some European, and it is said American streams with this species. Canals of navigation and irrigation interchange the fish of lakes and rivers widely separated by natural barriers, as well as the plants which drop their seeds into the waters. The Erie Canal, as measured by its own channel, has a length of about three hundred and sixty miles, and it has ascending and descending locks in both directions. By this route, the fresh-water fish of the Hudson and the Upper Lakes, and some of the indigenous vegetables of these respective basins, have intermixed, and the fauna and flora of the two regions have now more species common to both than before the canal was opened. [Footnote: The opening or rather the reconstruction of the Claudian emissary by Prince Torlonia, designed to drain the Lake Fucinus, or Celano, has introduced the fish of that lake into the Liri or Garigliano which received the discharge from the lake.—Dorotea, Sommario storico dell' Alieutica, p. 60.]The opening of the Suez Canal will, no doubt, produce very interesting revolutions in the animal and vegetable population of both basins. The Mediterranean, with some local exceptions—such as the bays of Calabria, and the coast of Sicily so picturesquely described by Quatrefages [Footnote: Souvenire d'un Naturaliste, i., pp. 204 et seqq.]-is comparatively poor in marine vegetation, and in shell as well as in fin fish. The scarcity of fish in some of its gulfs is proverbial, and you may scrutinize long stretches of beach on its northern shores, after every south wind for a whole winter, without finding a dozen shells to reward your search. But no one who has not looked down into tropical or subtropical seas can conceive the amazing wealth of the Red Sea in organic life. Its bottom is carpeted or paved with marine plants, with zoophytes and with shells, while its waters are teeming with infinitely varied forms of moving life. Most of its vegetables and its animals, no doubt, are confined by the laws of their organization to a warmer temperature than that of the Mediterranean, but among them there must be many whose habitat is of a wider range, many whose powers of accommodation would enable them to acclimate themselves in a colder sea.
We may suppose the less numerous aquatic fauna and flora of the Mediterranean to be equally capable of climatic adaptation, and hence there will be a partial interchange of the organic population not already common to both seas. Destructive species, thus newly introduced, may diminish the numbers of their proper prey in either basin, and, on the other hand, the increased supply of appropriate food may greatly multiply the abundance of others, and at the same time add important contributions to the aliment of man in the countries bordering on the Mediterranean. [Footnote: The dissolution of the salts in the bed of the Bitter Lake impregnated the water admitted from the Red Sea so highly that for some time fish were not seen in that basin. The flow of the current through the canal has now reduced the proportion of saline matter to five per cent, and late travellers speak of fish as abundant in its waters.]
Some accidental attraction not unfrequently induces fish to follow a vessel for days in succession, and they may thus be enticed into zones very distant from their native habitat. Several years ago, I was told at Constantinople, upon good authority, that a couple of fish, of a species wholly unknown to the natives had just been taken in the Bosphorus. They were alleged to have followed an English ship from the Thames, and to have been frequently observed by the crew during the passage; but I was unable to learn their specific character. [Footnote: Seven or eight years ago, the Italian government imported from France a dredging machine for use in the harbor of La Spezia. The dredge brought attached to its hull a shell-fish not known in Italian waters. The mollusk, finding the local circumstances favorable, established itself in this new habitat, multiplied rapidly, and is now found almost everywhere on the west coast of the Peninsula.] Many of the fish which pass the greater part of the year in salt water spawn in fresh, and some fresh-water species, the common brook-trout of New England for instance, which under ordinary circumstances never visit the sea, will, if transferred to brooks emptying directly into the ocean, go down into the salt water after spawning-time, and return again the next season. Some sea fish have been naturalized in fresh water, and naturalists have argued from the character of the fish of Lake Baikal, and especially from the existence of the seal in that locality, that all its inhabitants were originally marine species, and have changed their habits with the gradual conversion of the saline waters of the lake-once, as is assumed, a maritime bay-into fresh. [Footnote: Babinet, Etudes et Lectures, ii, pp. 108,110.] The presence of the seal is hardly conclusive on this point, for it is sometimes seen in Lake Champlain at the distance of some hundreds of miles from even brackish water. One of these animals was killed on the ice in that lake in February, 1810, another in February, 1846, [Footnote: Thompson, Natural History of Vermont, p. 38, and Appendix, p. 18. There is no reason to believe that the seal breeds in Lake Champlain, but the individual last taken there must have been some weeks, at least, in its waters. It was killed on the ice in the widest part of the lake, on the 23d of February, thirteen days after the surface was entirely frozen, except the usual small cracks, and a month or two after the ice closed at all points north of the place where the seal was found.] and remains of the seal have been found at other times in the same waters.
The intentional naturalization of foreign fish, as I have said, has not thus far yielded important fruits; but though this particular branch of what is called, not very happily, pisciculture, has not yet established its claims to the attention of the physical geographer or the political economist, the artificial breeding of domestic fish, of the lobster and other crustacea, has already produced very valuable results, and is apparently destined to occupy an extremely conspicuous place in the history of man's efforts to compensate his prodigal waste of the gifts of nature. The arrangements for breeding fish in the Venetian lagoon of Comacchio date far back in the Middle Ages, but the example does not seem to have been followed elsewhere in Europe at that period, except in small ponds where the propagation of the fish was left to nature without much artificial aid. The transplantation of oysters to artificial ponds has long been common, and it appears to have recently succeeded well on a large scale in the open sea on the French coast. A great extension of this fishery is hoped for, and it is now proposed to introduce upon the same coast the American soft clam, which is so abundant in the tide-washed beach sands of Long Island Sound as to form an important article in the diet of the neighboring population. Experimental pisciculture has been highly successful in the United States, and will probably soon become a regular branch of rural industry, especially as Congress, at the session of 1871-2, made liberal provision for its promotion.
The restoration of the primitive abundance of salt and fresh water fish, is perhaps the greatest material benefit that, with our present physical resources, governments can hope to confer upon their subjects. The rivers, lakes, and seacoasts once restocked, and protected by law from exhaustion by taking fish at improper seasons, by destructive methods, and in extravagant quantities, would continue indefinitely to furnish a very large supply of most healthful food, which, unlike all domestic and agricultural products, would spontaneously renew itself and cost nothing but the taking. There are many sterile or wornout soils in Europe so situated that they might, at no very formidable cost, be converted into permanent lakes, which would serve not only as reservoirs to retain the water of winter rains and snow, and give it out in the dry season for irrigation, but as breeding ponds for fish, and would thus, without further cost, yield a larger supply of human food than can at present be obtained from them even at a great expenditure of capital and labor in agricultural operations. [Footnote: See Ackerhof, Die Nutzung der Seiche und Gewasser. Quedlinburg, 1860.] The additions which might be made to the nutriment of the civilized world by a judicious administration of the resources of the waters, would allow some restriction of the amount of soil at present employed for agricultural purposes, and a corresponding extension of the area of the forest, and would thus facilitate a return to primitive geographical arrangements which it is important partially to restore.
Destruction of Fish.
The inhabitants of the waters seem comparatively secure from human pursuit or interference by the inaccessibility of their retreats, and by our ignorance of their habits—a natural result of the difficulty of observing the ways of creatures living in a medium in which we cannot exist. Human agency has, nevertheless, both directly and incidentally, produced great changes in the population of the sea, the lakes, and the rivers, and if the effects of such revolutions in aquatic life are apparently of small importance in general geography, they are still not wholly inappreciable. The great diminution in the abundance of the larger fish employed for food or pursued for products useful in the arts is familiar, and when we consider how the vegetable and animal life on which they feed must be effected by the reduction of their numbers, it is easy to see that their destruction may involve considerable modifications in many of the material arrangements of nature. The whale [Footnote: I use WHALE not in a technical sense, but as a generic term for all the large inhabitants of the sea popularly grouped under that name. The Greek kaetos and Latin Balaena, though sometimes, especially in later classical writers, specifically applied to true cetaceans, were generally much more comprehensive in their signification than the modern word whale. This appears abundantly from the enumeration of the marine animals embraced by Oppian under the name <Greek: kaetos>, in the first book of the Halieutica.
There is some confusion in Oppian's account of the fishery of the <Greek: kaetos> in the fifth book of the Halieutica. Part of it is probably to be understood of cetaceans which have GROUNDED, as some species often do; but in general it evidently applies to the taking of large fish—sharks, for example, as appear by the description of the teeth—with hook and bait.] does not appear to have been an object of pursuit by the ancients, for any purpose, nor do we know when the whale fishery first commenced. It was, however, very actively prosecuted in the Middle Ages, and the Biscayans seem to have been particularly successful in this as indeed in other branches of nautical industry. [Footnote: From the narrative of Ohther, introduced by King Alfred into his translation of Orosius, it is clear that the Northmen pursued the whale fishery in the ninth century, and it appears, both from the poem called The Whale, in the Codex Exoniensis, and from the dialogue with the fisherman in the Colloquies of Aelfric, that the Anglo-Saxons followed this dangerous chore at a period not much later. I am not aware of any evidence to show that any of the Latin nationals engaged in this fishery until a century or two afterward, though it may not be easy to disprove their earlier participation in it. In mediaeval literature, Latin and Romance, very frequent mention is made of a species of vessel called in Latin baleneria, balenerium, balenerius, balaneria, etc.; in Catalan, balener; in French, balenier; all of which words occur the many other forms. The most obvious etymology of these words would suggest the meaning, whaler, baleinier; but some have supposed that the name was descriptive of the great size of the ships, and others have referred it to a different root. From the fourteenth century, the word occurs oftener, perhaps, in old Catalan, than in any other language; but Capmany does not notice the whale fishery as one of the maritime pursuits of the very enterprising Catalan people, nor do I find any of the products of the whale mentioned in the old Catalan tariffs. The WHALEBONE of the mediaeval writers, which is described as very white, is doubtless the ivory of the walrus or of the narwhale.] Five hundred years ago, whales abounded in every sea. They long since became so rare in the Mediterranean as not to afford encouragement for the fishery as a regular occupation; and the great demand for oil and whalebone for mechanical and manufacturing purposes, in the present century, has stimulated the pursuit of the "hugest of living creatures" to such activity, that he has now almost wholly disappeared from many favorite fishing grounds, and in others is greatly diminished in numbers.
What special functions, besides his uses to man, are assigned to the whale in the economy of nature, wo do not know; but some considerations, suggested by the character of the food upon which certain species subsist, deserve to be specially noticed. None of the great mammals grouped under the general name of whale are rapacious. They all live upon small organisms, and the most numerous species feed almost wholly upon thesoft gelatinous mollusks in which the sea abounds in all latitudes. We cannot calculate even approximately the number of the whales, or the quantity of organic nutriment consumed by an individual, and of course we can form no estimate of the total amount of animal matter withdrawn by them, in a given period, from the waters of the sea. It is certain, however, that it must have been enormous when they were more abundant, and that it is still very considerable. In 1846 the United States had six hundred and seventy-eight whaling ships chiefly employed in the Pacific, and the product of the American whale fishery for the year ending June 1st, 1860, was seven millions and a half of dollars. [Footnote: In consequence of the great scarcity of the whale, the use of coal-gas for illumination, the substitution of other fatty and oleaginous substances, such as lard, palm-oil, and petroleum for right-whale oil and spermaceti, the whale fishery has rapidly fallen off within a few years. The great supply of petroleum, which is much used for lubricating machinery as well as for numerous other purposes, has produced a more perceptible effect on the whale fishery than any other single circumstance. According to Bigelow, Les Etats-Unis en 1863, p. 346, the American whaling fleet was diminished by 29 in 1858, 57 in 1860, 94 in 1861, and 65 in 1862. The number of American ships employed in that fishery in 1862 was 353. In 1868, the American whaling fleet was reduced to 223. The product of the whale fishery in that year was 1,485,000 gallons of sperm oil, 2,065,612 gallons of train oil, and 901,000 pounds of whalebone. The yield of the two species of whale is about the same, being estimated at from 4,000 to 5,000 gallons for each fish. Taking the average at 4,500 gallons, the American whalers must have captured 789 whales, besides, doubtless, many which were killed or mortally wounded and not secured. The returns for the year are valued at about five million and a half dollars. Mr. Cutts, from a report by whom most of the above facts are taken, estimates the annual value of the "products of the sea" at $90,000,000.
According to the New Bedford Standard, the American whalers numbered 722, measuring 230,218 tons, in 1846. On the 31st December, 1872, the number was reduced to 204, with a tonnage of 47,787 tons, and the importation of whale and sperm oil amounted in that year to 79,000 barrels. Svend Foyn, an energetic Norwegian, now carries on the whale fishery in the Arctic Ocean in a steamer of 20 horse-power, accompanied by freight-ships for the oil. The whales are killed by explosive shells fired from a small cannon. The number usually killed by Foyn is from 35 to 45 per year.—The Commerce in the Products of the Sea, a report by Col. R. D. Cutts, communicated to the U. S. Senate. Washington, 1872.] The mere bulk of the whales destroyed in a single year by the American and the European vessels engaged in this fishery would form an island of no inconsiderable dimensions, and each one of those taken must have consumed, in the course of his growth, many times his own weight of mollusks. The destruction of the whales must have been followed by a proportional increase of the organisms they feed upon, and if we had the means of comparing the statistics of these humble forms of life, for even so short a period as that between the years 1760 and 1860, we should find a difference possibly sufficient to suggest an explanation of some phenomena at present unaccounted for. For instance, as I have observed in another work, [Footnote: The Origin and History of the English Language, &c., pp. 423, 424.] the phosphorescence of the sea was unknown to ancient writers, or at least scarcely noticed by them, and even Homer—who, blind as tradition makes him when he composed his epics, had seen, and marked, in earlier life, all that the glorious nature of the Mediterranean and its coasts discloses to unscientific observation—nowhere alludes to this most beautiful and striking of maritime wonders. In the passage just referred to, I have endeavored to explain the silence of ancient writers with respect to this as well as other remarkable phenomena on psychological grounds; but is it not possible that, in modern times, the animalculae which produce it may have immensely multiplied, from the destruction of their natural enemies by man, and hence that the gleam shot forth by their decomposition, or by their living processes, is both more frequent and more brilliant than in the days of classic antiquity?
Although the whale does not prey upon smaller creatures resembling himself in form and habits, yet true fishes are extremely voracious, and almost every tribe devours unsparingly the feebler species, and even the spawn and young of its own. [Footnote: Two young pickerel, Gystes fasciatus, five inches long, ate 128 minnows, an inch long, the first day they were fed, 132 the second, and 150 the third.—Fifth Report of Commissioners of Massachusetts for Introduction of Fish. 1871. p. 17.] The enormous destruction of the shark [Footnote: The shark is pursued in all the tropical and subtropical seas for its fins—for which there is a great demand in China as an article of diet—its oil and other products. About 40,000 are taken annually in the Indian Ocean and the contiguous seas. In the North Sea and the Arctic Ocean large numbers are annually caught. See MERK. Waarenlexikon—a work of great accuracy and value (Leipzig, 1870), article Haifisch.] the pike, the trout family, and other ravenous fish, as well as of the fishing birds, the seal, and the otter, by man, would naturally have occasioned a great increase in the weaker and more defenceless fish on which they feed, had he not been as hostile to them also as to their persecutors.
Destruction of Aquatic Animals.
It does not seem probable that man, with all his rapacity and all his enginery, will succeed in totally extirpating any salt-water fish, but he has already exterminated at least one marine warm-blooded animal—Steller's sea cow—and the walrus, the sea lion, and other large amphibia, as well as the principal fishing quadrupeds, are in imminent danger of extinction. Steller's sea cow, Rhytina Stelleri, was first seen by Europeans in the year 1741, on Bering's Island. It was a huge amphibious mammal, weighing not less than eight thousand pounds, and appears to have been confined exclusively to the islands and coasts in the neighborhood of Bering's Strait. Its flesh was very palatable, and the localities it frequented were easily accessible from the Russian establishments in Kamtschatka. As soon as its existence and character, and the abundance of fur animals in the same waters, were made known to the occupants of those posts by the return of the survivors of Bering's expedition, so active a chase was commenced against the amphibia of that region, that, in the course of twenty-seven years, the sea cow, described by Steller as extremely numerous in 1741, is believed to have been completely extirpated, not a single individual having been seen since the year 1768. The various tribes of seals [Footnote: The most valuable variety of fur seal, formerly abundant in all cold latitudes, is stated to have been completely exterminated in the Southern hemisphere, and to be now found only on one or two small islands of the Aleutian group. In 1867 more than 700,000 seal skins were imported into Great Britain, and at least 600,000 seals are estimated to have been taken in 1870. These numbers do not include the seals killed by the Esquimaux and other rude tribes.] in the Northern and Southern Pacific, the walrus [Footnote: In 1868, a few American ships engaged in the North Pacific whale fishery turned their attention to the walrus, and took from 200 to 600 each. In 1869 other whalers engaged in the same pursuit, and in 1870 the American fleet is believed to have destroyed not less than fifty thousand of these animals. They yield about twenty gallons of oil and four or five pounds of ivory each.] and the sea otter, are already so reduced in numbers that they seem destined soon to follow the sea cow, unless protected by legislation stringent enough, and a police energetic enough, to repress the ardent cupidity of their pursuers. The seals, the otter tribe, and many other amphibia which feed almost exclusively upon fish, are extremely voracious, and of course their destruction or numerical reduction must have favored the multiplication of the species of fish principally preyed upon by them. I have been assured by the keeper of several young seals that, if supplied at frequent intervals, each seal would devour not less than fourteen pounds of fish, or about a quarter of his own weight, in a day. A very intelligent and observing hunter, who has passed a great part of his life in the forest, after carefully watching the habits of the fresh-water otter of the North American States, estimates their consumption of fish at about four pounds per day. Man has promoted the multiplication of fish by making war on their brute enemies, but he has by no means thereby compensated his own greater destructiveness. [Footnote: According to Hartwig, the United Provinces of Holland had, in 1618, three thousand herring busses, and nine thousand vessels engaged in the transport of these fish to market. The whole number of persons employed in the Dutch herring fishery was computed at 200,000.
In the latter part of the eighteenth century, this fishery was most successfully prosecuted by the Swedes, and in 1781, the town of Gottenburg alone exported 136,649 barrels, each containing 1,200 herrings, making a total of about 164,000,000; but so rapid was the exhaustion of the fish, from this keen pursuit, that in 1799 it was found necessary to prohibit the exportation of them altogether.—Das Leben des Meeres, p. 182.
In 1855, the British fisheries produced 900,000 barrels, or almost enough to supply a fish to every human inhabitant of the globe.
On the shores of Long Island Sound, the white fish, a species of herring too bony to be easily eaten, is used as manure in very great quantities. Ten thousand are employed as a dressing for an acre, and a single net has sometimes taken 200,000 in a day.—Dwight's Travels, ii. pp. 512, 515. The London Times of May 11, 1872, informs us that 1,100 tons of mackerel estimated to weigh one pound each had recently been taken in a single night at a fishing station on the British coast.
About ten million eels are sold annually in Billingsgate market, but vastly greater numbers of the young fry, when but three or four inches long, are taken. So abundant are they at the mouths of many French and English rivers, that they are carried into the country by cart-loads, and not only eaten, but given to swine or used as manure.] The bird and beast of prey, whether on land or in the water, hunt only as long as they feel the stimulus of hunger, their ravages are limited by the demands of present appetite, and they do not wastefully destroy what they cannot consume. Man, on the contrary, angles to-day that he may dine to-morrow; he takes and dries millions of fish on the banks of Newfoundland and the coast of Norway, that the fervent Catholic of the shores of the Mediterranean may have wherewithal to satisfy the cravings of the stomach during next year's Lent, without violating the discipline of the papal church; [Footnote: The fisheries of Sicily alone are said to yield 20,000 tons of tunny a year. The tunny is principally consumed in Italy during Lent, and a large proportion of the twenty millions of codfish taken annually at the Lofoden fishery on the coast of Norway is exported to the Mediterranean.] and all the arrangements of his fisheries are so organized as to involve the destruction of many more fish than are secured for human use, and the loss of a large proportion of the annual harvest of the sea in the process of curing, or in transportation to the places of its consumption. [Footnote According to Berthelote, in the Gulf of Lyons, between Marseilles and the easternmost spur of the Pyrenees, about 5,000,000 small fish ate taken annually with the drag-net, and not lees than twice as many more, not to spekak of spawn, are destroyed by the use of this act.
Between 1861 and 1865 France imported from Norway, for use as bait in the Sardine fishery, cod-roes to the value of three million francs.—Cutts, Report on Commerce in the Products of the Sea, 1872, p. 82.
The most reckless waste of aquatic life I remember to have seen noticed, if we except the destruction of herring and other fish with upawn, is that of the eggs of the turtle in the Amazon for the sake of the oil extracted from then. Bates estimates the eggs thus annually sacrificed at 48,000,000.-Naturalits inthe Amazon, 2d edition, 1864, p. 805.] Fish are more affected than quadrupeds by slight and even imperceptible differences in their breeding places and feeding grounds. Every river, every brook, every lake stamps a special character upon its salmon, its shad, and its trout, which is at once recognized by those who deal in or consume them. No skill can give the fish fattened by food selected and prepared by man the flavor of those which are nourished at the table of nature, and the trout of the artificial pouds in Germany and Switzerland are so inferior to the brook-fish of the same species and climate, that it is hard to believe them identical. The superior sapidity of the American trout and other fresh-water fishes to the most nearly corresponding European species, which is familiar to every one acquainted with both continents, is probably due less to specific difference than to the fact that, even in the parts of the New World which have been longest cultivated, wild nature is not yet tamed down to the character it has assumed in the Old, and which it will acquire in America also when her civilization shall be as ancient as is now that of Europe. [Footnote: It is possible that time may modify the habits of the fresh-water fish the North American States, and accommodate them to the new physical conditions of their native waters. Hence it may be hoped that nature, even unaided by art, will do something towards restoring the ancient plenty of our lakes and rivers. The decrease of our fresh-water fish cannot be alone to exhaustion by fishing, for in the waters of the valleys and flanks of the Alps, which have been inhabited and fished ten times as long by a denser population, fish are still very abundant, and they thrive and multiply under circumstances where no American species could live at all. On the southern slope of those mountains, trout are caught in great numbers, in the swift streams which rush from the glaciers, and where the water is of icy coldness, and so turbid with particles of fine-ground rock, that you cannot see an inch below the surface. The glacier streams of Switzerland, however, are less abundant in fish.]
Man has hitherto hardly anywhere produced such climatic or other changes as would suffice of themselves totally to banish the wild inhabitants of the dry land, and thedisappearance of the native birds and quadrupeds from particular localities is to be ascribed quite as much to his direct persecutions as to the want of forest shelter, of appropriate food, or of other conditions indispensable to their existence. But almost all the processes of agriculture, and of mechanical and chemical industry, are fatally destructive to aquatic animals within reach of their influence. When, in consequence of clearing the woods, the changes already described as thereby produced in the beds and currents of rivers, are in progress, the spawning grounds of fish, are exposed from year to year to a succession of mechanical disturbances; the temperature of the water is higher in summer, colder in winter, than when it was shaded and protected by wood; the smaller organisms, which formed the sustenance of the young fry, disappear or are reduced in numbers, and new enemies are added to the old foes that preyed upon them; the increased turbidness of the water in the annual inundations chokes the fish; and, finally, the quickened velocity of its current sweeps them down into the larger rivers or into the sea, before they are yet strong enough to support so great a change of circumstances. [Footnote: A fact mentioned by Schubert—and which in its causes and many of its results corresponds almost precisely with those connected with the escape of Barton Pond in Vermont, so well known to geological students—is important, as showing that the diminution of the fish in rivers exposed to inundations is chiefly to be ascribed to the mechanical action of the current, and not mainly, as some have supposed, to changes of temperature occasioned by clearing.
Our author states that, in 1796, a terrible inundation was produced in the Indalself, which rises in the Storsjo in Jemtland, by drawing off into it the waters of another lake near Ragunda. The flood destroyed houses and fields; much earth was swept into the channel, and the water made turbid and muddy; the salmon and the smaller fish forsook the river altogether, and never returned. The banks of the river have never regained their former solidity, and portions of their soil are still continually falling into the water and destroying its purity.—Resa genom Sverge, ii, p. 61.] Industrial operations are not less destructive to fish which live or spawn in fresh water. Mill-dams impede their migrations, if they do not absolutely prevent them, the sawdust from lumber mills clogs their gills, and the thousand deleterious mineral substances, discharged into rivers from metallurgical, chemical, and manufacturing establishments, poison them by shoals. [Footnote: The mineral water discharged from a colliery on the river Doon in Scotland discolored the stones in the bed of the river, and killed the fish for twenty miles below. The fish of the streams in which hemp is macerated in Italy are often poisoned by the juices thus extracted from the plant.-Dorotea, Sommario della storia dell' Alieutica, pp. 64, 65.] We have little evidence that any fish employed as human food has naturally multiplied in modern times, while all the more valuable tribes have been immensely reduced in numbers. This reduction must have affected the more voracious species not used as food by man, and accordingly the shark, and other fish of similar habits, even when not objects of systematic pursuit, are now comparatively rare in many waters where they formerly abounded. The result is, that man has greatly reduced thenumbers of all larger marine animals, and consequently indirectly favored the multiplication of the smaller aquatic organisms which entered into their nutriment. This change in the relations of the organic and inorganic matter of the sea must have excercised an influence on the latter. What that influence has been we cannot say, still less can we predict what it will be hereafter; but its action is not for that reason the less certain. [Footnote: Among the unexpected results of human action, the destruction or multiplication of fish, as well as of other animals, is a not unfrequent occurrence. Footnote: Williams, in his History of Vermont, i., p. 140, records such a case of the increase of trout. In a pond formed by damming a small stream to obtain water power for a sawmill, and covering one thousand acres of primitive forest, the increased supply of food brought within reach of the fish multiplied them to that degree, that, at the head of the pond, where, in the spring, they crowded together in the brook which supplied it, they were taken by the hands at pleasure, and swine caught them without difficulty. A single sweep of a small scoopnet would bring up half a bushel, carts were filled with them as fast as if picked up on dry land, and in the fishing season they were commonly sold at a shilling (eightpence halfpenny, or about seventeen cents) a bushel. The increase in the size of the trout was as remarkable as the multiplication of their numbers.
The construction of dams and mills is destructive to many fish, but operates as a protection to their prey. The mills on Connecticut River greatly diminished the number of the salmon, but the striped bass, on which the salmon feeds, multiplied in proportion.—Dr. Dwight, Travels, vol. ii., p. 323.]
Geographical Importance of Birds.
Wild birds form of themselves a very conspicuous and interesting feature in the staffage, as painters call it, of the natural landscape, and they are important elements in the view we are taking of geography, whether we consider their immediate or their incidental influence. Birds affect vegetation directly by sowing seeds and by consuming them; they affect it indirectly by destroying insects injurious, or, in some cases, beneficial to vegetable life. Hence, when we kill a seed-sowing bird, we check the dissemination of a plant; when we kill a bird which digests the seed it swallows, we promote the increase of a vegetable. Nature protects the seeds of wild, much more effectually than those of domesticated plants. The cereal grains are completely digested when consumed by birds, but the germ of the smaller stone fruits and of very many other wild vegetables is uninjured, perhaps even stimulated to more vigorous growth, by the natural chemistry of the bird's stomach. The power of flight and the restless habits of the bird enable it to transport heavy seeds to far greater distances than they could be carried by the wind. A swift-winged bird may drop cherry stones a thousand miles from the tree they grow on; a hawk, in tearing a pigeon, may scatter from its crop the still fresh rice it had swallowed at a distance of ten degrees of latitude, and thus the occurrence of isolated plants in situations where their presence cannot otherwise well be explained, is easily accounted for. [Footnote: Pigeons were shot near Albany, in New York, a few years ago, with green rice in their crops, which it was thought must have been growing, a very few hours before, at the distance of seven or eight hundred miles. The efforts of the Dutch to confine the cultivation of the nutmeg to the island of Banda are said to have been defeated by the birds, which transported this heavy fruit to other islands.] There is a large class of seeds apparently specially fitted by nature for dissemination by animals. I refer to those which attach themselves, by means of hooks, or by viscous juices, to the coats of quadrupeds and the feathers of birds, and are thus transported wherever their living vehicles may chance to wander. Some birds, too, deliberately bury seeds in the earth, or in holes excavated by them in the bark of trees, not indeed with a foresight aiming directly at the propagation of the plant, but from apparently purposeless secretiveness, or as a mode of preserving food for future use.
The tame fowls play a much less conspicuous part in rural life than the quadrupeds, and, in their relations to the economy of nature, they are of very much less moment than four-footed animals, or than the undomesticated birds. The domestic turkey [Footnote: The wild turkey takes readily to the water, and is able to cross rivers of very considerable width by swimming. By way of giving me an idea of the former abundance of this bird, an old and highly respectable gentleman who was among the early white settlers of the West, told me that he once counted, in walking down the northern bank of the Ohio River, within a distance of four miles, eighty-four turkeys as they landed singly, or at most in pairs, after swimming over from the Kentucky side.] is probably more numerous in the territory of the United States than the wild bird of the same species ever was, and the grouse cannot, at the period of their greatest abundance, have counted as many as we now number of the common hen. The dove, however, must fall greatly short of the wild pigeon in multitude, and it is hardly probable that the flocks of domestic geese and ducks are as numerous as once wore those of their wild congeners. The pigeon, indeed, seems to have multiplied immensely, for some years after the first clearings in the woods, because the settlers warred unsparingly upon the hawk, while the crops of grain and other vegetable growths increased the supply of food within the reach of the young birds, at the age when their power of flight is not yet great enough to enable them to seek it over a wide area. [Footnote: The wood-pigeon, as well as the domestic dove, has been observed to increase in numbers in Europe also, when pains have been taken to exterminate the hawk. The American pigeons, which migrated in flocks so numerous that they were whole days in passing a given point, were no doubt injurious to the grain, but probably less so than is generally supposed; for they did not confine themselves exclusively to the harvests for their nourishment. ] The pigeon is not described by the earliest white inhabitants of the American States as filling the air with such clouds of winged life as astonished naturalists in the descriptions of Audubon, and, at the present day, the net and the gun have so reduced its abundance, that its appearance in large numbers is recorded only at long intervals, and it is never seen in the great flocks remembered by many still living observers as formerly very common.
INTRODUCTION OF BIRDS.
Man has undesignedly introduced into now districts perhaps fewer species of birds than of quadrupeds; [Footnote: The first mention I have found of the naturalization of a wild bird in modern Europe is in the Menagiana, vol. iii., p. 174, edition of 1715, where it is stated that Rene, King of Sicily and Duke of Anjou, who died in 1480, introduced the red-legged partridge into the latter country. Attempts have been made, and I believe with success, to naturalize the European lark on Long Island, and the English sparrow has been introduced into various parts of the Northern States, where he is useful by destroying noxious insects and worms not preyed upon by native birds. The humming-bird has resisted all efforts to acclimate him in Europe, though they have not unfrequently survived the passage across the ocean. In Switzerland and some other parts of Europe the multiplication of insectivorous birds is encouraged by building nests for them, and it is alleged that both fruit and forest trees have been essentially benefited by the protection thus afforded them.] but the distribution of birds is very much influenced by the character of his industry, and the transplantation, of every object of agricultural production is, at a longer or shorter interval, followed by that of the birds which feed upon its seeds, or more frequently upon the insects it harbors. The vulture, the crow, and other winged scavengers, follow the march of armies as regularly as the wolf. Birds accompany ships on long voyages, for the sake of the offal which is thrown overboard, and, in such cases, it might often happen that they would breed and become naturalized in countries where they had been unknown before. [Footnote: Gulls hover about ships in port, and often far out at sea, diligently watching for the waste of the caboose. While the four great fleets, English, French, Turkish, and Egyptian, were lying in the Bosphorus, in the summer and autumn of 1853, a young lady of my family called my attention to the fact that the gulls were far more numerous about the ships of one of the fleets than about the others. This was verified by repeated observation, and the difference was owing no doubt to the greater abundance of the refuse from the cookrooms of the naval squadron most frequented by the birds. Persons acquainted with the economy of the navies of the states in question, will be able to conjecture which fleet was most favored with these delicate attentions. The American gull follows the steamers up the Mississippi, and has been shot 1,500 miles from the sea.] There is a familiar story of an English bird which built its nest in an unused block in the rigging of a ship, and made one or two short voyages with the vessel while hatching its eggs. Had the young become fledged while lying in a foreign harbor, they would of course have claimed the rights of citizenship in the country where they first took to the wing. [Footnote: Birds do not often voluntarily take passage on board ships bound for foreign countries, but I can testify to one such case. A stork, which had nested near one of the palaces on the Bosphorus, had, by some accident, injured a wing, and was unable to join his fellows when they commenced their winter migration to the banks of the Nile. Before he was able to fly again, he was caught, and the flag of the nation to which the palace belonged was tied to his leg, so that he was easily identified at a considerable distance. As his wing grew stronger, he made several unsatisfactory experiments at flight, and at last, by a vigorous effort, succeeded in reaching a passing ship bound southward, and perched himself on a topsail-yard. I happened to witness this movement, and observed him quietly maintaining his position as long as I could discern him with a spy-glass. I supposed he finished the voyage, for he certainly did not return to the palace.]
An unfortunate popular error greatly magnifies the injury done to the crops of grain and leguminous vegetables by wild birds. Very many of those generally supposed to consume large quantities of the seeds of cultivated plants really feed almost exclusively upon insects, and frequent the wheatfields, not for the sake of the grain, but for the eggs, larvae, and fly of the multiplied tribes of insect life which are so destructive to the harvests. This fact has been so well established by the examination of the stomachs of great numbers of birds in Europe and the United States, at different seasons of the year, that it is no longer open to doubt, and it appears highly probable that even the species which consume more or less grain generally make amends by destroying insects whose ravages would have been still more injurious. [Footnote: Even the common crow has found apologists, and it has been asserted that he pays for the Indian corn he consumes by destroying the worms and larva which infest that plant.
Professor Treadwell, of Massachusetts, found that a half-grown American robin in confinement ate in one day sixty-eight worms, weighing together nearly once and a half as much as the bird himself, and another had previously starved upon a daily allowance of eight or ten worms, or about twenty per cent. of his own weight. The largest of these numbers appeared, so far as could be judged by watching parent birds of the same species, as they brought food to their young, to be much greater than that supplied to them when fed in the nest; for the old birds did not return with worms or insects oftener than once in ten minutes on an average. It we suppose the parents to hunt for food twelve hours in a day, and a nest to contain four young, we should have seventy-two worms, or eighteen each, as the daily supply of the brood. It is probable enough that some of the food collected by the parents may be more nutritious than the earthworms, and consequently that a smaller quantity sufficed for the young in the nest than when reared under artificial conditions.
The supply required by growing birds is not the measure of their wants after they have arrived at maturity, and it is not by any means certain that great muscular exertion always increases the demand for nourishment, either in the lower animals or in man. The members of the English Alpine Club are not distinguished for appetites which would make them unwelcome guests to Swiss landlords, and I think every man who has had the personal charge of field or railway hands, must have observed that laborers who spare their strength the least are not the most valiant trencher champions. During the period when imprisonment for debt was permitted in New England, persons confined in country jails had no specific allowance, and they were commonly fed without stint. I have often inquired concerning their diet, and been assured by the jailers that their prisoners, who were not provided with work or other means of exercise, consumed a considerably larger supply of food than common out-door laborers.] On this subject, we have much other evidence besides that derived from dissection. Direct observation has shown, in many instances, that the destruction of wild birds has been followed by a great multiplication of noxious insects, and, on the other hand, that these latter have been much reduced in numbers by the protection and increase of the birds that devour them. Many interesting facts of this nature have been collected by professed naturalists, but I shall content myself with a few taken from familiar and generally accessible sources. The following extract is from Michelet, L'Oiseau, pp. 169,170:
"The STINGY farmer—an epithet justly and feelingly bestowed by Virgil. Avaricious, blind, indeed, who proscribes the birds—those destroyers of insects, those defenders of his harvests. Not a grain for the creature which, during the rains of winter, hunts the future insect, finds out the nests of the larvae, examines, turns over every leaf, and destroys, every day, thousands of incipient caterpillars. But sacks of corn for the mature insect, whole fields for the grasshoppers, which the bird would have made war upon. With eyes fixed upon his furrow, upon the present moment only, without seeing and without foreseeing, blind to the great harmony which is never broken with impunity, he has everywhere demanded or approved laws for the extermination of that necessary ally of his toil—the insectivorous bird. And the insect has well avenged the bird. It has become necessary to revoke in haste the proscription. In the Isle of Bourbon, for instance, a price was set on the head of the martin; it disappeared, and the grasshopper took possession of the island, devouring, withering, scorching with a biting drought all that they did not consume. In North America it has been the same with the starling, the protector of Indian corn. [Footnote: I hope Michelet has good authority for this statement, but I am unable to confirm it.] Even the sparrow, which really does attack grain, but which protects it still more, the pilferer, the outlaw, loaded with abuse and smitten with curses—it has been found in Hungary that they were likely to perish without him, that he alone could sustain the mighty war against the beetles and the thousand winged enemies that swarm in the lowlands; they have revoked the decree of banishment, recalled in haste this valiant militia, which, though deficient in discipline, is nevertheless the salvation of the country. [Footnote: Apropos of the sparrow—a single pair of which, according to Michelet, p. 315, carries to the nest four thousand and three hundred caterpillar or coleoptera in a week—I find in an English newspaper a report of a meeting of a "Sparrow Club," stating that the member who took the first prize had destroyed 1,467 of these birds within the year, and that the prowess of the other members had brought the total number up to 11,944 birds, besides 2,553 eggs. Every one of the fourteen thousand hatched and unhatched birds, thus sacrificed to puerile vanity and ignorant prejudice, would have saved his bushel of wheat by preying upon insects that destroy the grain.]
"Not long since, in the neighborhood of Ronen and in the valley of Monville, the blackbird was for some time proscribed. The beetles profited well by this proscription; their larvae, infinitely multiplied, carried on their subterranean labors with such success, that a meadow was shown me, the surface of which was completely dried up, every herbaceous root was consumed, and the whole grassy mantle, easily loosened, might have been rolled up and carried away like a carpet."
The general hostility of the European populace to the smaller birds is, in part, the remote effect of the reaction created by the game laws. When the restrictions imposed upon the chase by those laws were suddenly removed in France, the whole people at once commenced a destructive campaign against every species of wild animal. Arthur Young, writing in Provence, on the 30th of August, 1789, soon after the National Assembly had declared the chase free, thus complains of the annoyance he experienced from the use made by the peasantry of their newly-won liberty. "One would think that every rusty firelock in all Provence was at work in the indiscriminate destruction of all the birds. The wadding buzzed by my ears, or fell into my carriage, five or six times in the course of the day." … "The declaration of the Assembly that every man is free to hunt on his own land … has filled all France with an intolerable cloud of sportsmen. … The declaration speaks of compensations and indemnities [to the seigneurs], but the ungovernable populace takes advantage of the abolition of the game laws and laughs at the obligation imposed by the decree."
The contagious influence of the French Revolution occasioned the removal of similar restrictions, with similar results, in other countries. The habits then formed have become hereditary on the Continent, and though game laws still exist in England, there is little doubt that the blind prejudices of the ignorant and half-educated classes in that country against birds are, in some degree, at least, due to a legislation, which, by restricting the chase of game worth killing, drives the unprivileged sportsman to indemnify himself by slaughtering all wild life which is not reserved for the amusement of his betters. Hence the lord of the manor buys his partridges and his hares by sacrificing the bread of his tenants, and so long as the members of "Sparrow Clubs" are forbidden to follow higher game, they will suicidally revenge themselves by destroying the birds which protect their wheatfields.
On the Continent, and especially in Italy, the comparative scarcity and dearness of animal food combine with the feeling I have just mentioned to stimulate still further the destructive passions of the fowler. In the Tuscan province of Grosseto, containing less than 2,000 square miles, nearly 300,000 thrushes and other small birds are annually brought to market. [Footnote: Salvagnoli, Memorie sulle Maremme Toscane, p. 143. The country about Naples is filled with slender towers fifteen or twenty feet high, which are a standing puzzle to strangers. They are the stations of the fowlers who watch from them the flocks of small birds and drive them down into the nets by throwing stones over them.
In Northern and Central Italy, one often sees hillocks crowned with grove-like plantations of small trees, much resembling large arbors. These serve to collect birds, which are entrapped in nets in great numbers. These plantatious are called ragnaje, and the reader will find, in Bindi's edition of Davanzati, a very pleasant description of a ragnaja, though its authorship is not now ascribed to that eminent writer. Tschudi has collected in his little work, Ueber die Landwirthschaftliche Bedeutung der Vogel, many interesting facts respecting the utility of birds, and, the wanton destruction of them in Italy and elsewhere. Not only the owl, but many other birds more familiarly known as predacious in their habits, are useful by destroying great numbers of mice and moles. The importance of this last service becomes strikingly apparent when it is known that the burrows of the moles are among the most frequent causes of rupture in the dikes of the Po, and, consequently, of inundations which lay many square miles of land under water. See Annales des Ponts et Chaussees, 1847, 1 semestre, p. 150; VOGT, Nutzliche und schadliche Thiere; and particularly articles in the Giornale del Club Alpino, vol. iv., no. 15, and vol. v., no. 16. See also in Aus der Natur, vol. 54, p. 707, an article entitled Nutzen der Vogel fur die Landwirthschaft, where it is affirmed that "without birds no agriculture or even vegetation would be possible." In an interesting memoir by Rondani, published in the Bolletino del Comizio agrario di Parma for December, 1868, it is maintained that birds are often injurious to the agriculturist, by preying not only on noxious insects, but sometimes exclusively, or at least by preference, on entomophagous tribes which would otherwise destroy those injurious to cultivated plants. See also articles by Prof. Sabbioni in the Giornale di Agricoltura di Bologna, November and December, 1870, and other articles in the same journal of 15th and 30th April, 1870.]
Birds are less hardy in constitution, they possess less facility of accommodation, [Footnote: Wild birds are very tenacious in their habits. The extension of particular branches of agriculture introduces new birds; but unless in the case of such changes in physical conditions, particular species seem indissolubly attached to particular localities. The migrating tribes follow almost undeviatingly the same precise line of flight in their annual journeys, and establish themselves in the same breeding-places from year to year. The stork is a strong-winged bird and roves far for food, but very rarely establishes new colonies. He is common in Holland, but unknown in England. Not above five or six pairs of storks commonly breed in the suburbs of Constantinople along the European shore of the narrow Bosphorous, while—much to the satisfaction of the Moslems, who are justly proud of the marked partiality of so orthodox a bird—dozens of chimneys of the true believers on the Asiatic side are crowned with his nests. The appearance of the dove-like grouse, Tetrao paradoxus, or Syrrhaptus Pallassi, in various parts of Europe, in 1850 and the following years, is a noticable exception to the law of regularity which seems to govern the movements and determine the habitat of birds. The proper home of this bird is the Steppes of Tartary, and it is no recorded to have been observed in Europe, or at least west of Russia, until the year above mentioned, when many flocks of twenty or thirty, and even a hundred individuals, were seen in Bohemia, Germany, Holland, Denmark, England, Ireland, and France. A considerable flock frequented the Frisian island of Borkum for more than five months. It was hoped that they would breed and remain permanently in the island but this expectation has now been disappointed, and the steppe-grouse seems to have disappeared again altogether.] and they are more severely affected by climatic excess than quadrupeds. Besides, they generally want the special means of shelter against the inclemency of the weather and against pursuit by their enemies, which holes and dens afford to burrowing animals and to some larger beasts of prey. The egg is exposed to many dangers before hatching, and the young bird is especially tender, defenceless, and helpless. Every cold rain, every violent wind, every hailstorm during the breeding season, destroys hundreds of nestlings, and the parent often perishes with her progeny while brooding over it in the vain effort to protect it. [Footnote: It is not the unfledged and the nursing bird alone that are exposed to destruction by severe weather. Whole flocks of adult and strong-winged tribes are killed by hail. Severe winters are usually followed by a sensible diminution in the numbers of the non-migrating birds, and a cold storm in summer often proves fatal to the more delicate species. On the 10th of June, 184-, five or six inches of snow fell in Northern Vermont. The next morning I found a hummingbird killed by the cold, and hanging by its claws just below a loose clapboard on the wall of a small wooden building where it had sought shelter.] The great proportional numbers of birds, their migratory habits, and the ease with which, by their power of flight they may escape most dangers that beset them, would seem to secure them from extirpation, and even from very great numerical reduction. But experience shows that when not protected by law, by popular favor or superstition, or by other special circumstances, they yield very readily to the hostile influences of civilization, and, though the first operations of the settler are favorable to the increase of many species, the great extension of rural and of mechanical industry is, in a variety of ways, destructive even to tribes not directly warred upon by man. [Footnote: Lyell, Antiquity of Man, p. 400, observes: "Of birds it is estimated that the number of those which die every year equals the aggregate number by which the species to which they respectively belong is, on the average, permanently represented." A remarkable instance of the influence of new circumstances upon birds was observed upon the establishment of a light-house on Cape Cod some years since. The morning after the lamps were lighted for the first time, more than a hundred dead birds of several different species, chiefly water-fowl, were found at the foot of the tower. They had been killed in the course of the night by flying against the thick glass or grating of the lantern. From an article by A. Esquiros, in the Revue des Deux Mondes for Sept. 1, 1864, entitled, La vie Anglaise, p. 110, it appears that such occurrences as that stated in the note have been not unfrequent on the British coast. Are the birds thus attracted by new lights, flocks in migration?
Migrating birds, whether for greater security from eagles, hawks, and other enemies, or for some unknown reason, perform a great part of their annual journeys by night; and it is observed in the Alps that they follow the high roads in their passage across the mountains. This is partly because the food in search of which they must sometimes descend is principally found near the roads. It is, however, not altogether for the sake of consorting with man, or of profiting by his labors, that their line of flight conforms to the paths he has traced, but rather because the great roads are carried through the natural depressions in the chain, and hence the birds can cross the summit by these routes without rising to a height where at the seasons of migration the cold would be excessive. The instinct which guides migratory birds in their course is not in all cases infallible, and it seems to be confounded by changes in the condition of the surface. I am familiar with a village in New England, at the junction of two valleys, each drained by a mill-stream, where the flocks of wild geese which formerly passed, every spring and autumn, were very frequently lost, as it was popularly phrased, and I have often heard their screams in the night as they flew wildly about in perplexity as to the proper course. Perhaps the village lights embarrassed them, or perhaps the constant changes in the face of the country, from the clearings then going on, introduced into the landscape features not according with the ideal map handed down in the anserine family, and thus deranged its traditional geography.]
Nature sets bounds to the disproportionate increase of birds, while at the same time, by the multitude of their resources, she secures them from extinction through her own spontaneous agencies. Man both preys upon them and wantonly destroys them. The delicious flavor of game-birds, and the skill implied in the various arts of the sportsman who devotes himself to fowling, make them favorite objects of the chase, while the beauty of their plumage, as a military and feminine decoration, threatens to involve the sacrifice of the last survivor of many once numerous species. Thus far, but few birds described by ancient or modern naturalists are known to have become absolutely extinct, though there are some cases in which they are ascertained to have utterly disappeared from the face of the earth in very recent times. The most familiar instances are those of the dodo, a large bird peculiar to the Mauritius or Isle of France, exterminated about the year 1690, and now known only by more or less fragmentary skeletons, and the solitary, which inhabited the islands of Bourbon and Rodriguez, but has not been seen for more than a century. A parrot and some other birds of the Norfolk Island group are said to have lately become extinct. The wingless auk, Alca impennis, a bird remarkable for its excessive fatness, was very abundant two or three hundred years ago in the Faroe Islands, and on the whole Scandinavian seaboard. The early voyagers found either the same or a closely allied species, in immense numbers, on all the coasts and islands of Newfoundland. The value of its flesh and its oil made it one of the most important resources of the inhabitants of those sterile regions, and it was naturally an object of keen pursuit. It is supposed to be now completely extinct, and few museums can show even its skeleton. There seems to be strong reason to believe that modern civilization is guiltless of one or two sins of extermination which have been committed in recent ages. Now Zealand formerly possessed several species of dinornis, one of which, called moa by the islanders, was larger than the ostrich. The condition in which the bones of these birds have been found and the traditions of the natives concur to prove that, though the aborigines had probably extirpated them before the discovery of New Zealand by the whites, they still existed at a comparatively late period. The same remarks apply to a winged giant the eggs of which have been brought from Madagascar. This bird must have much exceeded the dimensions of the moa, at least so far as we can judge from the egg, which is eight times as large as the average size of the ostrich egg, or about one hundred and fifty times that of the hen.
But though we have no evidence that man has exterminated many species of birds, we know that his persecutions have caused their disappearance from many localities where they once were common, and greatly diminished their numbers in others. The cappercailzie, Tetrao urogallus, the finest of the grouse family, formerly abundant in Scotland, had become extinct in Great Britain, but has been reintroduced from Sweden. [Footnote: Thecappercailzie, or tjader, as he is called in Sweden, is a bird of singular habits, and seems to want some of the protective instincts which secure most other wild birds from destruction. The younger Laestadius frequently notices the tjader, in his very remarkable account of the Swedish Laplanders. The tjader, though not a bird of passage, is migratory, or rather wandering in domicile, and appears to undertake very purposeless and absurd journeys. "When he flits," says Laestadius, "he follows a straight course, and sometimes pursues it quite out of the country. It is said that, in foggy weather, he sometimes flies out to sea, and, when tired, falls into the water and is drowned. It is accordingly observed that, when he flies westwardly, towards the mountains, he soon comes back again; but when he takes an eastwardly course, he returns no more, and for a long time is very scarce in Lapland. From this it would seem that he turns back from the bald mountains, when he discovers that he has strayed from his proper home, the wood; but when he finds himself over the Baltic, where he cannot alight to rest and collect himself, he flies on until he is exhausted and falls into the sea."—Petrus Laestadius, Journal of forsta aret, etc., p. 325.]
The ostrich is mentioned, by many old travellers, as common on the Isthmus of Suez down to the middle of the seventeenth century. It appears to have frequented Palestine, Syria, and even Asia Minor at earlier periods, but is now rarely found except in the seclusion of remoter deserts. [Footnote: Frescobaldi saw ostriches between Suez and Mt. Sinai. Viaggio in Terra Santa, p. 65. See also Vansler, Voyage d'Egypte, p. 103, and an article in Petermann, Mittheilungen, 1870, p. 880, entitled Die Verbreitung des Straussee in Asien.]
The modern increased facilities of transportation have brought distant markets within reach of the professional hunter, and thereby given a new impulse to his destructive propensities. Not only do all Great Britain and Ireland contribute to the supply of game for the British capital, but the canvas-back duck of the Potomac, and even the prairie hen from the basin of the Mississippi, may be found at the stalls of the London poulterer. Kohl [Footnote: Die Herzogthumer Schleswig und Holstein, i., p. 203.] informs us that, on the coasts of the North Sea, twenty thousand wild ducks are usually taken in the course of the season in a single decoy, and sent to the large maritime towns for sale. The statistics of the great European cities show a prodigious consumption of game-birds, but the official returns fall far below the truth, because they do not include the rural districts, and because neither the poacher nor his customers report the number of his victims. Reproduction, in cultivated countries, cannot keep pace with this excessive destruction, and there is no doubt that all the wild birds which are chased for their flesh or their plumage are diminishing with a rapidity which justifies the fear that the last of them will soon follow the dodo and the wingless auk.
Fortunately the larger birds which are pursued for their flesh or for their feathers, and those the eggs of which are used as food, are, so far as we know the functions appointed to them by nature, not otherwise specially useful to man, and, therefore, their wholesale destruction is an economical evil only in the same sense in which all waste of productive capital is an evil. [Footnote: The increased demand for animal oils for the use of the leather-dresses is now threatening the penguin with the fate of the wingless auk. According to the Report of the Agricultural Department of the U. S. for August and September, 1871, p. 840, small vessels are fitted out for the chase of this bird, and return from a six week's cruise with 25,000 or 30,000 gallons of oil. About eleven birds are required for a gallon, and consequently the vessels take upon an average 800,000 penguins each.]
If it were possible to confine the consumption of game-fowl to a number equal to the annual increase, the world would be a gainer, but not to the same extent as it would be by checking the wanton sacrifice of millions of the smaller birds, which are of no real value as food, but which, as we have seen, render a most important service by battling, in our behalf, as well as in their own, against the countless legions of humming and of creeping things, with which the prolific powers of insect life would otherwise cover the earth.
Utility and Destruction of Reptiles.
The disgust and fear with which the serpent is so universally regarded expose him to constant persecution by man, and perhaps no other animal is so relentlessly sacrificed by him. Nevertheless, snakes as well as lizards and other reptiles are not wholly useless to their great enemy. The most formidable foes of the insect, and even of the small rodents, are the reptiles. The chameleon approaches the insect perched upon the twig of a tree, with an almost imperceptible slowness of motion, until, at the distance of a foot, he shoots out his long, slimy tongue, and rarely fails to secure the victim. Even the slow toad catches the swift and wary housefly in the same manner; and in the warm countries of Europe, the numerous lizards contribute very essentially to the reduction of the insect population, which they both surprise in the winged state upon walls and trees, and consume as egg, worm, and chrysalis, in their earlier metamorphoses. The serpents feed much upon insects, as well as upon mice, moles, and small reptiles, including also other snakes.
In temperate climates, snakes are consumed by scarcely any beast or bird of prey except the stork, and they have few dangerous enemies but man, though in the tropics other animals prey upon them. [Footnote: It is very questionable whether there is any foundation for the popular belief in the hostility of swine and of deer to the rattlesnake, and careful experiments as to the former quadruped seem to show that the supposed enmity is wholly imaginary. It is however affirmed in an article in Nature, June 11, 1872, p. 215, that the pigs have exterminated the rattlesnake in some parts of Oregon, and that swine are destructive to the cobra de capello in India. Observing that the starlings, stornelli, which bred in an old tower in Piedmont, carried something from their nests and dropped it upon the ground about as often they brought food to their young, I watched their proceedings, and found every day lying near the tower numbers of dead or dying slowworms, and, in a few cases, small lizards, which had, in every Instance, lost about two inches of the tail. This part I believe the starlings gave to their nestlings, and threw away the remainder.] It is doubtful whether any species of serpent has been exterminated within the human period, and even the dense population of China has not been able completely to rid itself of the viper. They have, however, almost entirely disappeared from particular localities. The rattlesnake is now wholly unknown in many large districts where it was extremely common half a century ago, and Palestine has long been, if not absolutely free from venomous serpents, at least very nearly so. [Footnote: Russell denies the existence of poisonous snakes in Northern Syria, and states that the last instance of death known to have occurred from the bite of a serpent near Aleppo took place a hundred years before his time. In Palestine, the climate, the thinness of population, the multitude of insects and of lizards, all circumstances, in fact, seem very favorable to the multiplication of serpents, but the venomous species, at least, are extremely rare, if at all known, in that country. I have, however, been assured by persons very familiar with Mount Lebanon, that cases of poisoning from the bite of snakes had occurred within a few years, near Hasbeiyeh, and at other places on the southern declivities of Lebanon and Hermon. In Egypt, on the other hand, the cobra, the asp, and the cerastes are as numerous as ever, and are much dreaded by all the natives except the professional snake charmers.
The recent great multiplication of vipers in some parts of France is a singular and startling fact. Toussenel, quoting from official documents, states, that upon the offer of a reward of fifty centimes, or ten cents, a head, TWELVE THOUSAND vipers were brought to the prefect of a single department, and that in 1850 fifteen hundred snakes and twenty quarts of snakes' eggs were found under a farm-house hearthstone. The granary, the stables, the roof, the very beds swarmed with serpents, and the family were obliged to abandon its habitation. Dr. Viaugrandmarais, of Nantes, reported to the prefect of his department more than two hundred recent cases of viper bites, twenty-four of which proved fatal.—Tristia, p. 176 et seqq. According to the Journal del Debats for Oct. 1st, 1867, the Department of the Cote d'Or paid in the year 1866 eighteen thousand francs for the destruction of vipers. The reward was thirty centimes a head, and consequently the number killed was about sixty thousand. A friend residing in that department informs me that it was strongly suspected that many of these snakes were imported from other departments for the sake of the premium.
In Nature for 1870 and 1871 we are told that the number of deaths from the bites of venomous serpents in the Bengal Presidency, in the year 1869, was 11,416, and that in the whole of British India not less than 40,000 human lives are annually lost from this cause. In one small department, a reward of from three to six pence a head for poisonous serpents brought in 1,200 a day, and in two months the government paid L10,000 sterling for their destruction.] The serpent does not appear to have any natural limit of growth, and we are therefore not authorized wholly to discredit the evidence of ancient naturalists in regard to the extraordinary dimensions which those reptiles are said by them to have sometimes attained. The use of firearms has enabled man to reduce the numbers of the larger serpents, and they do not often escape him long enough to arrive at the size ascribed to them by travellers a century or two ago. Captain Speke, however, shot a serpent in Africa which measured fifty-one and a half feet in length.
Some enthusiastic entomologist will, perhaps, by and by discover that insects and worms are as essential as the larger organisms to the proper working of the great terraqueous machine, and we shall have as eloquent pleas in defence of the mosquito, and perhaps oven of the tzetze-fly, as Toussenel and Michelet have framed in behalf of the bird. The silkworm, the lac insect, and the bee need no apologist; a gallnut produced by the puncture of a cynips on a Syrian oak is a necessary ingredient in the ink I am writing with, and from my windows I recognize the grain of the kermes and the cochineal in the gay habiliments of the holiday groups beneath them.
These humble forms of being are seldom conspicuous by more mass, and though the winds and the waters sometimes sweep together large heaps of locusts and even of may-flies, their remains are speedily decomposed, their exuviae and their structures form no strata, and still less does nature use them, as she does the calcareous and silicious cases and dwellings of animalcular species, to build reefs and spread out submarine deposits, which subsequent geological action may convert into islands and even mountains. [Footnote: Although the remains of extant animals are rarely, if ever, gathered In sufficient quantities to possess any geographical importance by their mere mass, the decayed exuviae of even the smaller and humbler forms of life are sometimes abundant enough to exercise a perceptible influence on soil and atmosphere. "The plain of Cumana," saya Humboldt, "presents a remarkable phenomenon, after heavy rains. The moistened earth, when heated by the rays of the sun, diffuses the musky odor common in the torrid zone to animals of very different classes, to the jaguar, the small species of tiger-cat, the cabiai, the gallinazo vulture, the crocodile, the viper, and the rattlesnake. The gaseous emanations, the vehicles of this aroma, appear to be disengaged in proportion as the soil, which contains the remains of an innumerable multitude of reptiles, worms, and insects, begins to be impregnated with water. Wherever we stir the earth, we are struck with the mass of organic substances which in turn are developed and become transformed or decomposed. Nature in these climes seems more active, more prolific, and, so to speak, more prodigal of life."]
But the action of the creeping and swarming things of the earth, though often passed unnoticed, is not without important effects in the general economy of nature. The geographical importance of insects proper, as well as of worms, depends principally on their connection with vegetable life as agents of its fecundation, and of its destruction. We learn from Darwin, "On Various Contrivances by which British and Foreign Orchids are Fertilized by Insects," that some six thousand species of orchids are absolutely dependent upon the agency of insects for their fertilization, and that consequently, were those plants unvisited by insects, they would all rapidly disappear. What is true of the orchids is more or less true of many other vegetable families. [Footnote: Later observations of Darwin and other naturalists have greatly raised former estimates of the importance of insect life in the fecundation of plants, and among other remarkable discoveries it has been found that, in many cases at least, insects are necessary even to monoecious vegetables, because the male flower does not impregnate the female growing on the same stem, and the latter can be fecundated only by pollen supplied to it by insects from another plant of the same species.
"Who would ever have thought," says Preyer, "that the abundance and beauty of the pansy and of the clover were dependent upon the number of cats and owls But so it is. The clover and the pansy cannot exist without the bumble-bee, which, in search of his vegetable nectar, transports unconciously the pollen from the masculine to the feminine flower, a service which other insects perform only partially for these plants. Their existence therefore depends upon that of the bumble-bee. The mice make war upon this bee. In their fondness for honey they destroy the nest and at the same time the bee. The principal enemies of mice are cats and owls, and therefore the finest clovers and the most beautiful pansies are found near villages where cats and owls abound."—Preyer, Der Kampf um daas Dasein, p. 22. See also Delpino, Pensieri sulla biologia vegetale, and other works of the same able observer on vegetable physiology.]
We do not know the limits of this agency, and many of the insects habitually regarded as unqualified pests, may directly or indirectly perform functions as important to the most valuable plants as the services rendered by certain tribes to the orchids. I say directly or indirectly, because, besides the other arrangements of nature for chocking the undue multiplication of particular species, she has established a police among insects themselves, by which some of them keep down or promote the increase of others; for there are insects, as well as birds and beasts, of prey. The existence of an insect which fertilizes a useful vegetable may depend on that of another insect which constitutes his food in some stage of his life, and this other again may be as injurious to some plant as his destroyer is to a different species.
The ancients, according to Pliny, were accustomed to hang branches of the wild fig upon the domestic tree, in order that the insects which frequented the former might hasten the ripening of the cultivated fig by their punctures—or, as others suppose, might fructify it by transporting to it the pollen of the wild fruit—and this process, called caprification, is not yet entirely obsolete. [Footnote: The utility of caprification has been a good deal disputed, and it has, I believe, been generally abandoned in Italy, though still practised in Greece. See Browne, The Trees of America, p. 475, and on caprification in Kabylia, N. Bibesco, Les Kabyles du Djardjura, in Revue des Deux Mondes for April 1st, 1805, p. 580; also, Aus der Natur, vol. xxx., p. 684, and Phipson,
Utilization of Minute Life, p. 50. In some parts of Sicily, sprigs of mint, mentha pulegium, are used instead of branches of the wild for caprification. Pitre, Usi popolari Siciliani, 1871, p. 18.]
The perforations of the earthworms and of many insect larvae mechanically affect the texture of the soil and its permeability by water, and they therefore have a certain influence on the form and character of terrestrial surface. The earthworms long ago made good their title to the respect and gratitude of the farmer as well as of the angler. Their utility has been pointed out in many scientific as well as in many agricultural treatises. The following extract from an essay on this subject will answer my present purpose:
"Worms are great assistants to the drainer, and valuable aids to the fanner in keeping up the fertility of the soil. They love moist, but not wet soils; they will bore down to, but not into water; they multiply rapidly on land after drainage, and prefer a deeply-dried soil. On examining part of a field which had been deeply drained, after long-previous shallow drainage, it was found that the worms had greatly increased in number, and that their bores descended quite to the level of the pipes. Many worm-bores were large enough to receive the little finger. A piece of land near the sea, in Lincolnshire, over which the sea had broken and killed all the worms, remained sterile until the worms again inhabited it. A piece of pasture land, in which worms were in such numbers that it was thought their casts interfered too much with its produce, was rolled at night in order to destroy the worms. The result was, that the fertility of the field greatly declined, nor was it restored until they had recruited their numbers, which was aided by collecting and transporting multitudes of worms from the fields.
"The great depth into which worms will bore, and from which they push up fine fertile soil, and cast it on the surface, have been well shown by the fact that in a few years they have actually elevated the surface of fields by a largo layer of rich mould, several inches thick, thus affording nourishment to the roots of grasses, and increasing the productiveness of the soil."
It should be added that the writer quoted, and all others who have discussed the subject, have, so far as I know, overlooked one very important element in the fertilization produced by earthworms. I refer to the enrichment of the soil by their excreta during life, and by the decomposition of their remains when they die. Themanure thus furnished is as valuable as the like amount of similar animal products derived from higher organisms, and when we consider the prodigious numbers of these worms found on a single square yard of some soils, we may easily see that they furnish no insignificant contribution to the nutritive material required for the growth of plants. [Footnote: I believe there is no foundation for the supposition that earthworms attack the tuber of the potato. Some of them, especially one or two species employed by anglers as bait, if natives of the woods, are at least rare in shaded grounds, but multiply very rapidly after the soil is brought under cultivation. Forty or fifty years ago they were so scarce in the newer parts of New England, that the rustic fishermen of every village kept secret the few places where they were to be found in their neighborhood, as a professional mystery, but at present one can hardly turn over a shovelfull of rich moist soil anywhere, without unearthing several of them. A very intelligent lady, born in the woods of Northern New England, told me that, in her childhood, these worms were almost unknown in that region, though anxiously sought for by the anglers, but that they increased as the country was cleared, and at last became so numerous in some places, that the water of springs, and even of shallow wells, which had formerly been excellent, was rendered undrinkable by the quantity of dead worms that fell into them. The increase of the robin and other small birds which follow the settler when he has prepared a suitable home for them, at last checked the excessive multiplication of the worms, and abated the nuisance.]
The carnivorous and often herbivorous insects render another important service to man by consuming dead and decaying animal and vegetable matter, the decomposition of which would otherwise fill the air with effluvia noxious to health. Some of them, the grave-digger beetle, for instance, bury the small animals in which they lay their eggs, and thereby prevent the escape of the gases disengaged by putrefaction. The prodigious rapidity of development in insect life, the great numbers of the individuals in many species, and the voracity of most of them while in the larva state, justify the appellation of nature's scavengers which has been bestowed upon them, and there is very little doubt that, in warm countries, they consume a larger quantity of putrescent organic matter than the quadrupeds and birds which feed upon such aliment.
INJURY TO THE FOREST BY INSECTS.
The action of the insect on vegetation, as we have thus far described it, is principally exerted on smaller and less conspicuous plants, and it is therefore matter rather of agricultural than of geographical interest. But in the economy of the forest European writers ascribe to insect life an importance which it has not reached in America, where the spontaneous woods are protected by safeguards of nature's own devising.
The insects which damage primitive forests by feeding upon products of trees essential to their growth, are not numerous, nor is their appearance, in destructive numbers, frequent, and those which perforate the stems and branches, to deposit and hatch their eggs, more commonly select dead trees for that purpose, though, unhappily, there are important exceptions to this latter remark. [Footnote: The locust Insect, Clitus pictus, which deposits its eggs in the American locust, Robinia pseudacacia, is one of these, and its ravages have been and still are more destructive to that very valuable tree, so remarkable for combining rapidity of growth with strength and durability of wood. This insect, I believe, has not yet appeared in Europe, where, since the so general employment of the Robinia to clothe and protect embankments and the scarps of deep cuts on railroads, it would do incalculable mischief. As a traveller, however, I should find some compensation for this evil in the destruction of these acacia hedges, which as completely obstruct the view on hundreds of miles of French and Italian railways, as do the garden walls of the same countries on the ordinary roads.
The lignivorous insects that attack living trees almost uniformly confine their ravages to trees already unsound or diseased in growth from the depredations of leaf-eaters, such as caterpillars and the like, or from other causes. The decay of the tree, therefore, is the cause not the consequence of the invasions of the borer. This subject has been discussed by Perris in the Annales de la Societe Entomologique de la France for 1852, and his conclusions are confirmed by the observations of Samanos, who quotes, at some length, the views of Perris. "Having, for fifteen years," says the latter author, "incessantly studied the habits of lignivorous insects in one of the best wooded regions of France, I have observed facts enough to feel myself warranted in expressing my conclusions, which are: that insects in general—I am trees in sound health, and they assail those only whose normal conditions and functions have been by some cause impaired."
See, more fully, Samanos, Traite de la Culture du Pin Maritime, Paris, 1864, pp. 140-145, and Siemoni, Manuale dell' Arte Forestale. 2d edition. Florence, 1872.]
I do not know that we have any evidence of the destruction or serious injury of American forests by insects before or even soon after the period of colonization; but since the white man has laid bare a vast proportion of the earth's surface, and thereby produced changes favorable, perhaps, to the multiplication of these pests, they have greatly increased in numbers, and, apparently, in voracity also. Not many years ago, the pines on thousands of acres of land in North Carolina were destroyed by insects not known to have ever done serious injury to that tree before. In such cases as this and others of the like sort, there is good reason to believe that man is the indirect cause of an evil for which he pays so heavy a penalty. Insects increase whenever the birds which feed upon them disappear. Hence, in the wanton destruction of the robin and other insectivorous birds, the bipes implumis, the featherless biped, man, is not only exchanging the vocal orchestra which greets the rising sun for the drowny beetle's evening drone, and depriving his groves and his fields of their fairest ornament, but he is waging a treacherous warfare on his natural allies. [Footnote: In the artificial woods of Europe, insects are far more numerous and destructive to trees than in the primitive forests of America, and the same remark may be made of the smaller rodents, such as moles, mice, and squirrels. In the dense native wood, the ground and the air are too humid, the depth of shade too great, for many tribes of these creatures, while near the natural meadows and other open grounds, where circumstances are otherwise more favorable for their existence and multiplication, their numbers are kept down by birds, serpents, foxes, and smaller predacious quadrupeds. In civilized countries these natural enemies of the worm, the beetle, and the mole, are persecuted, sometimes almost exterminated, by man, who also removes from his plantations the decayed or wind-fallen trcea, the shrubs and underwood, which, in a state of nature, furnished food and shelter to the borer and the rodent, and often also to the animals that preyed upon them. Hence the insect and the gnawing quadruped are allowed to increase, from the expulsion of the police which, in the natural wood, prevent their excessive multiplication, and they become destructive to the forest because they are driven to the living tree for nutriment and cover. The forest of Fontainebleau is almost wholly without birds, and their absence is ascribed by some writers to the want of water, which, in the thirsty sands of that wood, does not gather into running brooks; but the want of undergrowth is perhaps an equally good reason for their scarcity.
On the other hand, the thinning out of the forest and the removal of underwood and decayed timber, by which it is brought more nearly to the condition of an artificial wood, is often destructive to insect tribes which, though not injurious to trees, are noxious to man. Thus the troublesome woodtick, formerly very abundant in the North Eastern, as it unhappily still is in native forests in the Southern and Western States, has become nearly or quite extinct in the former region since the woods have been reduced in extent and laid more open to the sun and air.—Asa Fitch, in Report of New York Agricultural Society for 1870, pp. 868,864.]
Introduction of Insects.
The general tendency of man's encroachments upon spontaneous nature has been to increase insect life at the expense of vegetation and of the smaller quadrupeds and birds. Doubtless there are insects in all woods, but in temperate climates they are comparatively few and harmless, and the most numerous tribes which breed in the forest, or rather in its waters, and indeed in all solitudes, are those which little injure vegetation, such as mosquitoes, gnats, and the like. With the cultivated plants of man come the myriad tribes which feed or breed upon them, and agriculture not only introduces new speciss, but so multiplies the number of individuals as to defy calculation. Newly introduced vegetables frequently escape for years the insect plagues which had infested them in their native habitat; but the importation of other varieties of the plant, the exchange of seed, or some more accident, is sure in the long run to carry the egg, the larva, or the chrysalis to the most distant shores where the plant assigned to it by nature as its possession has preceded it. For many years after the colonization of the United States, few or none of the insects which attack wheat in its different stages of growth, were known in America. During the Revolutionary war, the Hessian fly, Cecidomyia destructrix, made its appearance, and it was so called because it was first observed in the year when the Hessian troops were brought over, and was popularly supposed to have been accidentally imported by those unwelcome strangers. Other destroyers of cereal grains have since found their way across the Atlantic, and a noxious European aphis has first attacked the American wheatfields within the last fifteen years. Unhappily, in these cases of migration, the natural corrective of excessive multiplication, the parasitic or voracious enemy of the noxious insect, does not always accompany the wanderings of its prey, and the bane long precedes the antidote. Hence, in the United States, the ravages of imported insects injurious to cultivated crops, not being checked by the counteracting influences which nature had provided to limit their devastations in the Old World, are more destructive than in Europe. It is not known that the wheat midge is preyed upon in America by any other insect, and in seasons favorable to it, it multiplies to a degree which would prove almost fatal to the entire harvest, were it not that, in the great territorial extent of the United States, there is room for such differences of soil and climate as, in a given year, to present in one State all the conditions favorable to the increase of a particular insect, while in another, the natural influences are hostile to it. The only apparent remedy for this evil is, to balance the disproportionate development of noxious foreign species by bringing from their native country the tribes which prey upon them. This, it seems, has been attempted. The United States Census Report for 1860, p. 82, states that the New York Agricultural Society "has introduced into this country from abroad certain parasites which Providence has created to counteract the destructive powers of some of these depredators." [Footnote: On parasitic and entomophagous insects, see a paper by Rondani referred to p. 119 ante.]
This is, however, not the only purpose for which man has designedly introduced foreign forms of insect life. The eggs of the silkworm are known to have been brought from the farther East to Europe in the sixth century, and new silk-spinners which feed on the castor-oil bean and the ailanthus, have recently been reared in France and in South America with promising success. [Footnote: The silkworm which feeds on the ailanthus has naturalized itself in the United States, but also the promises of its utility have not been realized.] The cochineal, long regularly bred in aboriginal America, has been transplanted to Spain, and both the kermes insect and the cantharides have been transferred to other climates than their own. The honey—bee must be ranked next to the silkworm in economical importance. This useful creature was carried to the United States by European colonists, in the latter part of theseventeenth century; it did not cross the Mississippi till the close of the eighteenth, and it is only in 1853 that it was transported to California, where it was previously unknown. The Italian bee, which seldom stings, has lately been introduced into the United States. [Footnote: Bee husbandry, now very general in Switzerland and other Alpine regions, was formerly an important branch of industry in Italy. It has lately been revived and is now extensively prosecuted it that country. It is interesting to observe that many of the methods recently introduced into this art in England and United States, such for example as the removable honey—boxes, are reinventions of Italian systeams at least three hundred years old. See Gallo, Le Venti Giornate dell' Agricultura, cap. XV. The temporary decline of this industry in Italy was doubtless in great measure due to the use of sugar which had taken the place of honed, but perhaps also in part to the decrease of the wild vegetation from which the bee draws more or less of his nutriment. A new was-producing insect, a species of coccus, very abundant in China, where its annual produce is said to amount to the value of ten millions of francs, has recently attracted notice in France. The wax is white, resembling spermaceti, and is said to be superior to that of the bee.]
The insects and worms intentionally transplanted by man bear but a small portion to those accidentally introduced by him. Plants and animals often carry their parasites with them, and the traffic of commercial countries, which exchange their products with every zone and every stage of social existence, cannot fail to transfer in both directions the minute organisms that are, in one way or another associated with almost every object important to the material interests of man. [Footnote: A few years ago, a laborer, employed at a North American port in discharging a cargo of hides from the opposite extremity of the continent, was fatally poisoned by the bite or the sting of an unknown insect, which ran out from a hide he was handling.
The Phylloxera vastatrix, the most destructive pest which has ever attacked European vineyards—for its ravages are fatal not merely to the fruit, but to the vine itself—in said by many entomologists to be of American origin, but I have seen no account of the mode of its introduction.]
The tenacity of life possessed by many insects, their prodigious fecundity, the length of time they often remain in the different phases of their existence, [Footnote: In many insects, some of the stages of life regularly continue for several years, and they may, under peculiar circumstances, be almost indefinitely prolonged. Dr. Dwight mentions the following remarkable case of this sort: "I saw here an insect, about an inch in length, of a brown color tinged with orange, with two antennae, not unlike a rosebug. This insect came out of a tea-table made of the boards of an apple-tree." Dr. Dwight found the "cavity whence the insect had emerged into the light," to be "about two inches in length. Between the hole, and the outside of the leaf of the table, there were forty grains of the wood." It was supposed that the sawyer and the cabinet-maker must have removed at least thirteen grains more, and the table had been in the possession of its proprietor for twenty years.] the security of the retreats into which their small dimensions enable them to retire, are all circumstances very favorable not only to the perpetuity of their species, but to their transportation to distant climates and their multiplication in their new homes. The teredo, so destructive to shipping, has been carried by the vessels whose wooden walls it mines to almost every part of the globe. The termite, or white ant, is said to have been brought to Rochefort by the commerce of that port a hundred years ago. [Footnote: It does not appear to be quite settled whether the termites of France are indigenous or imported. See Quatrefaces, Souvenirs d'un naturaliste, ii., pp. 400, 542, 543.
The white ant has lately appeared at St. Helena and is in a high degree destructive, no wood but teak, and even that not always, resisting it.—Nature for March 2d, 1871, p. 362.] This creature is more injurious to wooden structures and implements than any other known insect. It eats out almost the entire substance of the wood, leaving only thin partitions between the galleries it excavates in it; but as it never gnaws through the surface to the air, a stick of timber may be almost wholly consumed without showing any external sign of the damage it has sustained. The termite is found also in other parts of France, and particularly at Rochelle, where, thus far, its ravages are confined to a single quarter of the city. A borer, of similar habits, is not uncommon in Italy, and you may see in that country handsome chairs and other furniture which have been reduced by this insect to a framework of powder of post, covered, and apparently held together, by nothing but the varnish.
DESTRUCTION OF INSECTS.
It is well known to naturalists, but less familiarly to common observers, that the aquatic larvae of some insects which in other stages of their existence inhabit the land, constitute, at certain seasons, a large part of the food of fresh-water fish, while other larvae, in their turn, prey upon the spawn and even the young of their persecutors. [Footnote: I have seen the larva of the dragon-fly in an aquarium bite off the head of a young fish as long as itself.] The larvae of the mosquito and the gnat are the favorite food of the trout in the wooded regions where those insects abound. [Footnote: Insects and fish—which prey upon and feed each other—are the only forms of animal life that are numerous in the native woods, and their range is, of course, limited by the extent of the waters. The great abundance of the trout, and of other more or less allied genera in the lakes of Lapland, seems to be due to the supply of food provided for them by the swarms of insects which in the larva state inhabit the waters, or, in other stages of their life, are accidentally swept into them. All travellers in the north of Europe speak of the gnat and the mosquito as very serious drawbacks upon the enjoyments of the summer tourist, who visits the head of the Gulf of Bothnia to see the midnight sun, and the brothers Laestadius regard them as one of the great plagues of sub-arctic life. "The persecutions of these insects," says Lars Levi Laestadius [Culex pipiens, Culex reptans, and Culex pulicaris], "leave not a moment's peace, by day or night, to any living creature. Not only man, but cattle, and even birds and wild beasts, suffer intolerably from their bite." He adds in a note, "I will not affirm that they have ever devoured a living man, but many young cattle, such as lambs and calves, have been worried out of their lives by them. All the people of Lapland declare that young birds are killed by them, and this is not improbable, for birds are scarce after seasons when the midge, the gnlat, and the mosquito are numerous."—Om Uppodlingar i Lappmarken, p. 50.
Petrus Laestadius makes similar statements in his Journal for forsta urst, p. 283.]
Earlier in the year the trout feeds on the larvae of the May fly, which is itself very destructive to the spawn of the salmon, and hence, by a sort of house-that-Jack-built, the destruction of the mosquito, that feeds the trout that preys on the May fly that destroys the eggs that hatch the salmon that pampers the epicure, may occasion a scarcity of this latter fish in waters where he would otherwise be abundant. Thus all nature is linked together by invisible bonds, and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life with which the Creator has peopled the earth.
I have said that man has promoted the increase of the insect and the worm, by destroying the bird and the fish which feed upon them. Many insects, in the four different stages of their growth, inhabit in succession the earth, the water, and the air. In each of these elements they have their special enemies, and, deep and dark as are the minute recesses in which they hide themselves, they are pursued to the remotest, obscurest corners by the executioners that nature has appointed to punish their delinquencies, and furnished with cunning contrivances for ferreting out the offenders and dragging them into the light of day. One tribe of birds, the woodpeckers, seems to depend for subsistence almost wholly on those insects which breed in dead or dying trees, and it is, perhaps, needless to say that the injury these birds do the forest is imaginary. They do not cut holes in the trunk of the tree to prepare a lodgment for a future colony of boring larvae, but to extract the worm which has already begun his mining labors. Hence these birds are not found where the forester removes trees as fast as they become fit habitations for such insects. In clearing new lands in the United States, dead trees, especially of the spike-leaved kinds, too much decayed to serve for timber, and which, in that state, are worth little for fuel, are often allowed to stand until they fall of themselves. Such stubs, as they are popularly called, are filled with borers, and often deeply cut by the woodpeckers, whose strong bills enable them to penetrate to the very heart of the tree and drag out the lurking larvae. After a few years, the stubs fall, or, as wood becomes valuable, are cut and carried off for firewood, and, at the same time, the farmer selects for felling, in the forest he has reserved as a permanent source of supply of fuel and timber, the decaying trees which, like the dead stems in the fields, serve as a home for both the worm and his pursuer. We thus gradually extirpate this tribe of insects, and, with them, the species of birds which subsist principally upon them. Thus the fine, large, red-headed woodpecker, Picus erythrocephalus, formerly very common in New England, has almost entirely disappeared from those States, since the dead trees are gone, and the apples, his favorite vegetable food, are less abundant.
There are even large quadrupeds which feed almost exclusively upon insects. The ant-bear is strong enough to pull down the clay houses built by the species of termites that constitute his ordinary diet, and the curious ai-ai, a climbing quadruped of Madagascar, is provided with a very slender, hook-nailed finger, long enough to reach far into a hole in the trunk of a tree, and extract the worm which bored it. [Footnote: On the destruction of insects by reptiles, see page 125 ante.]
Minute Organisms.
Besides the larger inhabitants of the land and of the sea, the quadrupeds, the reptiles, the birds, the amphibia, the crustacea, the fish, the insects, and the worms, there are other countless forms of vital being. Earth, water, the ducts and fluids of vegetable and of animal life, the very air we breathe, are peopled by minute organisms which perform most important functionsin both the living and the inanimate kingdoms of nature. Of the offices assigned to these creatures, the most familiar to common observation is the extraction of lime, and, more rarely, of silex, from the waters inhabited by them, and the deposit of these minerals in a solid form, either as the material of their habitations or as the exuviae of their bodies. The microscope and other means of scientific observation assure us that the chalk-beds of England and of France, the coral reefs of marine waters in warm climates, vast calcareous and silicious deposits in the sea and in many fresh-water ponds, the common polishing earths and slates, and many species of apparently dense and solid rock, are the work of the humble organisms of which I speak, often, indeed, of animaculae so small as to become visible only by the aid of lenses magnifying thousands of times the linear measures. It is popularly supposed that animalculae, or what are commonly embraced under the vague name of infusoria, inhabit the water alone, but naturalists have long known that the atmospheric dust transported by every wind and deposited by every calm is full of microscopic life or of its relics. The soil on which the city of Berlin stands, contains, at the depth of ten or fifteen feet below the surface, living elaborators of silex; [Footnote: Wittwer, Physikalische Geographie, p. 142.] and a microscopic examination of a handful of earth connected with the material evidences of guilt has enabled the naturalist to point out the very spot where a crime was committed. It has been computed that one-sixth part of the solid matter let fall by great rivers at their outlets consists of still recognizable infusory shells and shields, and, as the friction of rolling water must reduce many of these fragile structures to a state of comminution which even the microscope cannot resolve into distinct particles and identify as relics of animal or of vegetable life, we must conclude that a considerably larger proportion of river deposits is really the product of animalcules. [Footnote: To vary the phrase, I make occasional use of animaloule, which, as a popular designation, embraces all microscopic organisms. The name is founded on the now exploded supposition that all of them are animated, which was the general belief of naturalists when attention was first drawn to them. It was soon discovered that many of them were unquestionably vegetable, and there are numerous genera the true classification of which is a matter of dispute among the ablest observers. There are cases in which objects formerly taken for living animalcules turn out to be products of the decomposition of matter once animated, and it is admitted that neither spontaneous motion nor even apparent irritability are sure signs of animal life.]
It is evident that the chemical, and in many cases mechanical, character of a great number of the objects important in the material economy of human life, must be affected by the presence of so large an organic element in their substance, and it is equally obvious that all agricultural and all industrial operations tend to disturb the natural arrangements of this element, to increase or to diminish the special adaptation of every medium in which it lives to the particular orders of being inhabited by it. The conversion of woodland into pasturage, of pasture into plough land, of swamp or of shallow sea into dry ground, the rotations of cultivated crops, must prove fatal to millions of living things upon every rood of surface thus deranged by man, and must, at the same time, more or less fully compensate this destruction of life by promoting the growth and multiplication of other tribes equally minute in dimensions. I do not know that man has yet endeavored to avail himself, by artificial contrivances, of the agency of these wonderful architects and manufacturers. We are hardly well enough acquainted with their natural economy to devise means to turn their industry to profitable account, and they are in very many cases too slow in producing visible results for an age so impatient as ours. The over-civilization of the nineteenth century cannot wait for wealth to be amassed by infinitesimal gains, and we are in haste to SPECULATE upon the powers of nature, as we do upon objects of bargain and sale in our trafficking one with another. But there are still some cases where the little we know of a life, whose workings are invisible to the naked eye, suggests the possibility of advantageously directing the efforts of troops of artisans that we cannot see. Upon coasts occupied by the corallines, the reef-building animalcule does not work near the mouth of rivers. Hence the change of the outlet of a stream, often a very busy matter, may promote the construction of a barrier to coast navigation at one point, and check the formation of a reef at another, by diverting a current of fresh water from the former and pouring it into the sea at the latter. Cases may probably be found, in tropical seas, where rivers have prevented the working of the coral animalcules in straits separating islands from each other or from the mainland. The diversion of such streams might remove this obstacle, and reefs consequently be formed which should convert an archipelago into a single large island, and finally join that to the neighboring continent. Quatrefages proposed to destroy the teredo in harbors by impregnating the water with a mineral solution fatal to them. Perhaps the labors of the coralline animals might be arrested over a considerable extent of sea-coast by similar means. The reef-builders are leisurely architects, but the precious coral is formed so rapidly that the beds may be refished advantageously as often as once in ten years. [Footnote: The smallest twig of the precious coral thrown back into the sea attaches itself to the bottom or a rock, and grows as well as on its native stem. See an interesting report on the coral fishery, by Sant' Agabio, Italian Consul-General at Algiers, in the Bollettino Consolare, published by the Department of Foreign Affairs, 1862, pp. 139, 151, and in the Annali di Agricoltura Industria e Commercio, No. ii., pp. 300, 373.]
It does not seem impossible that branches of this coral might be attached to the keel of a ship and transplanted to the American coast, where the Gulf stream would furnish a suitable temperature beyond the climatic limits that otherwise confine its growth; and thus a new source of profit might perhaps be added to the scanty returns of the hardy fisherman. In certain geological formations, the diatomaceae deposit, at the bottom of fresh-water ponds, beds of silicious shields, valuable as a material for a species of very light firebrick, in the manufacture of water-glass and of hydraulic cement, and ultimately, doubtless, in many yet undiscovered industrial processes. An attentive study of the conditions favorable to the propagation of the diatomaceae might perhaps help us to profit directly by the productivity of this organism, and, at the same time, disclose secrets of nature capable of being turned to valuable account in dealing with silicious rocks, and the metal which is the base of them.
Our acquaintance with the obscure and infinitesimal life of which I have now been treating is very recent, and still very imperfect. We know that it is of vast importance in geology, but we are so ambitious to grasp the great, so little accustomed to occupy ourselves with the minute, that we are not yet prepared to enter seriously upon the question how far we can control and utilize the operations, not of unembodied physical forces merely, but of beings, in popular apprehension, almost as immaterial as they.
Disturbance of Natural Balances.
It is highly probable that the reef-builders and other yet unstudied minute forms of vital existence have other functions in the economy of nature besides aiding in the architecture of the globe, and stand in important relations not only to man but to the plants and the larger sentient creatures over which he has dominion. The diminution or multiplication of these unseen friends or foes may be attended with the gravest consequences to all his material interests, and he is dealing with dangerous weapons whenever he interferes with arrangements pre-established by a power higher than his own. The equation of animal and vegetable life is too complicated a problem for human intelligence to solve, and we can never know how wide a circle of disturbance we produce in the harmonics of nature when we throw the smallest pebble into the ocean of organic being. This much, however, the facts I have hitherto presented authorize us to conclude: as often as we destroy the balance by deranging the original proportions between different orders of spontaneous life, the law of self-preservation requires us to restore the equilibrium, by either directly returning the weight abstracted from one scale, or removing a corresponding quantity from the other. In other words, destruction must be either repaired by reproduction, or compensated by new destruction in an opposite quarter. The parlor aquarium has taught even those to whom it is but an amusing toy, that the balance of animal and vegetable life must be preserved, and that the excess of either is fatal to the other, in the artificial tank as well as in natural waters. A few years ago, the water of the Cochituato aqueduct at Boston became so offensive in smell and taste as to be quite unfit for use. Scientific investigation found the cause in the too scrupulous care with which aquatic vegetation had been excluded from the reservoir, and the consequent death and decay of the animalculae, which could not be shut out, nor live in the water without the vegetable element. [Footnote: It is remarkable that Pulisay, to whose great merits as an acute observer I am happy to have frequent occasion to bear testimony, had noticed that vegetation was necessary to maintain the purity of water in artificial reservoirs, though he mistook the rationale of its influence, which he ascribed to the elemental "salt" supposed by him to play an important part in all the operations of nature. In his treatise upon Waters and Fountains, p. 174, of the reprint of 1844, he says: "And in special, thou shalt note one point, the which is understood of few: that is to say, that the leaves of the trees which fall upon the parterre, and the herbs growing beneath, and singularly the fruits, if any there be upon the trees, being decayed, the waters of the parterre shall draw onto them the salt of the said fruits, leaves, and herbs, the which shall greatly better the water of thy fountains, and hinder the putrefaction thereof."]
Animalcular Life.
Nature has no unit of magnitude by which she measures her works. Man takes his standards of dimension from himself. The hair's breadth was his minimum until the microscope told him that there are animated creatures to which one of the hairs of his head is a larger cylinder than is the trunk of the giant California sequoia to him. He borrows his inch from the breadth of his thumb, his palm and span from the width of his hand and the spread of his fingers, his foot from the length of the organ so named; his cubit is the distance from the tip of his middle finger to his elbow, and his fathom is the space he can measure with his outstretched arms. [Footnote: The French metrical system seems destined to be adopted throughout the civilized world. It is indeed recommended by great advantages, but it is very doubtful whether they are not more than counterbalanced by the selection of too large a unit of measure, and by the inherent intractability of all decimal systems with reference to fractional divisions. The experience of the whole world has established the superior convenience of a smaller unit, such as the braccio, the cubit, the foot, and the palm or span, and in practical life every man finds that he haa much more frequent occasion to use a fraction than a multiple of the metre. Of course, he must constantly employ numbers expressive of several centimetres or millimetres instend of the name of a single smaller unit than the metre. Besides, the metre is not divisible into twelfths, eighths, sixths, or thirds, or the multiples of any of these proportions, two of which at least—the eighth and the third—are of as frequent use as any other fractions. The adoption of a fourth of the earth's circumference as a base for the new measures was itself a departure from the decimal system. Had the Commissioners taken the entire circumference as a base, and divided it into 100,000,000 instead of 10,000,000 parts, we should have had a unit of about sixteen inches, which, as a compromise between the foot and the cubit, would have been much better adapted to universal use than so large a unit as the metre.] To a being who instinctively finds the standard of all magnitudes in his own material frame, all objects exceeding his own dimensions are absolutely great, all falling short of them absolutely small. Hence we habitually regard the whale and the elephant as essentially large and therefore important creatures, the animalcule as an essentially small and therefore unimportant organism. But no geological formation owes its origin to the labors or the remains of the huge mammal, while the animalcule composes, or has furnished, the substance of strata thousands of feet in thickness, and extending, in unbroken beds, over many degrees of terrestrial surface. If man is destined to inhabit the earth much longer, and to advance in natural knowledge with the rapidity which has marked his progress in physical science for the last two or three centuries, he will learn to put a wiser estimate on the works of creation, and will derive not only great instruction from studying the ways of nature in her obscurest, humblest walks, but great material advantage from stimulating her productive energies in provinces of her empire hitherto regarded as forever inaccessible, utterly barren. [Footnote: The fermentation of liquids, and in many cases the decomposition of semi-solids, formerly supposed to be owing purely to chemical action, are now ascribed by many chemists to vital processes of living minute organisms, both vegetable and animal, and consequently to physiological as well as to chemical forces. Even alcohol is stated to be an animal product. The whole subject of animalcular, or rather minute organic, life, has assumed a now and startling importance from the recent researches of naturalists and physiologists, in the agency of such life, vegetable or animal, in exciting and communicating contagious diseases, and it is extremely probable that what are vaguely called germs, to whichever of the organic kingdoms they may be assigned, creatures inhabiting various media, and capable of propagating their kind and rapidly multiplying, are the true seeds of infection and death in the maladies now called zymotic, as well perhaps as in many others.
The literature of this subject is now very voluminous. For observations with high microscopic power on this subject, see Beale, Disease Germs, their supposed Nature, and Disease Germs, their real Nature, both published in London in 1870.
The increased frequency of typhoidal, zymotic, and malarious diseases in some parts of the United States, and the now common occurrence of some of them in districts where they were unknown forty years ago, are startling facts, and it is a very interesting question how far man's acts or neglects may have occasioned the change. See Third Anual Report of Massachusetts State Board of Health for 1873. The causes and remedies of the insalubrity of Rome and its environs have been for some time the object of careful investigation, and many valuable reports have been published on the subject. Among the most recent of these are: Relazione sulle condizioni agrarie ed igieniche della Campagna di Roma, per Raffaele Pareto; Cenni Storici sulla questione dell' Agro Romano di G. Guerzoni; Cenni sulle condizioni Fisico-economiche di Roma per F. Giordano; and a very important paper in the journal Lo Sperimentale for 1870, by Dr. D. Pantaleoni.
There are climates, parts of California, for instance, where the flesh of dead animals, freely exposed, shows no tendency to putrefaction but dries up and may be almost indefinitely preserved in this condition. Is this owing to the absence of destructive animalcular life in such localities, and has man any agency in the introduction and naturalization of these organisms in regions previously not infested by them ]
CHAPTER III.
THE WOODS.
The habitable earth originally wooded—General meteorological influence of the forest—Electrical action of trees—Chemical influence of woods—Trees as protection against malaria—Trees as shelter to ground to the leeward—Influence of the forest as inorganic on temperature—Thermometrical action of trees as organic—Total influence of the forest on temperature—Influence of forests as inorganic on humidity of air and earth—Influence as organic—Balance of conflicting influences—Influence of woods on precipitation—Total climatic action of the forest—Influence of the forest on humidity of soil—The forest in winter—Summer rain, importance of—Influence of the forest on the flow of springs—Influence of the forest on inundations and torrents—Destructive action of torrents—Floods of the Ardeche—Excavation by torrents—Extinction of torrents—Crushing force of torrents—Transporting power of water—The Po and its deposits—Mountain slides—Forest as protection against avalanches—Minor uses of the forest—Small forest plants and vitality of seeds—Locusts do not breed in forests—General functions of forest—General consequences of destruction of—Due proportion of woodland—Proportion of woodland in European countries—Forests of Great Britain—Forests of France—Forests of Italy—Forests of Germany—Forests of United States—American forest trees—European and American forest trees compared—The forest does not furnish food for man—First removal of the forest—Principal causes of destruction of forest—Destruction and protection of forests by governments—Royal forests and game-laws—Effects of the French revolution—Increased demand for lumber—Effects of burning forest—Floating of timber—Restoration of the forest—Economy of the forest—Forest legislation—Plantation of forests in America—Financial results of forest plantations—Instability of American life.
The Habitable Earth originally Wooded.
There is good reason to believe that the surface of the habitable earth, in all the climates and regions which have been the abodes of dense and civilized populations, was, with few exceptions, already covered with a forest growth when it first became the home of man. This we infer from the extensive vegetable remains—trunks, branches, roots, fruits, seeds, and leaves of trees—so often found in conjunction with works of primitive art, in the boggy soil of districts where no forests appear to have existed within the eras through which written annals reach; from ancient historical records, which prove that large provinces, where the earth has long been wholly bare of trees, were clothed with vast and almost unbroken woods when first made known to Greek and Roman civilization; [Footnote: The recorded evidence in support of the proposition in the text has been collected by L. F. Alfred Maury, in his Histoire des grandes Forets de la Gauls et de l'ancienne France, and by Becquerel, in his important work, Des climats et de l'Influence qu'exercent les Sols boises et non boises, livre ii., chap. i. to iv.
We may rank among historical evidences on this point, if not technically among historical records, old geographical names and terminations etymologically indicating forest or grove, which are so common in many parts of the Eastern Continent now entirely stripped of woods—such as, in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Bruhl, and the endings -dean, -den, -don, -ham, -holt, -horst, -hurst, -lund, -shaw, -shot, -skog, -skov, -wald, -weald, -wold, -wood.] and from the state of much of North and of South America, as well as of many islands, when they were discovered and colonized by the European race. [Footnote: The island of Madeira, whose noble forests wore devastated by fire not Iong after its colonization by European settlors, takes its name from the Portuguese word tor wood.]
These evidences are strengthened by observation of the natural economy of our time; for, whenever a tract of country once inhabited and cultivated by man, is abandoned by him and by domestic animals, and surrendered to the undisturbed influences of spontaneous nature, its soil sooner of later clothes itself with herbaceous and arborescent plants, and, at no long interval, with a dense forest growth. Indeed, upon surfaces of a certain stability and not absolutely precipitous inclination the special conditions required for the spontaneous propagation of trees may all be negatively expressed and reduced to these three: exemption from defect or excess of moisture, from perpetual frost, and from the depredations of man and browsing quadrupeds. Where these requisites are secured, the hardest rock is as certain to be overgrown with wood as the most fertile plain, though, for obvious reasons, the process is slower in the former than in the latter case. Lichens and mosses first prepare the way for a more highly organized vegetation. They retain the moisture of rains and dews, and bring it to act, in combination with the gases evolved by their organic processes, in decomposing the surface of the rocks they cover; they arrest and confine the dust which the wind scatters over them, and their final decay adds new material to the soil already half formed beneath and upon them. A very thin stratum of mould is sufficient for the germination of seeds of the hardy evergreens and birches, the roots of which are often found in immediate contact with the rock, supplying their trees with nourishment from a soil deepened and enriched by the decomposition of their own foliage, or sending out long rootlets into the surrounding earth in search of juices to feed them.
The eruptive matter of volcanoes, forbidding as is its aspect, does not refuse nutriment to the woods. The refractory lava of Etna, it is true, remains long barren, and that of the great eruption of 1669 is still almost wholly devoid of vegetation.
[Footnote: Even the volcanic dust of Etna remains very long unproductive. Near Nicolosi is a great extent of coarse black sand, thrown out in 1669, which, for almost two centuries, lay entirely bare, and can be made to grow plants only by artificial mixtures and much labor.
The increase in the price of wines, in consequence of the diminution of the product from the grape disease, however, has brought even these ashes under cultivation. "I found," says Waltershausen, referring to the years 1861-62, "plains of volcanic sand and half-subdued lava streams, which twenty years ago lay utterly waste, now covered with fine vineyards. The ashfield of ten square miles above Nicolosi, created by the eruption of 1669, which was entirely barren in 1835, is now planted with vines almost to the summits of Monte Rosso, at a height of three thousand feet" Ueber den Sicilianischen Ackerbau, p. 19.] But the cactus is making inroads even here, while the volcanic sand and molten rock thrown out by Vesuvius soon become productive. Before the great eruption of 1631 even the interior of the crater was covered with vegetation. George Sandys, who visited Vesuvius in 1611, after it had reposed for several centuries, found the throat of the volcano at the bottom of the crater "almost choked with broken rocks and trees that are falne therein." "Next to this," he continues, "the matter thrown up is ruddy, light, and soft: more removed, blacke and ponderous: the uttermost brow, that declineth like the seates in a theater, flourishing with trees and excellent pasturage. The midst of the hill is shaded with chestnut trees, and others bearing sundry fruits." [Footnote: A Relation of a Journey Begun An. Dom. 1610, lib. 4, p. 260, edition of 1615. The testimony of Sandys on this point is confirmed by that of Pighio, Braccini, Magliocco, Salimbeni, and Nicola di Rubco, all cited by Roth, Der Vesuv., p. 9. There is some uncertainty about the date of the last eruption previous to the great one of 163l. Ashes, though not lava, appear to have been thrown out about the year 1500, and some chroniclers have recorded an eruption in the year 1306; but this seems to be an error for 1036, when a great quantity of lava was ejected. In 1130, ashes were thrown out for many days. I take these dates from the work of Roth just cited.] I am convinced that forests would soon cover many parts of the Arabian and African deserts, if man and domestic animals, especially the goat and the camel, were banished from them. The hard palate and tongue and strong teeth and jaws of this latter quadruped enable him to break off and masticate tough and thorny branches as large as the finger. He is particularly fond of the smaller twigs, leaves, and seed-pods of the sont and other acacias, which, like the American Robinia, thrive well on dry and sandy soils, and he spares no tree the branches of which are within his reach, except, if I remember right, the tamarisk that produces manna. Young trees sprout plentifully around the springs and along the winter water-courses of the desert, and these are just the halting stations of the caravans and their routes of travel. In the shade of these trees, annual grasses and perennial shrubs shoot up, but are mown down by the hungry cattle of the Bedouin, as fast as they grow. A few years of undisturbed vegetation would suffice to cover such points with groves, and these would gradually extend themselves over soils where now scarcely any green thing but the bitter colocynth and the poisonous foxglove is ever seen.
General Meteorological Influence of the Forest.
The physico-geographical influence of forests may be divided into two great classes, each having an important influence on vegetable and on animal life in all their manifestations, as well as on every branch of rural economy and productive industry, and, therefore, on all the material interests of man. The first respects the meteorology of the countries exposed to the action of these influences; the second, their superficial geography, or, in other words, the configuration, consistence, and clothing of their surface.
For reasons assigned in the first chapter, and for others that will appear hereafter, the meteorological or climatic branch of the subject is the most obscure, and the conclusions of physicists respecting it are, in a great degree, inferential only, not founded on experiment or direct observation. They are, as might be expected, somewhat discordant, though one general result is almost universally accepted, and seems indeed too well supported to admit of serious question, and it may be considered as established that forests tend to mitigate, at least within their own precincts, extremes of temperature, humidity, and drought. By what precise agencies the meteorological effects of the forest are produced we cannot say, because elements of totally unknown value enter into its action, and because the relative intensity of better understood causes cannot be measured or compared. I shall not occupy much space in discussing questions which at present admit of no solution, but I propose to notice all the known forces whose concurrent or conflicting energies contribute to the general result, and to point out, in some detail, the value of those influeuces whose mode of action has been ascertained. Electrical Influence of Trees. The properties of trees, singly and in groups, as exciters or conductors of electricity, and their consequent influence upon the electrical state of the atmosphere, do not appear to have been much investigated; and the conditions of the forest itself are so variable and so complicated, that the solution of any general problem respecting its electrical influence would be a matter of extreme difficulty. It is, indeed, impossible to suppose that a dense cloud, a sea of vapor, can pass over miles of surface bristling with good conductors, without undergoing and producing some change of electrical condition. Hypothetical cases may be put in which the character of the change could be deduced from the known laws of electrical action. But in actual nature, the elements are too numerous for us to seize. The true electrical condition of neither cloud nor forest could be known, and it could seldom be predicted whether the vapors would be dissolved as they floated over the wood, or discharged upon it in a deluge of rain. With regard to possible electrical influences of the forest, wider still in their range of action, the uncertainty is even greater. The data which alone could lead to positive, or even probable, conclusions are wanting, and we should, therefore, only embarrass our argument by any attempt to discuss this meteorological element, important as it may be, in its relations of cause and effect to more familiar and bettor understood meteoric phenomena. It may, however, be observed that hail-storms—which were once generally supposed, and are still held by many, to be produced by a specific electrical action, and which, at least, appear to be always accompanied by electrical disturbances—are believed, in all countries particularly exposed to that scourge, to have become more frequent and destructive in proportion as the forests have been cleared. Caimi observes: "When the chains of the Alps and the Apennines had not yet been stripped of their magnificent crown of woods, the May hail, which now desolates the fertile plains of Lombardy, was much less frequent; but since the general prostration of the forest, these tempests are laying waste even the mountain-soils whose older inhabitants scarcely knew this plague. [Footnote: There are, in Northern Italy and in Switzerland, joint-stock companies which insure against damage by hail, as well as by fire and lightning. Between the years 1854 and 1861, a single one of these companies, La Riunione Adriatica, paid, for damage by hail in Piedmont, Venetian Lombardy, and the Duchy of Parma, above 6,500,000 francs, or nearly $200,000 per year.] The paragrandini, [Footnote: The paragrandine, or, as it is called in French, the paragrele, is a species of conductor by which it has been hoped to protect the harvests in countries particularly exposed to damage by hail. It was at first proposed to employ for this purpose poles supporting sheaves of straw connected with the ground by the same material; but the experiment was afterwards tried in Lombardy on a large scale, with more perfect electrical conductors, consisting of poles secured to the top of tall trees and provided with a pointed wire entering the ground and reaching above the top of the pole. It was at first thought that this apparatus, erected at numerous points over an extent of several miles, was of some service as a protection against hail, but this opinion was soon disputed, and does not appear to be supported by well-ascertained facts. The question of a repetition of the experiment over a wide area has been again agitated within a very few years in Lombardy; but the doubts expressed by very able physicists as to its efficacy, and as to the point whether hail is an electrical phenomenon, have discouraged its advocates from attempting it.] which the learned curate of Rivolta advised to erect, with sheaves of straw set up vertically, over a great extent of cultivated country, are but a Liliputian imago of the vast paragrandini, pines, larches, and fire, which nature had planted by millions on the crests and ridges of the Alps and the Apennines." [Footnote: Cenni sulla Importansa e Coltura dei Boschi, p. 6.] "Electrical action being diminished," says Meguscher, "and the rapid congelation of vapors by the abstraction of heat being impeded by the influence of the woods, it is rare that hail or waterspouts are produced within the precincts of a large forest when it is assailed by the tempest." [Footnote: Memoria sui Boschi, etc., p. 44.] Arthur Young was told that since the forests which covered the mountains between the Riviera and the county of Montferrat had disappeared, hail had become more destructive in the district of Acqui, [Footnote: Travels in Italy, chap. iii.] and a similar increase in the frequency and violence of hail-storms in the neighborhood of Saluzzo and Mondovi, the lower part of the Valtelline, and the territory of Verona and Vicenza, is probably to be ascribed to a similar cause. [Footnote: Le Alpi che cingono l'Italia, i., p. 377. See "On the Influence of the Forest in Preventing Hail-storms," a paper by Becquerel, in the Memoires de l'Academie des Sciences, vol. xxxv. The conclusion of this eminent physicist is, that woods do excercise, both within their own limits and in their vicinity, the influence popularly ascribed to them in this respect, and that the effect is probably produced partly by mechanical and partly by electrical action.] Chemical Influence of the Forest. We know that the air in a close apartment is appreciably affected through the inspiration and expiration of gases by plants growing in it. The same operations are performed on a gigantic scale by the forest, and it has even been supposed that the absorption of carbon, by the rank vegetation of earlier geological periods, occasioned a permanent change in the constitution of the terrestrial atmosphere. [Footnote: "Long before the appearance of man, … they [the forests] had robbed the atmosphere of the enormous quantity of carbonic acid it contained, and thereby transformed it into respirable air. Trees heaped upon trees had already filled up the ponds and marshes, and buried with them in the bowels of the earth—to restore it to us, after thousands of ages, in the form of bituminous coal and of anthracite—the carbon which was destined to become, by this wonderful condensation, a precious store of future wealth."—Clave, Etudes sur l'Economie Forestiere, p. 13.
This opinion of the modification of the atmosphere by vegetation is contested.
Mossman ascribes the great luxuriance and special character of the Australian and New Zealand forests, as well as other peculiarities of the vegetation of the Southern hemisphere, to a supposed larger proportion of carbon in the atmosphere of that hemisphere, though the fact of such excess does not appear to have been established by chemical analysis. Mossman, Origin of the Seasons. Edinburgh, 1869. Chaps. xvi. and xvil.] To the effects thus produced are to be added those of the ultimate gaseous decomposition of the vast vegetable mass annually shed by trees, and of their trunks and branches when they fall a prey to time. But the quantity of gases thus abstracted from and restored to the atmosphere is inconsiderable—infinitesimal, one might almost say—in comparison with the ocean of air from which they are drawn and to which they return; and though the exhalations from bogs, and other low grounds covered with decaying vegetable matter, are highly deleterious to human health, yet, in general, the air of the forest is hardly chemically distinguishable from that of the sand plains, and we can as little trace the influence of the woods in the analysis of the atmosphere, as we can prove that the mineral ingredients of landsprings sensibly affect the chemistry of the sea. I may, then, properly dismiss the chemical, as I have done the electrical, influences of the forest, and treat them both alike, if not as unimportant agencies, at least as quantities of unknown value in our meteorological equation. [Footnote: Schacht ascribes to the forest a specific, if not a measurable, influence upon the constitution of the atmosphere. "Plants imbibe from the air carbonic acid and other gaseous or volatile products exhaled by animals or developed by the natural phenomena of decomposition. On the other hand, the vegetable pours into the atmosphere oxygen, which is taken up by animals and appropriated by them. The tree, by means of its leaves and its young herbaceous twigs, presents a considerable surface for absorption and evaporation; it abstracts the carbon of carbonic acid, and solidifies it in wood, fecula, and a multitude of other compounds. The result is that a forest withdraws from the air, by its great absorbent surface, much more gas than meadows or cultivated fields, and exhales proportionally a considerably greater quantity of oxygen. The influence of the forests on the chemical composition of the atmosphere is, in a word, of the highest importance."—Les Arbres, p. 111.
See on this subject a paper by J. Jamin, in the Revue des Deux Mondes for Sept. 15, 1864; and, on the effects of human industry on the atmosphere, an article in Aus der Natur, vol. 29, 1864, pp. 443, 449, 465, et seq. See also Alfred Maury, Les Forete de la Gaule, p. 107.] Our inquiries upon this branch of the subject will accordingly be limited to the thermometrical and hygrometrical influences of the woods. There is, however, a special protective function of the forest, perhaps, in part, of a chemical nature, which may be noticed here.
Trees as a Protection against Malaria.
The influence of forests in preventing the diffusion of miasmatic vapors is not a matter of familiar observation, and perhaps it does not come strictly within the sphere of the present inquiry, but its importance will justify me in devoting some space to the subject. "It has been observed" (I quote from Becquerel) "that humid air, charged with miasmata, is deprived of them in passing through the forest. Rigaud de Lille observed localities in Italy where the interposition of a screen of trees preserved everything beyond it, while the unprotected grounds were subject to fevers." [Footnote: Becquerel, Des Climats, etc., p. 9.] Few European countries present better opportunities for observation on this point than Italy, because in that kingdom the localities exposed to miasmatic exhalations are numerous, and belts of trees, if not forests, are of so frequent occurrence that their efficacy in this respect can be easily tested. The belief that rows of trees afford an important protection against malarious influences is very general among Italians best qualified by intelligence and professional experience to judge upon the subject. The commissioners, appointed to report on the measures to be adopted for the improvement of the Tuscan Maremme, advised the planting of three or four rows of poplars, Populus alla, in such directions as to obstruct the currents of air from malarious localities, and thus intercept a great proportion of the pernicious exhalations." [Footnote: Salvagnoli, Rapporto sul Bonificamento delle Maremme Toscane, pp. xii., 124.] Maury believed that a few rows of sunflowers, planted between the Washington Observatory and the marshy banks of the Potomac, had saved the inmates of that establishment from the intermittent fevers to which they had been formerly liable. Maury's experiments have been repeated in Italy. Large plantations of sunflowers have been made upon the alluvial deposits of the Oglio, above its entrance into the Lake of Iseo, near Pisogne, and it is said with favorable results to the health of the neighborhood. [Footnote: Il Politecnico, Milano, Aprile e Maggio, 1863, p. 35.] In fact, the generally beneficial effects of a forest wall or other vegetable screen, as a protection against noxious exhalations from marshes or other sources of disease, situated to the windward of them, are very commonly admitted.
It is argued that, in these cases, the foliage of trees and of other vegetables exercises a chemical as well as a mechanical effect upon the atmosphere, and some, who allow that forests may intercept the circulation of the miasmatic effluvia of swampy soils, or even render them harmless by decomposing them, contend, nevertheless, that they are themselves active causes of the production of malaria. The subject has been a good deal discussed in Italy, and there is some reason to think that under special circumstances the influence of the forest in this respect may be prejudicial rather than salutary, though this does not appear to be generally the case. [Footnote: Salvagnoli, Memorie sulle Maremme Toscane, pp. 213, 214. The sanitary action of the forest has been lately matter of much attention in Italy. See Rendiconti del Congresso Medico del 1869 a Firenze, and especially the important observations of Selmi, Il Miasma Palustre, Padua, 1870, pp. 100 et seq. This action is held by this able writer to be almost wholly chemical, and he earnestly recommends the plantation of groves, at least of belts of trees, as an effectual protection against the miasmatic influence of marshes. Very interesting observations on this point will be found in Ebermayer, Die Physikalischen Einwirkungen des Waldes, Aschaffenburg, 1873, B. I., pp. 237 et seq., where great importance is ascribed to the development of ozone by the chemical action of the forest. The beneficial influence of the ozone of the forest atmosphere on the human system is, however, questioned by some observers. See also the able memoir: Del Miasma vegetale e delle Malattis Miasmatiche of Dr D. Pantaleoni in Lo Sperimentale, vol. xxii., 1870.
The necessity of such hygienic improvements as shall render the new capital of Italy a salubrious residence gives great present importance to this question, and it is much to be hoped that the Agro Romano, as well as more distant parts of the Campagna, will soon be dotted with groves and traversed by files of rapidly growing trees. Many forest trees grow with great luxuriance in Italy, and a moderate expense in plantation would in a very few years determine whether any amelioration of the sanitary condition of Rome can be expected from this measure.
It is said by recent writers that in India the villages of the natives and the encampments of European troops, situated in the midst or in the neighborhood of groves and of forests, are exempt from cholera. Similar observations were also made in 18S4 in Germany when this terrible disease was raging there. It is hence inferred that forests prevent the spreading of this malady, or rather the development of those unknown influences of which cholera is the result. These influences, if we may believe certain able writers on medical subjects, are telluric rather than meteoric; and they regard it as probable that the uniform moisture of soil in forests may be the immediate cause of the immunity enjoyed by such localities. See an article by Pettenkofer in the Sud-Deutsche Presse, August, 1869; and the observations of Ebermayer in the work above quoted, pp. 246 et seq.
In Australia and New Zealand, as well as generally in the Southern Hemisphere, the indigenous trees are all evergreens, and even deciduous trees introduced from the other side of the equator become evergreen. In those regions, even in the most swampy localities, malarious diseases are nearly, if not altogether, unknown. Is this most important fact due to the persistence of the foliage Mossman, Origin of Climates, pp. 374, 393, 410, 425, et seq.] It is, at all events, well known that the great swamps of Virginia and the Carolinas, in climates nearly similar to that of Italy, are healthy even to the white man, so long as the forests in and around them remain, but become very insalubrious when the woods are felled. [Footnote: Except in the seething marshes of northern tropical and subtropical regions, where vegetable decay is extremely rapid, the uniformity of temperature and of atmospheric humidity renders all forests eminently healthful. See Hohensten's observations on this subject, Der Wald, p. 41; also A. Maury, Les Forets de la Gaule, p. 7.
The flat and marshy district of the Sologne in France was salubrious until its woods were felled. It then became pestilential, but within the last few years its healthfulness has been restored by forest plantations. Jules Clave in Revue des Deux Mondes for 1st March, 1866, p. 209. There is no question that open squares and parks conduce to the salubrity of cities, and many observers are of opinion that the trees and other vegetables with which such grounds are planted contribute essentially to their beneficial influence. See an article in Aus der Natur, xxii, p. 813.]
Trees as Shelter to Ground to the Leeward.
As a mechanical obstruction, trees impede the passage of air-currents over the ground, which, as is well known, is one of the most efficient agents in promoting evaporation and the refrigeration resulting from it. [Footnote: It is perhaps too much to say that the influence of trees upon the wind is strictly limited to the mechanical resistance of their trunks, branches, and foliage. So far as the forest, by dead or by living action, raises or lowers the temperature of the air within it, so far it creates upward or downward currents in the atmosphere above it, and, consequently, a flow of air towards or from itself. These air-streams have a certain, though doubtless a very small, influence on the force and direction of greater atmospheric movements.] In the forest, the air is almost quiescent, and moves only as local changes of temperature affect the specific gravity of its particles. Hence there is often a dead calm in the woods when a furious blast is raging in the open country at a few yards' distance. The denser the forest—as, for example, where it consists of spike-leaved trees, or is thickly intermixed with them—the more obvious is its effect, and no one can have passed from the field to the wood in cold, windy weather, without having remarked it. [Footnote: As a familiar illustration of the influence of the forest in checking the movement of winds, I may mention the well-known fact, that the sensible cold is never extreme in thick woods, where the motion of the air is little felt. The lumbermen in Canada and the Northern United States labor in the woods, without inconvenience, when the mercury stands many degrees below the zero of Fahrenheit, while in the open grounds, with only a moderate breeze, the same temperature is almost insupportable. The engineers and firemen of locomotives, employed on railways running through forests of any considerable extent, observe that, in very cold weather, it is much easier to keep up the steam while the engine is passing through the woods than in the open ground. As soon as the train emerges from the shelter of the trees the steam-gauge falls, and the stoker is obliged to throw in a liberal supply of fuel to bring it up again.
Another less frequently noticed fact, due, no doubt, in a great measure to the immobility of the air, is, that sounds are transmitted to incredible distances in the unbroken forest. Many instances of this have fallen under my own observation, and others, yet more striking, have been related to me by credible and competent witnesses familiar with a more primitive condition of the Anglo-American world. An acute observer of natural phenomena, whose childhood and youth were spent in the interior of one of the newer New England States, has often told me that when he established his home in the forest, he always distinctly heard, in still weather, the plash of horses' feet, when they forded a small brook nearly seven-eighths of a mile from his house, though a portion of the wood that intervened consisted of a ridge seventy or eighty feet higher than either the house or the ford.
I have no doubt that, in such cases, the stillness of the air is the most important element in the extraordinary transmissibilty of sound; but it must be admitted that the absence of the multiplied, and confused noises, which accompany human industry in countries thickly peopled by man, contributes to the same result. We become, by habit, almost insensible to the familiar and never-resting voices of civilization in cities and towns; but the indistinguishable drone, which sometimes escapes even the ear of him who listens for it, deadens and often quite obstructs the transmission of sounds which would otherwise be clearly audible. An observer, who wishes to appreciate that hum of civic life which he cannot analyze, will find an excellent opportunity by placing himself on the hill of Capo di Monte at Naples, in the line of prolongation of the street called Spaccanapoli.
It is probably to the stillness of which I have spoken that we are to ascribe the transmission of sound to great distances at sea in calm weather. In June, 1853, I and my family were passengers on board a ship-of-war bound up the Aegean. On the evening of the 27th of that month, as we were discussing, at the tea-table, some observations of Humboldt on this subject, the captain of the ship told us that he had once heard a single gun at sea at the distance of ninety nautical miles. The next morning, though a light breeze had sprung up from the north, the sea was of glassy smoothness when we went on deck. As we came up, an officer told us that he had heard a gun at sunrise, and the conversation of the previous evening suggested the inquiry whether it could have been fired from the combined French and English fleet then lying at Beshika Bay. Upon examination of our position we were found to have been, at sunrise, ninety sea miles from that point. We continued beating up northwards, and between sunrise and twelve o'clock meridian of the 28th, we had made twelve miles northing, reducing our distance from Beshika Bay to seventy-eight sea miles. At noon we heard several guns so distinctly that we were able to count the number. On the 29th we came up with the fleet, and learned from an officer who came on board that a royal salute had been fired at noon on the 28th, in honor of the day as the anniversary of the Queen of England's coronation. The report at sunrise was evidently the morning gun, those at noon the salute.
Such cases are rare, because the sea is seldom still, and the [word in Greek] rarely silent, over so great a space as ninety or even seventy-eight nautical miles. I apply the epithet silent to [word in Greek] advisedly. I am convinced that Aeschylus meant the audible laugh of the waves, which is indeed of COUNTLESS multiplicity, not the visible smile of the sea, which, belonging to the great expanse as one impersonation, is single, though, like the human smile, made up of the play of many features.] The action of the forest, considered merely as a mechanical shelter to grounds lying to the leeward of it, might seem to be an influence of too restricted a character to deserve much notice; but many facts concur to allow that it is a most important element in local climate.
It is evident that the effect of the forest, as a mechanical impediment to the passage of the wind, would extend to a very considerable distance above its own height, and hence protect while standing, or lay open when felled, a much larger surface than might at first thought be supposed. The atmosphere, movable as are its particles, and light and elastic as are its masses, is nevertheless held together as a continuous whole by the gravitation of its atoms and their consequent pressure on each other, if not by attraction between them, and, therefore, an obstruction which mechanically impedes the movement of a given stratum of air will retard the passage of the strata above and below it. To this effect may often be added that of an ascending current from the forest itself, which must always exist when the atmosphere within the wood is warmer than the stratum of air above it, and must be of almost constant occurrence in the case of cold winds, from whatever quarter, because the still air in the forest is slow in taking up the temperature of the moving columns and currents around and above it. Experience, in fact, has shown that mere rows of trees, and even much lower obstructions, are of essential service in defending vegetation against the action of the wind. Hardy proposes planting, in Algeria, belts of trees at the distance of one hundred metres from each other, as a shelter which experience had proved to be useful in France. [Footnote: Becquerel, Des Climats, etc., p. 179.] "In the valley of the Rhone," says Becquerel, "a simple hedge, two metres in height, is a sufficient protection for a distance of twenty-two metres." [Footnote: Ibid., p. 116. Becquerel's views have been amply confirmed by recent extensive experiments on the bleak, stony, and desolate plain of the Cran in the Department of the Bouches-du-Rhone, which had remained a naked waste from the earliest ages of history. Belts of trees prove a secure protection even against the furious and chilly blasts of the Mistral, and in this shelter plantations of fruit-trees and vegetables, fertilized by the waters and the slime of the Durance, which are conducted and distributed over the Cran, thrive with the greatest luxuriance. [Footnote: Surrell, Etude sur les Torrents, 2d edition, 1872, ii, p. 85.] The mechanical shelter acts, no doubt, chiefly as a defence against the mechanical force of the wind, but its uses are by no means limited to this effect. If the current of air which it resists moves horizontally, it would prevent the access of cold or parching blasts to the ground for a great distance; and did the wind even descend at a large angle with the surface, still a considerable extent of ground would be protected by a forest to the windward of it.
In the report of a committee appointed in 1836 to examine an article of the forest code of France, Arago observes; "If a curtain of forest on the coasts of Normandy and of Brittany were destroyed, these two provinces would become accessible to the winds from the west, to the mild breezes of the sea. Hence a decrease of the cold of winter. If a similar forest were to be cleared on the eastern border of France, the glacial east wind would prevail with greater strength, and the winters would become more severe. Thus the removal of a belt of wood would produce opposite effects in the two regions." [Footnote: Becquerel, Des Climats, etc., Discours Prelim., vi.]
This opinion receives confirmation from an observation of Dr. Dwight, who remarks, in reference to the woods of New England: "Another effect of removing the forest will be the free passage of the winds, and among them of the southern winds, over the surface. This, I think, has been an increasing fact within my own remembrance. As the cultivation of the country has extended further to the north, the winds from the south have reached distances more remote from the ocean, and imparted their warmth frequently, and in such degrees as, forty years since, were in the same places very little known. This fact, also, contributes to lengthen the summer and to shorten the winter half of the year." [Footnote: Travels, i., p. 61.]
It is thought in Italy that the clearing of the Apennines has very materially affected the climate of the valley of the Po. It is asserted in Le Alpi che cingono l'Italia that: "In consequence of the felling of the woods on the Apennines, the sirocco prevails greatly on the right bank of the Po, in the Parmesan territory, and in a part of Lombardy; it injures the harvests and the vineyards, and sometimes ruins the crops of the season. To the same cause many ascribe the meteorological changes in the precincts of Modena and of Reggio. In the communes of these districts, where formerly straw roofs resisted the force of the winds, tiles are now hardly sufficient; in others, where tiles answered for roofs, large slabs of stone are now ineffectual; and in many neighboring communes the grapes and the grain are swept off by the blasts of the south and south-west winds."
According to the same authority, the pinery of Porto, near Ravenna—which is twenty miles long, and is one of the oldest pine woods in Italy—having been replanted with resinous trees after it was unfortunately cut, has relieved the city from the sirocco to which it had become exposed, and in a great degree restored its ancient climate. [Footnote: Le Alpi che cingono l'Italia, pp. 370, 371.]
The felling of the woods on the Atlantic coast of Jutland has exposed the soil not only to drifting sands, but to sharp sea-winds, that have exerted a sensible deteriorating effect on the climate of that peninsula, which has no mountains to serve at once as a barrier to the force of the winds, and as a storehouse of moisture received by precipitation or condensed from atmospheric vapors. [Footnote: Bergsoe, Reventlovs Virksomhed, ii., p. 125.
The following well-attested instance of a local change of climate is probably to be referred to the influence of the forest as a shelter against cold winds. To supply the extraordinary demand for Italian iron occasioned by the exclusion of English iron in the time of Napoleon I., the furnaces of the valleys of Bergamo were stimulated to great activity. "The ordinary production of charcoal not sufficing to feed the furnaces and the forges, the woods were felled, the copses cut before their time, and the whole economy of the forest was deranged. At Piazzatorre there was such a devastation of the woods, and consequently such an increased severity of climate, that maize no longer ripened. An association, formed for the purpose, effected the restoration of the forest, and maize flourishes again in the fields of Piazzatorre." —Report by G. Rosa, in Il Politecnico, Dicembre, 1861, p. 614.
Similar ameliorations have been produced by plantations in Belgium. In an interesting series of articles by Bande, entitled, "Les Cotes de la Manche," in the Revue des Deux Mondes, I find this statement: "A spectator, placed on the famous bell-tower of the cathedral of Antwerp, saw, not long since, on the opposite side of the Schelde, only a vast desert plain; now he sees a forest, the limits of which are confounded with the horizon. Let him enter within its shade. The supposed forest is but a system of regular rows of trees, the oldest of which is not forty years of age. These plantations have ameliorated the climate which had doomed to sterility the soil where they are planted. While the tempest is violently agitating their tops, the air a little below is still, and sands far more barren than the plateau of La Hague have been transformed, under their protection, into fertile fields."—Revue des Deux Mondes, January, 1859, p. 277.] The local retardation of spring, so much complained of in Italy, France, and Switzerland, and the increased frequency of late frosts at that season, appear to be ascribable to the admission of cold blasts to the surface, by the felling of the forests which formerly both screened it as by a wall, and communicated the warmth of their soil to the air and earth to the leeward.
Caimi states that since the cutting down of the woods of the Apennines, the cold winds destroy or stunt the vegetation, and that, in consequence of "the usurpation of winter on the domain of spring," the district of Mugello has lost all its mulberries, except the few which find in the lee of buildings a protection like that once furnished by the forest. [Footnote: Cenni sulla Importanza e Coltura dei Boschi, p. 31.]
The department of Ardeche, which now contains not a single considerable wood, has experienced within thirty years a climatic disturbance, of which the late frosts, formerly unknown in the country, are one of the most melancholy effects. Similar results have been observed in the plain of Alsace, in consequence of the denudation of several of the crests of the Vosges. [Footnote: Clave, Etudes, p. 44.] [Footnote It has been observed in Sweden that the spring, in many districts where the forests have been cleared off, now comes on a fortnight later than in the last century.—Asbjornsen, Om Skovene i norge, p. 101.] Dussard, as quoted by Ribbe, [Footnote: La Provence au point de vue des Torrents et des Inondations, p. 10.
Dussard is doubtless historically inaccurate in making the origin of the mistral so late as the time of Augustus. Diodorus Siculus, who was a contemporary of Julius Caesar, describes the north-west winds in Gaul as violent enough to hurl along stones as large as the fist with clouds of sand and gravel, to strip travellers of their arms and clothing, and to throw mounted men from their horses. Bibliotheca Historica, lib. v., c. xxvi. Diodorus, it is true, is speaking of the climate of Gaul in general, but his description can hardly refer to anything but the mistral of South-eastern France.] maintains that even the MISTRAL, or north-west wind, whose chilling blasts are so fatal to tender vegetation in the spring, "is the child of man, the result of his devastations." "Under the reign of Augustus," continues he, "the forests which protected the Cevennes were felled, or destroyed by fire, in mass. A vast country, before covered with impenetrable woods—powerful obstacles to the movement and even to the formation of hurricanes—was suddenly denuded, swept bare, stripped, and soon after, a scourge hitherto unknown, struck terror over the land from Avignon to the Bouches-du-Rhone, thence to Marseilles, and then extended its ravages, diminished indeed by a long career which had partially exhausted its force, over the whole maritime frontier. The people thought this wind a curse sent of God. They raised altars to it and offered sacrifices to appease its rage." It seems, however, that this plague was less destructive than at present, until the close of the sixteenth century, when further clearings had removed most of the remaining barriers to its course. Up to that time, the north-west wind appears not to have attained to the maximum of specific effect which now characterizes it as a local phenomenon. Extensive districts, from which the rigor of the seasons has now banished valuable crops, were not then exposed to the loss of their harvests by tempests, cold, or drought. The deterioration was rapid in its progress. Under the Consulate, the clearings had exerted so injurious an effect upon the climate, that the cultivation of the olive had retreated several leagues, and since the winters and springs of 1820 and 1836, this branch of rural industry has been abandoned in a great number of localities where it was advantageously pursued before. The orange now flourishes only at a few sheltered points of the coast, and it is threatened even at Hyeres, where the clearing of the hills near the town has proved very prejudicial to this valuable tree.
Marchand informs us that, since the felling of the woods, late spring frosts are more frequent in many localities north of the Alps; that fruit-trees thrive no longer, and that it is difficult even to raise young fruit-trees. [Footnote: Ueber die Entwaldung der Gebirge, p. 28. Interesting facts and observations on this point will be found in the valuable Report on the Effects of the Destruction of the Forests in Wisconsin, by LAPHAM and others, pp. 6, 18, 20.]
Influence of the Forest, considered as Inorganic Matter, on Temperature. The evaporation of fluids, and the condensation and expansion of vapors and gases, are attended with changes of temperature; and the quantity of moisture which the air is capable of containing, and of course, other things being equal, the evaporation, rise and fall with the thermometer. The hygroscopical and the thermoscopical conditions of the atmosphere are, therefore, inseparably connected as reciprocally dependent quantities, and neither can be fully discussed without taking notice of the other. The leaves of living trees exhale enormous quantities of gas and of aqueous vapor, and they largely absorb gases, and, under certain conditions, probably also water. Hence they affect more or less powerfully the temperature as well as the humidity of the air. But the forest, regarded purely as inorganic matter, and without reference to its living processes of absorption and exhalation of gases and of water, has, as an absorbent, a radiator and a conductor of heat, and as a mere covering of the ground, an influence on the temperature of the air and the earth, which may be considered by itself.
Absorbing and Emitting Surface.
A given area of ground, as estimated by the every-day rule of measurement in yards or acres, presents always the same apparent quantity of absorbing, radiating, and reflecting surface; but the real extent of that surface is very variable, depending, as it does, upon its configuration, and the bulk and form of the adventitious objects it bears upon it; and, besides, the true superficies remaining the same, its power of absorption, radiation, reflection, and conduction of heat will be much affected by its consistence, its greater or less humidity, and its color, as well as by its inclination of plane and exposure. An acre of clay, rolled hard and smooth, would have great reflecting power, but its radiation would be much increased by breaking it up into clods, because the actually exposed surface would be greater, though the outline of the field remained the same. The inequalities, natural or artificial, which always occur in the surface of ordinary earth, affect in the same way its quantity of superficies acting upon the temperature of the atmosphere, and acted on by it, though the amount of this action and reaction is not susceptible of measurement.
Analogous effects are produced by other objects, of whatever form or character, standing or lying upon the earth, and no solid can be placed upon a flat piece of ground, without itself exposing a greater surface than it covers. This applies, of course, to forest trees and their leaves, and indeed to all vegetables, as well as to other prominent bodies. If we suppose forty trees to be planted on an acre, one being situated in the centre of every square of two rods the side, and to grow until their branches and leaves everywhere meet, it is evident that, when in full foliage, the trunks, branches, and leaves would present an amount of thermoscopic surface much greater than that of an acre of bare earth; and besides this, the fallen leaves lying scattered on the ground, would somewhat augment the sum-total. [Footnote: "The Washington elm at Cambridge—a tree of no extraordinary size—was some years ago estimated to produce a crop of seven millions of leaves, exposing a surface of two hundred thousand square feet, or about five acres of foliage."—Gray, First Lessons in Botany and Vegetable Physiology.] On the other hand, the growing leaves of trees generally form a succession of stages, or, loosely speaking, layers, corresponding to the annual growth of the branches, and more or less overlying each other. This disposition of the foliage interferes with that free communication between sun and sky above, and leaf-surface below, on which the amount of radiation and absorption of light depends. From all these considerations, it appears that though the effective thermoscopic surface of a forest in full leaf does not exceed that of bare ground in the same proportion as does its measured superficies, yet the actual quantity of area capable of receiving and emitting heat must be greater in the former than in the latter case. [Footnote: See, on this particular point, and on the general influence of the forest on temperature, Humboldt, Ansichten der Natur, i., 158.]
It must further be remembered that the form and texture of a given surface are important elements in determining its thermoscopic character. Leaves are porous, and admit air and light more or less freely into their substance; they are generally smooth and even glazed on one surface; they are usually covered on one or both sides with spicula, and they very commonly present one or more acuminated points in their outline—all circumstances which tend to augment their power of emitting heat by reflection or radiation. Direct experiment on growing trees is very difficult, nor is it in any case practicable to distinguish how far a reduction of temperature produced by vegetation is due to radiation, and how far to exhalation of the gaseous and watery fluids of the plant; for both processes usually go on together. But the frigorific effect of leafy structure is well observed in the deposit of dew and the occurrence of hoarfrost on the foliage of grasses and other small vegetables, and on other objects of similar form and consistence, when the temperature of the air a few feet above has not been brought down to the dew-point, still less to 32 degrees, the degree of cold required to congeal dew to frost. [Footnote: The leaves and twigs of plants may be reduced by radiation to a temperature lower than that of the ambient atmosphere, and even be frozen when the air in contact with them is above 32 degrees. Their temperature may be communicated to the dew deposited on them and thus this dew be converted into frost when globules of watery fluid floating in the atmosphere near them, in the condition of fog or vapor, do not become congealed.
It has long been known that vegetables can be protected against frost by diffusing smoke through the atmosphere above them. This method has been lately practised in France on a large scale: vineyards of forty or fifty acres have been protected by placing one or two rows of pots of burning coal-tar, or of naphtha, along the north side of the vineyard, and thus keeping up a cloud of smoke for two or three hours before and after sunrise. The expense is said to be small, and probably it might be reduced by mixing some less combustible substance, as earth, with the fluid, and thus checking its too rapid burning.
The radiating and refrigerating power of objects by no means depends on their form alone. Melloni cut sheets of metal into the shape of leaves and grasses, and found that they produced little cooling effect, and were not moistened under atmospheric conditions which determined a plentiful deposit of dew on the leaves of vegetables.]
We are also to take into account the action of the forest as a conductor of heat between the atmosphere and the earth. In the most important countries of America and Europe, and especially in those which have suffered most from the destruction of the woods, the superficial strata of the earth are colder in winter, and warmer in summer, than those a few inches lower, and their shifting temperature approximates to the atmospheric mean of the respective seasons. The roots of large trees penetrate beneath the superficial strata, and reach earth of a nearly constant temperature, corresponding to the mean for the entire year. As conductors, they convey the heat of the atmosphere to the earth when the earth is colder than the air, and transmit it in the contrary direction when the temperature of the earth is higher than that of the atmosphere. Of course, then, as conductors, they tend to equalize the temperature of the earth and the air.
In countries where the questions I am considering have the greatest practical importance, a very large proportion, if not a majority, of the trees are of deciduous foliage, and their radiating as well as their shading surface is very much greater in summer than in winter. In the latter season, they little obstruct the reception of heat by the ground or the radiation from it; whereas, in the former, they often interpose a complete canopy between the ground and the sky, and materially interfere with both processes.
Dead Products of Trees.
Besides this various action of standing trees, considered as inorganic matter, the forest exercises, by the annual moulting of its foliage, still another influence on the temperature of the earth, and, consequently, of the atmosphere which rests upon it. If we examine the constitution of the superficial soil in a primitive or an old and undisturbed artificially planted wood, we find, first, a deposit of undecayed leaves, twigs, and seeds, lying in loose layers on the surface; then, more compact beds of the same materials in incipient, and, as we descend, more and more advanced, stages of decomposition; then, a mass of black mould, in which traces of organic structure are hardly discoverable except by microscopic examination; then, a stratum of mineral soil, more or less mixed with vegetable matter carried down into it by water, or resulting from the decay of roots; and, finally, the inorganic earth or rock itself. Without this deposit of the dead products of trees, this latter would be the superficial stratum, and as its powers of absorption, radiation, and conduction of heat would differ essentially from those of the layers with which it has been covered by the droppings of the forest, it would act upon the temperature of the atmosphere, and be acted on by it, in a very different way from the leaves and mould which rest upon it. Dead leaves, still entire, or partially decayed, are very indifferent conductors of light, and, therefore, though they diminish the warming influence of the summer sun on the soil below them, they, on the other hand, prevent the escape of heat from that soil in winter, and, consequently, in cold climates, even when the ground is not covered by a protecting mantle of snow, the earth does not freeze to as great a depth in the wood as in the open field.
Specific Heat.
Trees, considered as organisms, produce in themselves, or in the air, a certain amount of heat, by absorbing and condensing atmospheric gases, and they exert an opposite influence by absorbing water and exhaling it in the form of vapor; but there is still another mode by which their living processes may warm the air around them, independently of the thermometric effects of condensation and evaporation. The vital heat of a dozen persons raises the temperature of a room. If trees possess a specific temperature of their own, an organic power of generating heat like that with which the warm-blooded animals are gifted, though by a different process, a certain amount of weight is to be ascribed to this element in estimating the action of the forest upon atmospheric temperature.
Boussingault remarks: "In many flowers there has been observed a very considerable evolution of heat, at the approach of fecundation. In certain arums the temperature rises to 40 degrees or 50 degrees Cent. [= 104 degrees or 122 degrees Fahr.] It is very probable that this phenomenon in general, and varies only in the intensity which it is manifested." [Footnote: Economie Rurale, i., p. 22.]
If we suppose the fecundation of the flowers of forest trees to be attended with a tenth only of this calorific power, they could not fail to exert an important influence on the warmth of the atmospheric strata in contact with them.
Experiments by Meguscher, in Lombardy, led that observer to conclude "that the wood of a living tree maintains a temperature of + 12 degrees or 18 degrees Cent. [= 54 degrees, 56 degrees Fahr.] when the temperature of the air stands at 3 degrees, 7 degrees, and 8 degrees [= 37 degrees, 46 degrees, 47 degrees F.] above zero, and that the internal warmth of the tree does not rise and fall in proportion to that of the atmosphere. So long as the latter is below 18 degrees [= 67 degrees Fahr.], that of the tree is always the highest; but if the temperature of the air rises to 18 degrees, that of the vegetable growth is the lowest. Since then, trees maintain at all seasons a constant mean temperature of 12 degrees [= 54 degrees Fahr.], it is easy to see why the air in contact with the forest must be warmer in winter, cooler in summer than in situations where it is deprived of that influence." [Footnote: Memoria Sur Boschi Della Lombardia, p. 45. The results of recent experiments by Becquerel do not accord with those obtained by Meguscher, and the former eminent physicist holds that "a tree is warmed in the air like any inert body." At the same time he asserts, as a fact well ascertained by experiment, that "vegetables possess in themselves the power or resisting extreme cold for a certain length of time,…. and hence it is believed that there may exist in the organism of plants a force, independent of the conduction of caloric, which resists a degree of cold above the freezing-point." In a following page he cites observations made by Bugeaud, under the parallel of 58 degrees N. L., between the months of November and June, during most of which time, of course, vegetable life was in its deepest lethargy. Bugeaud found that when the temperature of the air was at -34.60 degrees, that of a poplar was only at -29.70 degrees, which certainly confirms the doctrine that trees exercise a certain internal resistance against cold.]
Professor Henry says: "As a general deduction from chemical and mechanical principles, we think no change of temperature is ever produced where the actions belonging to one or both of these principles are not present. Hence, in midwinter, when all vegetable functions are dormant, we do not believe that any heat is developed by a tree, or that its interior differs in temperature from its exterior further than it is protected from the external air. The experiments which have been made on this point, we think, have been directed by a false analogy. During the active circulation of the sap and the production of new tissue, variations of temperature belonging exclusively to the plant may be observed; but it is inconsistent with general principles that heat should be generated where no change is taking place." [Footnote: United States Patent Office Report for 1857, p. 504.]
There can be no doubt that moisture is given, out by trees and evaporated in extremely cold winter weather, and unless new fluid were supplied from the roots by the exercise of some vital function, the tree would be exhausted of its juices before winter was over. But this is not observed to be the fact, and, though the point is disputed, respectable authorities declare that "wood felled in the depth of winter is the heaviest and fullest of sap." [Footnote: Rossmassler, Der Wald, p. 158.] Warm weather in winter, of too short continuance to affect the temperature of the ground sensibly, stimulates a free flow of sap in the maple. Thus, in the last week of December, 1862, and the first week of January, 1863, sugar was made from that tree in various parts of New England. "A single branch of a tree, admitted into a warm room in winter through an aperture in a window, opened its buds and developed its leaves, while the rest of the tree in the external air remained in its winter sleep." [Footnote: Ibid., p. 160.] Like facts are matter of every-day observation in graperies where the vine is often planted outside the wall, the stem passing through an aperture into the warm interior. The roots, of course, stand in ground of the ordinary winter temperature, but vegetation is developed in the branches at the pleasure of the gardener. The roots of forest trees in temperate climates remain, for the most part, in a moist soil, of a temperature not much below the annual mean, through the whole winter; and we cannot account for the uninterrupted moisture of the tree, unless we suppose that the roots furnish a constant supply of water. Atkinson describes a ravine in a valley in Siberia, which was filled with ice to the depth of twenty-five feet. Poplars were growing in this ice, which was thawed to the distance of some inches from the stem. But the surface of the soil beneath it must have remained still frozen, for the holes around the trees were full of water resulting from its melting, and this would have escaped below if the ground had been thawed. In this case, although the roots had not thawed the thick covering of earth above them, the trunks must have melted the ice in contact with them. The trees, when observed by Atkinson, were in full leaf, but it does not appear at what period the ice around their stems had melted.
From these facts, and others of the like sort, it would seem that "all vegetable functions are" not absolutely "dormant in winter, and, therefore, that trees may give out SOME heat even at that season." [Footnote: All evergreens, even the broad-leaved trees, resist frosts of extraordinary severity better than the deciduous trees of the same climates. Is not this because the vital processes of trees of persistent foliage are less interrupted during winter than those of trees which annually shed their leaves, and that therefore more organic heat is developed?
In crossing Mont Cenis in October, 1869, when the leaves of the larches on the northern slope and near the top of the mountain were entirely dead and turned brown, I observed that these trees were completely white with hoar-frost. It was a wonderful sight to see how every leaf was covered with a delicate deposit of frozen aqueous vapor, which gave the effect of the most brilliant silver. On the other band, the evergreen coniferae, which were growing among the larches, and therefore in the same conditions of exposure, were almost entirely free from frost. The contrast between the verdure of the leaves of the evergreens and the crystalline splendor of those of the larches was strikingly beautiful. Was this fact due to a difference in the color and structure of the leaves, or rather is it a proof of a vital force of resistance to cold in the living foliage of the evergreen tree The low temperature of air and soil at which, in the frigid zone, as well as in warmer latitudes under special circumstances, the processes of vegetation go on, seems to necessitate the supposition that all the manifestations of vegetable life are attended with an evolution of heat. In the United States it is common to protect ice, in ice-houses, by a covering of straw, which naturally sometimes contains kernels of grain. These often sprout, and even throw out roots and leaves to a considerable length, in a temperature very little above the freezing-point. Three or four years since I saw a lump of very clear and apparently solid ice, about eight inches long by six thick, on which a kernel of grain had sprouted in an ice-house, and sent half a dozen or more very slender roots into the pores of the ice and through the whole length of the lump. The young plant must have thrown out a considerable quantity of heat; for though the ice was, as I have said, otherwise solid, the pores through which the roots passed were enlarged to perhaps double the diameter of the fibres, but still not so much as to prevent the retention of water in them by capillary attraction.]
It does not appear that observations have been made on the special point of the development of heat in forest trees during florification, or at any other period of intense vital action; and hence an important element in the argument remains undetermined. The "circulation of the sap" commences at a very early period in the spring, and the temperature of the air in contact with trees may then be sufficiently affected by heat evolved in the vital processes of vegetation, to raise the thermometric mean of wooded countries for that season, and, of course, for the year. The determination of this point is of much greater importance to vegetable physiology than the question of the winter temperature of trees, because a slight increment of heat in the trees of a forest might so affect the atmosphere in contact with them as to make possible the growing of many plants in or near the wood which could not otherwise he reared in that climate.
The evaporation of the juices of trees and other plants is doubtless their most important thermoscopic function, and as recent observations lead to the conclusion that the quantity of moisture exhaled by vegetables has been hitherto underrated, we must ascribe to this element a higher value than has been usually assigned to it as a meteorological influence.
The exhalation and evaporation of the juices of trees, by whatever process effected, take up atmospheric heat and produce a proportional refrigeration. This effect is not less real, though to common observation less sensible, in the forest than in meadow or pasture land, and it cannot be doubted that the local temperature is considerably affected by it. But the evaporation that cools the air diffuses through it, at the same time, a medium which powerfully resists the escape of heat from the earth by radiation. Visible vapors, fogs and clouds, it is well known, prevent frosts by obstructing radiation, or rather by reflecting back again the heat radiated by the earth, just as any mechanical screen would do. On the other hand, fogs and clouds intercept the rays of the sun also, and hinder its heat from reaching the earth. The invisible vapors given out by leaves impede the passage of heat reflected and radiated by the earth and by all terrestrial objects, bat oppose much less resistance to the transmission of direct solar heat, and indeed the beams of the sun seem more scorching when received through clear air charged with uncondensed moisture than after passing through a dry atmosphere. Hence the reduction of temperature by the evaporation of moisture from vegetation, though sensible, is less than it would be if water in the gaseous state were as impervious to heat given out by the sun as to that emitted by terrestrial objects.
Total Influence of the Forest on Temperature.
It has not yet been found practicable to measure, sum up, and equate the total influence of the forest, its processes and its products, dead and living, upon temperature, and investigators differ much in their conclusions on this subject. It seems probable that in every particular case the result is, if not determined, at least so much modified by local conditions which are infinitely varied, that no general formula is applicable to the question. In the report to which I referred on page 163, Gay-Lussac says; "In my opinion we have not yet any positive proof that the forest has, in itself, any real influence on the climate of a great country, or of a particular locality. By closely examining the effects of clearing off the woods, we should perhaps find that, far from being an evil, it is an advantage; but these questions are so complicated when they are examined in a climatological point of view, that the solution of them is very difficult, not to say impossible." Becquerel, on the other hand, considers it certain that in tropical climates the destruction of the forests is accompanied with an elevation of the mean temperature, and he thinks it highly probable that it has the same effect in the temperate zones. The following is the substance of his remarks on this subject: "Forests act as frigorific causes in three ways:
"1. They shelter the ground against solar irradiation and maintain a greater humidity.
"2. They produce a cutaneous transpiration by the leaves.
"3. They multiply, by the expansion of their branches, the surfaces which are cooled by radiation.
"These three causes acting with greater or less force, we must, in the study of the climatology of a country, take into account the proportion between the area of the forests and the surface which is bared of trees and covered with herbs and grasses.
"We should be inclined to believe, a priori, according to the foregoing considerations, that the clearing of the woods, by raising the temperature and increasing the dryness of the air, ought to react on climate. There is no doubt that, if the vast desert of the Sahara were to become wooded in the course of ages, the sands would cease to be heated as much as at the present epoch, when the mean temperature is twenty-nine degrees [Centigrade, = 85 degrees Fahr.]. In that case, the ascending currents of warm air would cease, or be less warm, and would not contribute, by descending in our latitudes, to soften the climate of Western Europe. Thus the clearing of a great country may react on the climates of regions more or less remote from it.
"The observations by Boussingault leave no doubt on this point. This writer determined the mean temperature of wooded and of cleared points, under the same latitude, and at the same elevation above the sea, in localities comprised between the eleventh degree of north and the fifth degree of south latitude, that is to say, in the portion of the tropics nearest to the equator, and where radiation tends powerfully during the night to lower the temperature under a sky without clouds." [Footnote: Becquerel, Des Climats, etc., pp. 139-141.]
The result of these observations, which has been pretty generally adopted by physicists, is that the mean temperature of cleared land in the tropics appears to be about one degree Centigrade, or a little less than two degrees of Fahrenheit, above that of the forest. On page 147 of the volume just cited, Becquerel argues that, inasmuch as the same and sometimes a greater difference is found in favor of the open ground, at points within the tropics so elevated as to have a temperate or even a polar climate, we must conclude that theforests in Northern America exert a refrigerating influence equally powerful. But the conditions of the soil are so different in the two regions compared, that I think we cannot, with entire confidence, reason from the one to the other, and it is much to be desired that observations be made on the summer and winter temperature of both the air and the ground in the depths of the North American forests, before it is too late.
Recent inquiries have introduced a new element into the problem of the influence of the forest on temperature, or rather into the question of the thermometrical effects of its destruction. I refer to the composition of the soil in respect to its hygroscopicity or aptitude to absorb humidity, whether in a liquid or a gaseous form, and to the conducting power of the particles of which it is composed. [Footnote: Composition, texture, and color of soil are important elements to be considered in estimating the effects of the removal of the forest upon its thermoscopic action. "Experience has proved," says Becquerel, "that when the soil is bared, it becomes more or less heated [by the rays of the sun] according to the nature and the color of the particles which compose it, and according to its humidity, and that, in the refrigeration resulting from radiation, we must take into the account the conducting power of those particles also. Other things being equal, siliceous and calcareous sands, compared in equal volumes with different argillaceous earths, with calcareous powder or dust, with humus, with arable and with garden earth, are the soils which least conduct heat. It is for this reason that sandy ground, in summer, maintains a high temperature even during the night. We may hence conclude that when a sandy soil is stripped of wood, the local temperature will be raised. After the sands follow successively argillaceous, arable, and garden ground, then humus, which occupies the lowest rank.
"The retentive power of humus is but half as great as that of calcareous sand. We will add that the power or retaining heat is proportional to the density. It has also a relation to the magnitude of the particles. It is for this reason that ground covered with siliceous pebbles cools more slowly than siliceous sand, and that pebbly soils are best suited to the cultivation of the vine, because they advance the ripening of the grape more rapidly than chalky and clayey earths, which cool quickly. Hence we see that in examining the calorific effects of clearing forests, it is important to take into account the properties of the soil laid bare."—Becquerel, Des Climats et des Sols boises, p. 137.]
The hygroscopicity of humus or vegetable earth is much greater than that of any mineral soil, and consequently forest ground, where humus abounds, absorbs the moisture of the atmosphere more rapidly and in larger proportion than common earth. The condensation of vapor by absorption develops heat, and consequently elevates the temperature of the soil which absorbs it, together with that of air in contact with the surface. Von Babo found the temperature of sandy ground thus raised from 68 degrees to 80 degrees F., that of soil rich in humus from 68 degrees to 88 degrees. The question of the influence of the woods on temperature does not, in the present state of our knowledge, admit of precise solution, and, unhappily, the primitive forests are disappearing so rapidly before the axe of the woodman, that we shall never be able to estimate with accuracy the climatological action of the natural wood, though all the physical functions of artificial plantations will, doubtless, one day be approximately known.
But the value of trees as a mechanical screen to the soil they cover, and often to ground far to the leeward of them, is most abundantly established, and this agency alone is important enough to justify extensive plantation in all countries which do not enjoy this indispensable protection.
Influence of Forests as Inorganic on the Humidity of the Air and the
Earth.
The most important hygroscopic as well as thermoscopic influence of the forest is, no doubt, that which it exercises on the humidity of the air and the earth, and this climatic action it exerts partly as dead, partly as living matter. By its interposition as a curtain between the sky and the ground it both checks evaporation from the earth, and mechanically intercepts a certain proportion of the dew and the lighter showers, which would otherwise moisten the surface of the soil, and restores it to the atmosphere by exhalation; [Footnote: Mangotti had observed and described, in his usual picturesque way, the retention of rain-water by the foliage and bark of trees, but I do not know that any attempts were made to measure the quantity thus intercepted before the experiments of Becquerel, communicated to the Academy of Sciences in 1866. These experiments embraced three series of observations continued respectively for periods of a year, a month, and two days. According to Becquerel's measurements, the quantity falling on bare and on wooded soil respectively was as 1 to 0.07; 1 to 0.5; and 1 to 0.6, or, in other words, he found that only from five-tenths to sixty-seven hundredths of the precipitation reached the ground.—Comptes Rendus de l'Academie des Sciences, 1866. It seemed, indeed, improbable that in rain-storms which last not hours but whole days in succession, so large a proportion of the downfall should continue to be intercepted by forest vegetation after the leaves, the bark, and the whole framework of the trees were thoroughly wet, but the conclusions of this eminent physicist appear to have been generally accepted until the very careful experiments of Mathieu at the Forest-School of Nancy were made known. The observations of Mathieu were made in a plantation of deciduous trees forty-two years old, and were continued through the entire years 1866, 1867, and 1868. The result was that the precipitation in the wood was to that in an open glade of several acres near the forest station as 043 to 1,000, and the proportion in each of the three years was nearly identical. According to Mathieu, then, only 57 thousandths or 5.7 per cent of the precipitation is intercepted by trees.—Surrell, Etude sur les Torrents, 2d ed., ii., p. 98.
By order of the Direction of the Forests of the Canton of Berne, a series of experiments on this subject was commenced at the beginning of the year 1869. During the first seven months of the year (the reports for which alone I have seen), including, of course, the season when the foliage is most abundant, as well as that when it is thinnest, the pluviometers in the woods received only fifteen per cent less than those in the open grounds in the vicinity.—Risler, in Revue des Eaux et Forets, of 10th January, 1870.] while in heavier rains, the large drops which fall upon the leaves and branches are broken into smaller ones, and consequently strike the ground with less mechanical force, or are perhaps even dispersed into vapor without reaching it. [Footnote: We are not, indeed, to suppose that the condensation of vapor and the evaporation of water are going on in the same stratum of air at the same time, or, in other words, that vapor is condensed into rain-drops, and rain-drops evaporated, under the same conditions; but rain formed in one stratum may fall through another, where vapor would not be condensed. Two saturated strata of different temperatures may be brought into contact in the higher regions, and discharge large rain-drops, which, it not divided by some obstruction, will reach the ground, though passing through strata which would vaporize them if they were in a state of more minute division.]
The vegetable mould, resulting from the decomposition of leaves and of wood, serves as a perpetual mulch to forest-soil by carpeting the ground with a spongy covering which obstructs the evaporation from the mineral earth below, [Footnote: The only direct experiments known to me on the evaporation from the SURFACE of the forest are those of Mathieu.—Surrell, Etude sur les Torrents, 2d ed., ii, p. 99.
These experiments were continued from March to December, inclusive, of the year 1868. It was found that during those months the evaporation from a recipient placed on the ground in a plantation of deciduous trees sixty-two years old, was less than one-fifth of that from a recipient of like form and dimensions placed in the open country.] drinks up the rains and melting snows that would otherwise flow rapidly over the surface and perhaps be conveyed to the distant sea, and then slowly gives out, by evaporation, infiltration, and percolation, the moisture thus imbibed. The roots, too, penetrate far below the superficial soil, conduct water along their surface to the lower depths to which they reach, and thus by partially draining the superior strata, remove a certain quantity of moisture out of the reach of evaporation. The Forest as Organic.
These are the principal modes in which the humidity of the atmosphere is affected by the forest regarded as lifeless matter. Let us inquire how its organic processes act upon this meteorological element. The commonest observation shows that the wood and bark of living trees are always more or less pervaded with watery and other fluids, one of which, the sap, is very abundant in trees of deciduous foliage when the buds begin to swell and the leaves to develop themselves in the spring. This fluid is drawn principally, if not entirely, from the ground by the absorbent action of the roots, for though Schacht and some other eminent botanical physiologists have maintained that water is absorbed by the leaves and bark of trees, yet most experiments lead to the contrary result, and it is now generally held that no water is taken in by the pores of vegetables. Late observations by Cailletet, in France, however, tend to the establishment of a new doctrine on this subject which solves many difficulties and will probably be accepted by botanists as definitive. Cailletet finds that under normal conditions, that is, when the soil is humid enough to supply sufficient moisture through the roots, no water is absorbed by the leaves, buds, or bark of plants, but when the roots are unable to draw from the earth the requisite quantity of this fluid, the vegetable pores in contact with the atmosphere absorb it from that source.
Popular opinion, indeed, supposes that all the vegetable fluids, during the entire period of growth, are drawn from the bosom of the earth, and that the wood and other products of the tree are wholly formed from matter held in solution in the water abstracted by the roots from the ground. This is an error, for the solid matter of the tree, in a certain proportion not important to our present inquiry, is received from the atmosphere in a gaseous form, through the pores of the leaves and of the young shoots, and, as we have just seen, moisture is sometimes supplied to trees by the atmosphere. The amount of water taken up by the roots, however, is vastly greater than that imbibed through the leaves and bark, especially at the season when the sap is most abundant, and when the leaves are yet in embryo. The quantity of water thus received from the air and the earth, in a single year, even by a wood of only a hundred acres, is very great, though experiments are wanting to furnish the data for even an approximate estimate of its measure; for only the vaguest conclusions can be drawn from the observations which have been made on the imbibition and exhalation of water by trees and other plants reared in artificial conditions diverse from those of the natural forest. [Footnote: The experiments of Hales and others on the absorption and exhalation of vegetables are of high physiological interest; but observations on sunflowers, cabbages, hops, and single branches of isolated trees, growing in artificially prepared soils and under artificial conditions, furnish no trustworthy data for computing the quantity of water received and given off by the natural wood.]
Flow of Sap.
The amount of sap which can be withdrawn from living trees furnishes, not indeed a measure of the quantity of water sucked up by their roots from the ground—for we cannot extract from a tree its whole moisture—but numerical data which may aid the imagination to form a general notion of the powerful action of the forest as an absorbent of humidity from the earth.
The only forest-tree known to Europe and North America, the sap of which is largely enough applied to economical uses to have made the amount of its flow a matter of practical importance and popular observation, is the sugar maple, Acer saccharinum, of the Anglo-American Provinces and States. In the course of a single "sugar season," which lasts ordinarily from twenty-five to thirty days, a sugar maple two feet in diameter will yield not less than twenty gallons of sap, and sometimes much more. [Footnote: Emerson (Trees of Massachusetts. p. 403) mentions a maple six feet in diameter, as having yielded a barrel, or thirty-one and a half gallons, of sap in twenty-four hours, and another, the dimensions of which are not stated, as having yielded one hundred and seventy-five gallons in the course of the season.
The Cultivator, an American agricultural journal, for June, 1842, states that twenty gallons of sap were drawn in eighteen hours from a single maple, two and a half feet in diameter, in the town of Warner, New Hampshire, and the truth of this account has been verified by personal inquiry made in my behalf. This tree was of the original forest growth, and had been left standing when the ground around it was cleared. It was tapped only every other year, and then with six or eight incisions. Dr. Williams (History of Vermont, i., p. 01) says: "A man much employed in milking maple sugar, found that, for twenty-one days together, a maple-tree discharged seven and a half gallons per day."
An intelligent correspondent, of much experience in the manufacture of maple sugar, writes me that a second-growth maple, of about two feet in diameter, standing in open ground, tapped with four incisions, has, for several seasons, generally run eight gallons per day in fair weather. He speaks of a very large tree, from which sixty gallons were drawn in the course of a season, and of another, something more than three feet through, which made forty-two pounds of wet sugar, and must have yielded not less than one hundred and fifty gallons.] This, however, is but a trifling proportion of the water abstracted from the earth by the roots during this season; for all this fluid runs from two or three incisions or auger-holes, so narrow as to intercept the current of comparatively few sap vessels, and besides, experience shows that large as is the quantity withdrawn from the circulation, it is relatively too small to affect very sensibly the growth of the tree. [Footnote: Tapping does not check the growth, but does injure the quality of the wood of maples. The wood of trees often tapped is lighter and less dense than that of trees which have not been tapped, and gives less heat in burning. No difference has been observed in the bursting of the buds of tapped and untapped trees.] The number of large maple-trees on an acre is frequently not less than fifty, [Footnote: Dr. Rush, in a letter to Jefferson, states the number of maples fit for tapping on an acre at from thirty to fifty. "This," observes my correspondent, "is correct with regard to the original growth, which is always more or less intermixed with other trees; but in second growth, composed of maples alone, the number greatly exceeds this. I have had the maples on a quarter of an acre, which I thought about an average of second-growth 'maple orchards,' counted. The number was found to be fifty-two, of which thirty-two were ten inches or more in diameter, and, of course, large enough to tap. This gives two hundred and eight trees to the acre, one hundred and twenty-eight of which were of proper size for tapping."] and of course the quantity of moisture abstracted from the soil by this tree alone is measured by thousands of gallons to the acre. The sugar orchards, as they are called, contain also many young maples too small for tapping, and numerous other trees—two of which, at least, the black birch, Betula lenta, and yellow birch, Betula excelsa, both very common in the same climate, are far more abundant in sap than the maple [Footnote: The correspondent already referred to informs me that a black birch, tapped about noon with two incisions, was found the next morning to have yielded sixteen gallons. Dr. Williams (History of Vermont, i., p. 91) says: "A large birch, tapped in the spring, ran at the rate of five gallons an hour when first tapped. Eight or nine days after, it was found to run at the rate of about two and a half gallons an hour, and at the end of fifteen days the discharge continued in nearly the same quantity. The sap continued to flow for four or five weeks, and it was the opinion of the observers that it must have yielded as much as sixty barrels [l,800 gallons]."]—are scattered among the sugar-trees; for the North American native forests are remarkable for the mixture of their crops. The sap of the maple, and of other trees with deciduous leaves which grow in the same climate, flows most freely in the early spring, and especially in clear weather, when the nights are frosty and the days warm; for it is then that the melting snows supply the earth with moisture in the justest proportion, and that the absorbent power of the roots is stimulated to its highest activity.
When the buds are ready to burst, and the green leaves begin to show themselves beneath their scaly covering, the ground has become drier, the absorption by the roots is diminished, and the sap, being immediately employed in the formation of the foliage, can be extracted from the stem in only small quantities.
Absorption and Exhalation by Foliage.
The leaves now commence the process of absorption, and imbibe both uncombined gases and an unascertained but probably inconsiderable quantity of aqueous vapor from the humid atmosphere of spring which bathes them.
The organic action of the tree, as thus far described, tends to the desiccation of air and earth; but when we consider what volumes of water are daily absorbed by a large tree, and how small a proportion of the weight of this fluid consists of matter which, at the period when the flow of sap is freest, enters into new combinations, and becomes a part of the solid framework of the vegetable, or a component of its deciduous products, it becomes evident that the superfluous moisture must somehow be carried back again almost as rapidly as it flows into the tree. At the very commencement of vegetation in spring, some of this fluid certainly escapes through the buds, the nascent foliage, and the pores of the bark, and vegetable physiology tells us that there is a current of sap towards the roots as well as from them. [Footnote: "The elaborated sap, passing out of the leaves, is received into the inner bark, . . . and a part of what descends finds its way even to the ends of the roots, and is all along diffused laterally into the stem, where it meets and mingles with the ascending crude sap or raw material. So there is no separate circulation of the two kinds of sap; and no crude sap exists separately in any part of the plant. Even in the root, where it enters, this mingles at once with some elaborated sap already there."—Gray, How Plants Grow, Section 273.]
I do not know that the exudation of water into the earth, through the bark or at the extremities of these latter organs, has been proved, but the other known modes of carrying off the surplus do not seem adequate to dispose of it at the almost leafless period when it is most abundantly received, and it is possible that the roots may, to some extent, drain as well as flood the water-courses of their stem. Later in the season the roots absorb less, and the now developed leaves exhale an increased quantity of moisture into the air. In any event, all the water derived by the growing tree from the atmosphere and the ground is parted with by transpiration or exudation, after having surrendered to the plant the small proportion of matter required for vegetable growth which it held in solution or suspension. [Footnote: Ward's tight glazed cases for raising and especially for transporting plants, go far to prove that water only circulates through vegetables, and is again and again absorbed and transpired by organs appropriated to these functions.
Seeds, growing grasses, shrubs, or trees planted in proper earth, moderately watered and covered with a glass bell or close frame of glass, live for months, and even years, with only the original store of air and water. In one of Ward's early experiments, a spire of grass and a fern, which sprang up in a corked bottle containing a little moist earth introduced as a bed for a snail, lived and flourished for eighteen years without a new supply of either fluid. In these boxes the plants grow till the enclosed air is exhausted of the gaseous constituents of vegetation, and till the water has yielded up the assimilable matter it held in solution, and dissolved and supplied to the roots the nutriment contained in the earth in which they are planted. After this, they continue for a long time in a state of vegetable sleep, but if fresh air and water be introduced into the cases, or the plants be transplanted into open ground, they rouse themselves to renewed life, and grow vigorously, without appearing to have suffered from their long imprisonment. The water transpired by the leaves is partly absorbed by the earth directly from the air, partly condensed on the glass, along which it trickles down to the earth, enters the roots again, and thus continually repeats the circuit. See Aus der Natur, 21, B. S. 537.] The hygrometrical equilibrium is then restored, so far as this: the tree yields up again the moisture it had drawn from the earth and the air, though it does not return it each to each; for the vapor carried off by transpiration greatly exceeds the quantity of water absorbed by the foliage from the atmosphere, and the amount, if any, carried back to the ground by the roots.
The present estimates of some eminent vegetable physiologists in regard to the quantity of aqueous vapor exhaled by trees and taken up by the atmosphere are much greater than those of former inquirers. Direct and satisfactory experiments on this point are wanting, and it is not easy to imagine how they could be made on a sufficiently extensive and comprehensive scale. Our conclusions must therefore be drawn from observations on small plants, or separate branches of trees, and of course are subject to much uncertainty. Nevertheless, Schleiden, arguing from such analogies, comes to the surprising result, that a wood evaporates ten times as much water as it receives from atmospheric precipitation. [Footnote: Fur Baum und Wald, pp. 46, 47, notes. Pfaff, too, experimenting on branches of a living oak, weighed immediately after being cut from the tree, and again after an exposure to the air for three minutes, and computing the superficial measure of all the leaves of the tree, concludes that an oak-tree evaporates, during the season of growth, eight and a half times the mean amount of rain-fall on an area equal to that shaded by the tree.] In the Northern and Eastern States of the Union, the mean precipitation during the period of forest growth, that is from the swelling of the buds in the spring to the ripening of the fruit, the hardening of the young shoots, and the full perfection of the other annual products of the tree, exceeds on the average twenty-four inches. Taking this estimate, the evaporation from the forest would be equal to a precipitation of two hundred and forty inches, or very nearly one hundred and fifty standard gallons to the square foot of surface.
The first questions which suggest themselves upon this statement are: what becomes of this immense quantity of water and from what source does the tree derive it We are told in reply that it is absorbed from the air by the humus and mineral soil of the wood, and supplied again to the tree through its roots, by a circulation analogous to that observed in Ward's air-tight cases. When we recall the effect produced on the soil even of a thick wood by a rain-fall of one inch, we find it hard to believe that two hundred and forty times that quantity, received by the ground between early spring and autumn, would not keep it in a state of perpetual saturation, and speedily convert the forest into a bog.
No such power of absorption of moisture by the earth from the atmosphere, or anything approaching it, has ever been shown by experiment, and all scientific observation contradicts the supposition. Schubler found that in seventy-two hours thoroughly dried humus, which is capable of taking up twice its own weight of water in the liquid state, absorbed from the atmosphere only twelve per cent. of its weight of humidity; garden-earth five and one-fifth per cent. and ordinary cultivated soil two and one-third per cent. After seventy-two hours, and, in most of his experiments with thirteen different earths, after forty-eight hours, no further absorption took place. Wilhelm, experimenting with air-dried field-earth, exposed to air in contact with water and protected by a bell-glass, found that the absorption amounted in seventy-two hours to two per cent. and a very small fraction, nearly the whole of which was taken up in the first forty-eight hours. In other experiments with carefully heat-dried field-soil, the absorption was five per cent. in eighty-four hours, and when the water was first warmed to secure the complete saturation of the air, air-dried garden-earth absorbed five and one-tenth per cent. in seventy-two hours.
In nature, the conditions are never so favorable to the absorption of vapor as in those experiments. The ground is more compact and of course offers less surface to the air, and, especially in the wood, it is already in a state approaching saturation. Hence, both these physicists conclude that the quantity of aqueous vapor absorbed by the earth from the air is so inconsiderable "that we can ascribe to it no important influence on vegetation." [Footnote: Wilhelm, Der Boden und das Wasser, pp. 14,20.] Besides this, trees often grow luxuriantly on narrow ridges, on steep declivities, on partially decayed stumps many feet above the ground, on walls of high buildings, and on rocks, in situations where the earth within reach of their roots could not possibly contain the tenth part of the water which, according to Schleiden and Pfaff, they evaporate in a day. There are, too, forests of great extent on high bluffs and well-drained table-lands, where there can exist, neither in the subsoil nor in infiltration from neighboring regions, an adequate source of supply for such consumption. It must be remembered, also, that in the wood the leaves of the trees shade each other, and only the highest stratum of foliage receives the full influence of heat and light; and besides, the air in the forest is almost stagnant, while in the experiments of Unger, Marshal, Vaillant, Pfaff and others, the branches were freely exposed to light, sun, and atmospheric currents. Such observations can authorize no conclusions respecting the quantitative action of leaves of forest trees in normal conditions.
Further, allowing two hundred days for the period of forest vital action, the wood must, according to Schleiden's position, exhale a quantity of moisture equal to an inch and one-fifth of precipitation per day, and it is hardly conceivable that so large a volume of aqueous vapor, in addition to the supply from other sources, could be diffused through the ambient atmosphere without manifesting its presence by ordinary hygrometrical tests much more energetically than it has been proved to do, and in fact, the observations recorded by Ebermayer show that though the RELATIVE humidity of the atmosphere is considerably greater in the cooler temperature of the wood, its ABSOLUTE humidity does not sensibly differ from that of the air in open ground. [Footnote: Ebermeyer, Die Physikalischen, Einwirkungen des Waldes, i., pp. 150 et seqq. It may be well here to guard my readers against the common error which supposes that a humid condition of the AIR is necessarily indicated by the presence of fog or visible vapor. The air is rendered humid by containing INVISIBLE vapor, and it becomes drier by the condensation of such vapor into fog, composed of solid globules or of hollow vesicles of water—for it is a disputed point whether the particles of fog are solid or vesicular. Hence, though the ambient atmosphere may hold in suspension, in the form of fog, water enough to obscure its transparency, and to produce the sensation of moisture on the skin, the air, in which the finely divided water floats, may be charged with even less than an average proportion of humidity.]
The daily discharge of a quantity of aqueous vapor corresponding to a rain-fall of one inch and a fifth into the cool air of the forest would produce a perpetual shower, or at least drizzle, unless, indeed, we suppose a rapidity of absorption and condensation by the ground, and of transmission through the soil to the roots and through them and the vessels of the tree to the leaves, much greater than has been shown by direct observation. Notwithstanding the high authority of Schleiden, therefore, it seems impossible to reconcile his estimates with facts commonly observed and well established by competent investigators. Hence the important question of the supply, demand, and expenditure of water by forest vegetation must remain undecided, until it can be determined by something approaching to satisfactory direct experiment. [Footnote: According to Cezanne, Surrell, Etude sur les Torrents, 2e edition, ii., p. 100, experiments reported in the Revue des Eaux et Forets for August, 1868, showed the evaporation from a living tree to be "almost insignificant." Details are not given.]
Balance of Conflicting Influences of Forest on Atmospheric Heat and
Humidity.
We have shown that the forest, considered as dead matter, tends to diminish the moisture of the air, by preventing the sun's rays from reaching the ground and evaporating the water that falls upon the surface, and also by spreading over the earth a spongy mantle which sucks up and retains the humidity it receives from the atmosphere, while, at the same time, this covering acts in the contrary direction by accumulating, in a reservoir not wholly inaccessible to vaporizing influences, the water of precipitation which might otherwise suddenly sink deep into the bowels of the earth, or flow by superficial channels to other climatic regions. We now see that, as a living organism, it tends, on the one hand, to diminish the humidity of the air by sometimes absorbing moisture from it, and, on the other, to increase that humidity by pouring out into the atmosphere, in a vaporous form, the water it draws up through its roots. This last operation, at the same time, lowers the temperature of the air in contact with or proximity to the wood, by the same law as in other cases of the conversion of water into vapor.
As I have repeatedly said, we cannot measure the value of any one of those elements of climatic disturbance, raising or lowering of temperature, increase or diminution of humidity, nor can we say that in any one season, any one year, or any one fixed cycle, however long or short, they balance and compensate each other. They are sometimes, but certainly not always, contemporaneous in their action, whether their tendency is in the same or in opposite directions, and, therefore, their influence is sometimes cumulative, sometimes conflicting; but, upon the whole, their general effect is to mitigate extremes of atmospheric heat and cold, moisture and drought. They serve as equalizers of temperature and humidity, and it is highly probable that, in analogy with most other works and workings of nature, they, at certain or uncertain periods, restore the equilibrium which, whether as lifeless masses or as living organisms, they may have temporarily disturbed. [Footnote: There is one fact which I have nowhere seen noticed, but which seems to me to have an important bearing on the question whether forests tend to maintain an equilibrium between the various causes of hygroscopic action, and consequently to keep the air within their precincts in an approximately constant condition, so far as this meteorological element is concerned. I refer to the absence of fog or visible vapor in thick woods in full leaf, even when the air of the neighboring open grounds is so heavily charged with condensed vapor as completely to obscure the sun. The temperature of the atmosphere in the forest is not subject to so sudden and extreme variations as that of cleared ground, but at the same time it is far from constant, and so large a supply of vapor as is poured out by the foliage of the trees could not fail to be sometimes condensed into fog by the same causes as in the case of the adjacent meadows, which are often covered with a dense mist while the forest-air remains clear, were there not some potent counteracting influence always in action. This influence, I believe, is to be found partly in the equalization of the temperature of the forest, and partly in the balance between the humidity exhaled by the trees and that absorbed and condensed invisibly by the earth.] When, therefore, man destroys these natural harmonizors of climatic discords, he sacrifices an important conservative power, though it is far from certain that he has thereby affected the mean, however much he may have exaggerated the extremes of atmospheric temperature and humidity, or, in other words, may have increased the range and lengthened the scale of thermometric and hygrometric variation.
Special Influence of Woods on Precipitation.
With the question of the action of forests upon temperature and upon atmospheric humidity is intimately connected that of their influence upon precipitation, which they may affect by increasing or diminishing the warmth of the air and by absorbing or exhaling uncombincd gas and aqueous vapor. The forest being a natural arrangement, the presumption is that it exercises a conservative action, or at least a compensating one, and consequently that its destruction must tend to produce pluviometrical disturbances as well as thermometrical variations. And this is the opinion of perhaps the greatest number of observers. Indeed, it is almost impossible to suppose that, under certain conditions of time and place, the quantity and the periods of rain should not depend, more or less, upon the presence or absence of forests; and without insisting that the removal of the forest has diminished the sum-total of snow and rain, we may well admit that it has lessened the quantity which annually falls within particular limits. Various theoretical considerations make this probable, the most obvious argument, perhaps, being that drawn from the generally admitted fact, that the summer and even the mean temperature of the forest is below that of the open country in the same latitude. If the air in a wood is cooler than that around it, it must reduce the temperature of the atmospheric stratum immediately above it, and, of course, whenever a saturated current sweeps over it, it must produce precipitation which would fall upon it, or at a greater or less distance from it.
We must here take into the account a very important consideration. It is not universally or even generally true, that the atmosphere returns its condensed humidity to the local source from which it receives it. The air is constantly in motion,
—howling tempests scour amain
From sea to land, from land to sea;
[Footnote: Und Sturme brausen um die Wette
Vom Meer aufs Land, vom Land aufs Meer.
Goethe, Faust, Song of the Archangels.]
and, therefore, it is always probable that the evaporation drawn up by the atmosphere from a given river, or sea, or forest, or meadow, will be discharged by precipitation, not at or near the point where it rose, but at a distance of miles, leagues, or even degrees. The currents of the upper air are invisible, and they leave behind them no landmark to record their track. We know not whence they come, or whither they go. We have a certain rapidly increasing acquaintance with the laws of general atmospheric motion, but of the origin and limits, the beginning and end of that motion, as it manifests itself at any particular time and place, we know nothing. We cannot say where or when the vapor, exhaled to-day from the lake on which we float, will be condensed and fall; whether it will waste itself on a barren desert, refresh upland pastures, descend in snow on Alpine heights, or contribute to swell a distant torrent which shall lay waste square miles of fertile corn-land; nor do we know whether the rain which feeds our brooklets is due to the transpiration from a neighboring forest, or to the evaporation from a far-off sea. If, therefore, it were proved that the annual quantity of rain and dew is now as great on the plains of Castile, for example, as it was when they were covered with the native forest, it would by no means follow that those woods did not augment the amount of precipitation elsewhere. The whole problem of the pluviometrical influence of the forest, general or local, is so exceedingly complex and difficult that it cannot, with our present means of knowledge, be decided upon a priori grounds. It must now be regarded as a question of fact which would probably admit of scientific explanation if it were once established what the actual fact is.
Unfortunately, the evidence is conflicting in tendency, and sometimes equivocal in interpretation, but I believe that a majority of the foresters and physicists who have studied the question are of opinion that in many, if not in all cases, the destruction of the woods has been followed by a diminution in the annual quantity of rain and dew. Indeed, it has long been a popularly settled belief that vegetation and the condensation and fall of atmospheric moisture are reciprocally necessary to each other, and even the poets sing of
Afric's barren sand,
Where nought can grow, because it raineth not,
And where no rain can fall to bless the land,
Because nought grows there.
[Footnote: Det golde Strog i Afrika,
Der Intet voxe kan, da ei det regner,
Og, omvendt, ingen Regn kan falde, da
Der Intet voxer.
Paudan-Muller, Adam Hamo, ii., 408.]
Before going further with the discussion, however, it is well to remark that the comparative rarity or frequency of inundations in earlier or later centuries is not necessarily, in most cases not probably, entitled to any weight whatever, as a proof that more or less rain fell formerly than now; because the accumulation of water in the channel of a river depends far less upon the quantity of precipitation in its valley, than upon the rapidity with which it is conducted, on or under the surface of the ground, to the central artery that drains the basin. But this point will be more fully discussed in a subsequent chapter.
In writers on the subject we are discussing, we find many positive assertions about the diminution of rain in countries which have been stripped of wood within the historic period, but these assertions very rarely rest upon any other proof than the doubtful recollection of unscientific observers, and I am unable to refer to a single instance where the records of the rain-gauge, for a considerable period before and after the felling or planting of extensive woods, can be appealed to in support of either side of the question. The scientific reputation of many writers who have maintained that precipitation has been diminished in particular localities by the destruction of forests, or augmented by planting them, has led the public to suppose that their assertions rested on sufficient proof. We cannot affirm that in none of these cases did such proof exist, but I am not aware that it has ever been produced. [Footnote: Among recent writers, Clave, Schacht, Sir John F. W. Herschel, Hohenstein, Barth, Asbjornsen, Boussingault, and others, maintain that forests tend to produce rain and clearings to diminish it, and they refer to numerous facts of observation in support of this doctrine; but in none of these does it appear that these observations are supported by actual pluviometrical measure. So far as I know, the earliest expression of the opinion that forests promote precipitation is that attributed to Christopher Columbus, in the Historie del S. D. Fernando Colombo, Venetia, 157l, cap. lviii., where it is said that the Admiral ascribed the daily showers which fell in the West Indies about vespers to "the great forests and trees of those countries," and remarked that the same effect was formerly produced by the same cause in the Canary and Madeira Islands and in the Azores, but that "now that the many woods and trees that covered them have been felled, there are not produced so many clouds and rains as before."
Mr. H. Harrisse, in his very learned and able critical essay, Fernand Colomb, sa Vie et ses Oeuvres, Paris, 1872, has made it at least extremely probable that the Historie is a spurious work. The compiler may have found this observation in some of the writings of Columbus now lost, but however that may be, the fact, which Humboldt mentions in Cosmos with much interest, still remains, that the doctrine in question was held, if not by the great discoverer himself, at least by one of his pretended biographers, as early as the year 1571.]
The effect of the forest on precipitation, then, is by no means free from doubt, and we cannot positively affirm that the total annual quantity of rain is even locally diminished or increased by the destruction of the woods, though both theoretical considerations and the balance of testimony strongly favor the opinion that more rain falls in wooded than in open countries. One important conclusion, at least, upon the meteorological influence of forests is certain and undisputed: the proposition, namely, that, within their own limits, and near their own borders, they maintain a more uniform degree of humidity in the atmosphere than is observed in cleared grounds. Scarcely less can it be questioned that they tend to promote the frequency of showers, and, if they do not augment the amount of precipitation, they probably equalize its distribution through the different seasons. [Footnote: The strongest direct evidence which I am able to refer to in support of the proposition that the woods produce even a local augmentation of precipitation is furnished by the observations of Mathieu, sub-director of the Forest-School at Nancy. His pluviometrical measurements, continued for three years, 1866-1868, show that during that period the annual mean of rain-fall in the centre of the wooded district of Cinq-Tranchees, at Belle Fontaine on the borders of the forest, and at Amance, in an open cultivated territory in the same vicinity, was respectively as the numbers 1,000, 957, and 853.
The alleged augmentation of rain-fall in Lower Egypt, in consequence of large plantations by Mehemet Ali, is very frequently appealed to as a proof of this influence of the forest, and this case has become a regular common-place in all discussions of the question. It is, however, open to the same objection as the alleged instances of the diminution of precipitation in consequence of the felling of the forest.
This supposed increase in the frequency and quantity of rain in Lower Egypt is, I think, an error, or at least not an established fact. I have heard it disputed on the spot by intelligent Franks, whose residence in that country began before the plantations of Mehemet Ali and Ibrahim Pacha, and I have been assured by them that meterological observations, made at Alexandria about the begiuning of this century, show an annual fall of rain as great as is usual at this day. The mere fact that it did not rain during the French occupation is not conclusive. Having experienced a gentle shower of nearly twenty-four hours' duration in Upper Egypt, I inquired of the local governor in relation to the frequency of this phenomenon, and was told by him that not of drop of rain had fallen at that point for more than two years previous.
The belief in the increase of rain in Egypt rests almost entirely on the observations of Marshal Marmont, and the evidence collected by him in 1836. His conclusions have been disputed, if not confuted, by Joinard and others, and are probably erroneous. See Foissac, Meteorologie, German translation, pp. 634-639.
It certainly sometimes rains briskly at Cairo, but evaporation is exceedingly rapid in Egypt—as any one who ever saw a Fellah woman wash a napkin in the Nile, and dry it by shaking it a few moments in the air, can testify; and a heap of grain, wet a few inches below the surface, would probably dry again without injury. At any rate, the Egyptian Government often has vast quantities of wheat stored at Boulak in uncovered yards through the winter, though it must be admitted that the slovenliness and want of foresight in Oriental life, public and private, are such that we cannot infer the safety of any practice followed in the East merely from its long continuance.
Grain, however, may be long kept in the open air in climates much less dry than that of Egypt, without injury, except to the superficial layers; for moisture does not penetrate to a great depth in a heap of grain once well dried and kept well aired. When Louis IX. was making his preparations for his campaign in the East, he had large quantities of wine and grain purchased in the Island of Cyprus, and stored up for two years to await his arrival. "When we were come to Cyprus," says Joinville, Histoire de Saint Louis, Section 72, 73, "we found there greate foison of the Kynge's purveyance. . . The wheate and the barley they had piled up in greate heapes in the feeldes, and to looke vpon, they were like vnto mountaynes; for the raine, the whyche hadde beaten vpon the wheate now a longe whyle, had made it to sproute on the toppe, so that it seemed as greene grasse. And whanne they were mynded to carrie it to Egypte, they brake that sod of greene herbe, and dyd finde under the same the wheate and the barley, as freshe as yf menne hadde but nowe thrashed it."]
Total Climatic Influence of the Forest.
Aside from the question of local disturbances and their compensations, it does not seem probable that the forests sensibly affect the general mean of atmospheric temperature of the globe, or the total quantity of precipitation, or even that they had this influence when their extent was vastly greater than at present. The waters cover about three-fourths of the face of the earth, and if we deduct the frozen zones, the peaks and crests of lofty mountains and their craggy slopes, the Sahara and other great African and Asiatic deserts, and all such other portions of the solid surface as are permanently unfit for the growth of wood, we shall find that probably not one-tenth of the total superficies of our planet was ever, at any one time in the present geological period, covered with forests. Besides this, the distribution of forest land, of desert, and of water, is such as to reduce the possible influence of the woods to a low expression; for the forests are, in large proportion, situated in cold or temperate climates, where the action of the sun is comparatively feeble both in elevating temperature and in promoting evaporation; while, in the torrid zone, the desert and the sea—the latter of which always presents an evaporable surface—enormously preponderate. It is, upon the whole, not probable that so small an extent of forest, so situated, could produce a sensible influence on the general climate of the globe, though it might appreciably affect the local action of all climatic elements. The total annual amount of solar heat absorbed and radiated by the earth, and the sum of terrestrial evaporation and atmospheric precipitation, must be supposed constant; but the distribution of heat and of humidity is exposed to disturbance in both time and place by a multitude of local causes, among which the presence or absence of the forest is doubtless one.
So far as we are able to sum up the results, it would appear that, in countries in the temperate zone still chiefly covered with wood, the summers would be cooler, moister, shorter, the winters milder, drier, longer, than in the same regions after the removal of the forest, and that the condensation and precipitation of atmospheric moisture would be, if not greater in total quantity, more frequent and less violent in discharge. The slender historical evidence we possess seems to point to the same conclusion, though there is some conflict of testimony and of opinion on this point.
Among the many causes which, as we have seen, tend to influence the general result, the mechanical action of the forest, if not more important, is certainly more obvious and direct than the immediate effects of its organic processes. The felling of the woods involves the sacrifice of a valuable protection against the violence of chilling winds and the loss of the shelter afforded to the ground by the thick coating of leaves which the forest sheds upon it and by the snow which the woods prevent from blowing away, or from melting in the brief thaws of winter. I have already remarked that bare ground freezes much deeper than that which is covered by beds of leaves, and when the earth is thickly coated with snow, the strata frozen before it fell begin to thaw. It is not uncommon to find the ground in the woods, where the snow lies two or three feet deep, entirely free from frost, when the atmospheric temperature has been for several weeks below the freezing-point, and for some days even below the zero of Fahrenheit. When the ground is cleared and brought under cultivation, the leaves are ploughed into the soil and decomposed, and the snow, especially upon knolls and eminences, is blown off, or perhaps half thawed, several times during the winter. The water from the melting snow runs into the depressions, and when, after a day or two of warm sunshine or tepid rain, the cold returns, it is consolidated to ice, and the bared ridges and swells of earth are deeply frozen. [Footnote: I have seen, in Northern New England, the surface of the open ground frozen to the depth of twenty-two inches, in the month of November, when in the forest-earth no frost was discoverable; and later in the winter, I have known an exposed sand-knoll to remain frozen six feet deep, after the ground in the woods was completely thawed.] It requires many days of mild weather to raise the temperature of soil in this condition, and of the air in contact with it, to that of the earth in the forests of the same climatic region. Flora is already plaiting her sylvan wreath before the corn-flowers which are to deck the garland of Ceres have waked from their winter's sleep; and it is probably not a popular error to believe that, where man has substituted his artificial crops for the spontaneous harvest of nature, spring delays her coming. [Footnote: The conclusion arrived at by Noah Webster, in his very learned and able paper on the supposed change in the temperature of winter, read before the Connecticut Academy of Arts and Sciences in 1799, was as follows: "From a careful comparison of these facts, it appears that the weather, in modern winters, in the United States, is more inconstant than when the earth was covered with woods, at the first settlement of Europeans in the country; that the warm weather of autumn extends further into the winter months, and the cold weather of winter and spring encroaches upon the summer; that, the wind being more variable, snow is less permanent, and perhaps the same remark may be applicable to the ice of the rivers. These effects seem to result necessarily from the greater quantity of heat accumulated in the earth in summer since the ground has been cleared of wood and exposed to the rays of the sun, and to the greater depth of frost in the earth in winter by the exposure of its uncovered surface to the cold atmosphere."—Collection of Papers by Noah Webster, p. 162.]
There are, in the constitution and action of the forest, many forces, organic and inorganic, which unquestionably tend powerfully to produce meteorological effects, and it may, therefore, be assumed as certain that they must and do produce such effects, UNLESS they compensate and balance each other, and herein lies the difficulty of solving the question. To some of these elements late observations give a new importance. For example, the exhalation of aqueous vapor by plants is now believed to be much greater, and the absorption of aqueous vapor by them much less, than was formerly supposed, and Tyndall's views on the relations of vapor to atmospheric heat give immense value to this factor in the problem. In like manner the low temperature of the surface of snow and the comparatively high temperature of its lower strata, and its consequent action on the soil beneath, and the great condensation of moisture by snow, are facts which seem to show that the forest, by protecting great surfaces of snow from melting, must inevitably exercise a great climatic influence. If to these influences we add the mechanical action of the woods in obstructing currents of wind, and diminishing the evaporation and refrigeration which such currents produce, we have an accumulation of forces which MUST manifest great climatic effects, unless—which is not proved and cannot be presumed—they neutralize each other. These are points hitherto little considered in the discussion, and it seems difficult to deny that as a question of ARGUMENT, the probabilities are strongly in favor of the meteorological influence of the woods. The EVIDENCE, indeed, is not satisfactory, or, to speak more accurately, it is non-existent, for there really is next to no trustworthy proof on the subject, but it appears to me a case where the burden of proof must be taken by those who maintain that, as a meteorological agent, the forest is inert.
The question of a change in the climate of the Northern American States is examined in the able Meteorological Report of Mr. Draper, Director of the New York Central Park Observatory, for 1871. The result arrived at by Mr. Draper is, that there is no satisfactory evidence of a diminution in the rainfall, or of any other climatic change in the winter season, in consequence of clearing of the forests or other human action. The proof from meteorological registers is certainly insufficient to establish the fact of a change of climate, but, on the other hand, it is equally insufficient to establish the contrary. Meteorological stations are too few, their observations, in many cases, extend over a very short period, and, for reasons I have already given, the great majority of their records are entitled to little or no confidence. [Footnote: Since these pages were written, the subject of forest meteorology has received the most important contribution ever made to it, in several series of observations at numerous stations in Bavaria, from the year 1866 to 1871, published by Ebermayer, at Aschaffenburg, in 1873, under the title: Die Physikalischen Einwirkungen des Waldes auf Luft und Boden, und seine Klimatologische und Hygienische Bedeutung. I. Band. So far as observations of only five years' duration can prove anything, the following propositions, not to speak of many collateral and subsidiary conclusions, seem to be established, at least for the localities where the observations were made:
1. The yearly mean temperature of wooded soils, at all depths, is lower than that of open grounds, p. 85.
This conclusion, it may be remarked, is of doubtful applicability in regions of excessive climate like the Northern United States and Canada, where the snow keeps the temperature of the soil in the forest above the freezing-point, for a large part and sometimes the whole of the winter, while in unwooded ground the earth remains deeply frozen.
2. The yearly mean atmospheric temperature, other things being equal, is lower in the forest than in cleared grounds, p. 84.
3. Climates become excessive in consequence of extensive clearings, p. 117.
4. The ABSOLUTE humidity of the air in the forest is about the same as in open ground, while the RELATIVE humidity is greater in the former than in the latter case, on account of the lower temperature of the atmosphere in the wood, p. 150.
5. The evaporation from an exposed surface of water in the forest is sixty-four per cent. less than in unwooded grounds, pp. 159,161.
6. About twenty-six per cent. of the precipitation is interrupted and prevented from reaching the ground by the foliage and branches of forest trees, p. 194.
7. In the interior of thick woods, the evaporation from water and from earth is much less than the precipitation, p. 210.
8. The loss of the water of precipitation intercepted by the trees in the forest is compensated by the smaller evaporation from the ground, p. 219.
9. In elevated regions and during the summer half of the year, woods tend to increase the precipitation, p. 202.]
Influence of the Forest on the Humidity of the Soil.
I have hitherto confined myself to the influence of the forest on meteorological conditions, a subject, as has been seen, full of difficulty and uncertainty. Its comparative effects on the temperature, the humidity, the texture and consistence, the configuration and distribution of the mould or arable soil, and, very often, of the mineral strata below, and on the permanence and regularity of springs and greater superficial water-courses, are much less disputable as well as more easily estimated and more important, than its possible value as a cause of strictly climatic equilibrium or disturbance.
The action of the forest on the earth is chiefly mechanical, but the organic process of absorption of moisture by its roots affects the quantity of water contained in the vegetable mould and in the mineral strata near the surface, and, consequently, the consistency of the soil. In treating of the effects of trees on the moisture of the atmosphere, I have said that the forest, by interposing a canopy between the sky and the ground, and by covering the surface with a thick mantle of fallen leaves, at once obstructed insulation and prevented the radiation of heat from the earth. These influences go far to balance each other; but familiar observation shows that, in summer, the forest-soil is not raised to so high a temperature as open grounds exposed to irradiation. For this reason, and in consequence of the mechanical resistance opposed by the bed of dead leaves to the escape of moisture, we should expect that, except after recent rains, the superficial strata of woodland-soil would be more humid than that of cleared land. This agrees with experience. The soil of the natural forest is always moist, except in the extremest droughts, and it is exceedingly rare that a primitive wood suffers from want of humidity. How far this accumulation of water affects the condition of neighboring grounds by lateral infiltration, we do not know, but we shall see, in a subsequent chapter, that water is conveyed to great distances by this process, and we may hence infer that the influence in question is an important one.
It is undoubtedly true that loose soils, stripped of vegetation and broken up by the plough or other processes of cultivation, may, until again carpeted by grasses or other plants, absorb more rain and snow-water than when they were covered by a natural growth; but it is also true that the evaporation from such soils is augmented in a still greater proportion. Rain scarcely penetrates beneath the sod of grass-ground, but runs off over the surface; and after the heaviest showers a ploughed field will often be dried by evaporation before the water can be carried off by infiltration, while the soil of a neighboring grove will remain half saturated for weeks together. Sandy soils frequently rest on a tenacious subsoil, at a moderate depth, as is usually seen in the pine plains of the United States, where pools of rain-water collect in slight depressions on the surface of earth the upper stratum of which is as porous as a sponge. In the open grounds such pools are very soon dried up by the sun and wind; in the woods they remain unevaporated long enough for the water to diffuse itself laterally until it finds, in the subsoil, crevices through which it may escape, or slopes which it may follow to their outcrop or descend along them to lower strata.
Drainage by Roots of Trees.
Becquerel notices a special function of the forest to which I have already alluded, but to which sufficient importance has not, until very recently, been generally ascribed. I refer to the mechanical action of the roots as conductors of the superfluous humidity of the superficial earth to lower strata. The roots of trees often penetrate through subsoil almost impervious to water, and in such cases the moisture, which would otherwise remain above the subsoil and convert the surface-earth into a bog, follows the roots downwards and escapes into more porous strata or is received by subterranean canals or reservoirs. [Footnote: "The roots of vegetables," says d'Hericourt, "perform the office of draining in a manner analogous to that artificially practised in parts of Holland and the British islands. This method consists in driving deeply down into the soil several hundred stakes to the acre; the water filters down along the stakes, and in some cases as favorable results have been obtained by this means as by horizontal drains."-Annales Forestieres, 1837, p. 312.] When the forest is felled, the roots perish and decay, the orifices opened by them are soon obstructed, and the water, after having saturated the vegetable earth, stagnates on the surface and transforms it into ponds and morasses. Thus in La Brenne, a tract of 200,000 acres resting on an impermeable subsoil of argillaceous earth, which ten centuries ago was covered with forests interspersed with fertile and salubrious meadows and pastures, has been converted, by the destruction of the woods, into a vast expanse of pestilential pools and marshes. In Sologne the same cause has withdrawn from cultivation and human inhabitation not less than 1,100,000 acres of ground once well wooded, well drained, and productive.
It is an important observation that the desiccating action of trees, by way of drainage or external conduction by the roots, is greater in the artificial than in the natural wood, and hence that the surface of the ground in the former is not characterized by that approach to a state of saturation which it so generally manifests in the latter. In the spontaneous wood, the leaves, fruits, bark, branches, and dead trunks, by their decayed material and by the conversion of rock into loose earth through the solvent power of the gases they develop in decomposition, cover the ground with an easily penetrable stratum of mixed vegetable and mineral matter extremely favorable to the growth of trees, and at the same time too retentive of moisture to part with it readily to the capillary attraction of the roots.
The trees, finding abundant nutriment near the surface, and so sheltered against the action of the wind by each other as not to need the support of deep and firmly fixed stays, send their roots but a moderate distance downwards, and indeed often spread them out like a horizontal network almost on the surface of the ground. In the artificial wood, on the contrary, the spaces between the trees are greater; they are obliged to send their roots deeper both for mechanical support and in search of nutriment, and they consequently serve much more effectually as conduits for perpendicular drainage.
It is only under special circumstances, however, that this function of the forest is so essential a conservative agent as in the two cases just cited. In a champaign region insufficiently provided with natural channels for the discharge of the waters, and with a subsoil which, though penetrable by the roots of trees, is otherwise impervious to water, it is of cardinal importance; but though trees everywhere tend to carry off the moisture of the superficial strata by this mode of conduction, yet the precise condition of soil which I have described is not of sufficiently frequent occurrence to have drawn much attention to this office of the wood. In fact, in most soils, there are counteracting influences which neutralize, more or less effectually, the desiccative action of roots, and in general it is as true as it was in Seneca's time, that "the shadiest grounds are the moistest." [Footnote: Seneca, Questiones Naturales, iii. 11, 2.]
It is always observed in the American States, that clearing the ground not only causes running springs to disappear, but dries up the stagnant pools and the spongy soils of the low grounds. The first roads in those States ran along the ridges, when practicable, because there only was the earth dry enough to allow of their construction, and, for the same reason, the cabins of the first settlers were perched upon the hills. As the forests have been from time to time removed, and the face of the earth laid open to the air and sun, the moisture has been evaporated, and the removal of the highways and of human habitations from the bleak hills to the sheltered valleys, is one of the most agreeable among the many improvements which later generations have witnessed in the interior of the Northern States. [Footnote: The Tuscan poet Ginati, who hod certainly had little opportunity of observing primitive conditions of nature and of man, was aware that such must have been the course of things in new countries. "You know," says he in a letter to a friend, "that the hills were first occupied by man, because stagnant waters, and afterwards continual wars, excluded men from the plains. But when tranquillity was established and means provided for the discharge of the waters, the low grounds were soon covered with human habitations."— Letters, Firenze, 1864, p. 98.]
Recent observers in France affirm that evergreen trees exercise a special desiccating action on the soil, and cases are cited where large tracts of land lately planted with pines have been almost completely drained of moisture by some unknown action of the trees. It is argued that the alleged drainage is not due to the conducting power of the roots, inasmuch as the roots of the pine do not descend lower than those of the oak and other deciduous trees which produce no such effect, and it is suggested that the foliage of the pine continues to exhale through the winter a sufficient quantity of moisture to account for the drying up of the soil. This explanation is improbable, and I know nothing in American experience of the forest which accords with the alleged facts. It is true that the pines, the firs, the hemlock, and all the spike-leaved evergreens prefer a dry soil, but it has not been observed that such soils become less dry after the felling of their trees. The cedars and other trees of allied families grow naturally in moist ground, and the white cedar of the Northern States, Thuya occidentalis, is chiefly found in swamps. The roots of this tree do not penetrate deeply into the earth, but are spread out near the surface, and of course do not carry off the waters of the swamp by perpendicular conduction. On the contrary, by their shade, the trees prevent the evaporation of the superficial water; but when the cedars are felled, the swamp—which sometimes rather resembles a pool filled with aquatic trees than a grove upon solid ground—often dries up so completely as to be fit for cultivation without any other artificial drainage than, in the ordinary course of cultivation, is given to other new soils. [Footnote: A special dessicative influence has long been ascribed to the maritime pine, which has been extensively planted on the dunes and sand-plains of western France, and it is well established that, under certain conditions, all trees, whether evergreen or deciduous, exercise this function, but there is no convincing proof that in the cases now referred to there is any difference in the mode of action of the two classes of trees. An article by D'Arbois de Jubainville in the Revue des Eaux et Forets for April, 1869, ascribing the same action to the Pinus sylvestris, has excited much attention in Europe, and the facts stated by this writer constitute the strongest evidence known to me in support of the alleged influence of evergreen trees, as distinguished from the draining by downward conduction, which is a function exercised by all trees, under ordinary circumstances, in proportion to their penetration of a bibulous subsoil by tap or other descending roots. The question has been ably discussed by Beraud in the Revue des Deux Mondes for April, 1870, the result being that the drying of the soil by pines is due simply to conduction by the roots, whatever may be the foliage of the tree. See post: Influence of the Forest on Flow of Springs. It is however certain, I believe, that evergreens exhale more moisture in winter than leafless deciduous trees, and consequently some weight is to be ascribed to this element.]
The Forest in Winter.
The influence of the woods on the flow of springs, and consequently on the supply for the larger water-courses, naturally connects itself with the general question of the action of the forest on the humidity of the ground. But the special condition of the woodlands, as affected by snow and frost in the winter of excessive climates, like that of the United States, has not been so much studied as it deserves; and as it has a most important bearing on the superficial hydrology of the earth, I shall make some observations upon it before I proceed to the direct discussion of the influence of the forest on the flow of springs.
To estimate rightly the importance of the forest in our climate as a natural apparatus for accumulating the water that falls upon the surface and transmitting it to the subjacent strata, we must compare the condition and properties of its soil with those of cleared and cultivated earth, and examine the consequently different action of these soils at different seasons of the year. The disparity between them is greatest in climates where, as in the Northern American States and in the extreme North of Europe, the open ground freezes and remains impervious to water during a considerable part of the winter; though, even in climates where the earth does not freeze at all, the woods have still an important influence of the same character. The difference is yet greater in countries which have regular wet and dry seasons, rain being very frequent in the former period, while, in the latter, it scarcely occurs at all. These countries lie chiefly in or near the tropics, but they are not wanting in higher latitudes; for a large part of Asiatic and even of European Turkey is almost wholly deprived of summer rains. In the principal regions occupied by European cultivation, and where alone the questions discussed in this volume are recognized as having, at present, any practical importance, more or less rain falls at all seasons, and it is to these regions that, on this point as well as others, I chiefly confine my attention.
Importance of Snow.
Recent observations in Switzerland give a new importance to the hygrometrical functions of snow, and of course to the forest as its accumulator and protector. I refer to statements of the condensation of atmospheric vapor by the snows and glaciers of the Rhone basin, where it is estimated to be nearly equal to the entire precipitation of the valley. Whenever the humidity of the atmosphere in contact with snow is above the point of saturation at the temperature to which the air is cooled by such contact, the superfluous moisture is absorbed by the snow or condensed and frozen upon its surface, and of course adds so much to the winter supply of water received from the snow by the ground. This quantity, in all probability, much exceeds the loss by evaporation, for during the period when the ground is covered with snow, the proportion of clear dry weather favorable to evaporation is less than that of humid days with an atmosphere in a condition to yield up its moisture to any bibulous substance cold enough to condense it. [Footnote: The hard snow-crust, which in the early spring is a source of such keen enjoyment to the children and youth of the North—and to many older persons in whom the love of nature has kept awake a relish for the simple pleasures of rural life—is doubtless due to the congelation of the vapor condensed by the snow rather than to the thawing and freezing of the superficial stratum; for when the surface is melted by the sun, the water is taken up by the absorbent mass beneath before the temperature falls low enough to freeze it.]
In our Northern States, irregular as is the climate, the first autumnal snows pretty constantly fall before the ground is frozen at all, or when the frost extends at most to the depth of only a few inches. [Footnote: The hard autumnal frosts are usually preceded by heavy rains which thoroughly moisten the soil, and it is a common saying in the North that "the ground will not freeze till the swamps are full."] In the woods, especially those situated upon the elevated ridges which supply the natural irrigation of the soil and feed the perennial fountains and streams, the ground remains covered with snow during the winter; for the trees protect the snow from blowing from the general surface into the depressions, and new accessions are received before the covering deposited by the first fall is melted. Snow is of a color unfavorable for radiation, but, even when it is of considerable thickness, it is not wholly impervious to the rays of the sun, and for this reason, as well as from the warmth of lower strata, the frozen crust of the soil, if one has been formed, is soon thawed, and does not again fall below the freezing-point during the winter. [Footnote: Dr. Williams, of Vermont, made some observations on the comparative temperature of the soil in open and in wooded ground In the years 1789 and 1791, but they generally belonged to the warmer months, and I do not know that any extensive series of comparisons between the temperature of the ground in the woods and in the fields has been attempted in America. Dr. Williams's thermometer was sunk to the depth of ten inches, and gave the following results:
——
| Temperature | Temperature |
Time. | of ground in| of ground in| Difference.
| pasture. | woods. |
——
May 23………………….| 52 | 46 | 6
" 28………………….| 57 | 48 | 9
June 15………………….| 64 | 51 | 13 " 27………………….| 62 | 51 | 11 July 16………………….| 62 | 51 | 11 " 30………………….| 65 1/2 | 55 1/2 | 10 Aug. 15………………….| 68 | 58 | 10 " 31………………….| 59 1/2 | 55 | 4 1/2 Sept.15………………….| 59 1/2 | 55 | 4 1/2 Oct. 1………………….| 59 1/2 | 55 | 4 1/2 " 15………………….| 49 | 49 | 0 Nov. 1………………….| 43 | 43 | 0 " 16………………….| 43 1/2 | 43 1/2 | 0
On the 14th of January, 1791, in a winter remarkable for its extreme severity, he found the ground, on a plain open field where the snow had been blown away, frozen to the depth of three feet and five inches; in the woods where the snow was three feet deep, and where the soil had frozen to the depth of six inches before the snow fell, the thermometer, at six inches below the surface of the ground, stood at 39 degrees. In consequence of the covering of the snow, therefore, the previously frozen ground had been thawed and raised to seven degrees above the freezing-point.—William's Vermont, i., p. 74.
Boussingault's observations are important. Employing three thermometers, one with the bulb an inch below the surface of powdery snow; one on the surface of the ground beneath the snow, then four inches deep; and one in the open air, forty feet above the ground, on the north side of a building, he found, at 5 P.M., the FIRST thermometer at -1.5 degrees Centigrade, the second at 0 degrees, and the THIRD at + 2.5 degrees; at 7 A.M. the next morning, the first stood at -12 degrees, the second at -3.5 degrees and the third at -3 degrees; at 5.30 the same evening No. 1 stood at -1.4 degrees, No. 2 at 0 degrees, and No. 3 at + 3 degrees. Other experiments were tried, and though the temperature was affected by the radiation, which varied with the hour of the day and the state of the sky, the upper surface of the snow was uniformly colder than the lower, or than the open air.
According to the Report of the Department of Agriculture for May and June, 1872, Mr. C. G. Prindle, of Vermont, in the preceding winter, found, for four successive days, the temperature immediately above the snow at 13 degrees below zero; beneath the snow, which was but four inches deep, at 19 degrees above zero; and under a drift two feet deep, at 27 degrees above.
On the borders and in the glades of the American forest, violets and other small plants begin to vegetate as soon as the snow has thawed the soil around their roots, and they are not unfrequently found in full flower under two or three feet of snow.—American Naturalist, May, 1869, pp. 155, 156.
In very cold weather, when the ground is covered with light snow, flocks of the grouse of the Eastern States often plunge into the snow about sunset, and pass the night in this warm shelter. If the weather moderates before morning, a frozen crust is sometimes formed on the surface too strong to be broken by the birds, which consequently perish.] The snow in contact with the earth now begins to melt, with greater or less rapidity, according to the relative temperature of the earth and the air, while the water resulting from its dissolution is imbibed by the vegetable mould, and carried off by infiltration so fast that both the snow and the layers of leaves in contact with it often seem comparatively dry, when, in fact, the under-surface of the former is in a state of perpetual thaw. No doubt a certain proportion of the snow is given off to the atmosphere by direct evaporation, but in the woods, the protection against the sun by even leafless trees prevents much loss in this way, and besides, the snow receives much moisture from the air by absorption and condensation. Very little water runs off in the winter by superficial water-courses, except in rare cases of sudden thaw, and there can be no question that much the greater part of the snow deposited in the forest is slowly melted and absorbed by the earth.
The immense importance of the forest, as a reservoir of this stock of moisture, becomes apparent, when we consider that a large proportion of the summer rain either flows into the valleys and the rivers, because it falls faster than the ground can imbibe it; or, if absorbed by the warm superficial strata, is evaporated from them without sinking deep enough to reach wells and springs, which, of course, depend much on winter rains and snows for their entire supply. This observation, though specially true of cleared and cultivated grounds, is not wholly inapplicable to the forest, particularly when, as is too often the case in Europe, the underwood and the decaying leaves are removed.
The quantity of snow that falls in extensive forests, far from the open country, has seldom been ascertained by direct observation, because there are few meteorological stations in or near the forest. According to Thompson, [Footnote: Thompson's Vermont, Appendix, p. 8.] the proportion of water which falls in snow in the Northern States does not exceed one-fifth of the total precipitation, but the moisture derived from it is doubtless considerably increased by the atmospheric vapor absorbed by it, or condensed and frozen on its surface. I think I can say from experience—and I am confirmed in this opinion by the testimony of competent observers whose attention has been directed specially to the point—that though much snow is intercepted by the trees, and the quantity on the ground in the woods is consequently less than in open land in the first part of the winter, yet most of what reaches the ground at that season remains under the protection of the wood until melted, and as it occasionally receives new supplies the depth of snow in the forest in the latter half of winter is considerably greater than in the cleared fields. Careful measurements in a snowy region in New England, in the month of February, gave a mean of 38 inches in the open ground and 44 inches in the woods. [Footnote: As the loss of snow by evaporation has been probably exaggerated by popular opinion, an observation or two on the subject may not be amiss in this place. It is true that in the open grounds, in clear weather and with a dry atmosphere, snow and ice are evaporated with great rapidity even when the thermometer is much below the freezing-point; and Darwin informs us that the snow on the summit of Aconcagua, 23,000 feet high, and of course in a temperature of perpetual frost, is sometimes carried off by evaporation. The surface of the snow in our woods, however, does not indicate much loss in this way. Very small deposits of snow-flakes remain unevaporated in the forest, for many days after snow which fell at the same time in the cleared field has disappeared without either a thaw to melt it or a wind powerful enough to drift it away. Even when bared of their leaven, the trees of a wood obstruct, in an important degree, both the direct action of the sun's rays on the snow and the movement of drying and thawing winds.
Dr. Piper (Trees of America, p. 48) records the following observations: "A body of snow, one foot in depth and sixteen feet square, was protected from the wind by a tight board fence about five feet high, while another body of snow, much more sheltered from the sun than the first, six feet in depth, and about sixteen feet square, was fully exposed to the wind. When the thaw came on, which lasted about a fortnight, the larger body of snow was entirely dissolved in less than a week, while the smaller body was not wholly gone at the end of the second week. "Equal quantities of snow were placed in vessels of the samekind and capacity, the temperature of the air being seventy degrees. In the one case, a constant current of air was kept passing over the open vessel, while the other was protected by a cover. The snow in the first was dissolved in sixteen minutes, while the latter had a small unthawed proportion remaining at the end of eighty-five minutes." The snow in the woods is protected in the same way, though not literally to the same extent, as by the fence in one of these cases and the cover in the other.]
The general effect of the forest in cold climates is to assimilate the winter state of the ground to that of wooded regions under softer skies; and it is a circumstance well worth noting, that in Southern Europe, where Nature has denied to the earth a warm winter-garment of flocculent snow, she has, by one of those compensations in which her empire is so rich, clothed the hillsides with umbrella and other pines, ilexes, cork-oaks, bays and other trees of persistent foliage, whose evergreen leaves afford to the soil a protection analogous to that which it derives from snow in more northern climates.
The water imbibed by the soil in winter sinks until it meets a more or less impermeable or a saturated stratum, and then, by unseen conduits, slowly finds its way to the channels springs, or oozes out of the ground in drops which unite in rills, and so all is conveyed to the larger streams, and by them finally to the sea. The water, in percolating through the vegetable and mineral layers, acquires their temperature, and is chemically affected by their action, but it carries very little matter in mechanical suspension.
The process I have described is a slow one, and the supply of moisture derived from the snow, augmented by the rains of the following seasons, keeps the forest-ground, where the surface is level or but moderately inclined, in a state of approximate saturation throughout almost the whole year. [Footnote: The statements I have made, here and elsewhere, respecting the humidity of the soil in natural forests, have been, I understand, denied by Mr. T. Meehan, a distinguished American naturalist, in a paper which I have not seen He is quoted as maintaining, among other highly questionable propositions that no ground is "so dry in its subsoil as that which sustains a forest on its surface." In open, artificially planted woods, with a smooth and regular surface, and especially in forests where the fallen leaves and branches are annually burnt or carried off, both the superficial and the subjacent strata may under certain circumstances, become dry, but this rarely, if ever, happens in a wood of spontaneous growth, undeprived of the protection afforded by its own droppings, and of the natural accidents of surface which tend to the retention of water. See, on this point, a very able article by Mr. Henry Stewart, in the New York Tribune of November 23, 1873.] It may be proper to observe here that in Italy, and in many parts of Spain and France, the Alps, the Apennines, and the Pyrenees, not to speak of less important mountains, perform the functions which provident nature has in other regions assigned to the forest, that is, they act as reservoirs wherein is accumulated in winter a supply of moisture to nourish the parched plains during the droughts of summer. Hence, however enormous may be the evils which have accrued to the above-mentioned countries from the destruction of the woods, the absolute desolation which would otherwise have smitten them through the folly of man, has been partially prevented by those natural dispositions, by means of which there are stored up in the glaciers, in the snow-fields, and in the basins of mountains and valleys, vast deposits of condensed moisture which are afterwards distributed in a liquid form during the season in which the atmosphere furnishes a slender supply of the beneficent fluid so indispensable to vegetable and animal life. [Footnote: The accumulation of snow and ice upon the Alps and other mountains—which often fills up valleys to the height of hundreds of feet—is due not only to the fall or congealed and crystallized vapor in the form of snow, to the condensation of atmospheric vapor on the surface of snow-fields and glaciers, and to a temperature which prevents the rapid melting of snow, but also to the well-known fact that, at least up to the height of 10,000 feet, rain and snow are more abundant on the mountains than at lower levels.
But another reason may be suggested for the increase of atmospheric humidity, and consequently of the precipitation of aqueous vapor on mountain chains. In discussing the influence of mountains on precipitation, meteorologists have generally treated the popular belief, that mountains "attract" to them clouds floating within a certain distance from them, as an ignorant prejudice, and they ascribe the appearance of clouds about high peaks solely to the condensation of the humidity of the air carried by atmospheric currents up the slopes of the mountain to a colder temperature. But if mountains do not really draw clouds and invisible vapors to them, they are an exception to the universal law of attraction. The attraction of the small Mount Shehallien was found sufficient to deflect from the perpendicular, by a measurable quantity, a plummet weighing but a few ounces. Why, then, should not greater masses attract to them volumes of vapor weighing many tons, and floating freely in the atmosphere within moderate distances of the mountains ]
Summer Rains, Importance of.
Babinet quotes a French proverb: "Summer rain wets nothing," and explains it by saying that at that season the rainwater is "almost entirely carried off by evaporation." "The rains of summer," he adds, "however abundant they may be, do not penetrate the soil beyond the depth of six or eight inches. In summer the evaporating power of the heat is five or six times greater than in winter, and this force is exerted by an atmosphere capable of containing five or six times as much vapor as in winter." "A stratum of snow which prevents evaporation [from the ground], causes almost all the water that composes it to filter into the earth, and forms a provision for fountains, wells, and streams which could not be furnished by any quantity whatever of summer rain. This latter, useful to vegetation like the dew, neither penetrates the soil nor accumulates a store to supply the springs and to be given out again into the open air." [Footnote: Etudes et Lectures, vol. vi., p. 118. The experiments or Johnstrup in the vicinity of Copenhagen, where the mean annual precipitation is 23 1/2 inches, and where the evaporation must be less than in the warmer and drier atmosphere of France, form the most careful series of observations on this subject which I have met with. Johnstrup found that at the depth at a metre and a half (50 inches) the effects of rain and evaporation were almost imperceptible, and became completely so at a depth of from two to three metres (6 1/2 to 10 feet). During the summer half of the year the evaporation rather exceeded the rainfall; during the winter half the entire precipitation was absorbed by the soil and transmitted to lower strata by infiltration. The stratum between one metre and a half (50 inches) and three metres (10 feet) from the surface was then permanently in the condition of a saturated sponge, neither receiving nor losing humidity during the summer half of the year, but receiving from superior, and giving off to lower, strata an equal amount of moisture during the winter half.—Johnstrup, Om Fugtighedens Bezagelse i den naturlige Jordbund. Kjobenhavn, 1866.]
This conclusion, however applicable to the climate and to the soil of France, is too broadly stated to be received as a general truth; and in countries like the United States, where rain is comparatively rare during the winter and abundant during the summer half of the year, common observation shows that the quantity of water furnished by deep wells and by natural springs depends almost as much upon the rains of summer as upon those of the rest of the year, and consequently that a large portion of the rain of that season must find its way into strata too deep for the water to be wasted by evaporation.
[Footnote: According to observations at one hundred military stations in the United States, the precipitation ranges from three and a quarter inches at Fort Yuma in California to about seventy-two inches at Fort Pike, Louisiana, the mean for the entire territory, not including Alaska, being thirty-six inches. In the different sections of the Union it is as follows:
North-eastern States……………… 41 inches,
New York………………………… 36 "
Middle States……………………. 40 1/2 "
Ohio……………………………. 40 "
Southern States………………….. 51 "
S. W. States and Indian Territories… 39 1/2 "
Western States and Territories…….. 30 "
Texas and New Mexico……………… 24 1/2 "
California………………………. 18 1/2 "
Oregon and Washington Territory……. 50 "
The mountainous regions, it appears, do not recieve the greatest amount of precipitation. The avenge downfall of the Southern States bordering on the Atlantic and the Gulf of Mexico exceeds the mean of the whole United States, being no less than fifty-one inches, while on the Pacific coast it ranges from fifty to fifty-six inches.
As a general rule, it may be stated that at the stations on or near the sea-coast the precipitation is greatest in the spring months, though there are several exceptions to this remark, and at a large majority of the stations the downfall is considerably greater in the summer months than at any other season.]
Dalton's experiments in the years 1796, 1797, and 1798 appeared to show that the mean absorption of the downfall by the earth in those years was twenty-nine per cent.
Dickinson, employing the same apparatus for eight years, found the absorption to vary widely in different years, the mean being forty-seven per cent.
Charnock's experiments in two years show an absorption of from seventeen to twenty-seven per cent.] Besides, even admitting that the water from summer rains is so completely evaporated as to contribute nothing directly to the supply of springs, it at least tends indirectly to maintain their flow, because it saturates in part the atmosphere, and at the same time it prevents the heat of the sun from drying the earth to still greater depths, and bringing within the reach of evaporation the moisture of strata which ordinarily do not feel the effects of solar irradiation.
Influence of the Forest on the Flow of Springs.
It is an almost universal and, I believe, well-founded opinion, that the protection afforded by the forest against the escape of moisture from its soil by superficial flow and evaporation insures the permanence and regularity of natural springs, not only within the limits of the wood, but at some distance beyond its borders, and thus contributes to the supply of an element essential to both vegetable and animal life. As the forests are destroyed, the springs which flowed from the woods, and, consequently, the greater water-courses fed by them, diminish both in number and in volume. This fact is so familiar throughout the American States and the British Provinces, that there are few old residents of the interior of those districts who are not able to testify to its truth as a matter of personal observation. My own recollection suggests to me many instances of this sort, and I remember one case where a small mountain spring, which disappeared soon after the clearing of the ground where it rose, was recovered about twenty years ago, by simply allowing the bushes and young trees to grow up on a rocky knoll, not more than half an acre in extent, immediately above the spring. The ground was hardly shaded before the water reappeared, and it has ever since continued to flow without interruption. The hills in the Atlantic States formerly abounded in springs and brooks, but in many parts of these States which were cleared a generation or two ago, the hill-pastures now suffer severely from drought, and in dry seasons furnish to cattle neither grass nor water.
Almost every treatise on the economy of the forest adduces facts in support of the doctrine that the clearing of the woods tends to diminish the flow of springs and the humidity of the soil, and it might seem unnecessary to bring forward further evidence on this point. [Footnote: "Why go so far for the proof of a phenomenon that is repeated every day under our own eyes, and of which every Parisian may convince himself, without venturing beyond the Bois de Boulogne or the forest of Meudon Let him, after a few rainy days, pass alone the Chevreuse road, which is bordered on the right by the wood, on the left by cultivated fields. The fall of water and the continuance of the rain have been the same on both sides; but the ditch on the side of the forest will remain filled with water proceeding from the infiltration through the wooded soil, long after the other, contiguous to the open ground, has performed its office of drainage and become dry. The ditch on the left will have discharged in a few hours a quantity of water, which the ditch on the right requires several days to receive and carry down to the valley."—Clave, Etudes, etc., pp. 53, 54.] But the subject is of too much practical importance and of too great philosophical interest to be summarily disposed of; and it ought to be noticed that there is at least one case—that of some loose sandy soils which, as observed by Valles, [Footnote: Valles, Etudes sur les Inondations, p. 472.] when bared of wood very rapidly absorb and transmit to lower strata the water they receive from the atmosphere—where the removal of the forest may increase the flow of springs at levels below it, by exposing to the rain and melted snow a surface more bibulous, and at the same time less retentive, than its original covering. Under such circumstances, the water of precipitation, which had formerly been absorbed by the vegetable mould and retained until it was evaporated, might descend through porous earth until it meets an impermeable stratum, and then be conducted along it, until, finally, at the outcropping of this stratum, it bursts from a hillside as a running spring. But such instances are doubtless too rare to form a frequent or an important exception to the general law, because it is very seldom the case that such a soil as has just been supposed is covered by a layer of vegetable earth thick enough to retain, until it is evaporated, all the rain that falls upon it, without imparting any water to the strata below it.
If we look at the point under discussion as purely a question of fact, to be determined by positive evidence and not by argument, the observations of Boussingault are, both in the circumstances they detail and in the weight to be attached to the testimony, among the most important yet recorded. The interest of the question will justify me in giving, nearly in Boussingault's own words, the facts and some of the remarks with which he accompanies the detail of them. "In many localities," he observes, [Footnote: Economie Rurale t. ii, p. 780.] "it has been thought that, within a certain number of years, a sensible diminution has been perceived in the volume of water of streams utilized as a motive-power; at other points, there are grounds for believing that rivers have become shallower, and the increasing breadth of the belt of pebbles along their banks seems to prove the loss of a part of their water; and, finally, abundant springs have almost dried up. These observations have been principally made in valleys bounded by high mountains, and it has been noticed that this diminution of the waters has immediately followed the epoch when the inhabitants have begun to destroy, unsparingly, the woods which were spread over the face of the land. "And here lies the practical point of the question; for if it is once established that clearing diminishes the volume of streams, it is less important to know to what special cause this effect is due. The rivers which rise within the valley of Aragua, having no outlet to the ocean, form, by their union, the Lake of Tacarigua or Valencia, having a length of about two leagues and a half [= 7 English miles].
At the time of Humboldt's visit to the valley of Aragua, the inhabitants were struck by the gradual diminution which the lake had been undergoing for thirty years. In fact, by comparing the descriptions given by historians with its actual condition, even making large allowance for exaggeration, it was easy to see that the level was considerably depressed. The facts spoke for themselves. Oviedo, who, toward the close of the sixteenth century, had often traversed the valley of Aragua, says positively that New Valencia was founded, in 1555, at half a league from the Lake of Tacarigua; in 1800, Humboldt found this city 5,260 metres [= 3 1/2 English miles] from the shore.
"The aspect of the soil furnished new proofs. Many hillocks on the plain retain the name of islands, which they more justly bore when they were surrounded by water. The ground laid bare by the retreat of the lake was converted into admirable plantations; and buildings erected near the lake showed the sinking of the water from year to year. In 1796, new islands made their appearance. A fortress built in 1740 on the island of Cabrera, was now on a peninsula; and, finally, on two granitic islands, those of Cura and Cabo Blanco, Humboldt observed among the shrubs, somo metres above the water, fine sand filled with helicites.
"These clear and positive facts suggested numerous explanations, all assuming a subterranean outlet, which permitted the discharge of the water to the ocean. Humboldt disposed of these hypotheses, and did not hesitate to ascribe the diminution of the waters of the lake to the numerous clearings which had been made in the valley of Aragua within half a century."
Twenty-two years later, Boussingault explored the valley of Aragua. For some years previous, the inhabitants had observed that the waters of the lake were no longer retiring, but, on the contrary, were sensibly rising. Grounds, not long before occupied by plantations, were submerged. The islands of Nuevas Aparecidas, which appeared above the surface in 1796, had again become shoals dangerous to navigation. Cabrera, a tongue of land on the north side of the valley, was so narrow that the least rise of the water completely inundated it. A protracted north wind sufficed to flood the road between Maracay and New Valencia. The fears which the inhabitants of the shores had so long entertained were reversed. Those who had explained the diminution of the lake by the supposition of subterranean channels were suspected of blocking them up, to prove themselves in the right.
During the twenty-two years which had elapsed, the valley of Aragua had been the theatre of bloody struggles, and war had desolated these smiling lands and decimated their population. At the first cry of independence a great number of slaves found their liberty by enlisting under the banners of the new republic; the great plantations were abandoned, and the forest, which in the tropics so rapidly encroaches, had soon recovered a large proportion of the soil which man had wrested from it by more than a century of constant and painful labor.
Boussingault proceeds to state that two lakes near Ubate, in New Granada, had formed but one, a century before his visit; that the waters were gradually retiring, and the plantations extending over the abandoned bed; that, by inquiry of old hunters and by examination of parish records, he found that extensive clearings had been made and were still going on.
He found, also, that the length of the Lake of Fuquene, in the same valley, had, within two centuries, been reduced from ten leagues to one and a half, its breadth from three leagues to one. At the former period, the neighboring mountains were well wooded, but at the time of his visit the mountains had been almost entirely stripped of their wood. Our author adds that other cases, similar to those already detailed, might be cited, and he proceeds to show, by several examples, that the waters of other lakes in the same regions, where the valleys had always been bare of wood, or where the forests had not been disturbed, had undergone no change of level.
Boussingault further states that the lakes of Switzerland have sustained a depression of level since the too prevalent destruction of the woods, and arrives at the general conclusion that, "in countries where great clearings have been made, there has most probably been a diminution in the living waters which flow upon the surface of theground." This conclusion he further supports by two examples: one, where a fine spring, at the foot of a wooded mountain in the Island of Ascension, dried up when the mountain was cleared, but reappeared when the wood was replanted; the other at Marmato, in the province of Popayan, where the streams employed to drive machinery were much diminished in volume, within two years after the clearing of the heights from which they derived their supplies. This latter is an interesting case, because, although the rain-gauges, established as soon as the decrease of water began to excite alarm, showed a greater fall of rain for the second year of observation than the first, yet there was no appreciable increase in the flow of the mill-streams. From these cases, the distinguished physicist infers that very restricted local clearings may diminish and even suppress springs and brooks, without any reduction in the total quantity of rain.
It will have been noticed that these observations, with the exception of the last two cases, do not bear directly upon the question of the diminution of springs by clearings, but they logically infer it from the subsidence of the natural reservoirs which springs once filled. There is, however, no want of positive evidence on this subject. Marchand cites the following instances: "Before the felling of the woods, within the last few years, in the valley of the Soulce, the Combe-es-Monnin and the Little Valley, the Sorne furnished a regular and sufficient supply of water for the ironworks of Unterwyl, which was almost unaffected by drought or by heavy rains. The Sorne has now become a torrent, every shower occasions a flood, and after a few days of fine weather, the current falls so low that it has been necessary to change the water-wheels, because those of the old construction are no longer able to drive the machinery, and at last to introduce a steam-engine to prevent the stoppage of the works for want of water.
"When the factory of St. Ursanne was established, the river that furnished its power was abundant, and had, from time immemorial, sufficed for the machinery of a previous factory. Afterwards, the woods near its sources were cut. The supply of water fell off in consequence, the factory wanted water for half the year, and was at last obliged to stop altogether.
"The spring of Combefoulat, in the commune of Seleate, was well known as one of the best in the country; it was remarkably abundant, and sufficient, in the severest droughts, to supply all the fountains of the town; but as soon as considerable forests were felled in Combe-de-pre Martin and in the valley of Combefoulat, the famous spring, which lies below these woods, has become a mere thread of water, and disappears altogether in times of drought.
"The spring of Varieux, which formerly supplied the castle of Pruntrut, lost more than half its water after the clearing of Varieux and Rougeoles. These woods have been replanted, the young trees are growing well, and, with the woods, the waters of the spring are increasing.
"The Dog Spring between Pruntrut and Bressancourt has entirely vanished since the surrounding forest-grounds were brought under cultivation.
"The Wolf Spring, in the commune of Soubey, furnishes a remarkable example of the influence of the woods upon fountains. A few years ago this spring did not exist. At the place where it now rises, a small thread of water was observed after very long rains, but the stream disappeared with the rain. The spot is in the middle of a very steep pasture inclining to the south. Eighty years ago, the owner of the land, perceiving that young firs were shooting up in the upper part of it, determined to let them grow, and they soon formed a flourishing grove. As soon as they were well grown, a fine spring appeared in place of the occasional rill, and furnished abundant water in the longest droughts. For forty or fifty years this spring was considered the best in the Clos du Doubs. A few years since, the grove was felled, and the ground turned again to a pasture. The spring disappeared with the wood, and is now as dry as it was ninety years ago." [Footnote: Ueber Die Entwaldung Der Gebirge, pp. 20 et seqq.]
Siemoni gives the following remarkable facts from his own personal observation:
"In a rocky nook near the crest of a mountain in the Tuscan Apennines, there flowed a clear, cool, and perennial fountain, uniting three distinct springs in a single current. The ancient beeches around and particularly above the springs were felled. On the disappearance of the wood, the springs ceased to flow, except in a thread of water in rainy weather, greatly inferior in quality to that of the old fountain. The beeches were succeeded by firs, and as soon as they had grown sufficiently to shade the soil, the springs begun again to flow, and they gradually returned to their former abundance and quality." [Footnote: Manuale D'arte Forestale. 2me editione, p. 492.]
This and the next preceding case are of great importance both as to the action of the wood in maintaining springs, and particularly as tending to prove that evergreens do not exercise the desiccative influence ascribed to them in France. The latter instance shows, too, that the protective influence of the wood extends far below the surface, for the quality of the water was determined, no doubt, by the depth from which it was drawn. The slender occasional supply after the beeches were cut was rain-water which soaked through the superficial humus and oozed out at the old orifices, carrying the taste and temperature of the vegetable soil with it; the more abundant and grateful water which flowed before the beeches were cut, and after the firs were well grown, came from a deeper source and had been purified, and cooled to the mean temperature of the locality, by filtering through strata of mineral earth. "The influence of the forest on springs," says Hummel, "is strikingly shown by an instance at Heilbronn. The woods on the hills surrounding the town are cut in regular succession every twentieth year. As the annual cuttings approach a certain point, the springs yield less water, some of them none at all; but as the young growth shoots up, they flow more and more freely, and at length bubble up again in all their original abundance." [Footnote: Physische Geographie, p. 32.] Dr. Piper states the following case: "Within about half a mile of my residence there is a pond upon which mills have been standing for a long time, dating back, I believe, to the first settlement of the town. These have been kept in constant operation until within some twenty or thirty years, when the supply of water began to fail. The pond owes its existence to a stream that has its source in the hills which stretch some miles to the south. Within the time mentioned, these hills, which were clothed with a dense forest, have been almost entirely stripped of trees; and to the wonder and loss of the mill-owners, the water in the pond has failed, except in the season of freshets; and, what was never heard of before, the stream itself has been entirely dry. Within the last ten years a new growth of wood has sprung up on most of the land formerly occupied by the old forest; and now the water runs through the year, notwithstanding the great droughts of the last few years, going back from 1856."
Dr. Piper quotes from a letter of William C. Bryant the following remarks: "It is a common observation that our summers are becoming drier and our streams smaller. Take the Cuyahoga as an illustration. Fifty years ago large barges loaded with goods went up and down that river, and one of the vessels engaged in the battle of Lake Erie, in which the gallant Perry was victorious, was built at Old Portage, six miles north of Albion, and floated down to the lake. Now, in an ordinary stage of the water, a canoe or skiff can hardly pass down the stream. Many a boat of fifty tons burden has been built and loaded in the Tuscarawas, at New Portage, and sailed to New Orleans without breaking bulk. Now, the river hardly affords a supply of water at New Portage for the canal. The same may be said of other streams—they are drying up. And from the same cause—the destruction of our forests—our summers are growing drier and our winters colder." [Footnote: The Trees of America, pp. 50, 51.]
No observer has more carefully studied the influence of the forest upon the flow of the waters, or reasoned more ably on the ascertained phenomena, than Cantegril. The facts presented in the following case, communicated by him to the Ami des Sciences for December, 1859, are as nearly conclusive as any single instance well can be:
"In the territory of the commune of Labruguiere there is a forest of 1,834 hectares [4,530 acres], known by the name of the Forest of Montaut, and belonging to that commune. It extends along thenorthern slope of the Black Mountains. The soil is granitic, the maximum altitude 1,243 metres [4,140 feet], and the inclination ranges between 15 and 60 to 100.
"A small current of water, the brook of Caunan, takes its rise in this forest, and receives the waters of two-thirds of its surface. At the lower extremity of the wood and on the stream are several fulleries, each requiring a force of eight horse-power to drive the water-wheels which work the stampers. The commune of Labruguiere had been for a long time famous for its opposition to forest laws. Trespasses and abuses of the right of pasturage had converted the wood into an immense waste, so that this vast property now scarcely sufficed to pay the expense of protecting it, and to furnish the inhabitants with a meagre supply of fuel. While the forest was thus ruined, and the soil thus bared, the water, after every abundant rain, made an eruption into the valley, bringing down a great quantity of pebbles which still clog the current of the Caunan. The violence of the floods was sometimes such that they were obliged to stop the machinery for some time. During the summer another inconvenience was felt. If the dry weather continued a little longer than usual, the delivery of water became insignificant. Each fullery could for the most part only employ a single set of stampers, and it was not unusual to see the work entirely suspended.
"After 1840, the municipal authority succeeded in enlightening the population as to their true interests. Protected by a more watchful supervision, aided by well-managed replantation, the forest has continued to improve to the present day. In proportion to the restoration of the forest, the condition of the manufactories has become less and less precarious, and the action of the water is completely modified. For example, sudden and violent floods, which formerly made it necessary to stop the machinery, no longer occur. There is no increase in the delivery until six or eight hours after the beginning of the rain; the floods follow a regular progression till they reach their maximum, and decrease in the same manner. Finally, the fulleries are no longer forced to suspend work in summer; the water is always sufficiently abundant to allow the employment of two sets of stampere at least, and often even of three.
"This example is remarkable in this respect, that, all other circumstances having remained the same, the changes in the action of the stream can be attributed only to the restoration of the forest—changes which may be thus summed up: diminution of flood-water during rains—increase of delivery at other seasons."
Becquerel and other European writers adduce numerous other cases where the destruction of forests has caused the disappearance of springs, a diminution in the volume of rivers, and a lowering of the level of lakes, and in fact, the evidence in support of the doctrine I have been maintaining on this subject seems to be as conclusive as the nature of the case admits. [Footnote: See, in the Revue des Eaux et Forets for April, 1867, an article entitled De l'influence des Forets sur le Regime des Eaux, and the papers in previous numbers of the same journal therein referred to.] We cannot, it is true, arrive at the same certainty and precision of result in these inquiries as in those branches of physical research where exact quantitative appreciation is possible, and we must content ourselves with probabilities and approximations. We cannot positively affirm that the precipitation in a given locality is increased by the presence, or lessened by the destruction, of the forest, and from our ignorance of the subterranean circulation of the waters, we cannot predict, with certainty, the drying up of a particular spring as a consequence of the felling of the wood which shelters it; but the general truth, that the flow of springs and the normal volume of rivers rise and fall with the extension and the diminution of the woods where they originate and through which they run, is as well established as any proposition in the science of physical geography. [Footnote: Some years ago it was popularly believed that the volume of the Mississippi, like that of the Volga and other rivers of the Eastern Hemisphere, was diminished by the increased evaporation from its basin and the drying up of the springs in consequence of the felling of the forests in the vicinity of the source of its eastern affluents. The boatmen of this great river and other intelligent observers now assure us, however, that the mean and normal level of the Mississippi has risen within a few years, and that in consequence the river is navigable at low water for boats of greater draught and at higher points in its course than was the case twenty-five years ago. This supposed increase of volume has been attributed by some to the recent re-wooding of the prairies, but the plantations thus far made are not yet sufficiently extensive to produce an appreciable effect of this nature; and besides, while young trees have covered some of the prairies, the destruction of the forest has been continued perhaps in a greater proportion in other parts of the basin of the river. A more plausible opinion is that the substitution of ground that is cultivated, and consequently spongy and absorbent, for the natural soil of the prairies, has furnished a reservoir for the rains which are absorbed by the earth and carried gradually to the river by subterranean flow, instead of running off rapidly from the surface, or, as is more probable, instead of evaporating or being taken up by the vigorous herbaceous vegetation which covers the natural prairie.
A phenomenon so contrary to common experience, as would be a permanent increase in the waters of a great river, will not be accepted without the most convincing proofs. The present greater facility of navigation may be attributed to improvements in the model of the boats, to the removing of sand-banks and other impediments to the flow of the waters, or to the confining of these waters in a narrower channel, by extending the embankments of the river, or to yet other causes. So remarkable a change could not have escaped the notice of Humphreys and Abbot, whose most able labors comprise the years 1850-1861, had it occurred during that period or at any former time within the knowledge of the many observers they consulted; but no such fact is noticed in their exhaustive report. However, even if an increase in the volume of the Mississippi, for a period of ten or twenty years, were certain, it would still be premature to consider this increase as normal and constant, since it might very well be produced by causes yet unknown and analogous to those which influence the mysterious advance and retreat of those Alpine ice-rivers, the glaciers. Among such causes we may suppose a long series of rainy seasons in regions where important tributaries have their far-off and almost unknown sources; and with no less probability, we may conceive of the opening of communications with great subterranean reservoirs, which may from year to year empty large quantities of water into the bed of the stream; or the closing up of orifices through which a considerable portion of the water of the river once made its way for the supply of such reservoirs.—See upon this point, Chap. IV., Of Subterranean Waters; post.]
Of the converse proposition, namely, that the planting of new forests gives rise to new springs and restores the regular flow of rivers, I find less of positive proof, however probable it may be that such effects would follow. [Footnote: According to the Report of the Department of Agriculture for February, 1872, it is thought in the Far West that the young plantations have already influenced the water-courses in that region, and it is alleged that ancient river-beds, never known to contain water since the settlement of the country, have begun to flow since these plantations were commenced. See also Hayden, Report on Geological Survey of Wyoming, 1870, p. 104, and Bryant. Forest Trees, 1871, chap. iv.
In the Voyage autour du Monde of the Comte da Beauvoir, chap. x., this passage occurs: Dr. Muller, Director of the Botanic Garden at Melbourne, "has distributed through the interior of Australia millions of seedling trees from his nursuries. Small rivulets are soon formed under the young wood; the results are superb, and the observation of every successive year confirms them. On bare soils he has created, at more than a hundred points, forests and water-courses."] A reason for the want of evidence on the subject may be, that, under ordinary circumstances, the process of conversion of bare ground to soil with a well-wooded surface is so gradual and slow, and the time required for a fair experiment is consequently so long, that many changes produced by the action of the new geographical element escape the notice and the memory of ordinary observers. The growth of a forest, including the formation of a thick stratum of vegetable mould beneath it, is the work of a generation, its destruction may be accomplished in a day; and hence, while the results of the one process may, for a considerable time, be doubtful if not imperceptible, those of the other are immediate and readily appreciable. Fortunately, the plantation of a wood produces other beneficial consequences which are both sooner realized and more easily estimated; and though he who drops the seed is sowing for a future generation as well as for his own, the planter of a grove may hope himself to reap a fair return for his expenditure and his labor.
Influence of the Forest on Inundations and Torrents.
Inasmuch as it is not yet proved that the forests augment or diminish the precipitation in the regions they principally cover, we cannot positively affirm that their presence or absence increases or lessens the total volume of the water annually delivered by great rivers or by mountain torrents. It is nevertheless certain that they exercise an action on the discharge of the water of rain and snow into the valleys, ravines, and other depressions of the surface, where it is gathered into brooks and finally larger currents, and consequently influence the character of floods, both in rivers and in torrents. For this reason, river inundations and the devastations of torrents, and the geographical effects resulting from them, so far as they are occasioned or modified by the action of forests or of the destruction of the woods, may properly be discussed in this chapter, though they might seem otherwise to belong more appropriately to another division of this work.
Besides the climatic question, which I have already sufficiently discussed, and the obvious inconveniences of a scanty supply of charcoal, of fuel, and of timber for architectural and naval construction and for the thousand other uses to which wood is applied in rural and domestic economy, and in the various industrial processes of civilized life, the attention of European foresters and public economists has been specially drawn to three points, namely: the influence of the forests on the permanence and regular flow of springs or natural fountains; on inundations by the overflow of rivers; and on the abrasion of soil and the transportation of earth, gravel, pebbles, and even of considerable masses of rock, from higher to lower levels, by torrents. There are, however, connected with this general subject, several other topics of minor or strictly local interest, or of more uncertain character, which I shall have occasion more fully to speak of hereafter.
The first of these three principal subjects—the influence of the woods on springs and other living waters—has been already considered; and if the facts stated in that discussion are well established, and the conclusions I have drawn from them are logically sound, it would seem to follow, as a necessary corollary, that the action of the forest is as important in diminishing the frequency and violence of river-floods as in securing the permanence and equability of natural fountains; for any cause which promotes the absorption and accumulation of the water of precipitation by the superficial strata of the soil, to be slowly given out by infiltration and percolation, must, by preventing the rapid flow of surface-water into the natural channels of drainage, tend to check the sudden rise of rivers, and, consequently, the overflow of their banks, which constitutes what is called inundation.
The surface of a forest, in its natural condition, can never pour forth such deluges of water as flow from cultivated soil. Humus, or vegetable mould, is capable of absorbing almost twice its own weight of water. The soil in a forest of deciduous foliage is composed of humus, more or less unmixed, to the depth of several inches, sometimes even of feet, and this stratum is usually able to imbibe all the water possibly resulting from the snow which at any one time covers, or the rain which in any one shower falls upon it. But the vegetable mould does not cease to absorb water when it becomes saturated, for it then gives off a portion of its moisture to the mineral earth below, and thus is ready to receive a new supply; and, besides, the bed of leaves not yet converted to mould takes up and retains a very considerable proportion of snow-water, as well as of rain.
The stems of trees, too, and of underwood, the trunks and stumps and roots of fallen timber, the mosses and fungi and the numerous inequalities of the ground observed in all forests, oppose a mechanical resistance to the flow of water over the surface, which sensibly retards the rapidity of its descent down declivities, and diverts and divides streams which may have already accumulated from smaller threads of water. [Footnote: In a letter addressed to the Minister of Public Works, after the terrible inundations of 1857, the late Emperor of France thus happily expressed himself: "Before we seek the remedy for an evil, we inquire into its cause. Whence come the sudden floods of our rivers From the water which falls on the mountains, not from that which falls on the plains. The waters which fall on our fields produce but few rivulets, but these which fall on our roofs and are collected in the gutters, form small streams at once. Now, the roofs are mountains—the gutters are valleys."
"To continue the comparison," observes D'Hericourt, "roofs are smooth and impermeable, and the rain-water pours rapidly off from their surfaces; but this rapidity of flow would be greatly diminished if the roofs were carpeted with mosses and grasses; more still, if they were covered with dry leaves, little shrubs, strewn branches, and other impediments—in short, if they were wooded."—Annales Forestieres, Dec. 1857, p. 311.
The mosses and fungi play a more important part in regulating the humidity of the air and of the soil than writers on the forest have usually assigned to them. They perish with the trees they grow on; but, in many situations, nature provides a compensation for the tree-mosses and fungi in ground species, which, on cold soils, especially those with a northern exposure, spring up abundantly both before the woods are felled, and when the land is cleared and employed for pasturage, or deserted. These humble plants discharge a portion of the functions appropriated to the wood, and while they render the soil of improved lands much less fit for agricultural use, they, at the same time, prepare it for the growth of a new harvest of trees, when the infertility they produce shall have driven man to abandon it and suffer it to relapse into the hands of nature.
In primitive forests, when the ground is not too moist to admit of a dense growth of trees, the soil is generally so thickly covered with leaves that there is little room for ground mosses and mushrooms. In the more open artificial woods of Europe these forms of vegetation, as well as many more attractive plants, are more frequent than in the native groves of America. See, on cryptogamic and other wood plants, Rossmassler, Der Wald, pp. 82 et seqq., and on the importance of such vegetables in checking the flow of water, Mengotti, Idraulica Fisica e Sperimentale, chapters xvi. and xvii. No writer known to me has so well illustrated this function of forest vegetation as Mengotti, though both he and Rossmassler ascribe to plants a power of absorbing water from the atmosphere which they do not possess, or rather can only rarely exercise.]
The value of the forest as a mechanical check to a too rapid discharge of rain-water was exemplified in numerous instances in the great floods of 1866 and 1868, in France and Switzerland, and I refer to the observations made on those occasions as of special importance because no previous inundations in those countries had been so carefully watched and so well described by competent investigators. In the French Department of Lozere, which was among those most severely injured by the inundation of 1866—an inundation caused by diluvial rains, not by melted snow—it was everywhere remarked that "grounds covered with wood sustained no damage even on the steepest slopes, while in cleared and cultivated fields the very soil was washed away and the rocks laid bare by the pouring rain." [Footnote: See, for other like observations, an article entitled Le Reboisement et les Inondations, in the Revue des Eaux et Forets of September, 1868]
The Italian journals of the day state that the province of Brescia and a part of that of Bergamo, which have heretofore been exposed to enormous injury, after every heavy rain, from floods of the four principal streams which traverse them, in a great degree escaped damage in the terrible inundation of October, 1872, and their immunity is ascribed to the forestal improvements executed by the former province, within ten or twelve years, in the Val Camonica and in the upper basins of the other rivers which drain that territory. Similar facts were noticed in the extraordinary floods of September and October, 1868, in the valley of the Upper Rhine, and Coaz makes the interesting observation that not even dense greensward was so efficient a protection to the earth as trees, because the water soaked through the sod and burst it up by hydrostatic pressure. [Footnote: Die Hochwasser in 1868 im Bandnerischen Rheingebiet, pp. 12, 68.
Observations of Forster, cited by Cezanne from the Annales Forestieres for 1859, p. 358, are not less important than those adduced in the text. The field of these observations was a slope of 45 degrees divided into three sections, one luxuriantly wooded from summit to base with oak and beech, one completely cleared through its whole extent, and one cleared in its upper portion, but retaining a wooded belt for a quarter of the height of the slope, which was from 1,360 to 1,800 feet above the brook at its foot.
In the first section, comprising six-sevenths of the whole surface, the rains had not produced a single ravine; in the second, occupying about a tenth of the ground, were three ravines, increasing in width from the summit to the valley beneath, where they had, all together, a cross-section of 600 square feet; in the third section, of about the same extent as the second, four ravines had been formed, widening from the crest of the slope to the belt of wood, where they gradually narrowed and finally disappeared.
For important observations to the same purpose, see Marchand, Les
Torrents des Alpes, in Revue des Eaux et Forets for September, 1871.]
The importance of the mechanical resistance of the wood to the flow of water OVER THE SURFACE has, however, been exaggerated by some writers. Rain-water is generally absorbed by the forest-soil as fast as it falls, and it is only in extreme cases that it gathers itself into a superficial sheet or current overflowing the ground. There is, nevertheless, besides the absorbent power of the soil, a very considerable mechanical resistance to the transmission of water BENEATH the surface through and along the superior strata of the ground. This resistance is exerted by the roots, which both convey the water along their surface downwards, and oppose a closely wattled barrier to its descent along the slope of the permeable strata which have absorbed it. [Footnote: In a valuable report on a bill for compelling the sale of waste communal lands, now pending in the Parliament of Italy, Senator Torelli, an eminent man of science, calculates that four-fifths of the precipitation in the forest are absorbed by the soil, or detained by the obstructions of the surface, only one-fifth being delivered to the rivers rapidly enough to create danger of floods, while in open grounds, in heavy rains, the proportions are reversed. Supposing a rain-fall of four inches, an area measuring 100,000 acres, or a little more than four American townships, would receive 53,777,777 cubic yards of water. Of this quantity it would retain, or rather detain, if wooded, 41,000,000 yards, if bare, only 11,000,000. The difference of discharge from wooded and unwooded soils is perhaps exaggerated in Col. Torelli's report, but there is no doubt that in very many cases it is great enough to prevent, or to cause, destructive inundations.] Rivers fed by springs and shaded by woods are comparatively uniform in volume, in temperature, and in chemical composition. [Footnote: Dumont gives an interesting extract from the Misopogon of the Emperor Julian, showing that, in the fourth century, the Seine—the level of which now varies to the extent of thirty feet between extreme high and extreme low water mark—was almost wholly exempt from inundations, and flowed with a uniform current through the whole year. "Ego olim eram in hibernis apud curam Lutetiam, [sic] enim Galli Parisiorum oppidum appellant, quae insula est non magna, in fluvio sita, qui eam omni ex parte cingit. Pontes sublicii utrinque ad eam ferunt, raroque fluvius minuitur ac crescit; sed qualis aestate talis esse solet hyeme."—Des Travaux Publics dans leur Rapports avec l'Agriculture, p. 361, note.
As Julian was six years in Gaul, and his principal residence was at Paris, his testimony as to the habitual condition of the Seine, at a period when the provinces where its sources originate were well wooded, is very valuable.] Their banks are little abraded, nor are their courses much obstructed by fallen timber, or by earth and gravel washed down from the highlands. Their channels are subject only to slow and gradual changes, and they carry down to the lakes and the sea no accumulation of sand or silt to fill up their outlets, and, by raising their beds, to force them to spread over the low grounds near their mouth. [Footnote: Forest rivers seldom if ever form large sedimentary deposits at their points of discharge into lakes or larger streams, such accumulations beginning or at least advancing far more rapidly, after the valleys are cleared.]
Causes of Inundations.
The immediate cause of river inundations is the flow of superficial and subterranean waters into the beds of rivers faster than those channels can discharge them. The insufficiency of the channels is occasioned partly by their narrowness and partly by obstructions to their currents, the most frequent of which is the deposit of sand, gravel, and pebbles in their beds by torrential tributaries during the floods. [Footnote: The extent of the overflow and the violence of the current in river- floods are much affected by the amount of sedimentary matter let fall in their channels by their affluents, which have usually a swifter flow than the main stream, and consequently deposit more or less of their transported material when they join its more slowly-moving waters. Such deposits constitute barriers which at first check the current and raise its level, and of course its violence at lower points is augmented, both by increased volume and by the solid material it carries with it, when it acquires force enough to sweep away the obstruction.—Risler, Sur L influence des Forets sur les Cours d eau, in Revue des Eaux et Forets, 10th January, 1870.
In the flood of 1868 the torrent Illgraben, which had formerly spread its water and its sediment over the surface of a vast cone of dejection, having been forced, by the injudicious confinement of its current to a single channel, to discharge itself more directly into the Rhone, carried down a quantity of gravel, sand, and mud, sufficient to dam that river for a whole hour, and in the same great inundation the flow of the Rhine at Thusis was completely arrested for twenty minutes by a similar discharge from the Nolla. Of course, when the dam yielded to the pressure of the accumulated water, the damage to the country below was far greater than it would have ben had the currents of the rivers not been thus obstructed.—Marchand, Les Torrents des Alpes, in Revue des Eaux et Forets, Sept., 1871.]
In accordance with the usual economy of nature, we should presume that she had everywhere provided the means of discharging, without disturbance of her general arrangements or abnormal destruction of her products, the precipitation which she sheds upon the face of the earth. Observation confirms this presumption, at least in the countries to which I confine my inquiries; for, so far as we know the primitive conditions of the regions brought under human occupation within the historical period, it appears that the overflow of river-banks was much less frequent and destructive than at the present day, or, at least, that rivers rose and fell less suddenly, before man had removed the natural checks to the too rapid drainage of the basins in which their tributaries originate. The affluents of rivers draining wooded basins generally transport, and of course let fall, little or no sediment, and hence in such regions the special obstruction to the currents of water-courses to which I have just alluded does not occur. The banks of the rivers and smaller streams in the North American colonies were formerly little abraded by the currents. [Footnote: In primitive countries, running streams are very generally fringed by groves, for almost every river is, as Pliny, Nat. Hist., v. 10, says of the Upper Nile, an opifex silvarum, or, to use the quaint and picturesque language of Holland's translation, "makes shade of woods as he goeth."] Even now the trees come down almost to the water's edge along the rivers, in the larger forests of the United States, and the surface of the streams seems liable to no great change in level or in rapidity of current. [Footnote: A valuable memoir by G. Doni, in the Rivista Forestale for October, 1863, p. 438, is one of the best illustrations I can cite of the influence of forests in regulating and equalizing the flow of running water, and of the comparative action of water-courses which drain wooded valleys and valleys bared of trees, with regard to the erosion of their banks and the transportation of sediment.
"The Sestajone," remarks this writer, "and the Lima, are two considerable torrents which collect the waters of two great valleys of the Tuscan Apennines, and empty them into the Serchio. At the junction of these two torrents, from which point the combined current takes the name of Lima, a curious phenomenon is observed, which is in part easily explained. In rainy weather the waters of the Sestajone are in volume only about one-half those of the Lima, and while the current of the Lima is turbid and muddy, that of the Sestajone appears limpid and I might almost say drinkable. In clear weather, on the contrary, the waters of the Sestajone are abundant and about double those of the Lima. Now the extent of the two valleys is nearly equal, but the Sestajone winds down between banks clothed with firs and beeches, while the Lima flows through a valley that has been stripped of trees, and in great part brought under cultivation."
The Sestajone and the Lima are neither of them what is technically termed a torrent—a name strictly applicable only to streams whose current is not derived from springs and perennial, but is the temporary effect of a sudden accumulation of water from heavy rains or from a rapid melting of the snows, while their beds are dry, or nearly so, at other times. The Lima, however, in a large proportion of its course, has the erosive character of a torrent, for the amount of sediment which it carries down, even when it is only moderately swollen by rains, surpasses almost everything of the kind which I have observed, under analogous circumstances, in Italy.
Still more striking is the contrast in the regime of the Saint-Phalez and the Combe-d'Yeuse in the Department of Vancluse, the latter of which became subject to the most violent torrential floods after the destruction of the woods of its basin between 1823 and 1833, but has now been completely subdued, and its waters brought to a peaceful flow, by replanting its valley. See Labussiere, Revue Agric. et Forestiere de Provence, 1866, and Revue des Eaux et Forets, 1866.]
Inundations in Winter.
In the Northern United States, although inundations are not very unfrequently produced by heavy rains in the height of summer, it will be found generally true that the most rapid rise of the waters, and, of course, the most destructive "freshets," as they are called in America, are occasioned by the sudden dissolution of the snow before the open ground is thawed in the spring. It frequently happens that a powerful thaw sets in after a long period of frost, and the snow which had been months in accumulating is dissolved and carried off in a few hours. When the snow is deep, it, to use a popular expression, "takes the frost out of the ground" in the woods, and, if it lies long enough, in the fields also. But the heaviest snows usually fall after midwinter, and are succeeded by warm rains or sunshine, which dissolve the snow on the cleared land before it has had time to act upon the frost-bound soil beneath it. In this case, the snow in the woods is absorbed as fast as it melts, by the soil it has protected from freezing, and does not materially contribute to swell the current of the rivers. If the mild weather, in which great snow-storms usually occur, does not continue and become a regular thaw, it is almost sure to be followed by drifting winds, and the inequality with which they distribute the snow over the cleared ground leaves the ridges of the surface-soil comparatively bare, while the depressions are often filled with drifts to the height of many feet. The knolls become frozen to a great depth; succeeding partial thaws melt the surface-snow, and the water runs down into the furrows of ploughed fields, and other artificial and natural hollows, and then often freezes to solid ice. In this state of things, almost the entire surface of the cleared land is impervious to water, and from the absence of trees and the general smoothness of the ground, it offers little mechanical resistance to superficial currents. If, under these circumstances, warm weather accompanied by rain occurs, the rain and melted snow are swiftly hurried to the bottom of the valleys and gathered to raging torrents. It ought further to be considered that, though the lighter ploughed soils readily imbibe a great deal of water, yet grass-lands, and all the heavy and tenacious earths, absorb it in much smaller quantities, and less rapidly than the vegetable mould of the forest. Pasture, meadow, and clayey soils, taken together, greatly predominate over sandy ploughed fields, in all large agricultural districts, and hence, even if, in the case we are supposing, the open ground chance to have boon thawed before the melting of the snow which covers it, it is already saturated with moisture, or very soon becomes so, and, of course, cannot relieve the pressure by absorbing more water. The consequence is that the face of the country is suddenly flooded with a quantity of melted snow and rain equivalent to a fall of six or eight inches of the latter, or even more. This runs unobstructed to rivers often still-bound with thick ice, and thus inundations of a fearfully devastating character are produced. The ice bursts, from the hydrostatic pressure from below, or is violently torn up by the current, and is swept by the impetuous stream, in large masses and with resistless fury, against banks, bridges, dams, and mills erected near them. The bark of the trees along the rivers is often abraded, at a height of many feet above the ordinary water-level, by cakes of floating ice, which are at last stranded by the receding flood on meadow or ploughland, to delay, by their chilling influence, the advent of the tardy spring.
Another important effect of the removal of the forest shelter in cold climates may be noticed here. We have observed that the ground in the woods either does not freeze at all, or that if frozen it is thawed by the first considerable snow-fall. On the contrary, the open ground is usually frozen when the first spring freshet occurs, but is soon thawed by the warm rain and melting snow. Nothing more effectually disintegrates a cohesive soil than freezing and thawing, and the surface of earth which has just undergone those processes is more subject to erosion by running water than under any other circumstances. Hence more vegetable mould is washed away from cultivated grounds in such climates by the spring floods than by the heaviest rain at other seasons.
In the warm climates of Southern Europe, as I have already said, the functions of the forest, so far as the disposal of the water of precipitation is concerned, are essentially the same at all seasons, and are analogous to those which it performs in the Northern United States in summer. Hence, in the former countries, the winter floods have not the characteristics which mark them in the latter, nor is the conservative influence of the woods in winter relatively so important, though it is equally unquestionable.
If the summer floods in the United States are attended with less pecuniary damage than those of the Loire and other rivers of France, the Po and its tributaries in Italy, the Emme and her sister torrents which devastate the valleys of Switzerland, it is partly because the banks of American rivers are not yet lined with towns, their shores and the bottoms which skirt them not yet covered with improvements whose cost is counted by millions, and, consequently, a smaller amount of property is exposed to injury by inundation. But the comparative exemption of the American people from the terrible calamities which the overflow of rivers has brought on some of the fairest portions of the Old World, is, in a still greater degree, to be ascribed to the fact that, with all our thoughtless improvidence, we have not yet bared all the sources of our streams, not yet overthrown all the barriers which nature has erected to restrain her own destructive energies. Let us be wise in time, and profit by the errors of our older brethren!
The influence of the forest in preventing inundations has been very generally recognized, both as a theoretical inference and as a fact of observation; but the eminent engineer Belgrand and his commentator Valles have deduced an opposite result from various facts of experience and from scientific considerations. They contend that the superficial drainage is more regular from cleared than from wooded ground, and that clearing diminishes rather than augments the intensity of inundations. Neither of these conclusions appears to be warranted by their data or their reasoning, and they rest partly upon facts, which, truly interpreted, are not inconsistent with the received opinions on these subjects, partly upon assumptions which are contradicted by experience. Two of these latter are, first, that the fallen leaves in the forest constitute an impermeable covering of the soil over, not through, which the water of rains and of melting snows flows off, and secondly, that the roots of trees penetrate and choke up the fissures in the rocks, so as to impede the passage of water through channels which nature has provided for its descent to lower strata.
As to the first of those, we may appeal to familiar facts within the personal knowledge of every man acquainted with the operations of sylvan nature. Rain-water never, except in very trifling quantities, flows over the leaves in the woods in summer or autumn. Water runs over them only in the spring, in the rare cases when they have been pressed down smoothly and compactly by the weight of the snow—a state in which they remain only until they are dry, when shrinkage and the action of the wind soon roughen the surface so as effectually to stop, by absorption, all flow of water. I have observed that when a sudden frost succeeds a thaw at the close of the winter, after the snow has principally disappeared, the water in and between the layers of leaves sometimes freezes into a solid crust, which allows the flow of water over it. But this occurs only in depressions and on a very small scale; and the ice thus formed is so soon dissolved that no sensible effect is produced on the escape of water from the general surface.
As to the influence of roots upon drainage, we have seen that there is no doubt that they, independently of their action as absorbents, mechanically promote it. Not only does the water of the soil follow them downwards, but their swelling growth powerfully tends to enlarge, not to obstruct, the crevices of rock into which they enter; and as the fissures in rocks are longitudinal, not mere circular orifices, every line of additional width gained by the growth of roots within them increases the area of the crevice in proportion to its length. Consequently, the widening of a fissure to the extent of one inch might give an additional drainage equal to a square foot of open tubing.
The observations and reasonings of Belgrand and Valles, though their conclusions have not been accepted by many, are very important in one point of view. There writers insist much on the necessity of taking into account, in estimating the relations between precipitation and evaporation, the abstraction of water from the surface and surface-currents, by absorption and infiltration—an element unquestionably of great value, but hitherto much neglected by meteorological inquirers, who have very often reasoned as if the surface-earth were either impermeable to water or already saturated with it; whereas, in fact, it is a sponge, always imbibing humidity and always giving it off, not by evaporation only, but by infiltration and percolation.
The remarkable historical notices of inundations in France in the Middle Ages collected by Champion [Footnote: Les Inondations en France depuis le VIe siecle jusqu'a nos jours, 6 vols, 8vo. Paris, 1858-64. See a very able review of this learned and important work by Prof. Messedaglia, read before the Academy of Agriculture at Verona in 1864.] are considered by many as furnishing proof, that when that country was much more generally covered with wood than it now is, destructive inundations of the French rivers were not less frequent than they are in modern days. But this evidence is subject to this among other objections: we know, it is true, that the forests of certain departments of France were anciently much more extensive than at the present day; but we know also that in many portions of that country the soil has been bared of its forests, and then, in consequence of the depopulation of great provinces, left to reclothe itself spontaneously with trees, many times during the historic period; and our acquaintance with the forest topography of ancient Gaul or of mediaeval France is neither sufficiently extensive nor sufficiently minute to permit us to say, with certainty, that the sources of this or that particular river were more or less sheltered by wood at any given time, ancient or mediaeval, than at present. [Footnote: Alfred Maury has, nevertheless, collected, in his erudite and able work, Les Forets de la Gaule et de l'ancienne France, Paris, 1867, an immense amount of statistical detail on the extent, the distribution, and the destruction of the forests of France, but it still remains true that we can very seldom pronounce on the forestal condition of the upper valley of a particular river at the time of a given inundation in the ancient or the mediaeval period.] I say the sources of the rivers, because the floods of great rivers are occasioned by heavy rains and snows which fall in the more elevated regions around the primal springs, and not by precipitation in the main valleys or on the plains bordering on the lower course.
The destructive effects of inundations, considered simply as a mechanical power by which life is endangered, crops destroyed, and the artificial constructions of man overthrown, are very terrible. Thus far, however, the flood is a temporary and by no means an irreparable evil, for if its ravages end here, the prolific powers of nature and the industry of man soon restore what had been lost, and the face of the earth no longer shows traces of the deluge that had overwhelmed it. Inundations have even their compensations. The structures they destroy are replaced by better and more secure erections, and if they sweep off a crop of corn, they not unfrequently leave behind them, as they subside, a fertilizing deposit which enriches the exhausted field for a succession of seasons. [Footnote: The productiveness of Egypt has been attributed too exclusively to the fertilizing effects of the slime deposited by the inundations of the Nile; for in that climate a liberal supply of water would produce good crops on almost any ordinary sand, while, without water, the richest soil would yield nothing. The sediment deposited annually is but a very small fraction of an inch in thickness. It is alleged that in quantity it would be hardly sufficient for a good top-dressing, and that in quality it is not chemically distinguishable from the soil inches or feet below the surface. But to deny, as some writers have done, that the slime has any fertilizing properties at all, is as great a error as the opposite one of ascribing all the agricultural wealth of Egypt to that single cause of productiveness. Fine soils deposited by water are almost uniformly rich in all climates; those brought down by rivers, carried out into salt-water, and then returned again by the tide, seem to be more permanently fertile than any others. The polders of the Netherland coast are of this character, and the meadows in Lincolnshire, which have been covered with slime by warping, as it is called, or admitting water over them at high tide, are remarkably productive.
Recent analysis is said to have detected in the water of the Nile a quantity of organic matter—derived mainly, no doubt, from the decayed vegetation it bears down from its tropical course—sufficiently large to furnish an important supply of fertilizing ingredients to the soil.
It is computed that the Durance—a river fed chiefly by torrents, of great erosive power—carries down annually solid material enough to cover 272,000 acres of soil with a deposit of two-fifths of an inch in thickness, and that this deposit contains, in the combination most favorable to vegetation, more azote than 110,000 tons of guano, and more carbon than 121,000 acres of woodland would assimilate in a year. Elisee Reclus, La Terre, vol. i., p. 467. On the chemical composition, quantity, and value of the solid matter transported by river, see Herve Magnon, Sur l'Emploi des Eaux dans les Irrigations, 8vo. Paris, 1869, pp. 132 et seqq. Duponchel, Traite d'Hydraulique et de Geologie Agricoles. Paris, 1868, chap. i., xii., and xiii.]
If, then, the too rapid flow of the surface-waters occasioned no other evil than to produce, once in ten years upon the average, an inundation which should destroy the harvest of the low grounds along the rivers, the damage would be too inconsiderable, and of too transitory a character, to warrant the inconveniences and the expense involved in the measures which the most competent judges in many parts of Europe believe the respective governments ought to take to obviate it.
Destructive Action of Torrents.
But the great, the irreparable, the appalling mischiefs which have already resulted, and which threaten to ensue on a still more extensive scale hereafter, from too rapid superficial drainage, are of a properly geographical, we may almost say geological, character, and consist primarily in erosion, displacement, and transportation of the superficial strata, vegetable and mineral—of the integuments, so to speak, with which nature has clothed the skeleton frame-work of the globe. It is difficult to convey by description an idea of the desolation of the regions most exposed to the ravages of torrent and of flood; and the thousands who, in these days of swift travel, are whirled by steam near or even through the theatres of these calamities, have but rare and imperfect opportunities of observing the destructive causes in action. Still more rarely can they compare the past with the actual condition of the provinces in question, and trace the progress of their conversion from forest-crowned hills, luxuriant pasture grounds, and abundant cornfields and vineyards well watered by springs and fertilizing rivulets, to bald mountain ridges, rocky declivities, and steep earth-banks furrowed by deep ravines with beds now dry, now filled by torrents of fluid mud and gravel hurrying down to spread themselves over the plain, and dooming to everlasting barrenness the once productive fields. In surveying such scenes, it is difficult to resist the impression that nature pronounced a primal curse of perpetual sterility and desolation upon these sublime but fearful wastes, difficult to believe that they wore once, and but for the folly of man might still be, blessed with all the natural advantages which Providence has bestowed upon the most favored climes. But the historical evidence is conclusive as to the destructive changes occasioned by the agency of man upon the flanks of the Alps, the Apennines, the Pyrenees, and other mountain ranges in Central and Southern Europe, and the progress of physical deterioration has been so rapid that, in some localities, a single generation has witnessed the beginning and the end of the melancholy revolution.
I have stated, in a general way, the nature of the evils in question, and of the processes by which they are produced; but I shall make their precise character and magnitude better understood by presenting some descriptive and statistical details of facts of actual occurrence. I select for this purpose the south-eastern portion of France, not because that territory has suffered more severely than some others, but because its deterioration is comparatively recent, and has been watched and described by very competent and trustworthy observers, whose reports are more easily accessible than those published in other countries. [Footnote: Streffleur (Ueber die Natur und die Wirkungen der Wildbuche, p. 3) maintains that all the observations and speculations of French authors on the nature of torrents had been anticipated by Austrian writers. In proof of this assertion he refers to the works of Franz von Zallinger, 1778, Von Arretin, 1808, Franz Duile, 1826, all published at Innsbruck, and Hagenus Beschreibung neuerer Wasserbauwerke, Konigsberg, 1826, none of which works are known to me. It is evident, however, that the conclusions of Surell and other French writers whom I cite, are original results of personal investigation, and not borrowed opinions.]
The provinces of Dauphiny and Provence comprise a territory of fourteen or fifteen thousand square miles, bounded north-west by the Isere, north-east and east by the Alps, south by the Mediterranean, west by the Rhone, and extending from 42 degrees to about 45 degrees of north latitude. The surface is generally hilly and even mountainous, and several of the peaks in Dauphiny rise above the limit of perpetual snow. Except upon the mountain ridges, the climate, as compared with that of the United States in the same latitude, is extremely mild. Little snow falls, except upon the higher mountains, the frosts are light, and the summers long, as might, indeed, be inferred from the vegetation; for in the cultivated districts, the vine and the fig everywhere flourish; the olive thrives as far north as 43 and one half degrees, and upon the coast grow the orange, the lemon, and the date-palm. The forest trees, too, are of southern type, umbrella pines, various species of evergreen oaks, and many other trees and shrubs of persistent broad-leaved foliage, characterizing the landscape.
The rapid slope of the mountains naturally exposed these provinces to damage by torrents, and the Romans diminished their injurious effects by erecting, in the beds of ravines, barriers of rocks loosely piled up, which permitted a slow escape of the water, but compelled it to deposit above the dikes the earth and gravel with which it was charged. [Footnote: Whether Palissy was acquainted with this ancient practice, or whether it was one of those original suggestions of which his works are so full, I know not, but in his treatise, Des Eaux et Fontaines, he thus recommends it, by way of reply to the objections of "Theorique," who had expressed the fear that "the waters which rush violently down from the heights of the mountain would bring with them much earth, sand, and other things," and thus spoil the artificial fountain that "Practique" was teaching him to make: "And for hindrance of the mischiefs of great waters which may be gathered in a few hours by great storms, when thou shalt have made ready thy parterre to receive the water, thou must lay great atones athwart the deep channels which lead to thy parterre. And so the force of the rushing currents shall be deadened, and thy water shall flow peacefully into his cisterns."—Oeuvres Completes, p. 178.] At a later period the Crusaders brought home from Palestine, with much other knowledge gathered from the wiser Moslems, the art of securing the hillsides and making them productive by terracing and irrigation. The forests which covered the mountains secured an abundant flow of springs, and the process of clearing the soil went on so slowly that, for centuries, neither the want of timber and fuel, nor the other evils about to be depicted, were seriously felt. Indeed, throughout the Middle Ages, these provinces were well wooded, and famous for the fertility and abundance, not only of the low grounds, but of the hills.
Such was the state of things at the close of the fifteenth century. The statistics of the seventeenth show that while there had been an increase of prosperity and population in Lower Provence, as well as in the correspondingly situated parts of the other two provinces I have mentioned, there was an alarming decrease both in the wealth and in the population of Upper Provence and Dauphiny, although, by the clearing of the forests, a great extent of plough-land and pasturage had been added to the soil before reduced to cultivation. It was found, in fact, that the augmented violence of the torrents had swept away, or buried in sand and gravel, more land than had been reclaimed by clearing; and the taxes computed by fires or habitations underwent several successive reductions in consequence of the gradual abandonment of the wasted soil by its starving occupants. The growth of the large towns on and near the Rhone and the coast, their advance in commerce and industry, and the consequently enlarged demand for agricultural products, ought naturally to have increased the rural population and the value of their lands; but the physical decay of the uplands was such that considerable tracts were deserted altogether, and in Upper Provence, the fires which, in 1471 counted 897, were reduced to 747 in 1699, to 728 in 1733, and to 635 in 1776. [Footnote: These facts I take from the La Provence au point de vue des Bois, des Torrents et des Inondations, of Charles de Ribbe, one of the highest authorities.]
Surell—whose admirable work, Etude sur les Torrents des Hautes Alpes, first published in 1841, [Footnote: A second edition of this work, with an additional volume of great value by Ernest Cezanne, was published at Paris, in two 8vo volumes, in 1871-72.] presents a most appalling picture of the desolations of the torrent, and, at the same time, the most careful studies of the history and essential character of this great evil—in speaking of the valley of Devoluy, on page 152, says: "Everything concurs to show that it was anciently wooded. In its peat-bogs are found buried trunks of trees, monuments of its former vegetation. In the framework of old houses, one sees enormous timber, which is no longer to be found in the district. Many localities, now completely bare, still retain the name of 'wood,' and one of them is called, in old deeds, Comba nigra [Black forest or dell], on account of its dense woods. These and many other proofs confirm the local traditions which are unanimous on this point.
"There, as everywhere in the Upper Alps, the clearings began on the flanks of the mountains, and were gradually extended into the valleys and then to the highest accessible peaks. Then followed the Revolution, and caused the destruction of the remainder of the trees which had thus far escaped the woodman's axe."
In a note to this passage the writer says: "Several persons have told me
that they had lost flocks of sheep, by straying, in the forests of Mont
Auroux, which covered the flanks of the mountain from La Cluse to
Agneres. These declivities are now as bare as the palm of the hand."
The ground upon the steep mountains being once bared of trees, and the underwood killed by the grazing of horned cattle, sheep, and goats, every depression becomes a water-course. "Every storm," says Surell, page 153, "gives rise to a new torrent. [Footnote: No attentive observer can frequent the southern flank of the Piedmontese Alps or the French province of Dauphiny, for half a dozen years, without witnessing with his own eyes the formation and increase of new torrents. I can bear personal testimony to the conversion of more than one grassy slope into the bed of a furious torrent by baring the hills above of their woods.] Examples of such are shown, which, though not yet three years old, have laid waste the finest fields of their valleys, and whole villages have narrowly escaped being swept into ravines formed in the course of a few hours. Sometimes the flood pours in a sheet over the surface, without ravine or even bed, and ruins extensive grounds, which are abandoned forever."
I cannot follow Surell in his description and classification of torrents, and I must refer the reader to his instructive work for a full exposition of the theory of the subject. In order, however, to show what a concentration of destructive energies may be effected by felling the woods that clothe and support the sides of mountain abysses, I cite his description of a valley descending from the Col Isoard, which he calls "a complete type of a basin of reception," that is, a gorge which serves as a common point of accumulation and discharge for the waters of several lateral torrents. "The aspect of the monstrous channel," says he, "is frightful. Within a distance of less than two English miles, more than sixty torrents hurl into the depths of the gorge the debris torn from its two flanks. The smallest of these secondary torrents, if transferred to a fertile valley, would be enough to ruin it."
The eminent political economist Blanqui, in a memoir read before the Academy of Moral and Political Science on the 25th of November, 1843, thus expresses himself: "Important as are the causes of impoverishment already described, they are not to be compared to the consequences which have followed from the two inveterate evils of the Alpine provinces of France, the extension of clearing and the ravages of torrents. … The most important result of this destruction is this; that the agricultural capital, or rather the ground itself—which, in a rapidly increasing degree, is daily swept away by the waters—is totally lost. Signs of unparalleled destitution are visible in all the mountain zone, and the solitudes of those districts are assuming an indescribable character of sterility and desolation. The gradual destruction of the woods has, in a thousand localities, annihilated at once the springs and the fuel. Between Grenoble and Briancon, in the valley of the Romanche, many villages are so destitute of wood that they are reduced to the necessity of baking their bread with sun-dried cow-dung, and even this they can afford to do but once a year.
"Whoever has visited the valley of Barcelonette, those of Embrun, and of Verdun, and that Arabia Petraea of the department of the Upper Alps, called Devoluy, knows that there is no time to lose—that in fifty years from this date France will be separated from Savoy, as Egypt from Syria, by a desert." [Footnote: Ladoucette says the peasant of Devoluy "often goes a distance of five hours over rocks and precipices for a single [man's] load of wood;" and he remarks on another page, that "the justice of peace of that canton had, in the course of forty-three years, but once heard the voice of the nightingale."—Histoire, etc, des Hautes Alpes, pp. 220, 434.]
It deserves to be specially noticed that the district here referred to, though now among the most hopelessly waste in France, was very productive even down to so late a period as the commencement of the French Revolution. Arthur Young, writing in 1789, says: "About Barcelonette and in the highest parts of the mountains, the hill-pastures feed a million of sheep, besides large herds of other cattle;" and he adds: "With such a soil and in such a climate, we are not to suppose a country barren because it is mountainous. The valleys I have visited are, in general, beautiful." [Footnote: The valley of Embrun, now almost completely devastated, was once remarkable for its fertility. In 1800, Hericart de Thury said of it: "In this magnificent valley nature had been prodigal of her gifts. Its inhabitants have blindly revelled in her favors, and fallen asleep in the midst of her profusion."—Becquerel, Des Climats, etc., p. 314.] He ascribes the same character to the provinces of Dauphiny, Provence, and Auvergne, and, though he visited, with the eye of an attentive and practised observer, many of the scenes since blasted with the wild desolation described by Blanqui, the Durance and a part of the course of the Loire are the only streams he mentions as inflicting serious injury by their floods. The ravages of the torrents had, indeed, as we have seen, commenced earlier in some other localities, but we are authorized to infer that they were, in Young's time, too limited in range, and relatively too insignificant, to require notice in a general view of the provinces where they have now ruined so large a proportion of the soil.
But I resume my citations.
"I do not exaggerate," says Blanqui. "When I shall have finished my description and designated localities by their names, there will rise, I am sure, more than one voice from the spots themselves, to attest the rigorous exactness of this picture of their wretchedness. I have never seen its equal even in the Kabyle villages of the province of Constantine; for there you can travel on horseback, and you find grass in the spring, whereas in more than fifty communes in the Alps there is absolutely nothing.
"The clear, brilliant, Alpine sky of Embrun, of Gap, of Barcelonette, and of Digne, which for months is without a cloud, produces droughts interrupted only by diluvial rains like those of the tropics. The abuse of the right of pasturage and the felling of the woods have stripped the soil of all its grass and all its trees, and the scorching sun bakes it to the consistence of porphyry. When moistened by the rain, as it has neither support nor cohesion, it rolls down to the valleys, sometimes in floods resembling black, yellow, or reddish lava, sometimes in streams of pebbles, and over huge blocks of stone, which pour down with a frightful roar, and in their swift course exhibit the most convulsive movements. If you overlook from an eminence one of these landscapes furrowed with so many ravines, it presents only images of desolation and of death. Vast deposits of flinty pebbles, many feet in thickness, which have rolled down and spread far over the plain, surround large trees, bury even their tops, and rise above them, leaving to the husbandman no longer a ray of hope. One can imagine no sadder spectacle than the deep fissures in the flanks of the mountains, which seem to have burst forth in eruption to cover the plains with their ruins. Those gorges, under the influence of the sun which cracks and shivers to fragments the very rocks, and of the rain which sweeps them down, penetrate deeper and deeper into the heart of the mountain, while the beds of the torrents issuing from them are sometimes raised several feet in a single year, by the debris, so that they reach the level of the bridges, which, of course, are then carried off. The torrent-beds are recognized at a great distance, as they issue from the mountains, and they spread themselves over the low grounds, in fan-shaped expansions, like a mantle of stone, sometimes ten thousand feet wide, rising high at the centre, and curving towards the circumference till their lower edges meet the plain.
"Such is their aspect in dry weather. But no tongue can give an adequate description of their devastations in one of those sudden floods winch resemble, in almost none of their phenomena, the action of ordinary river-water. They are now no longer overflowing brooks, but real seas, tumbling down in cataracts, and rolling before them blocks of stone, which are hurled forwards by the shock of the waves like balls shot out by the explosion of gunpowder. Sometimes ridges of pebbles are driven down when the transporting torrent does not rise high enough to show itself, and then the movement is accompanied with a roar louder than the crash of thunder. A furious wind precedes the rushing water and announces its approach. Then comes a violent eruption, followed by a flow of muddy waves, and after a few hours all returns to the dreary silence which at periods of rest marks these abodes of desolation. [Footnote: These explosive gushes of mud and rock appear to be occasioned by the caving-in of large masses of earth from the banks of the torrent, which dam up the stream and check its flow until it has acquired volume enough to burst the barrier and carry all before it. In 1827, such a sudden eruption of a torrent, after the current had appeared to have ceased, swept off forty-two houses and drowned twenty-eight persons in the village of Goncelin, near Grenoble, and buried with rubbish a great part of the remainder of the village."
The French traveller, D'Abbadie, relates precisely similar occurrences as not unfrequent in the mountains of Abyssinia.—Surrell, Etudes, etc; 2d edition, pp. 224, 295.]
"The elements of destruction are increasing in violence. The devastation advances in geometrical progression as the higher slopes are bared of their wood, and 'the ruin from above,' to use the words of a peasant, 'helps to hasten the desolation below.'
"The Alps of Provence present a terrible aspect. In the more equable climate of Northern France, one can form no conception of those parched mountain gorges where not even a bush can be found to shelter a bird, where, at most, the wanderer sees in summer here and there a withered lavender, where all the springs are dried up, and where a dead silence, hardly broken by even the hum of an insect, prevails. But if a storm bursts forth, masses of water suddenly shoot from the mountain heights into the shattered gulfs, waste without irrigating, deluge without refreshing the soil they overflow in their swift descent, and leave it even more seared than it was from want of moisture. Man at last retires from the fearful desert, and I have, the present season, found not a living soul in districts where I remember to have enjoyed hospitality thirty years ago."
In 1853, ten years after the date of Blanqui's memoir, M. de Bonville, prefect of the Lower Alps, addressed to the Government a report in which the following passages occur:
"It is certain that the productive mould of the Alps, swept off by the increasing violence of that curse of the mountains, the torrents, is daily diminishing with fearful rapidity. All our Alps are wholly, or in large proportion, bared of wood. Their soil, scorched by the sun of Provence, cut up by the hoofs of the sheep, which, not finding on the surface the grass they require for their sustenance, gnaw and scratch the ground in search of roots to satisfy their hunger, is periodically washed and carried off by melting snows and summer storms.
"I will not dwell on the effects of the torrents. For sixty years they have been too often depicted to require to be further discussed, but it is important to show that their ravages are daily extending the range of devastation. The bed of the Durance, which now in some places exceeds a mile and a quarter in width, and, at ordinary times, has a current of water less than eleven yards wide, shows something of the extent of the damage." [Footnote: In the days of the Roman Empire the Durance was a navigable, or at least a boatable, river, with a commerce so important that the boatmen upon it formed a distinct corporation.—Ladoucette, Histoire, etc., des Hautes Alpes, p. 354.
Even as early as 1789 the Durance was computed to have already covered with gravel and pebbles not less than 130,000 acres, "which, but for its inundations, would have been the finest land in the province."—Arthur Young, Travels in France, vol i., ch. i.] Where, ten years ago, there were still woods and cultivated grounds to be seen, there is now but a vast torrent; there is not one of our mountains which has not at least one torrent, and new ones are daily forming.
"An indirect proof of the diminution of the soil is to be found in the depopulation of the country. In 1852 I reported to the General Council that, according to the census of that year, the population of the department of the Lower Alps had fallen off no less than 5,000 souls in the five years between 1846 and 1851.
"Unless prompt and energetic measures are taken, it is easy to fix the epoch when the French Alps will be but a desert. The interval between 1851 and 1856 will show a further decrease of population. In 1862 the ministry will announce a continued and progressive reduction, in the number of acres devoted to agriculture; every year will aggravate the evil and in half a century France will count more ruins, and a department the less."
Time has verified the predictions of De Bonville. The later census returns show a progressive diminution in the population of the departments of the Lower Alps, the Isere, Drome, Ariege, the Upper and the Lower Pyrenees, Lozere, the Ardennes, Doubs, the Vosges, and, in short, in all the provinces formerly remarkable for their forests. This diminution is not to be ascribed to a passion for foreign emigration, as in Ireland, and in parts of Germany and of Italy; it is simply a transfer of population from one part of the empire to another, from soils which human folly has rendered uninhabitable, by ruthlessly depriving them of their natural advantages and securities, to provinces where the face of the earth was so formed by nature as to need no such safeguards, and where, consequently, she preserves her outlines in spite of the wasteful improvidence of man. [Footnote: Between 1851 and 1856 the population of Languedoc and Provence had increased by 101,000 souls. The augmentation, however, was wholly in the provinces of the plains, where all the principal cities are found. In these provinces the increase was 204,000, while in the mountain provinces there was a diminution of 103,000. The reduction of the area of arable land is perhaps even more striking. In 1842 the department of the Lower Alps possessed 90,000 hectares, or nearly 245,000 acres, of cultivated soil. In 1852 it had but 74,000 hectares. In other words, in ten years 25,000 hectares, or 61,000 acres, had been washed away, or rendered worthless for cultivation, by torrents and the abuses of pasturage.—Clave, Etudes, pp. 66, 67.]
Floods of the Ardeche.
The River Ardeche, in the French department of that name, has a perennial current in a considerable part of its course, and therefore is not, technically speaking, a torrent; but the peculiar character and violence of its floods is due to the action of the torrents which discharge themselves into it in its upper valley, and to the rapidity of the flow of the water of precipitation from the surface of a basin now almost bared of its once luxuriant woods. [Footnote: The original forests in which the basin of the Ardeche was rich have been rapidly disappearing for many years, and the terrific violence of the inundations which are now laying it waste is ascribed, by the ablest investigators, to that cause. In an article inserted in the Annales Forestieres for 1843, quoted by Hohenstein, Der Wald, p. 177, it is said that about one-third of the area of the department had already become absolutely barren, in consequence of clearing, and that the destruction of the woods was still going on with great rapidity. New torrents were constantly forming, and they were estimated to have covered more than 70,000 acres of good land, or one-eighth of the surface of the department, with sand and gravel.] A notice of these floods may therefore not inappropriately be introduced in this place.
The floods of the Ardeche and other mountain streams are attended with greater immediate danger to life and property than those of rivers of less rapid flow, because their currents are more impetuous, and they rise more suddenly and with less previous warning. At the same time, their ravages are confined within narrower limits, the waters retire sooner to their accustomed channel, and the danger is more quickly over, than in the case of inundations of larger rivers. The Ardeche drains a basin of 600,238 acres, or a little less than nine hundred and thirty-eight square miles. Its remotest source is about seventy-five miles, in a straight line, from its junction with the Rhone, and springs at an elevation of four thousand feet above that point. At the lowest stage of the river, the bed of the Chassezac, its largest and longest tributary, is in many places completely dry on the surface—the water being sufficient only to supply the subterranean channels of infiltration—and the Ardeche itself is almost everywhere fordable, even below the mouth of the Chassezac. But in floods, the river has sometimes risen more than sixty feet at the Pont d'Arc, a natural arch of two hundred feet chord, which spans the stream below its junction with all its important affluents. At the height of the inundation of 1857, the quantity of water passing this point—after deducting thirty per cent. for material transported with the current and for irregularity of flow—was estimated at 8,845 cubic yards to the second, and between twelve o'clock at noon on the 10th of September of that year and ten o'clock the next morning, the water discharged through the passage in question amounted to more than 450,000,000 cubic yards. This quantity, distributed equally through the basin of the river, would cover its entire area to a depth of more than five inches.
The Ardeche rises so suddenly that, in the inundation of 1846, the women who were washing in the bed of the river had not time to save their linen, and barely escaped with their lives, though they instantly fled upon hearing the roar of the approaching flood. Its waters and those of its affluents fall almost as rapidly, for in less than twenty-four hours after the rain has ceased in the Cevennes, where it rises, the Ardeche returns within its ordinary channel, even at its junction with the Rhone. In the flood of 1772, the water at La Beaume de Ruoms, on the Beaume, a tributary of the Ardeche, rose thirty-five feet above low water but the stream was again fordable on the evening of the same day. The inundation of 1827 was, in this respect, exceptional, for it continued three days, during which period the Ardeche poured into the Rhone 1,305,000,000 cubic yards of water.
The Nile delivers into the sea 101,000 cubic feet or 3,741 cubic yards per second, on an average of the whole year. [Footnote: Sir John F. Herschel, citing Talabot as his authority, Physical Geography (24).
In an elaborate paper on "Irrigation," printed in the United States Patent Report for 1860, p. 169, it is stated that the volume of water poured into the Mediterranean by the Nile in twenty-four hours, at low water, is 150,566,392,368 cubic meters; at high water, 705,514,667,440 cubic metres. Taking the mean of these two numbers, the average daily delivery of the Nile would be 428,081,059,808 cubic metres, or more than 550,000,000,000 cubic yards. There is some enormous mistake, probably a typographical error, in this statement, which makes the delivery of the Nile seventeen hundred times as great as computed by Talabot, and more than physical geographers have estimated the quantity supplied by all the rivers on the face of the globe.] This is equal to 323,222,400 cubic yards per day. In a single day of flood, then, the Ardeche, a river too insignificant to be known except in the local topography of France, contributed to the Rhone once and a half, and for three consecutive days once and one third, as much as the average delivery of the Nile during the same periods, though the basin of the latter river probably contains 1,000,000 square miles of surface, or more than one thousand times as much as that of the former.
The average annual precipitation in the basin of the Ardeche is not greater titan in many other parts of Europe, but excessive quantities of rain frequently fall in that valley in the autumn. On the 9th. of October, 1827, there fell at Joyeuse, on the Beaume, no less than thirty-one inches between three o'clock in the morning and midnight. Such facts as this explain the extraordinary suddenness and violence of the floods of the Ardeche, and the basins of many other tributaries of the Rhone exhibit meteorological phenomena not less remarkable. [Footnote: The Drac, a torrent emptying into the Isere a little below Grenoble, has discharged 5,200, the Isere, which receives it, 7,800 cubic yards, and the Durance, above its junction with the Isere, an equal quantity, per second.—Montluisant, Note sur les Dessechements, etc., Annales des Ponts et Chaussees, 1833, 2me semestre p. 288.
The Upper Rhone, which drains a basin of about 1,900 square miles, including seventy-one glaciers, receives many torrential affluents, and rain-storms and thaws are sometimes extensive enough to affect the whole tributary system of its narrow valley. In such cases its current swells to a great volume, but previously to the floods of the autumn of 1868 it was never known to reach a discharge of 2,600 cubic yards to the second. On the 28th of September in that year, however, its delivery amounted to 3,700 cubic yards to the second, which is about equal to the mean discharge of the Nile.—Berichte der Experten-Commission uber die Ueberschaeemmungen im Jahr 1868, pp. 174,175.
The floods of some other French rivers, which have a more or less torrential character, scarcely fall behind those of the Rhone. The Loire, above Roanne, has a basin of 2,471 square miles, or about twice and a half the area of that of the Ardeche. In some of its inundations it has delivered above 9,500 cubic yards per second, or 400 times its low-water discharge.—Belgrand, De l'Influence des Forets, etc., Annales des Ponts et Chaussees, 1854, 1er semestre, p.15, note.
The ordinary low-water discharge of the Seine at Paris is nearly 100 cubic yards per second. Belgrand gives a list of eight floods of that river within the last two centuries, in which it has delivered thirty times that quantity.]
The Rhone, therefore, is naturally subject to great and sudden inundations, and the same remark may be applied to most of the principal rivers of France, because the geographical character of all of them is approximately the same.
The volume of water in the floods of most great rivers is determined by the degree in which the inundations of the different tributaries are coincident in time. Were all the affluents of the Lower Rhone to pour their highest annual floods into its channel at once—as the smaller tributaries of the Upper Rhone sometimes do—were a dozen Niles to empty themselves into its bed at the same moment, its water would rise to a height and rush with an impetus that would sweep into the Mediterranean the entire population of its banks, and all the works that man has erected upon the plains which border it. But such a coincidence can never happen. The tributaries of this river run in very different directions, and some of them are swollen principally by the melting of the snows about their sources, others almost exclusively by heavy rains. When a damp southeast wind blows up the valley of the Ardeche, its moisture is condensed, and precipitated in a deluge upon the mountains which embosom the headwaters of that stream, thus producing a flood, while a neighboring basin, the axis of which lies transversely or obliquely to that of the Ardeche, is not at all affected. [Footnote: "There is no example of a coincidence between great floods of the
Ardeche and of the Rhone, all the known inundations of the former having taken place when the latter was very low."—MARDIGNY, Memoire sur les Inondations des Rivieres de l'Ardeche, p. 26.
The same observation may be applied to the tributaries of the Po, their floods being generally successive, not contemporaneous. The swelling of the affluents of the Amazon, and indeed of most large rivers, is regulated by a similar law. See Messedaglia, Analisi dell' opera di Champion, etc., p. 103.
The floods of the affluents of the Tiber form an exception to this law, being generally coincident, and this is one of the explanations of the frequency of destructive inundations in that river.—Lombardini, Guida allo Studio dell' Idrologia, ff. 68; same author, Esame degli studi sul Tevere.
I take this occasion to acknowledge myself indebted to Mardigny's interesting memoir just quoted for all the statements I make respecting the floods of the Ardeche, except the comparison of the volume of its water with that of the Nile.] It is easy to see that the damage occasioned by such floods as I have described must be almost incalculable, and it is by no means confined to the effects produced by overflow and the mechanical force of the superficial currents. In treating of the devastations of torrents, I have hitherto confined myself principally to the erosion of surface and the transportation of mineral matter to lower grounds by them. The general action of torrents, as thus fur shown, tends to the ultimate elevation of their beds by the deposit of the earth, gravel, and stone conveyed by them; but until they have thus raised their outlets so as sensibly to diminish the inclination of their channels—and sometimes when extraordinary floods give the torrents momentum enough to sweep away the accumulations which they have themselves heaped up—the swift flow of their currents, aided by the abrasion of the rolling rocks and gravel, scoops their beds constantly deeper, and they consequently not only undermine their banks, but frequently sap the most solid foundations which the art of man can build for the support of bridges and hydraulic structures. [Footnote: In some cases where the bed of rapid Alpine streams is composed of very hard rock—as is the case in many of the valleys once filled by ancient glaciers—and especially where they are fed by glaciers not overhung by crumbling cliffs, the channel may remain almost unchanged for centuries. This is observable in many of the tributaries of the Dora Baltea, which drains the valley of Aosta. Several of these small rivers are spanned by more or less perfect Roman bridges—one of which, that over the Lys at Pont St. Martin, is still in good repair and in constant use. An examination of the rocks on which the abutments of this and some other similar structures are founded, and of the channels of the rivers they cross, shows that the beds of the streams cannot have been much elevated or depressed since the bridges were built. In other cases, as at the outlet of the Val Tournanche at Chatillon, where a single rib of a Roman bridge still remains, there is nothing to forbid the supposition that the deep excavation of the channel may have been partly effected at much later period.
The Roman aqueduct known as the Pont du Gard, near Nismes, was built, in all probability, nineteen centuries ago. The bed of the river Gardon, a rather swift stream, which flows beneath it, can have suffered but slight depression since the piers of the aqueduct were founded.]
In the inundation of 1857, the Ardeche destroyed a stone bridge near La Beaume, which had been built about eighty years before. The resistance of the piers, which were erected on piles, the channel at that point being of gravel, produced an eddying current that washed away the bed of the river above them, and the foundation, thus deprived of lateral support, yielded to the weight of the bridge, and the piles and piers fell up-stream.
By a curious law of compensation, the stream which, at flood, scoops out cavities in its bed, often fills them up again as soon as the diminished velocity of the current allows it to let fall the sand and gravel with which it is charged, so that when the waters return to their usual channel, the bottom shows no sign of having been disturbed. In a flood of the Escontay, a tributary of the Rhone, in 1846, piles driven sixteen feet into its gravelly bed for the foundation of a pier were torn up and carried off, and yet, when the river had fallen to low-water mark, the bottom at that point appeared to have been raised higher than it was before the flood, by new deposits of sand and gravel, while the cut stones of the half-built pier were found buried to a great depth in the excavation which the water had first washed out. The gravel with which rivers thus restore the level of their beds is principally derived from the crushing of the rocks brought down by the mountain torrents, and the destructive effects of inundations are immensely diminished by this reduction of large stones to minute fragments. If the blocks hurled down from the cliffs were transported unbroken to the channels of large rivers, the mechanical force of their movement would be irresistible. They would overthrow the strongest barriers, spread themselves over a surface as wide as the flow of the waters, and convert the most smiling valleys into scenes of the wildest desolation.
As I have before remarked, I have taken my illustrations of the action of torrents and mountain streams principally from French authorities, because the facts recorded by them are chiefly of recent occurrence, and as they have been collected with much care and described with great fulness of detail, the information furnished by them is not only more trustworthy, but both more complete and more accessible than that which can be gathered from any other source. It is not to be supposed, however, that the countries adjacent to France have escaped the consequences of a like improvidence. The southern flanks of the Alps, and, in a less degree, the northern slope of these mountains and the whole chain of the Pyrenees, afford equally striking examples of the evils resulting from the wanton sacrifice of nature's safeguards. But I can afford space for few details, and as an illustration of the extent of these evils in Italy, I shall barely observe that it was calculated ten years ago that four-tenths of the area of the Ligurian provinces had been washed away or rendered incapable of cultivation in consequence of the felling of the woods. [Footnote: Annali di Agricoltura, Industria e Commercio, vol. i., p. 77. Similar instances of the erosive power of running water might be collected by hundreds from the narratives of travellers in warm countries. The energy of the torrents of the Himalayas is such that the brothers Schlagintweit believe that they will cut gorges through that lofty chain wide enough to admit the passage of currents of warm wind from the south, and thereby modify the climate of the countries lying to the north of the mountains.]
Highly colored as these pictures seem, they are not exaggerated, although the hasty tourist through Southern France, Switzerland, the Tyrol, and Northern Italy, finding little in his high-road experiences to justify them, might suppose them so. The lines of communication by locomotive-train and diligence lead generally over safer ground, and it is only when they ascend the Alpine passes and traverse the mountain chains, that scenes somewhat resembling those just described fall under the eye of the ordinary traveller. But the extension of the sphere of devastation, by the degradation of the mountains and the transportation of their debris, is producing analogous effects upon the lower ridges of the Alps and the plains which skirt them; and even now one needs but an hour's departure from some great thoroughfares to reach sites where the genius of destruction revels as wildly as in the most frightful of the abysses which Blanqui has painted. [Footnote: The Skalara-Tobel, for instance, near Coire. See the description of this and other like scenes in Berlepsch, Die Alpen, pp. 169 et seqq., or in Stephen's English translation.
About an hour from Thusis, on the Splagen road, "opens the awful chasm of the Nolla which a hundred years ago poured its peaceful waters through smiling meadows protected by the wooded slopes of the mountains. But the woods were cut down and with them departed the rich pastures, the pride of the valley, now covered with piles of rock and rubbish swept down from the mountains. This result is the more to be lamented as it was entirely compassed by the improvidence of man in thinning the forests."—Morell, Scientific Guide to Switzerland, p. 100.
The recent change in the character of the Mella—a river anciently so remarkable for the gentleness of its current that it was specially noticed by Catullus as flowing molli flumine—deserves more than a passing remark. This river rises in the mountain-chain east of Lake Iseo, and traversing the district of Brescia, empties into the Oglio after a course of about seventy miles. The iron-works in the upper valley of the Mella had long created a considerable demand for wood, but their operations were not so extensive as to occasion any very sudden or general destruction of the forests, and the only evil experienced from the clearings was the gradual diminution of the volume of the river. Within the last thirty years, the superior quality of the arms manufactured at Brescia has greatly enlarged the sale of them, and very naturally stumulated the activity of both the forges and of the colliers who supply them, and the hillsides have been rapidly stripped of their timber. Up to 1850, no destructive inundation of the Mella had been recorded. Buildings in great numbers had been erected upon its margin, and its valley was conspicuous for its rural beauty and its fertility. But when the denudation of the mountains had reached a certain point, avenging nature began the work of retribution. In the spring and summer of 1850 several new torrents were suddenly formed in the upper tributary valleys, and on the 14th and 15th of August in that year a fall of rain, not heavier than had been often experienced, produced a flood which not only inundated much ground never before overflowed, but destroyed a great number of bridges, dams, factories, and other valuable structures, and, what was a far more serious evil, swept off from the rocks an incredible extent of soil, and converted one of the most beautiful valleys of the Italian Alps into a ravine almost us bare and as barren as the savagest gorge of Southern France. The pecuniary damage was estimated at many millions of francs, and the violence of the catastrophe was deemed so extraordinary, even in a country subject to similar visitations, that the sympathy excited for the sufferers produced, in five months, voluntary contributions for their relief to the amount of nearly $200,000.—Delle Inondazioni del Mella, etc., nella notte del 14 al 15 Agosto, 1850.
The author of this pamphlet has chosen as a motto a passage from the Vulgate translation of Job, which is interesting as showing accurate observation of the action of the torrent: "Mons cadens definit, et saxum transfertur de loco suo; lapides excavant aquae et alluvione paullatim terra consumitur."—Job xiv. 18, 19.
The English version is much less striking, and gives a different sense.
The recent date of the change in the character of the Mella is contested, and it is possible that, though the extent of the revolution is not exaggerated, the rapidity with which it has taken place may have been.]
There is one effect of the action of torrents which few travellers on the Continent are heedless enough to pass without notice. I refer to the elevation of the beds of mountain streams in consequence of the deposit of the debris with which they are charged. To prevent the spread of sand and gravel over the fields and the deluging overflow of the raging waters, the streams are confined by walls and embankments, which are gradually built higher and higher as the bed of the torrent is raised, so that, to reach a river, you ascend from the fields beside it; and sometimes the ordinary level of the stream is above the streets and even the roofs of the towns through which it passes. [Footnote: Streffleur quotes from Duile the following observations: "The channel of the Tyrelese brooks is often raised much above the valleys through which they flow. The bed of the Fersina is elevated high above the city of Trent, which lies near it. The Villerbach flows at a much more elevated level than that of the market-place of Neumarkt and Vill, and threatens to overwhelm both of them with its waters. The Talfer at Botzen is at least even with the roofs of the adjacent town, if not above them. The tower-steeples of the villages of Schlanders, Kortsch, and Laas, are lower than the surface of the Gadribach. The Saldurbach at Schluderus menaces the far lower village with destruction, and the chief town, Schwaz, is in similar danger from the Lahnbach."—Streffleur, Ueber die Wildbuche, etc., p. 7.] The traveller who visits the depths of an Alpine ravine, observes the length and width of the gorge and the great height and apparent solidity of the precipitous walls which bound it, and calculates the mass of rock required to fill the vacancy, can hardly believe that the humble brooklet which purls at his feet has been the principal agent in accomplishing this tremendous erosion. Closer observation will often teach him, that the seemingly unbroken rock which overhangs the valley is full of cracks and fissures, and really in such a state of disintegration that every frost must bring down tons of it. If he computes the area of the basin which finds here its only discharge, he will perceive that a sudden thaw of the winter's deposit of snow, or one of those terrible discharges of rain so common in the Alps, must send forth a deluge mighty enough to sweep down the largest masses of gravel and of rock. The simple measurement of the cubical contents of the semicircular hillock which he climbed before he entered the gorge, the structure and composition of which conclusively show that it must have been washed out of this latter by torrential action, will often account satisfactorily for the disposal of most of the matter which once filled the ravine. When a torrent escapes from the lateral confinement of its mountain walls and pours out of the gorge, it spreads and divides itself into numerous smaller streams which shoot out from the mouth of the ravine as from a centre, in different directions, like the ribs of a fan from the pivot, each carrying with it its quota of stones and gravel. The plain below the point of issue from the mountain is rapidly raised by newly-formed torrents, the elevation depending on the inclination of the bed and the form and weight of the matter transported. Every flood both increases the height of this central point and extends the entire circumference of the deposit. Other things being equal, the transporting power of the water is greatest where its flow is most rapid. This is usually in the direction of the axis of the ravine. The stream retaining most nearly this direction moves with the greatest momentum, and consequently transports the solid matter with which it is charged to the greatest distance.
The untravelled reader will comprehend this the better when he is informed that the southern slope of the Alps generally rises suddenly out of the plain, with no intervening hill to break the abruptness of the transition, except those consisting of comparatively small heaps of its own debris brought down by ancient glaciers or recent torrents. The torrents do not wind down valleys gradually widening to the rivers or the sea, but leap at once from the flanks of the mountains upon the plains below. This arrangement of surfaces naturally facilitates the formation of vast deposits at their points of emergence, and the centre of the accumulation in the case of very small torrents is not unfrequently a hundred feet high, and sometimes very much more.
The deposits of the torrent which has scooped out the Nantzen Thal, a couple of miles below Brieg in the Valais, have built up a semicircular hillock, which most travellers by the Simplon route pass over without even noticing it, though it is little inferior in dimensions to the great cones of dejection described by Blanqui. The principal course of the torrent having been—I know not whether spontaneously or artificially—diverted towards the west, the eastern part of the hill has been gradually brought under cultivation, and there are many trees, fields, and houses upon it; but the larger western part is furrowed with channels diverging from the summit of the deposit at the outlet of the Nantzen Thal, which serve as the beds of the water-courses into which the torrent has divided itself. All this portion of the hillock is subject to inundation after long and heavy rain, and as I saw it in the great flood of October, 1866, almost its whole surface seemed covered with an unbrokun sheet of rushing water.
The semi-conical deposit of detritus at the mouth of the Litznerthal, a lateral branch of the valley of the Adige, at the point where the torrent pours out of the gorge, is a thousand feet high and, measuring along the axis of the principal current, two and a half miles long. [Footnote: Sonklar, Die Octzthaler Gebirgsgruppe, 1861, p. 231.] The solid material of this hillock—which it is hardly an exaggeration to call a mountain, the work of a single insignificant torrent and its tributaries—including what the river which washes its base has carried off in a comparatively few years, probably surpasses the mass of the stupendous pyramid of the Matterhorn. In valleys of ancient geological formation, which extend into the very heart of the mountains, the streams, though rapid, have often lost the true torrential character, if, indeed, they ever possessed it. Their beds have become approximately constant, and their walls no longer crumble and fall into the waters that wash their bases. The torrent-worn ravines, of which I have spoken, are of later date, and belong more properly to what may be called the crust of the Alps, consisting of loose rocks, of gravel, and of earth, strewed along the surface of the great declivities of the central ridge, and accumulated thickly between their solid buttresses. But it is on this crust that the mountaineer dwells. Here are his forests, here his pastures, and the ravages of the torrent both destroy his world, and convert it into a source of overwhelming desolation to the plains below.
I do not mean to assert that all the rocky valleys of the Alps have been produced by the action of torrents resulting from the destruction of the forests. The greater, and many of the smaller channels, by which that chain is drained, owe their origin to higher causes. They are primitive fissures, ascribable to disruption in upheaval or other geological convulsion, widened and scarped, and often even polished, so to speak, by the action of glaciers during the ice period, and but little changed in form by running water in later eras.
It has been contended that all rivers which take their rise in mountains originated in torrents. These, it is said, have lowered the summits by gradual erosion, and, with the material thus derived, have formed shoals in the sea which once beat against the cliffs; then, by successive deposits, gradually raised them above the surface, and finally expanded them into broad plains traversed by gently flowing streams. If we could get back to earlier geological periods, we should find this theory often verified, and we cannot fail to see that the torrents go on at the present hour, depressing still lower the ridges of the Alps and the Apennines, raising still higher the plains of Lombardy and Provence, extending the coast still farther into the Adriatic and the Mediterranean, reducing the inclination of their own beds and the rapidity of their flow, and thus tending to become river-like in character.
We cannot measure the share which human action has had in augmenting the intensity of causes of mountain degradation, and of the formation of plains and marshes below, but we know that the clearing of the woods has, in some cases, produced, within two or three generations, effects as blasting as those generally ascribed to geological convulsions, and has laid waste the face of the earth more hopelessly than if it had been buried by a current of lava or a shower of volcanic sand. New torrents are forming every year in the Alps. Tradition, written records, and analogy concur to establish the belief that the ruin of most of the now desolate valleys in those mountains is to be ascribed to the same cause, and authentic descriptions of the irresistible force of the torrent show that, aided by frost and heat, it is adequate to level Mont Blanc and Monte Rosa themselves, unless new upheavals shall maintain their elevation.
There are cases where torrents cease their ravages of themselves, in consequence of some change in the condition of the basin where they originate, or of the face of the mountain at a higher level, while the plain or the sea below remains in substantially the same state as before. If a torrent rises in a small valley containing no great amount of earth and of disintegrated or loose rock, it may, in the course of a certain period, wash out all the transportable material, and if the valley is then left with solid walls, it will cease to furnish debris to be carried down by floods. If, in this state of things, a new channel be formed at an elevation above the head of the valley, it may divert a part or even the whole of the rain-water and melted snow which would otherwise have flowed into it, and the once furious torrent now sinks to the rank of a humble and harmless brooklet. "In traversing this department," says Suroll, "one often sees, at the outlet of a gorge, a flattened hillock, with a fan-shaped outline and regular slopes; it is the bed of dejection of an ancient torrent. It sometimes requires long and careful study to detect the primitive form, masked as it is by groves of trees, by cultivated fields, and often by houses, but, when examined closely, and from different points of view, its characteristic figure manifestly appears, and its true history cannot be mistaken. Along the hillock flows a streamlet, issuing from the ravine, and quietly watering the fields. This was originally a torrent, and in the background may be discovered its mountain basin. Such EXTINGUISHED torrents, if I may use the expression, are numerous." [Footnote: Surrell, Les Torrents des Hautes Alpes, chap. xxiv. In such cases, the clearing of the ground, which, in consequence of a temporary diversion of the waters, or from some other cause, has become rewooded, sometimes renews the ravages of the torrent. Thus, on the left bank of the Durance, a wooded declivity had been formed by the debris brought down by torrents, which had extinguished themselves after having swept off much of the superficial strata of the mountain of Morgon. "All this district was covered with woods, which have now been thinned out and are perishing from day to day; consequently, the torrents have recommenced their devastations, and if the clearings continue, this declivity, now fertile, will he ruined, like so many others."—Ibid, p. 155.]
But for the intervention of man and domestic animals, these latter beneficent revolutions would occur more frequently, proceed more rapidly. The new scarped mountains, the hillocks of debris, the plains elevated by sand and gravel spread over them, the shores freshly formed by fluviatile deposits, would clothe themselves with shrubs and trees, the intensity of the causes of degradation would be diminished, and nature would thus regain her ancient equilibrium. But these processes, under ordinary circumstances, demand, not years, generations, but centuries; [Footnote: Where a torrent has not been long in operation, and earth still remains mixed with the rocks and gravel it heaps up at its point of eruption, vegetation soon starts up and prospers, it protected from encroachment. In Provence, "several communes determined, about ten years ago, to reserve the soils thus wasted, that is, to abandon them for a certain time, to spontaneous vegetation, which was not slow in making its appearance."-Becquerel, Des Climats, p. 815.] and man, who even now finds scarce breathing-room on this vast globe, cannot retire from the Old World to some yet undiscovered continent, and wait for the slow action of such causes to replace, by a new creation, the Eden he has wasted.
Crushing Force of Torrents.
I must here notice a mechanical effect of the rapid flow of the torrent, which is of much importance in relation to the desolating action it exercises by covering large tracts of cultivated ground with infertile material. The torrent, as we have seen, shoots or rolls forwards, with great velocity, masses and fragments of rock, and sometimes rounded pebbles from more ancient formations. Every inch of this violent movement is accompanied with crushing concussion, or, at least, with great abrasion of the mineral material, and, as you follow it along the course of the waters which transport it, you find the stones gradually rounding off in form, and diminishing in size, until they pass successively into gravel, and, in the beds of the rivers to which the torrents convey it, sand, and lastly impalpable slime.
There are few operations of nature where the effect seems more disproportioned to the cause than in the crushing and comminution of rock in the channel of swift waters. Igneous rocks are generally so hard as to be wrought with great difficulty, and they bear the weight of enormous superstructures without yielding to the pressure; but to the torrent they are as wheat to the millstone. The streams which pour down the southern scarp of the Mediterranean Alps along the Riviera di Ponente, near Genoa, have short courses, and a brisk walk of a couple of hours or even less takes you from the sea-beach to the headspring of many of them. In their heaviest floods, they bring rounded masses of serpentine quite down to the sea, but at ordinary high water their lower course is charged only with finely divided particles of that rock. Hence, while, near their sources, their channels are filled with pebbles and angular fragments, intermixed with a little gravel, the proportions are reversed near their months, and, just above the points where their outlets are partially choked by the rolling shingle of the beach, their beds are composed of sand and gravel to the almost total exclusion of pebbles.
Guglielmini argued that the gravel and sand of the beds of running streams were derived from the trituration of rocks by the action of the currents, and inferred that this action was generally sufficient to reduce hard rock to sand in its passage from the source to the outlet of rivers. Frisi controverted this opinion, and maintained that river-sand was of more ancient origin, and he inferred from experiments in artificially grinding stones that the concussion, friction, and attrition of rock in the channel of running waters were inadequate to its comminution, though he admitted that these same causes might reduce silicious sand to a fine powder capable of transportation to the sea by the currents. [Footnote: Frisi, Del modo di regolare i Fiumi e i Torrenti, pp. 4-19. See in Lombardini, Sulle Inondazioni in Francia, p. 87, notices of the action of currents transporting only fine material in wearing down hard rock. In the sluices for gold-washing in California having a grade of 1 to 14 1/2, and paved with the hardest stones, the wear of the bottom is at the rate of two inches in three months.—Raymond, Mineral Statistics, 1870, p. 480.] Frisi's experiments were tried upon rounded and polished river-pebbles, and prove nothing with regard to the action of torrents upon the irregular, more or less weathered, and often cracked and shattered rocks which lie loose in the ground at the head of mountain valleys. The fury of the waters and of the wind which accompanies them in the floods of the French Alpine torrents is such, that large blocks of stone are hurled out of the bed of the stream to the height of twelve or thirteen feet. [Footnote: Surrell, Etude sur les Torrents, pp. 81-86.] The impulse of masses driven with such force overthrows the most solid masonry, and their concussion cannot fail to be attended with the crushing of the rocks themselves.
The greatest depth of the basin of the Ardeche is seventy-five miles, but most of its tributaries have a much shorter course. "These affluents," says Mardigny, "hurl into the bed of the Ardeche enormous blocks of rock, which this river, in its turn bears onwards, and grinds down, at high water, so that its current rolls only gravel at its confluence with the Rhone." [Footnote: At Rinkenberg, on the right bank of the Vorder Rhein, in the flood of 1868, a block of stone computed to weigh nearly 9,000 cwt. was carried bodily forwards, not rolled, by a torrent, a distance of three-quarter of a mile.—Coaz, die Hochwasser im 1868, p. 54.
Memoire sur les Inondations des Rivieres de l'Ardeche, p. 16. "The terrific roar, the thunder of the raging torrents proceeds principally from the stones which are rolled along in the bed of the stream. This movement is attended with such powerful attrition that, in the Southern Alps, the atmosphere of valleys where the limestone contains bitumen, has, at the time of floods, the marked bituminous smell produced by rubbing pieces of such limestone together."—Wessely, Die Oesterreichischen Alpenlander, i., p. 113.] Duponchel makes the following remarkable statement: "The river Herault rises in a granitic region, but soon reaches calcareous formations, which it traverses for more than sixty kilometres, rolling through deep and precipitous ravines, into which the torrents are constantly discharging enormous masses of pebbles belonging to the hardest rocks of the Jurassian period. These debris, continually renewed, compose, even below the exit of the gorge where the river enters into a regular channel cut in a tertiary deposit, broad beaches, prodigious accumulations of rolled pebbles, extending several kilometres down the stream, but they diminish in size and weight so rapidly that above the mouth of the river, which is at a distance of thirty or thirty-five kilometres from the gorge, every trace of calcareous matter has disappeared from the sands of the bottom, which are exclusively silicious." [Footnote: Avant-projet pour la creation d'un sol fertile, p. 20.]
Similar effects of the rapid flow of water and the concussion of stones against each other in river-beds may be observed in almost every Alpine gorge which serves as the channel of a swift stream. The tremendous cleft through which the well-known Via Mala is carried receives, every year, from its own crumbling walls and from the Hinter Rhein and its mild tributaries, enormous quantities of rock, in blocks and boulders. In fact, the masses hurled into it in a single flood like those of 1868 would probably fill it up, at its narrow points, to the level of the road 400 feet above its bottom, were not the stones crushed and carried off by the force of the current. Yet below the outlet at Thusis only small rounded boulders, pebbles, and gravel, not rock, are found in the bed of the river. The Swiss glaciers bring down thousands of cubic yards of hard rock every season. Where the glacier ends in a plain or wide valley, the rocks are accumulated in a terminal moraine, but in numerous instances the water which pours from the ice-river has forces enough to carry down to larger streams the masses delivered by the glacier, and there they, with other stones washed out from the earth by the current, are ground down, so that few of the affluents of the Swiss lakes deliver into them anything but fine sand and slime. Great rivers carry no boulders to the sea, and, in fact, receive none from their tributaries. Lombardini found, twenty years ago, that the mineral matter brought down to the Po by its tributaries was, in general, comminuted to about the same degree of fineness as the sands of its bed at their points of discharge. In the case of the Trebbia, which rises high in the Apennines and empties into the Po at Piacenza, it was otherwise, that river rolling pebbles and coarse gravel into the channel of the principal stream. The banks of the other affluents—excepting some of those which discharge their waters into the great lakes—then either retained their woods, or had been so long clear of them that the torrents had removed most of the disintegrated and loose rock in their upper basins. The valley of the Trebbia had been recently cleared, and all the forces which tend to the degradation and transportation of rock were in full activity. [Footnote: Since the date of Lombardini's observations, many Alpine valleys have been stripped of their woods. It would be interesting to know whether any sensible change has been produced in the character or quantity of the matter transported by the rivers to the Po.—Notice sur les Rivieres de la Lombardie, Annales des Ponts et Chaussees, 1847, 1er semestre, p. 131.]
Transporting Power of Water.
But the geographical effects of the action of torrents are not confined to erosion of earth and comminution of rock; for they and the rivers to which they contribute transport the debris of the mountains to lower levels and spread them out over the dry land and the bed of the sea, thus forming alluvial deposits, sometimes of a beneficial, sometimes of an injurious, character, and of vast extent. [Footnote: Lorentz, in an official report quoted by Marchand, says: "The felling of the woods produces torrents which cover the cultivated soil with pebbles and fragments of rock, and they do not confine their ravages to the vicinity of the mountains, but extend them into the fertile fields of Provence and other departments, to the distance of forty or fifty leagues."—Entwaldung der Gebirge, p. 17.]
A mountain rivulet swollen by rain or melted snow, when it escapes from its usual channel and floods the adjacent fields, naturally deposits pebbles and gravel upon them; but even at low water, if its course is long enough for its grinding action to have full scope, it transports the solid material with which it is charged to some larger stream, and there lets it fall in a state of minute division, and at last the spoil of the mountain is used to raise the level of the plains or carried down to the sea.
An instance that fell under my own observation, in 1857, will serve to show something of the eroding and transporting power of streams which, in these respects, fall incalculably below the torrents of the Alps. In a flood of the Ottaquechee, a small river which flows through Woodstock, Vermont, a mill-dam on that stream burst, and the sediment with which the pond was filled, estimated after careful measurement at 13,000 cubic yards, was carried down by the current. Between this dam and the slackwater of another, four miles below, the bed of the stream, which is composed of pebbles interspersed in a few places with larger stones, is about sixty-five feet wide, though, at low water, the breadth of the current is considerably less. The sand and fine gravel were smoothly and evenly distributed over the bed to a width of fifty-five or sixty feet, and, for a distance of about two miles, except at two or three intervening rapids, filled up all the interstices between the stones, covering them to the depth of nine or ten inches, so as to present a regularly formed concave channel, lined with sand, and reducing the depth of water, in some places, from five or six feet to fifteen or eighteen inches. Observing this deposit after the river had subsided and become so clear that the bottom could be seen, I supposed that the next flood would produce an extraordinary erosion of the banks and some permanent changes in the channel of the stream, in consequence of the elevation of the bed and the filling up of the spaces between the stones through which formerly much water had flowed; but no such result followed. The spring freshet of the next year entirely washed out the sand its predecessor had left, deposited some of it in ponds and still-water reaches below, carried the residue beyond the reach of observation, and left the bed of the river almost precisely in its former condition, though, of course, with the displacement of the pebbles which every flood produces in the channels of such streams. The pond, though often previously discharged by the breakage of the dam, had then been undisturbed for about twenty-five years, and its contents consisted almost entirely of sand, the rapidity of the current in floods being such that it would let fall little lighter sediment, even above an obstruction like a dam. The quantity I have mentioned evidently bears a very inconsiderable proportion to the total erosion of the stream during that period, because the wash of the banks consists chiefly of fine earth rather than of sand, and after the pond was once filled, or nearly so, even this material could no longer be deposited in it. The fact of the complete removal of the deposit I have described between the two dams in a single freshet, shows that, in spite of considerable obstruction from roughness of bed, large quantities of sand may be taken up and carried off by streams of no great rapidity of inclination; for the whole descent of the bed of the river between the two dams—a distance of four miles—is but sixty feet, or fifteen feet to the mile. [Footnote: In a sheet-iron siphon, 1,000 feet long, with a diameter of four inches, having the entrance 18 feet, the orifice of discharge 40 feet below the summit of the curve, employed in draining a mine In California, the force of the current was such as to carry through the tube great quantities of sand and coarse gravel, some of the grains of which were as large as an English walnut. —Raymond, Mining Statistics, 1870, p. 602.] The facts which I have adduced may aid us in forming an idea of the origin and mode of transportation of the prodigious deposits at the mouth of great rivers like the Mississippi, the Nile, the Ganges, and the Hoang-Ho, the delta of which last river, composed entirely of river sediment, has a superficial extent of not less than 96,500 square miles. But we shall obtain a clearer conception of the character of this important geographical process by measuring, more in detail, the mass of earth and rock which a well—known river and its tributaries have washed from the mountains and transported to the plains or the sea, within the historic period.
The Po and its Deposits.
The current of the River Po, for a considerable distance after its volume of water is otherwise sufficient for continuous navigation, is too rapid for that purpose until near Cremona, where its velocity becomes too much reduced to transport great quantities of mineral matter, except in a state of minute division. Its southern affluents bring down from the Apennines a large quantity of fine earth from various geological formations, while its Alpine tributaries west of the Ticino are charged chiefly with rock ground down to sand or gravel. The bed of the river has been somewhat elevated by the deposits in its channel, though not by any means above the level of the adjacent plains as has been so often represented. The dikes, which confine the current at high water, at the same time augment its velocity and compel it to carry most of its sediment to the Adriatic. It has, therefore, raised neither its own channel nor its alluvial shores, as it would have done if it had remained unconfined. But, as the surface of the water in floods is above the general level of the plains through which it flows, the Po can, at that period, receive no contributions of earth from the washing of the fields of Lombardy, and there is no doubt that a large proportion of the sediment it now deposits at its mouth descended from the Alps in the form of rock, though reduced by the grinding action of the waters, in its passage seaward, to the condition of fine sand, and often of silt.
We know little of the history of the Po, or of the geography of the coast near the point where it enters the Adriatic, at any period more than twenty centuries before our own. Still less can we say how much of the plains of Lombardy had been formed by its action, combined with other causes, before man accelerated its levelling operations by felling the first woods on the mountains whence its waters are derived. But we know that since the Roman conquest of Northern Italy, its deposits have amounted to a quantity which, if recemented into rock, recombined into gravel, common earth, and vegetable mould, and restored to the situations where eruption or upheaval originally placed or vegetation deposited it, would fill up hundreds of deep ravines in the Alps and Apennines, change the plan and profile of their chains, and give their southern and northern faces respectively a geographical aspect very different from that they now present. Ravenna, forty miles south of the principal mouth of the Po, was built like Venice, in a lagoon, and the Adriatic still washed its walls at the commencement of the Christian era. The mud of the Po has filled up the lagoon, and Ravenna is now four miles from the sea. The town of Adria, which lies between the Po and the Adige, at the distance of some four or five miles from each, was once a harbor famous enough to have given its name to the Adriatic Sea, and it was still accessible to large vessels, if not by the open sea at least by lagoons, in the time of Augustus. The combined action of the two rivers has so advanced the coast-line that Adria is now more than fourteen miles inland, and, in other places, the deposits made within the same period by these and other neighboring streams have a width of twenty miles.
What proportion of the earth with which they are charged these rivers have borne out into deep water, during the last two thousand years, we do not know, but as they still transport enormous quantities, as the North Adriatic appears to have shoaled rapidly, and as long islands, composed in great part of fluviatile deposits, have formed opposite their mouths, it must evidently have been very great. The floods of the Po occur but once, or sometimes twice, in a year. [Footnote: In the earlier medieval centuries, when the declivities of the mountains still retained a much larger proportion of their woods, the moderate annual floods of the Po were occasioned by the melting of the snows on the lower slopes, and, according to a passage of Tasso quoted by Castellani (Dell' Influenza delle Selve, i., p. 58, note), they took place in May. The usually more violent inundations of later ages are due to rains, the waters of which are no longer retained by a forest-soil, but conveyed at once to the rivers—and they occur almost uniformly in the autumn or late summer. Castellani, on the page just quoted, says that even so late as about 1780, the Po required a heavy rain of a week to overflow its banks, but that forty years later it was sometimes raised to full flood in a single day. Pliny says: "The Po, which is inferior to no river in swiftness of current, is in flood about the rising of the dog-star, the snow then melting, and though so rapid in flow, it washes nothing from the soil, but leaves it increased in fertility."—Natural History, Book iii, 20.
The first terrible inundation of the Po in 1872 took place in May, and appears to have been occasioned by heavy rains on the southern flank of the Alps, and to have received little accession from snow. The snow on the higher Alps does not usually thaw so as to occasion floods before August, and often considerably later. The more destructive flood of October, 1872, was caused both by thaws in the high mountains and by an extraordinary fall of rain. See River Embankments; post. Pliny's remark as to enrichment of the soil by the floods appear to be verified in the case of that of October, 1872, for it is found that the water has left very extensively a thick deposit of slime on the fields. See a list of the historically known great inundations of the Po by the engineer Zuccholli in Torelli, Progetto di Legge per la Vendita di Beni incolti. Roma, 1873.]
At other times, its waters are comparatively limpid and seem to hold no great amount of mud or fine sand in mechanical suspension; but at high water it contains a large proportion of solid matter, and, according to Lombardini, it annually transports to the shores of the Adriatic not less than 42,760,000 cubic metres, or very nearly 55,000,000 cubic yards, which carries the coast-line out into the sea at the rate of more than 200 feet in a year. [Footnote: This change of coast-line cannot be ascribed to upheaval, for a comparison of the level of old buildings—as, for instance, the church of San Vitale and the tomb of Theodoric at Ravenna—with that of the sea, tends to prove a depression rather than an elevation of their foundations. A computation by a different method makes the deposits at the mouth of the Po 2,123,000 metres less; but as both of them omit the gravel and silt carried down at ordinary and low water, we are safe in assuming the larger quantity.] The depth of the annual deposit is stated at eighteen centimetres, or rather more than seven inches, and it would cover an area of not much less than ninety square miles with a layer of that thickness. The Adige, also, brings every year to the Adriatic many million cubic yards of Alpine detritus, and the contributions of the Brenta from the same source are far from inconsiderable. The Adriatic, however, receives but a small proportion of the soil and rock washed away from the Italian slope of the Alps and the northern declivity of the Apennines by torrents. Nearly the whole of the debris thus removed from the southern face of the Alps between Monte Rosa and the sources of the Adda—a length of watershed [Footnote: Sir John F. W. Herschel (Physical Geography, 137, and elsewhere) spells this word water-sched, because he considers it a translation, or rather an adoption, of the German "Wasser-scheide, separation of the waters, not water-SHED the slope DOWN WHICH the waters run." As a point of historical etymology, it is probable that the word in question was suggested to those who first used it by the German Wasserscheide; but the spelling WATER-SCHED, proposed by Herschel, is objectionable, both because SCH is a combination of letters wholly unknown to modern English orthography, and properly representing no sound recognized in English orthoepy, and for the still better reason that WATER-SHED, in the sense of DIVISION-OF-THE-WATERS, has a legitimate English etymology. The Anglo-Saxon sceadan meant both to separate or divide, and to shade or shelter. It is the root of the English verbs TO SHED and TO SHADE, and in the former meaning is the A. S. equivalent of the German verb scheiden. SHED in Old English had the meaning to SEPARATE or DISTINGUISH. It is so used in the Owl and the Nightingale, v. 107. Palsgrave (Lesclarcissement, etc., p. 717) defines I SHEDE, I departe thinges asonder; and the word still means TO DIVIDE in several English local dialects. Hence, watershed, the division or separation of the waters, is good English both in etymology and in spelling.] not less than one hundred and fifty miles—is arrested by the still waters of the Lakes Maggiore and Como, and some smaller lacustrine reservoirs, and never reaches the sea. The Po is not continuously embanked except for the lower half of its course. Above Cremona, therefore, it spreads and deposits sediment over a wide surface, and the water withdrawn from it for irrigation at lower points, as well as its inundations in the occasional ruptures of its banks, carry over the adjacent soil a large amount of slime. [Footnote: The quantity of sediment deposited by the Po on the plains which border it, before the construction of the continuous dikes and in the floods which occasionally burst through them, is vast, and the consequent elevation of those plains is very considerable. I do not know that this latter point has been made a subject of special investigation, but vineyards, with the vines still attached to the elms which supported them, have been found two or three yards below the present surface at various points on the plains of Lombardy.]
If to the estimated annual deposits of the Po at its mouth, we add the earth and sand transported to the sea by the Adige, the Brenta, and other less important streams, the prodigious mass of detritus swept into Lago Maggioro by the Tosa, the Maggia, and the Ticino, into the lake of Como by the Maira and the Adda, into the lakes of Garda, Lugano, Iseo, and Idro, by their affluents, [Footnote: The Po receives about four-tenths of its waters from these lakes. See Lombardini, Dei cangiamenti nella condizione del Po, p. 29. All the sediment carried into the lakes by their tributaries is deposited in them, and the water which flows out of them is perfectly limpid. From their proximity to the Alps and the number of torrents which empty into them, they no doubt receive vastly more transported matter than is contributed to the Po by the six-tenths of its waters received from other sources.] and the yet vaster heaps of pebbles, gravel, and earth permanently deposited by the torrents near their points of eruption from mountain gorges, or spread over the wide plains at lower levels, we may safely assume that we have an aggregate of not less than ten times the quantity carried to the Adriatic by the Po, or 550,000,000 cubic yards of solid matter, abstracted every year from the Italian Alps and the Apennines, and removed out of their domain by the force of running water. [Footnote: Mengotti estimated the mass of solid matter annually "united to the waters of the Po" at 822,000,000 cubic metres, or nearly twenty times as much as, according to Lombardini, that river delivers into the Adriatic. Castellani supposes the computation of Mengotti to fall much below the truth, and there can be no doubt that a vastly larger quantity of earth and gravel is washed down from the Alps and the Apennines than is carried to the sea.—Castellani, Dell Immediata Influenza delle Salce sul corso delle Acqua, i., pp. 42,43.
I have contented myself with assuming less than one-half of Mengotti's estimate.] The present rate of deposit at the mouth of the Po has continued since the year 1600, the previous advance of the coast, after the year 1200, having been only one-third as rapid. The great increase of erosion and transport is ascribed by Lombardini chiefly to the destruction of the forests in the basin of that river and the valleys of its tributaries, since the beginning of the seventeenth century. [Footnote: Baumgarten, An. des Ponts et Chaussees, 1847, 1er semestre, p. 175.] We have no data to show the rate of deposit in any given century before the year 1200, and it doubtless varied according to the progress of population and the consequent extension of clearing and cultivation. The transporting power of torrents is greatest soon after their formation, because at that time their points of delivery are lower, and, of course, their general slope and velocity more rapid, than after years of erosion above, and deposit below, have depressed the beds of their mountain valleys, and elevated the channels of their lower course. Their eroding action also is most powerful at the same period, both because their mechanical force is then greatest, and because the loose earth and stones of freshly cleared forest-ground are most easily removed. Many of the Alpine valleys west of the Ticino—that of the Dora Baltea, for instance—were nearly stripped of their forests in the days of the Roman Empire, others in the Middle Ages, and, of course, there must have been, at different periods before the year 1200, epochs when the erosion and transportation of solid matter from the Alps and the Apennines were at least as great as since the year 1600.
Upon the whole, we shall not greatly err if we assume that, for a period of not less than two thousand years, the walls of the basin of the Po—the Italian slope of the Alps, and the northern and north-eastern declivities of the Apennines—have annually sent down into the lakes, the plains, and the Adriatic, not less than 375,000,000 cubic yards of earth and disintegrated rock. We have, then, an aggregate of 750,000,000,000 cubic yards of such material, which, allowing to the mountain surface in question an area of 50,000,000,000 square yards, would cover the whole to the depth of fifteen yards. [Footnote: The total superficies of the basin of the Po, down to Ponte Lagoscuro [Ferrara]—a point where it has received all its affluents—is 6,938,200 hectares, that is, 4,105,600 in mountain lands, 2,832,600 in plain lands.—Dumont, Travaux Publics, etc., p. 272. These latter two quantities are equal respectively to 10,145,348, and 6,999,638 acres, or 15,852 and 10,937 square miles.] There are very large portions of this area, where, as we know from ancient remains—roads, bridges, and the like—from other direct testimony, and from geological considerations, very little degradation has taken place within twenty centuries, and hence the quantity to be assigned to localities where the destructive causes have been most active is increased in proportion.
If this vast mass of pulverized rock and earth were restored to the localities from which it was derived, it certainly would not obliterate valleys and gorges hollowed out by great geological causes, but it would reduce the length and diminish the depth of ravines of later formation, modify the inclination of their walls, reclothe with earth many bare mountain ridges, essentially change the line of junction between plain and mountain, and carry back a long reach of the Adriatic coast many miles to the west. [Footnote: I do not use these quantities as factors the value of which is precisely ascertained; nor, for the purposes of the present argument, is quantitative exactness important. I employ numerical statements simply as a means of aiding the imagination to form a general and certainly not extravagant idea of the extent of geographical revolutions which man has done much to accelerate, if not, strictly speaking, to produce.
There is an old proverb, Dolus latet in generalibus, and Arthur Young in not the only public economist who has warned his readers against the deceitfulness of round numbers. I think, on the contrary, that vastly more error has been produced by the affectation of precision in cases where precision is impossible.
In all the great operations of terrestrial nature, the elements are so numerous and so difficult of exact appreciation, that, until the means of scientific observation and measurement are much more perfected than they now are, we must content ourselves with general approximations. I say TERRESTRIAL nature, because in cosmical movements we have fewer elements to deal with, and may therefore arrive at much more rigorous proportional accuracy in determination of time and place than we can in fixing and predicting the quantities and the epochs of variable natural phenomena on the earth's surface.
Travellers are often misled by local habits in the use of what may be called representative numbers, where a definite is put for an indefinite quantity. A Greek, who wished to express the notion of a great but undetermined number, "myriad, or ten thousand;" a Roman, "six hundred;" an Oriental, "forty," or, at present, very commonly, "fifteen thousand." Many a tourist has gravely repeated, as an ascertained fact; the vague statement of the Arabs and the monks of Mount Sinai, that the ascent from the convent of St. Catherine to the summit of Gebel Moosa counts "fifteen thousand" steps, though the difference of level is two thousand feet; and the "Forty" Thieves, the "forty" martyr-monks of the convent of El Arbain—not to speak of a similar use of this numeral in more important cases—have often been understood as expressions of a known number, when in fact they mean simply MANY. The number "fifteen thousand" has found its way to Rome, and De Quincey seriously informs us, on the authority of a lady who had been at much pains to ascertain the EXACT truth, that, including closets large enough for a bed, the Vatican contains fifteen thousand rooms. Any one who has observed the vast dimensions of most of the apartments of that structure will admit that we make a very small allowance of space when we assign a square rod, sixteen and a half feet square, to each room upon the average. On an acre, there might be one hundred and sixty such rooms, including partition walls; and, to contain fifteen thousand of them, a building must cover more than nine acres, and be ten stories high, or possess other equivalent dimensions, which, as every traveller knows, many times exceeds the truth.
The value of a high standard of accuracy in scientific observation can hardly be overrated; but habits of rigorous exactness will never be formed by an investigator who allows himself to trust implicitly to the numerical precision or the results of a few experiments. The wonderful accuracy of geodetic measurements in modern times is, in general, attained by taking the mean of a great number of observations at every station, and this final precision is but the mutual balance and compensation of numerous errors.
The pretended exactness of statistical tables is too often little better than an imposture; and those founded not on direct estimation by competent observers, but on the report of persons who have no particular interest in knowing the truth, but often have a motive for distorting it, are commonly to be regarded as but vague guesses at the actual fact.]
It is, indeed, not to be supposed that all the degradation of the mountains is due to the destruction of the forests—that the flanks of every Alpine valley in Central Europe below the snow-line were once covered with earth and green with woods, but there are not many particular cases in which we can, with certainty, or even with strong probability, affirm the contrary.
Mountain Slides.
Terrible as are the ravages of the torrent and the river-flood, the destruction of the woods exposes human life and industry to calamities even more appalling than those which I have yet described. The slide in the Notch of the White Mountains, by which the Willey family lost their lives, is an instance of the sort I refer to, though I am not able to say that in this particular case the slip of the earth and rock was produced by the denudation of the surface. It may have been occasioned by this cause, or by the construction of the road through the Notch, the excavations for which, perhaps, cut through the natural buttresses that supported the sloping strata above.
Not to speak of the fall of earth when the roots which held it together, and the bed of leaves and mould which sheltered it both from disintegrating frost and from sudden drenching and dissolution by heavy showers, are gone, it is easy to see that, in a climate with severe winters, the removal of the forest, and, consequently, of the soil it had contributed to form, might cause the displacement and descent of great masses of rock. The woods, the vegetable mould, and the soil beneath, protect the rocks they cover from the direct action of heat and cold, and from the expansion and contraction which accompany them. Most rocks, while covered with earth, contain a considerable quantity of water. [Footnote: Rock is permeable by water to a greater extent than is generally supposed. Freshly quarried marble, and even granite, as well as most other stones, are sensibly heavier, as well as softer and more easily wrought, than after they are dried and hardened by air-seasoning. Many sandstones are porous enough to serve as filters for liquids, and much of that of Upper Egypt and Nubia hisses audibly when thrown into water, from the escape of the air forced out of it by hydrostatic pressure and the capillary attraction of the pores for water. Even the denser silicious stones are penetrable by fluids and the coloring matter they contain, to such an extent that agates and other forms of silex may be artificially stained through their substance. The colors of the stones cut at Oberstein are generally produced, or at least heightened, by art. This art was known to and practised by the ancient lapidaries, and it has been revived in recent times.]
A fragment of rock pervaded with moisture cracks and splits, if thrown into a furnace, and sometimes with a loud detonation; and it is a familiar observation that the fire, in burning over newly cleared lands, breaks up and sometimes almost pulverizes the stones. This effect is due partly to the unequal expansion of the stone, partly to the action of heat on the water it contains in its pores. The sun, suddenly let in upon rock which had been covered with moist earth for centuries, produces more or less disintegration in the same way, and the stone is also exposed to chemical influences from which it was sheltered before. But in the climate of the United States as well as of the Alps, frost is a still more powerful agent in breaking up mountain masses. The soil that protects the lime and sandstone, the slate and the granite from the influence of the sun, also prevents the water which filters into their crevices and between their strata from freezing in the hardest winters, and the moisture descends, in a liquid form, until it escapes in springs, or passes off by deep subterranean channels. But when the ridges are laid bare, the water of the autumnal rains fills the minutest pores and veins and fissures and lines of separation of the rocks, then suddenly freezes, and bursts asunder huge, and apparently solid blocks of adamantine stone. [Footnote: Palissy had observed the action of frost in disintegrating rock, and he thus describes it, in his essay on the formation of ice: "I know that the stones of the mountains of Ardennes be harder than marble. Nevertheless, the people of that country do not quarry the said stones in winter, for that they be subject to frost; and many times the rocks have been seen to fall without being cut, by means whereof many people have been killed, when the said rocks were thawing." Palissy was ignorant of the expansion of water in freezing—in fact, he supposed that the mechanical force exerted by freezing-water was due to compression, not dilatation—and therefore he ascribes to thawing alone effects resulting not less from congelation.
Various forces combine to produce the stone avalanches of the higher Alps, the fall of which is one of the greatest dangers incurred by the adventurous explorers of those regions—the direct action of the sun upon the stone, the expansion of freezing-water, and the loosening of masses of rock by the thawing of the ice which supported them or held them together.]
Where the strata are inclined at a considerable angle, the freezing of a thin film of water over a large interstratal area might occasion a slide that should cover miles with its ruins; and similar results might be produced by the simple hydrostatic pressure of a column of water, admitted, by the removal of the covering of earth, to flow into a crevice faster than it could escape through orifices below. Earth or rather mountain slides, compared to which the catastrophe that buried the Willey family in New Hampshire was but a pinch of dust, have often occurred in the Swiss, Italian, and French Alps. The land-slip, which overwhelmed, and covered to the depth of seventy feet, the town of Plurs in the valley of the Maira, on the night of the 4th of September, 1618, sparing not a soul of a population of 2,430 inhabitants, is one of the most memorable of these catastrophes, and the fall of the Rossberg or Rufiberg, which destroyed the little town of Goldan in Switzerland, and 450 of its people, on the 2d of September, 1806, is almost equally celebrated. In 1771, according to Wessely, the mountain-peak Piz, near Alleghe in the province of Belluno, slipped into the bed of the Cordevole, a tributary of the Piave, destroying in its fall three hamlets and sixty lives. The rubbish filled the valley for a distance of nearly two miles, and, by damming up the waters of the Cordevole, formed a lake about three miles long, and a hundred and fifty feet deep, which still subsists, though reduced to half its original length by the wearing down of its outlet. [Footnote: Wessely, Die Oesterreichischen Alpenlander und ihre Forste, pp. 125, 126. Wessely records several other more or less similar occurrences in the Austrian Alps. Some of them, certainly, are not to be ascribed to the removal of the woods, but in most cases they are clearly traceable to that cause. See Revue des Eaux et Forets for 1860, pp. 182, 205.]
The important provincial town of Veleia, near Piacenza, where many interesting antiquities have been discovered within a few years, was buried by a vast land-slip, probably about the time of Probus, but no historical record of the event has survived to us.
On the 14th of February, 1855, the hill of Belmonte, a little below the parish of San Stefano, in Tuscany, slid into the valley of the Tiber, which consequently flooded the village to the depth of fifty feet, and was finally drained off by a tunnel. The mass of debris is stated to have been about 3,500 feet long, 1,000 wide, and not less than 600 high. [Footnote: Bianchi, Appendix to the Italian translation of Mrs. Somerville'S Physical Geography, p. xxxvi.]
Occurrences of this sort have been so numerous in the Alps and Apennines, that almost every Italian mountain commune has its tradition, its record, or its still visible traces of a great land-slip within its own limits. The old chroniclers contain frequent notices of such calamities, and Giovanni Villani even records the destruction of fifty houses and the loss of many lives by a slide of what seems to have been a spur of the hill of San Giorgio in the city of Florence, in the year 1284. [Footnote: Cronica di Giovani Villani, lib. vii., cap. 97. For descriptions of other slides in Italy, see same author, lib. xi, cap. 26; Fanfani, Antologia Italiana, parte ii., p. 95; Giuliani, Linguaggio vivente della Toscana, 1865, lettera 63.]
Such displacements of earth and rocky strata rise to the magnitude of geological convulsions, but they are of so rare occurrence in countries still covered by the primitive forest, so common where the mountains have been stripped of their native covering, and, in many cases, so easily explicable by the drenching of incohesive earth from rain, or the free admission of water between the strata of rocks—both of which a coating of vegetation would have prevented—that we are justified in ascribing them for the most part to the same cause as that to which the destructive effects of mountain torrents are chiefly due—the felling of the woods. [Footnote: There is good reason for thinking that many of the earth and rock slides in the Alps occurred at an earlier period than the origin of the forest vegetation which, in later ages, covered the flanks of those mountains. See Bericht uber die Untersuchung der Schweizerischen Hochgebirgswaldungen, 1862, p. 61.
Where more recent slides have been again clothed with woods, the trees, shrubs, and smaller plants which spontaneously grow upon them are usually of different species from those observed upon soil displaced at remote periods. This difference is so marked that the site of a slide can often be recognized at a great distance by the general color of the foliage of its vegetation.]
In nearly every case of this sort the circumstances of which are known—except the rare instances attributable to earthquakes—the immediate cause of the slip has been the imbibition of water in large quantities by bare earth, or its introduction between or beneath solid strata. If water insinuates itself between the strata, it creates a sliding surface, or it may, by its expansion in freezing, separate beds of rock, which had been nearly continuous before, widely enough to allow the gravitation of the superincumbent mass to overcome the resistance afforded by inequalities of face and by friction; if it finds its way beneath hard earth or rock reposing on clay or other bedding of similar properties, it converts the supporting layer into a semi-fluid mud, which opposes no obstacle to the sliding of the strata above.
The upper part of the mountain which buried Goldau was composed of a hard but brittle conglomerate, called nagelflue, resting on unctuous clay, and inclining rapidly towards the village. Much earth remained upon the rock, in irregular masses, but the woods had been felled, and the water had free access to the surface, and to the crevices which sun and frost had already produced in the rock, and, of course, to the slimy stratum beneath. The whole summer of 1806 had been very wet, and an almost incessant deluge of rain had fallen the day preceding the catastrophe, as well as on that of its occurrence. All conditions, then, were favorable to the sliding of the rock, and, in obedience to the laws of gravitation, it precipitated itself into the valley as soon as its adhesion to the earth beneath it was destroyed by the conversion of the latter into a viscous paste. The mass that fell measured between two and a half and three miles in length by one thousand feet in width, and its average thickness is thought to have been about a hundred feet. The highest portion of the mountain was more than three thousand feet above the village, and the momentum acquired by the rocks and earth in their descent carried huge blocks of stone far up the opposite slope of the Rigi.
The Piz, which fell into the Cordevole, rested on a steeply inclined stratum of limestone, with a thin layer of calcareous marl intervening, which, by long exposure to frost and the infiltration of water, had lost its original consistence, and become a loose and slippery mass instead of a cohesive and tenacious bed.
Protection against Avalanches.
In Switzerland and other snowy and mountainous countries, forests render a most important service by preventing the formation and fall of destructive avalanches, and in many parts of the Alps exposed to this catastrophe, the woods are protected, though too often ineffectually, by law. No forest, indeed, could arrest a large avalanche once in full motion, but the mechanical resistance afforded by the trees prevents their formation, both by obstructing the wind, which gives to the dry snow of the Staub-Lawine, or dust-avalanche, its first impulse, and by checking the disposition of moist snow to gather itself into what is called the Rutsch-Lawine, or sliding avalanche. Marchand states that, the very first winter after the felling of the trees on the higher part of a declivity between Sannen and Gsteig where the snow had never been known to slide, an avalanche formed itself in the clearing, thundered down the mountain, and overthrew and carried with it a hitherto unviolated forest to the amount of nearly a million cubic feet of timber. [Footnote: Entwaldung der Gebirge, p. 41.] Elisee Reclus informs us in his remarkable work, La Terre, vol. i., p. 212, that a mountain, which rises to the south of the Pyrenaean village Araguanet in the upper valley of the Neste, having been partially stripped of its woods, a formidable avalanche rushed down from a plateau above in 1846, and swept off more than 15,000 pine-trees. The path once opened down the flanks of the mountain, the evil is almost beyond remedy. The snow sometimes carries off the earth from the face of the rock, or, if the soil is left, fresh slides every winter destroy the young plantations, and the restoration of the wood becomes impossible. The track widens with every new avalanche. Dwellings and their occupants are buried in the snow, or swept away by the rushing mass, or by the furious blasts it occasions through the displacement of the air; roads and bridges are destroyed; rivers blocked up, which swell till they overflow the valley above, and then, bursting their snowy barrier, flood the fields below with all the horrors of a winter inundation. [Footnote: The importance of the wood in preventing avalanches is well illustrated by the fact that, where the forest is wanting, the inhabitants of localities exposed to snow-slides often supply the place of the trees by driving stakes through the snow into the ground, and thus checking its propensity to slip. The woods themselves are sometimes thus protected against avalanches originating on slopes above them, and as a further security, small trees are cut down along the upper line of the forest, and laid against the trunks of larger trees, transversely to the path of the slide, to serve as a fence or dam to the motion of an incipient avalanche, which may by this means be arrested before it acquires a destructive velocity and force.
In the volume cited in the text, Reclus informs us that "the village and the great thermal establishment of Bareges in the Pyrenees were threatened yearly by avalanches which precipitated themselves from a height of 1,200 metres and at an angle of 35 degrees; so that the inhabitants had been obliged to leave large spaces between the different quarters of the town for the free passage of the descending masses. Attempts have been recently made to prevent those avalanches by means similar to those employed by the Swiss mountaineers. They cut terraces three or four yards in width across the mountain slopes and supported these terraces by a row of iron piles. Wattled fences, with here and there a wall of stone, shelter the young shoots of trees, which grow up by degrees under the protection of these defences. Until natural trees are ready to arrest the snows, these artificial supports take their place and do their duty very well. The only avalanche which swept down the slope in the year 1860, when these works were completed, did not amount to 350 cubic yards, while the masses which fell before this work was undertaken contained from 75,000 to 80,000 cubic yards."—La Terre, vol. i., p. 233.]
Minor Uses of the Forest.
Besides the important conservative influences of the forest and its value as the source of supply of a material indispensable to all the arts and industries of human life, it renders other services of a less obvious and less generally recognized character.
Woods often subserve a valuable purpose in preventing the fall of rocks, by mere mechanical resistance. Trees, as well as herbaceous vegetation, grow in the Alps upon declivities of surprising steepness of inclination, and the traveller sees both luxuriant grass and flourishing woods on slopes at which the soil, in the dry air of lower regions, would crumble and fall by the weight of its own particles. When loose rocks lie scattered on the face of these declivities, they are held in place by the trunks of the trees, and it is very common to observe a stone that weighs hundreds of pounds, perhaps even tons, resting against a tree which has stopped its progress just as it was beginning to slide down to a lower level. When a forest in such a position is cut, these blocks lose their support, and a single wet season is enough not only to bare the face of a considerable extent of rock, but to cover with earth and stone many acres of fertile soil below. [Footnote: See in Kohl, Alpenreisen, i., 120, an account of the ruin of fields and pastures, and even of the destruction of a broad belt of forest, by the fall of rocks in consequence of cutting a few large trees. Cattle are very often killed in Switzerland by rock-avalanches, and their owners secure themselves from loss by insurance against this risk as against damage by fire or hail.]
In alluvial plains and on the banks of rivers trees are extremely useful as a check to the swift flow of the water in inundations, and the spread of the mineral material it transports; but this will be more appropriately considered in the chapter on the Waters; and another most important use of the woods, that of confining the loose sands of dunes and plains, will be treated of in the chapter on the Sands.
Small Forest Plants, and Vitality of Seed.
Another function of the woods, to which I have barely alluded, deserves a fuller notice than can be bestowed upon it in a treatise the scope of which is purely economical. The forest is the native habitat of a large number of humbler plants, to the growth and perpetuation of which its shade, its humidity, and its vegetable mould appear to be indispensable necessities. [Footnote: "A hundred and fifty paces from my house is a hill of drift-sand, on which stood a few scattered pines (Pinus sylvestris). Sempervivum tectorum in abundance, Statice armeria, Ammone vernalis, Dianthus carthusianorum, with other sand-plants, were growing there. I planted the hill with a few birches, and all the plants I have mentioned completely disappeared, though there were many naked spots of sand between the trees. It should be added, however, that the hillock is more thickly wooded than before. . . . It seems then that Sempervivum tectorum, etc., will not bear the neighborhood of the birch, though growing well near the Pinus sylvestris. I have found the large red variety of Agaricus deliciosus only among the roots of the pine; the greenish-blue Agaricus deliciosus among alder roots, but not near any other tree. Birds have their partialities among trees and shrubs. The Silvioe prefer the Pinus Larix to other trees. In my garden this Pinus is never without them, but I never saw a bird perch on Thuja occidentalis or Juniperus sabina, although the thick foliage of these latter trees affords birds a better shelter than the loose leafage of other trees. Not even a wren ever finds its way to one of them. Perhaps the scent of the Thuja and the Juniperus is offensive to them. I have spoiled one of my meadows by cutting away the bushes. It formerly bore grass four feet high, because many umbelliferous plants, such as Heracleum spondylium, Spiraea ulmaria, Laserpitium latifolia, etc., grew in it. Under the shelter of the bushes these plants ripened and bore seed, but they gradually disappeared as the shrubs wore extirpated, and the grass now does not grow to the height of more than two feet, because it is no longer obliged to keep pace with the umbellifera which flourished among it." See a paper by J.G. Buttner, of Kurland, in Berghaus s Geographicsches Jahrbuch, 1852, No. 4, pp. 14, 15.
These facts are interesting as illustrating the multitude of often obscure conditions upon which the life or vigorous growth of smaller organisms depends. Particular species of truffles and of mushrooms are found associated with particular trees, without being, as is popularly supposed, parasites deriving their nutriment from the dying or dead roots of those trees. The success of Rousseau's experiments seem decisive on this point, for he obtains larger crops of truffles from ground covered with young seedling oaks than from that filled with roots of old trees. See an article on Mont Ventoux, by Charles Martins, in the Revue des Deux Mondes, Avril, 1863, p. 626.
It ought to be much more generally known than it is, that most if not all mushrooms, even of the species reputed poisonous, may be rendered harmless and healthful as food by soaking them for two hours in acidulated or salt water. The water requires two or three spoonfuls of vinegar or two spoonful of gray salt to the quart, and a quart of water is enough for a pound of sliced mushrooms. After thus soaking, they are well washed in fresh water, thrown into cold water, which is raised to the boiling-point, and, after remaining half an hour, taken out and again washed, Gerard, to prove that "crumpets is wholesome," ate one hundred and seventy-five pounds of the most poisonous mushrooms thus prepared, in a single month, fed his family ad libitum with the same, and finally administered them, in heroic doses, to the members of a committee appointed by the Council of Health of the city of Paris. See Figuier, L'Annee Scientifique, 1862, pp. 353, 384. It should be observed that the venomous principle of poisonous mushrooms is not decomposed and rendered innocent by the process described in the note. It is merely extracted by the acidulated or saline water employed for soaking the plants, and care should be taken that this water be thrown away out of the reach of mischief.
It has long been known that the Russian peasantry eat, with impunity, mushrooms of species everywhere else regarded as very poisonous. Is it not probable that the secret of rendering them harmless—which was known to Pliny, though since forgotten in Italy—is possessed by the rustic Muscovites ]
We cannot positively say that the felling of the woods in a given vegetable province would involve the final extinction of the smaller plants which are found only within their precincts. Some of these, though not naturally propagating themselves in the open ground, may perhaps germinate and grow under artificial stimulation and protection, and finally become hardy enough to maintain an independent existence in very different circumstances from those which at present seem essential to their life.
Besides this, although the accounts of the growth of seeds, which have lain for ages in the ashy dryness of Egyptian catacombs, are to be received with great caution, or, more probably, to be rejected altogether, yet their vitality seems almost imperishable while they remain in the situations in which nature deposits them. When a forest old enough to have witnessed the mysteries of the Druids is felled, trees of other species spring up in its place; and when they, in their turn, fall before the axe, sometimes even as soon as they have spread their protecting shade over the surface, the germs which their predecessors had shed years, perhaps centuries before, sprout up, and in due time, if not choked by other trees belonging to a later stage in the order of natural succession, restore again the original wood. In these cases, the seeds of the new crop may have been brought by the wind, by birds, by quadrupeds, or by other causes; but, in many instances, this explanation is not probable.
When newly cleared ground is burnt over in the United States, the ashes are hardly cold before they are covered with a crop of fire-weed, Senecio hieracifolius, a tall, herbaceous plant, very seldom seen growing under other circumstances, and often not to be found for a distance of many miles from the clearing. Its seeds, whether the fruit of an ancient vegetation or newly sown by winds or birds, require either a quickening by a heat which raises to a certain high point the temperature of the stratum where they lie buried, or a special pabulum furnished only by the combustion of the vegetable remains that cover the ground in the woods.
Earth brought up from wells or other excavations soon produces a harvest of plants often very unlike those of the local flora, and Hayden informs us that on our great Western desert plains, "wherever the earth is broken up, the wild sun-flower (Helianthus) and others of the taller-growing plants, though previously unknown in the vicinity, at once spring up, almost as if spontaneous generation had taken place." [Footnote: Geological Survey of Wyoming, p. 455.]
Moritz Wagner, as quoted by Wittwer, [Footnote: Physikalische Geographie, p. 486.] remarks in his description of Mount Ararat: "A singular phenomenon to which my guide drew my attention is the appearance of several plants on the earth-heaps left by the last catastrophe [an earthquake], which grow nowhere else on the mountain, and had never been observed in this region before. The seeds of these plants were probably brought by birds, and found in the loose, clayey soil remaining from the streams of mud, the conditions of growth which the other soil of the mountain refused them." This is probable enough, but it is hardly less so that the flowing mud brought them up to the influence of air and sun, from depths where a previous convulsion had buried them ages before.
Seeds of small sylvan plants, too deeply buried by successive layers of forest foliage and the mould resulting from its decomposition to be reached by the plough when the trees are gone and the ground brought under cultivation, may, if a wiser posterity replants the wood which sheltered their parent stems, germinate and grow, after lying for generations in a state of suspended animation.
Darwin says: "On the estate of a relation there was a large and extremely barren heath, which had never been touched by the hand of man, but several hundred acres of exactly the same nature had been enclosed twenty-five years previously and planted with Scotch fir. The change in the native vegetation of the planted part of the heath was most remarkable—more than is generally seen in passing from one quite different soil to another; not only the proportional numbers of the heath-plants were wholly changed, but TWELVE SPECIES of plants (not counting grasses and sedges) flourished in the plantation which could not be found on the heath." [Footnote: Origin of Species, American edition, p. 60.] Had the author informed us that these twelve plants belonged to species whose seeds enter into the nutriment of the birds which appeared with the young wood, we could easily account for their presence in the soil; but he says distinctly that the birds were of insectivorous species, and it therefore seems more probable that the seeds had been deposited when an ancient forest protected the growth of the plants which bore them, and that they sprang up to new life when a return of favorable conditions awaked them from a sleep of centuries. Darwin indeed says that the heath "had never been touched by the hand of man." Perhaps not, after it became a heath; but what evidence is there to control the general presumption that this heath was preceded by a forest, in whose shade the vegetables which dropped the seeds in question might have grown [Footnote: Writers on vegetable physiology record numerous instances where seeds have grown after lying dormant for ages. The following cases are mentioned by Dr. Dwight (Travels, ii., pp. 438, 430).
"The lands [in Panton, Vermont], which have here been once cultivated, and again permitted to lie waste for several years, yield a rich and fine growth of hickory [Carya Porcina]. Of this wood there is not, I believe, a single tree in any original forest within fifty miles from this spot. The native growth was here white pine, of which I did not see a single stem in a whole grove of hickory."
The hickory is a walnut, bearing a fruit too heavy to be likely to be carried fifty miles by birds, and besides, I believe it is not eaten by any bird indigenous to Vermont. We have seen, however, on a former page, that birds transport the nutmeg, which when fresh is probably as heavy as the walnut, from one inland of the Indian archipelago to another.
"A field, about five miles from Northampton, on an eminence called Rail Hill, was cultivated about a century ago. The native growth here, and in all the surrounding region, was wholly oak, chestnut, etc. As the field belonged to my grandfather, I had the best opportunity of learning its history. It contained about five acres, in the form of an irregular parallelogram. As the savages rendered the cultivation dangerous, it was given up. On this ground there sprang up a grove of white pines covering the field and retaining its figure exactly. So far as I remember, there was not in it a single oak or chestnut tree … There was not a single pine whose seeds were, or, probably, had for ages been, sufficiently near to have been planted on this spot. The fact that these white pines covered this field exactly, go as to preserve both its extent and its figure, and that there were none in the neighborhood, are decisive proofs that cultivation brought up the seeds of a former forest within the limits of vegetation, and gave them an opportunity to germinate."
See, on the Succession of the Forest, Thoreau, Excursions, p. l35 et seqq.]
Although, therefore, the destruction of a wood and the reclaiming of the soil to agricultural uses suppose the death of its smaller dependent flora, these revolutions do not exclude the possibility of its resurrection. In a practical view of the subject, however, we must admit that when the woodman fells a tree he sacrifices the colony of humbler growths which had vegetated under its protection. Some wood-plants are known to possess valuable medicinal properties, and experiment may show that the number of these is greater than we now suppose. Few of them, however, have any other economical value than that of furnishing a slender pasturage to cattle allowed to roam in the woods; and even this small advantage is far more than compensated by the mischief done to the young trees by browsing animals. Upon the whole, the importance of this class of vegetables, as physic or as food, is not such as to furnish a very telling popular argument for the conservation of the forest as a necessary means of their perpetuation. More potent remedial agents may supply their place in the materia medica, and an acre of grass-land yields more nutriment for cattle than a range of a hundred acres of forest. But he whose sympathies with nature have taught him to feel that there is a fellowship between all God's creatures; to love the brilliant ore better than the dull ingot, iodic silver and crystallized red copper better than the shillings and the pennies forged from them by the coiner's cunning; a venerable oak-tree than the brandy-cask whose staves are split out from its heart-wood; a bed of anemones, hepaticas, or wood violets than the leeks and onions which he may grow on the soil they have enriched and in the air they made fragrant—he who has enjoyed that special training of the heart and intellect which can be acquired only in the unviolated sanctuaries of nature, "where man is distant, but God is near"—will not rashly assert his right to extirpate a tribe of harmless vegetables, barely because their products neither tickle his palate nor fill his pocket; and his regret at the dwindling area of the forest solitude will be augmented by the reflection that the nurselings of the woodland perish with the pines, the oaks, and the beeches that sheltered them. [Footnote: Quaint old Valvasor had observed the subduing influence of nature's solitudes. In describing the lonely Canker-Thal, which, though rocky, was in his time well wooded with "fir, larches, beeches and other trees," he says:
"Gladsomeness and beauty, which dwell in many valleys, may not be looked for there. The journey through it is cheerless, melancholy, wearisome, and serveth to temper and mortify orer-joyousness of thought … In sum it is a very desert, wherein the wildness of human pride doth grow tame."—Ehre der Crain, i., p. 186, b.]
Although, as I have said in a former chapter, birds do not frequent the deeper recesses of the wood, yet a very large proportion of them build their nests in trees, and find in their foliage and branches a secure retreat from the inclemencies of the seasons and the pursuit of the reptiles and quadrupeds which prey upon them. The borders of the forests are vocal with song; and when the gray and dewy morning calls the creeping things of the earth out of their night-cells, it summons from the neighboring wood legions of their winged enemies, which swoop down upon the fields to save man's harvests by devouring the destroying worm, and surprising the lagging beetle in his tardy retreat to the dark cover where he lurks through the hours of daylight.
The insects most injurious to the rural industry of the garden and the ploughland do not multiply in or near the woods. The locust, which ravages the East with its voracious armies, is bred in vast open plains which admit the full heat of the sun to hasten the hatching of the eggs, gather no moisture to destroy them, and harbor no bird to feed upon thelarvae. [Footnote: Smela, in the government of Kiew, has, for some years, not suffered at all from the locusts, which formerly came every year in vast swarms, and the curculio, so injurious to the turnip crops, is less destructive there than in other parts of the province. This improvement is owing partly to the more thorough cultivation of the soil, partly to the groves which are interspersed among the ploughlands. … When in the midst of the plains woods shall be planted and filled with insectivorous birds, the locusts will cease to be a plague and a terror to the farmer.—Rentzsch, Der Wald, pp. 45, 46.] It is only since the felling of the forests of Asia Minor and Cyrene that the locust has become so fearfully destructive in those countries; and the grasshopper, which now threatens to be almost as great a pest to the agriculture of some North American soils, breeds in seriously injurious numbers only where a wide extent of surface is bare of woods.
General Functions of Forests.
In the preceding pages we have seen that the electrical and chemical action of the forest, though obscure, exercises probably a beneficial, certainly not an injurious, influence on the composition and condition of the atmosphere; that it serves as a protection against the diffusion of miasmatic exhalations and malarious poisons; that it performs a most important function as a mechanical shelter from blasting winds to grounds and crops in the lee of it; that, as a conductor of heat, it tends to equalize the temperature of the earth and the air; that its dead products form a mantle over the surface, which protects the earth from excessive heat and cold; that the evaporation from the leaves of living trees, while it cools the air around them, diffuses through the atmosphere a medium which resists the escape of warmth from the earth by radiation, and hence that its general effect is to equilibrate caloric influences and moderate extremes of temperature.
We have seen, further, that the forest is equally useful as a regulator of terrestrial and of atmospheric humidity, preventing by its shade the drying up of the surface by parching winds and the scorching rays of the sun, intercepting a part of the precipitation, and pouring out a vast quantity of aqueous vapor into the atmosphere; that if it does not increase the amount of rain, it tends to equalize its distribution both in time and in place; that it preserves a hygrometric equilibrium in the superior strata of the earth's surface; that it maintains and regulates the flow of springs and rivulets; that it checks the superficial discharge of the waters of precipitation and consequently tends to prevent the sudden rise of rivers, the violence of floods, the formation of destructive torrents, and the abrasion of the surface by the action of running water; that it impedes the fall of avalanches and of rocks, and destructive slides of the superficial strata of mountains; that it is a safeguard against the breeding of locusts, and finally that it furnishes nutriment and shelter to many tribes of animal and of vegetable life which, if not necessary to man's existence, are conducive to his rational enjoyment. In fine, in well-wooded regions, and in inhabited countries where a due proportion of soil is devoted to the growth of judiciously distributed forests, natural destructive tendencies of all sorts are arrested or compensated, and man, bird, beast, fish, and vegetable alike find a constant uniformity of condition most favorable to the regular and harmonious coexistence of them all.
General Consequences of the Destruction of the Forest.
With the extirpation of the forest, all is changed. At one season, the earth parts with its warmth by radiation to an open sky—receives, at another, an immoderate heat from the unobstructed rays of the sun. Hence the climate becomes excessive, and the soil is alternately parched by the fervors of summer, and seared by the rigors of winter. Bleak winds sweep unresisted over its surface, drift away the snow that sheltered it from the frost, and dry up its scanty moisture. The precipitation becomes as irregular as the temperature; the melting snows and vernal rains, no longer absorbed by a loose and bibulous vegetable mould, rush over the frozen surface, and pour down the valleys seawards, instead of filling a retentive bed of absorbent earth, and storing up a supply of moisture to feed perennial springs. The soil is bared of its covering of leaves, broken and loosened by the plough, deprived of the fibrous rootlets which held it together, dried and pulverized by sun and wind, and at last exhausted by new combinations. The face of the earth is no longer a sponge, but a dust-heap, and the floods which the waters of the sky pour over it hurry swiftly along its slopes, carrying in suspension vast quantities of earthy particles which increase the abrading power and mechanical force of the current, and, augmented by the sand and gravel of falling banks, fill the beds of the streams, divert them into new channels, and obstruct their outlets. The rivulets, wanting their former regularity of supply and deprived of the protecting shade of the woods, are heated, evaporated, and thus reduced in their summer currents, but swollen to raging torrents in autumn and in spring. From these causes, there is a constant degradation of the uplands, and a consequent elevation of the beds of water-courses and of lakes by the deposition of the mineral and vegetable matter carried down by the waters. The channels of great rivers become unnavigable, their estuaries are choked up, and harbors which once sheltered large navies are shoaled by dangerous sand-bars. The earth, stripped of its vegetable glebe, grows less and less productive, and, consequently, less able to protect itself by weaving a new network of roots to bind its particles together, a new carpeting of turf to shield it from wind and sun and scouring rain. Gradually it becomes altogether barren. The washing of the soil from the mountains leaves bare ridges of sterile rock, and the rich organic mould which covered them, now swept down into the dank low grounds, promotes a luxuriance of aquatic vegetation, that breeds fever, and more insidious forms of mortal disease, by its decay, and thus the earth is rendered no longer fit for the habitation of man. [Footnote: Almost every narrative of travel in those countries which were the earliest seats of civilization, contains evidence of the truth of these general statements, and this evidence is presented with more or less detail in most of the special works on the forest which I have occasion to cite. I may refer particularly to Hohenstein, Der Wald, 1860, as full of important facts on this subject. See also Caimi, Cenni sulla Importanza dei Boschi, for some statistics, not readily found elsewhere, on this and other topics connected with the forest.]
To the general truth of this sad picture there are many exceptions, even in countries of excessive climates. Some of these are due to favorable conditions of surface, of geological structure, and of the distribution of rain; in many others, the evil consequences of man's improvidence have not yet been experienced, only because a sufficient time has not elapsed, since the felling of the forest, to allow them to develop themselves. But the vengeance of nature for the violation of her harmonies, though slow, is sure, and the gradual deterioration of soil and climate in such exceptional regions is as certain to result from the destruction of the woods as is any natural effect to follow its cause.
Due Proportion of Woodland.
The proportion of woodland that ought to be permanently maintained for its geographical and atmospheric influences varies according to the character of soil, surface, and climate. In countries with a humid sky, or moderately undulating surface and an equable temperature, a small extent of forest, enough to serve as a mechanical screen against the action of the wind in localities where such protection is needed, suffices. But most of the territory occupied by civilized man is exposed, by the character of its surface and its climate, to a physical degradation which cannot be averted except by devoting a large amount of soil to the growth of the woods.
From an economical point of view, the question of the due proportion of forest is not less complicated or less important than in its purely physical aspects. Of all the raw materials which nature supplies for elaboration by human art, wood is undoubtedly the most useful, and at the same time the most indispensable to social progress. [Footnote: In an imaginary dialogue in the Recepte Veritable, the author, Palissy, having expressed his indignation at the folly of men in destroying the woods, his interlocutor defends the policy of felling them, by citing the example of "divers bishops, cardinals, priors, abbots, monkeries and chapters, which, by cutting their woods, have made three profits, "the sale of the timber, the rent of the ground, and the "good portion" they received of the grain grown by the peasants upon it. To this argument Palissy replies: "I cannot enough detest this thing, and I call it not an error, but a curse and a calamity to all France; for when forests shall be cut, all arts shall cease, and they which practise them shall be driven out to eat grass with Nebuchadnezzar and the beasts of the field. I have divers times thought to set down in writing the arts which shall perish when there shall be no more wood; but when I had written down a great number, I did perceive that there could be no end of my writing, and having diligently considered, I found there was not any which could be followed without wood." … "And truly I could well allege to thee a thousand reasons, but 'tis so cheap a philosophy, that the very chamber-wenches, it they do but think, may see that without wood, it is not possible to exercise any manner of human art or cunning."—Oeuvres de Bernard Pallisy . Paris, 1844, p. 89.]
