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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/6019.txt b/6019.txt new file mode 100644 index 0000000..c685290 --- /dev/null +++ b/6019.txt @@ -0,0 +1,25657 @@ +Project Gutenberg's The Earth as Modified by Human Action, by George P. Marsh + +Copyright laws are changing all over the world. Be sure to check the +copyright laws for your country before downloading or redistributing +this or any other Project Gutenberg eBook. + +This header should be the first thing seen when viewing this Project +Gutenberg file. Please do not remove it. Do not change or edit the +header without written permission. + +Please read the "legal small print," and other information about the +eBook and Project Gutenberg at the bottom of this file. Included is +important information about your specific rights and restrictions in +how the file may be used. You can also find out about how to make a +donation to Project Gutenberg, and how to get involved. + + +**Welcome To The World of Free Plain Vanilla Electronic Texts** + +**eBooks Readable By Both Humans and By Computers, Since 1971** + +*****These eBooks Were Prepared By Thousands of Volunteers!***** + + +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 + +Character set encoding: ASCII + +*** START OF THE PROJECT GUTENBERG EBOOK EARTH AS MODIFIED BY HUMAN ACTION *** + + + + +Produced by Steve Harris, Charles Franks +and the Online Distributed Proofreading Team. + + + + + +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. 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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.] + +The demand for wood, and of course the quantity of forest required to +furnish it, depend upon the supply of fuel from other sources, such as +peat and coal, upon the extent to which stone, brick, or metal can +advantageously be substituted for wood in building, upon the development +of arts and industries employing wood and other forest products as +materials, and upon the cost of obtaining them from other countries, or +upon their commercial value as articles of export. + +Upon the whole, taking civilized Europe and America together, it is +probable that from twenty to twenty-five per cent. of well-wooded +surface is indispensable for the maintenance of normal physical +conditions, and for the supply of materials so essential to every branch +of human industry and every form of social life as those which compose +the harvest of the woods. + +There is probably no country--there are few large farms even--where at +least one-fourth of the soil is not either unfit for agricultural use, +or so unproductive that, as pasture or as ploughland, it yields less +pecuniary return than a thrifty wood. Every prairie has its sloughs +where willows and poplars would find a fitting soil, every Eastern farm +its rocky nooks and its barren hillsides suited to the growth of some +species from our rich forest flora, and everywhere belts of trees might +advantageously be planted along the roadsides and the boundaries and +dividing fences. In most cases, it will be found that trees may be made +to grow well where cultivated crops will not repay the outlay of +tillage, and it is a very plain dictate of sound economy that if trees +produce a better profit than the same ground would return if devoted to +grass or grain, the wood should be substituted for the field. + +Woodland in European Countries. + +In 1862, Rentzsch calculated the proportions of woodland in different +European countries as follows: [Footnote: Der Wald, pp. 123, 124.] + +Norway.................................. 66 per cent. +Sweden.................................. 60 " +Russia.................................. 30.00 " +Germany................................. 26.58 " +Belgium................................. 18.52 " +France.................................. 16.79 " +Switzerland............................. 15 " +Sardinia................................. 12.29 +Neapolitan States........................ 9.43 " +Holland.................................. 7.10 " +Spain.................................... 5.52 " +Denmark.................................. 5.50 " +Great Britain............................ 5 " +Portugal................................. 4.40 " + +The large proportion of woodland in Norway and Sweden is in a great +measure to be ascribed to the mountainous character of the surface, +which renders the construction of roads difficult and expensive, and +hence the forests are comparatively inaccessible, and transportation is +too costly to tempt the inhabitants to sacrifice their woods for the +sake of supplying distant markets. + +The industries which employ wood as a material have only lately been +much developed in these countries, and though the climate requires the +consumption of much wood as a fuel, the population is not numerous +enough to create, for this purpose, a demand exceeding the annually +produced supply, or to need any great extension of cleared ground for +agricultural purposes. Besides this, in many places peat is generally +employed as domestic fuel. Hence, though Norway has long exported a +considerable quantity of lumber, [Footnote: Railway-ties, or, as they +are called in England, sleepers, are largely exported from Norway to +India, and sold at Calcutta at a lower price than timber of equal +quality can be obtained from the native woods.--Reports on Forest +Conservancy, vol. i., pt. ii., p. 1533. + +From 1861 to 1870 Norway exported annually, on the average, more than +60,000,000 cubic feet of lumber.--Wulfsberg, Norges Velstandskilder. +Christiania, 1872.] and the iron and copper works of Sweden consume +charcoal very largely, the forests have not diminished rapidly enough to +produce very sensible climatic or even economic evils. + +At the opposite end of the scale we find Holland, Denmark, Great +Britain, Spain, and Portugal. In the three first-named countries a cold +and humid climate renders the almost constant maintenance of domestic +fires a necessity, while in Great Britain especially the demand of the +various industries which depend on wood as a material, or on mechanical +power derived from heat, are very great. Coal and peat serve as a +combustible instead of wood in them all, and England imports an immense +quantity of timber from her foreign possessions. Fortunately, the +character of soil, surface, and climate renders the forest of less +importance as a geographical agent in these northern regions than in +Spain and Portugal, where all physical conditions concur to make a large +extent of forest an almost indispensable means of industrial progress +and social advancement. + +Rentzsch, in fact, ascribes the political decadence of Spain almost +wholly to the destruction of the forest. "Spain," observes he, "seemed +destined by her position to hold dominion over the world, and this in +fact she once possessed. But she has lost her political ascendancy, +because, during the feeble administration of the successors of Philip +II., her exhausted treasury could not furnish the means of creating new +fleets, the destruction of the woods having raised the price of timber +above the means of the state." [Footnote: Der Wald, p. 63. Antonio Ponz +(Viage de Espana, i., prologo, p. lxiii.), says: "Nor would this be so +great an evil, were not some of them declaimers against TREES, thereby +proclaiming themselves, in some sort, enemies of the works of God, who +gave us the leafy abode of Paradise to dwell in, where we should be even +now sojourning, but for the first sin, which expelled us from it." + +I do not know at what period the two Castiles were bared of their woods, +but the Spaniard's proverbial "hatred of a tree" is of long standing. +Herrera combats this foolish prejudice; and Ponz, in the prologue to the +ninth volume of his journey, says that many carried it so far as +wantonly to destroy the shade and ornamental trees planted by the +municipal authorities. "Trees," they contended, and still believe, +"breed birds, and birds eat up the grain." Our author argues against the +supposition of the "breeding of birds by trees," which, he says, is as +absurd as to believe that an elm-tree can yield pears; and he charitably +suggests that the expression is, perhaps, a maniere de dire, a popular +phrase, signifying simply that trees harbor birds.] On the other hand, +the same writer argues that the wealth and prosperity of modern England +are in great part due to the supply of lumber, as well as of other +material for ship-building, which she imports from her colonies and +other countries with which she maintains commercial relations. + + +Forests of Great Britain. + +The proportion of forest is very small in Great Britain, where, as I +have said, on the one hand, a prodigious industrial activity requires a +vast supply of ligneous material, but where, on the other, the abundance +of coal, which furnishes a sufficiency of fuel, the facility of +importation of timber from abroad, and the conditions of climate and +surface combine to reduce the necessary quantity of woodland to its +lowest expression. + +With the exception of Russia, Denmark, and parts of Germany, no European +countries can so well dispense with the forests, in their capacity of +conservative influences, as England and Ireland. Their insular position +and latitude secure an abundance of atmospheric moisture; the general +inclination of surface is not such as to expose it to special injury +from torrents, and it is probable that the most important climatic +action exercised by the forest in these portions of the British empire, +is in its character of a mechanical screen against the effects of wind. +The due proportion of woodland in England and Ireland is, therefore, a +question not of geographical, but almost purely of economical, +expediency, to be decided by the comparative direct pecuniary return +from forest-growth, pasturage, and ploughland. + +Contrivances for economizing fuel came later into use in the British +Islands than on the Continent. Before the introduction of a system of +drainage, the soil, like the sky, was, in general, charged with +humidity; its natural condition was unfavorable for the construction and +maintenance of substantial common roads, and the transportation of so +heavy a material as coal, by land, from the remote counties where alone +it was mined in the Middle Ages, was costly and difficult. For all these +reasons, the consumption of wood was large, and apprehensions of the +exhaustion of the forests were excited at an early period. Legislation +there, as elsewhere, proved ineffectual to protect them, and many +authors of the sixteenth century express fears of serious evils from the +wasteful economy of the people in this respect. Harrison, in his curious +chapter "Of Woods and Marishes" in Holinshed's compilation, complains of +the rapid decrease of the forests, and adds: "Howbeit thus much I dare +affirme, that if woods go so fast to decaie in the next hundred yeere of +Grace, as they haue doone and are like to doo in this, . . . it is to be +feared that the fennie bote, broome, turfe, gall, heath, firze, brakes, +whinnes, ling, dies, hassacks, flags, straw, sedge, reed, rush, and also +seacole, will be good merchandize euen in the citie of London, whereunto +some of them euen now haue gotten readie passage, and taken up their +innes in the greatest merchants' parlours . . . . I would wish that I +might liue no longer than to see foure things in this land reformed, +that is: the want of discipline in the church: the couetous dealing of +most of our merchants in the preferment of the commodities of other +countries, and hinderance of their owne: the holding of faires and +markets vpon the sundaie to be abolished and referred to the +wednesdaies: and that euerie man, in whatsoeuer part of the champaine +soile enioieth fortie acres of land, and vpwards, after that rate, +either by free deed, copie hold, or fee farme, might plant one acre of +wood, or sowe the same with oke mast, hasell, beech, and sufficient +prouision be made that it may be cherished and kept. But I feare me that +I should then liue too long, and so long, that I should either be wearie +of the world, or the world of me." [Footnote: Holinshed, reprint of +1807, i., pp. 357, 358. It is evident from this passage, and from +another on page 397 of the same volume, that, though seacoal was largely +exported to the Continent, it had not yet come into general use in +England. It is a question of much interest, when mineral coal was first +employed in England for fuel. I can find no evidence that it was used as +a combustible until more than a century after the Norman conquest. It +has been said that it was known to the Anglo-Saxon population, but I am +acquainted with no passage in the literature of that people which proves +this. The dictionaries explain the Anglo-Saxon word grofa by sea-coal. I +have met with this word in no Anglo-Saxon work, except in the Chronicle, +A.D. 852, from a manuscript certainly not older than the 12th century, +and in two citations from Anglo-Saxon charters, one published by Kemble +in Codex Diplomaticus, the other by Thorpe in Diplomatarium Anglicum, in +all which passages it more probably means peat than mineral coal. +According to Way, Promptorium Parrulorum, p. 506, note, the Catholicon +Anglicanum has "A turfe grafte, turbarium." Grafte is here evidently the +same word as the A.-S. grafa, and the Danish Torvegraf, a turf-pit, +confirms this opinion. Coal is not mentioned in King Alfred's Bede, in +Neckam, in Glanville or in Robert of Gloucester, though the two latter +writers speak of the allied mineral, jet, and are very full in their +enumeration of the mineral productions of the island. In a Latin poem +ascribed to Giraldus Cambrensis, who died after the year 1220, but found +also in the manuesripts of Walter Mapes (see Camden Society edition, pp. +131 and 350), and introduced into Higden's Polychronicon (London, 1865, +pp. 398, 399), carbo sub terra cortice, which can mean nothing but +pit-coal, is enumerated among the natural commodities of England. Some +of the translations of the 13th and 14th century render carbo by cool or +col, some by gold, and some omit this line, as well as others +unintelligible to the translators. Hence, although Giraldus was +acquainted with coal, it certainly was not generally known to English +writers until at least a century after the time of that author. + +The earliest mediaeval notice of mineral coal I have met with is in a +passage cited by Ducange from a document of the year 1198, and it is an +etymological observation of some interest, that carbones ferrei, as +sea-coal is called in the document, are said by Ducange to have been +known in France by the popular name of hulla, a word evidently identical +with the modern French houille and the Cornish Huel, which in the form +wheal is an element in the name of many mining localities. + +England was anciently remarkable for its forests, but Caesar says it +wanted the fagus and the abies. There can be no doubt that fagus means +the beech, which, as the remains in the Danish peat-mosses show, is a +tree of late introduction into Denmark, where it succeeded the fir, a +tree not now native to that country. The succession of forest crops +seems to have been the same in England; for Harrison, p. 359, speaks of +the "great store of firre" found lying "at their whole lengths" in the +"fens and marises" of Lancashire and other counties, where not even +bushes grew in his time. We cannot be sure what species of evergreen +Caesar intended by abies. The popular designations of spike-leaved trees +are always more vague and uncertain in their application than those of +broad-leaved trees. PINUS, PINE, has been very loosely employed even in +botanical nomenclature, and KIEFER, FICHTE, and TANNE are often +confounded in German.--Rossmassler, Der Wald, pp. 256, 289, 324. A +similar confusion in the names of this family of trees exists in India. +Dr. Cleghorn, Inspector-General of the Indian Forests, informs us in his +official Circular No. 2, that the name of deodar is applied in some +provinces to a cypress, in some to a cedar, and in others to a juniper. +If it were certain that the abies of Caesar was the fir formerly and +still found in peat-mosses, and that he was right in denying the +existence of the beech in England in his time, the observation would be +very important, because it would fix a date at which the fir had become +extinct, and the beech had not yet appeared in the island. + +The English oak, though strong and durable, was not considered generally +suitable for finer work in the sixteenth century. There were, however, +exceptions. "Of all in Essex," observes Harrison, Holinshed, i., p. +357, "that growing in Bardfield parke is the finest for ioiners craft; +for oftentimes haue I seene of their workes made of that oke so fine and +faire, as most of the wainescot that is brought hither out of Danske +[Danzig]; for our wainescot is not made in England. Yet diuerse haue +assaied to deale with our okes to that end, but not with so good +successe as they haue hoped, bicause the ab or iuice will not so soone +be removed and cleane drawne out, which some attribute to want of time +in the salt water." This passage is also of interest as showing that +soaking in salt-water, as a mode of seasoning, was practised in +Harrison's time. + +But the importation of wainscot, or boards for ceiling, panelling, and +otherwise finishing rooms, which was generally of oak, commenced at +least three centuries before the time of Harrison. On page 204 of the +Liber Albus mention is made of "squared oak timber," brought in from the +country by carts, and of course of domestic growth, as free of city duty +or octroi, and of "planks of oak" coming in in the same way as paying +one plank a cart-load. But in the chapter on the "Customs of +Billyngesgate," pp. 208, 209, relating to goods imported from foreign +countries, an import duty of one halfpenny is imposed on every hundred +of boards called "weynscotte"--a term formerly applied only to oak--and +of one penny on every hundred of boards called "Rygholt." The editor +explains "Rygholt" as "wood of Riga." This was doubtless pine or fir. +The year in which these provisions were made does not appear, but they +belong to the reign of Henry III.] + +Evelyn's "Silva," the first edition of which appeared in 1664, rendered +an extremely important service to the cause of the woods, and there is +no doubt that the ornamental plantations in which England far surpasses +all other countries, are, in some measure, the fruit of Evelyn's +enthusiasm. In England, however, arboriculture, the planting and nursing +of single trees, has, until comparatively recent times, been better +understood than sylviculture, the sowing and training of the forest. But +this latter branch of rural improvement now receives great attention +from private individuals, though, so far as I know, not from the +National Government, except in the East Indian provinces, where the +forestal department has assumed great importance. [Footnote: The +improvidence of the population under the native and early foreign +governments has produced great devastations in the forests of the +British East Indian provinces, and the demands of the railways for fuel +and timber have greatly augmented the consumption of lumber, and of +course contributed to the destruction of the woods. The forests of +British India are now, and for several years have been, under the +control of an efficient governmental organization, with great advantage +both to the government and to the general private interests of the +people. + +The official Reports on Forest Conservancy from May, 1862, to August, +1871, in 4 vols. folio, contain much statistical and practical +information on all subjects connected with the administration of the +forest.] + +In fact, England is, I believe, the only European country where private +enterprise has pursued sylviculture on a really great scale, though +admirable examples have been set in many others. In England the law of +primogeniture, and other institutions and national customs which tend to +keep large estates long undivided and in the same line of inheritance, +the wealth of the landholders, the special adaptation of the climate to +the growth of forest-trees, and the difficulty of finding safe and +profitable investments of capital, combine to afford encouragements for +the plantation of forests, which scarcely exist elsewhere in the same +degree. + +In Scotland, where the country is for the most part broken and +mountainous, the general destruction of the forests has been attended +with very serious evils, and it is in Scotland that many of the most +extensive British forest plantations have now been formed. But although +the inclination of surface in Scotland is rapid, the geological +constitution of the soil is not of a character to promote such +destructive degradation by running water as in Southern France, and it +has not to contend with the parching droughts by which the devastations +of the torrents are rendered more injurious in those provinces. + +It is difficult to understand how either law or public opinion, in a +country occupied by a dense and intelligent population, and, +comparatively speaking, with an infertile soil, can tolerate the +continued withdrawal of a great portion of the territory from the +cultivation of trees and from other kinds of rural economy, merely to +allow wealthy individuals to amuse themselves with field-sports. In +Scotland, 2,000,000 acres, as well suited to the growth of forests and +for pasture as is the soil generally, are withheld from agriculture, +that they may be given up to herds of deer protected by the game laws. A +single nobleman, for example, thus appropriates for his own pleasures +not less than 100,000 acres. [Footnote: Robertson, Our Deer Forests. +London, 1867.] In this way one-tenth of all the land of Scotland is +rendered valueless in an economical point of view--for the returns from +the sale of the venison and other game scarcely suffice to pay the +game-keepers and other incidental expenses--and in these so-called +FORESTS there grows neither building timber nor fire-wood worth the +cutting, as the animals destroy the young shoots. + + +Forests of France. + +The preservation of the woods was one of the wise measures recommended +to France by Sully, in the time of Henry IV., but the advice was little +heeded, and the destruction of the forests went on with such alarming +rapidity, that, two generations later, Colbert uttered the prediction: +"France will perish for want of wood." Still, the extent of wooded soil +was very great, and the evils attending its diminution were not so +sensibly felt, that either the government or public opinion saw the +necessity of authoritative interference, and in 1750 Mirabeau estimated +the remaining forests of the kingdom at seventeen millions of hectares +[42,000,000 acres]. In 1860 they were reduced to eight millions +[19,769,000 acres], or at the rate of 82,000 hectares [202,600 acres] +per year. Troy, from whose valuable pamphlet, Etude sur le Reboisement +des Montagnes, I take these statistical details, supposes that +Mirabeau's statement may have been an extravagant one, but it still +remains certain that the waste has been enormous; for it is known that, +in some departments, that of Ariege, for instance, clearing has gone on +during the last half-century at the rate of three thousand acres a year, +and in all parts of the empire trees have been felled faster than they +have grown. [Footnote: Among the indirect proofs of the comparatively +recent existence of extensive forests in France, may be mentioned the +fact that wolves were abundant, not very long since, in parts of the +empire where there are now neither wolves nor woods to shelter them. +Arthur Young more than once speaks of the "innumerable multitudes" of +these animals which infested France in 1789, and George Sand states, in +the Histoire de ma Vie, that some years after the restoration of the +Bourbons, they chased travellers on horseback in the southern provinces, +and literally knocked at the doors of her father-in-law's country seat. +Eugenie de Guerin, writing from Rayssac in Languedoc in 1831 speaks of +hearing the wolves fighting with dogs in the night under her very +windows. Lettres, 2d ed., p. 6. + +There seems to have been a tendency to excessive clearing in Central and +Western, earlier than in South-eastern, France. Bernard Palissy, in the +Recepte Veritable, first printed in 1563, thus complains: "When I +consider the value of the least clump of trees, or even of thorns, I +much marvel at the great ignorance of men, who, as it seemeth, do +nowadays study only to break down, fell, and waste the fair forests +which their forefathers did guard so choicely. I would think no evil of +them for cutting down the woods, did they but replant again some part of +them; but they care nought for the time to come, neither reck they of +the great damage they do to their children which shall come after +them."--Oeuvres Completes de Bernard Pallisy, 1844, p. 88.] The total +area of France in Mirabeau's time, excluding Savoy, but including Alsace +and Lorraine, was about one hundred and thirty-one millions of acres. +The extent of forest supposed by Mirabeau would be about thirty-two per +cent. of the whole territory. In a country and a climate where the +conservative influences of the forest are so necessary as in France, +trees must cover a large surface and be grouped in large masses, in +order to discharge to the best advantage the various functions assigned +to them by nature. The consumption of wood is rapidly increasing in that +empire, and a large part of its territory is mountainous, sterile, and +otherwise such in character or situation that it can be more profitably +devoted to the growth of wood than to any agricultural use. Hence it is +evident that the proportion of forest in 1750, taking even Mirabeau's +large estimate, was not very much too great for permanent maintenance, +though doubtless the distribution was so unequal that it would have been +sound policy to fell the woods and clear land in some provinces, while +large forests should have been planted in others. [Footnote: The view I +have taken of this point is confirmed by the careful investigation of +Rentzsch, who estimates the proper proportion of woodland to entire +surface at twenty-three per cent. for the interior of Germany, and +supposes that near the coast, where the air is supplied with humidity by +evaporation from the sea, it might safely be reduced to twenty per cent. +See Rentzsch's very valuable prize essay, Der Wald im Haushalt der Natur +und der Volkswirthschaft. cap. viii. + +The due proportion in France would considerably exceed that for the +German States, because France has relatively more surface unfit for any +growth but that of wood, because the form and geological character of +her mountains expose her territory to much greater injury from torrents, +and beause at least her southern provinces are more frequently visited +both by extreme droughts and by deluging rains.] During the period in +question France neither exported manufactured wood or rough timber, nor +derived important collateral advantages of any sort from the destruction +of her forests. She is consequently impoverished and crippled to the +extent of the difference between what she actually possesses of wooded +surface and what she ought to have retained. [Footnote: In 1863, France +imported lumber to the value of twenty-five and a half millions of +dollars, and exported to the amount of six and a half millions of +dollars. The annual consumption of France was estimated in 1866 at +212,000,000 cubic feet for building and manufacturing, and 1,588,300,000 +for firewood and charcoal. The annual product of the forest-soil of +France does not exceed 70,000,000 cubic feet of wood fit for industrial +use, and 1,300,000,000 cubic feet consumed as fuel. This estimate does +not include the product of scattered trees on private grounds, but the +consumption is estimated to exceed the production of the forests by the +amount of about twenty millions of dollars. It is worth noticing that +the timber for building and manufacturing produced in France comes +almost wholly from the forests of the state or of the communes.--Jules +Clave, in Revue des Deux Mondes for March 1, 1866, p. 207.] + +The force of the various considerations which have been suggested in +regard to the importance of the forest has been generally felt in +France, and the subject has been amply debated special treatises, in +scientific journals, and by the public press, as well as in the +legislative body of that country. Perhaps no one point has been more +prominent in the discussions than the influence of the forest in +equalizing and regulating the flow of the water of precipitation. +Opinion is still somewhat divided on this subject, but the value of the +woods as a safeguard against the ravages of torrents is universally +acknowledged, and it is hardly disputed that the rise of river-floods +is, even if as great, at least less sudden in streams having their +sources in well-wooded territory. + +Upon the whole, the conservative action of the woods in regard to +torrents and to inundations has ben generally recognized by the public +of France as a matter of prime importance, and the Government of the +empire has made this principle the basis of a special system of +legislation for the protection of existing forests, and for the +formation of new. The clearing of woodland, and the organization and +functions of a police for its protection, are regulated by a law bearing +date June 18th, 1859, and provision was made for promoting the +restoration of private woods by a statute adopted on the 28th of July, +1860. The former of these laws passed the legislative body by a vote of +246 against 4, the latter with but a single negative voice. The +influence of the Government, in a country where the throne is as potent +as in France, would account for a large majority, but when it is +considered that both laws, the former especially, interfere very +materially with the rights of private domain, the almost entire +unanimity with which they were adopted is proof of a very general +popular conviction, that the protection and extension of the forests is +a measure more likely than any other to arrest the devastations of the +torrents and check the violence, if not to prevent the recurrence, of +destructive river inundations. The law of July 28th, 1860, appropriated +10,000,000 francs, to be expended, at the rate of 1,000,000 francs per +year, in executing or aiding the replanting of woods. It is computed +that this appropriation--which, considering the vast importance of the +subject, does not seem extravagant for a nation rich enough to be able +to expend annually six hundred times that sum in the maintenance of its +military establishments in times of peace--will secure the creation of +new forest to the extent of about 200,000 acres, or one fourteenth part +of the soil, where the restoration of the woods is thought feasible, +and, at the same time, specially important as a security against the +evils ascribed, in a great measure, to its destruction. [Footnote: In +1848 the Government of the so-called French Republic sold to the Bank of +France 187,000 acres of public forests, and notwithstanding the zeal +with which the Imperial Government had pressed the protective +Iegislation of 1860, it introduced, into the Legislative Assembly in +1865 a bill for the sale, and consequently destruction, of the forests +of the state to the amount of one hundred million francs. The question +was much debated in the Assembly, and public opinion manifested itself +so energetically against the measure that the ministry felt itself +compelled to withdraw it. See the discussions in D'Alienation des Forets +de l'Etat. Paris, 1865. The late Imperial Government sold about 170,000 +acres of woodland between 1852 and 1866, both inclusive. The other +Governments, since the restoration of the Bourbons in 1814, alienated +more than 700,000 acres of the public forests, exclusive of sales +between 1836 and 1857, which are not reported.--Annuaire des Eaux et +Forets, 1872, p. 9.] + +In 1865 the Legislative Assembly passed a bill amendatory of the law of +1860, providing, among other things, for securing the soil in exposed +localities by grading, and by promoting the growth of grass and the +formation of greensward over the surface. This has proved a most +beneficial measure, and its adoption under corresponding conditions in +the United States is most highly to be recommended. The leading features +of the system are: + +1. Marking out and securing from pasturage and all other encroachments a +zone along the banks and around the head of ravines. + +2. Turfing this zone, which in France accomplishes itself, if not +spontaneously, at least with little aid from art. + +3. Consolidation of the scarps of the ravines by grading and wattling +and establishing barriers, sometimes of solid masonry, but generally of +fascines or any other simple materials at hand, across the bed of the +stream. + +4. Cutting banquettes or narrow terraces along the scarps, and planting +rows of small deciduous trees and arborescent shrubs upon them, +alternating with belts of grass obtained by turfing with sods or sowing +grass-seeds. Planting the banquettes and slopes with bushes, and sowing +any other vegetables with tenacious roots, is also earnestly +recommended. [Footnote: See a description of similar processes +recommended and adopted by Mengotti, in his Idraulica, vol. ii., chap. +xvii.] + + +Remedies against Torrents. + +The rural population, which in France is generally hostile to all forest +laws, soon acquiesced in the adoption of this system, and its success +has far surpassed all expectation. At the end of the year 1868 about +190,000 acres had been planted with trees, [Footnote: Travellers +spending the winter at Nice may have a good opportunity of studying the +methods of forming and conducting the rewooding of mountain slopes, +under the most unfavorable conditions, by visiting Mont Boron, in the +immediate vicinity of that city, and other coast plantations in that +province, where great difficulties have been completely overcome by the +skill and perseverance of French foresters. See Les Forets des Maures, +Revue des Eaux et Forets, January, 1869.] and nearly 7,000 acres well +turfed over in the Department of the Hautes Alpes. Many hundred ravines, +several of which had been the channels of formidable torrents, had been +secured by barriers, grading and planting, and according to official +reports the aspect of the mountains in the Department, wherever these +methods were employed, had rapidly changed. The soil had acquired such +stability that the violent rains of 1868, so destructive elsewhere, +produced no damage in the districts which had been subjected to these +operations, and numerous growing torrents which threatened irreparable +mischief had been completely extinguished, or at least rendered +altogether harmless. [Footnote: For ample details of processes and +results, see the second volume of Surrell, Etudes sur les Torrents, +Paris, 1872, and a Report by De La Grye, in the Revue des Eaux et Forets +for January, 1869.] + +Besides the processes directed by the Government of France, various +subsidiary measures of an easily and economically practicable character +have been suggested. Among them is one which has long been favorably +known in our Southern States under the name of circling, and the +adoption of which in hilly regions in other States is to be strongly +recommended. + +It is simply a method of preventing the wash of surface by rains, and at +the same time of providing a substitute for irrigation of steep +pasture-grounds, consisting in little more than in running horizontal +furrows along the hillsides, thus converting the scarp of the hills into +a succession of small terraces which, when once turfed over, are very +permanent. Experience is said to have demonstrated that this simple +process at least partially checks the too rapid flow of surface-water +into the valleys, and, consequently, in a great measure obviates one of +the most prominent causes of inundations, and that it suffices to retain +the water of rains, of snows, and of small springs, long enough for the +irrigation of the soil, thus increasing its product of herbage in a +fivefold proportion. [Footnote: Troy, Etude sur le Reboisement des +Montagnes, sections 6, 7, 21.] + +As a further recommendation, it may be observed that this process is an +admirable preparation of the ground for forest plantations, as young +trees planted on the terraces would derive a useful protection from the +form of the surface and the coating of turf, and would also find a soil +moist enough to secure their growth. + + +Forests of Italy. + +According to the most recent statistics, Italy has 17.64 per cent. of +woodland, [Footnote: Siemoni, Manuale d'Arte Forestale, 2 ediz., +Firenze, 1872, p. 542.] a proportion which, considering the character of +climate and surface, the great amount of soil which is fit for no other +purpose than the growth of trees, and the fact that much of the land +classed as forest is either very imperfectly wooded, or covered with +groves badly administered, and not in a state of progressive +improvement, might advantageously be doubled. Taking Italy as a whole, +we may say that she is eminently fitted by climate, soil, and +superficial formation, to the growth of a varied and luxuriant arboreal +vegetation, and that in the interests of self-protection, the promotion +of forestal industry is among the first duties of her people. There are +in Western Piedmont valleys where the felling of the woods has produced +consequences geographically and economically as disastrous as in +South-eastern France, and there are many other districts in the Alps and +the Apennines where human improvidence has been almost equally +destructive. Some of these regions must be abandoned to absolute +desolation, and for others the opportunity of physical restoration is +rapidly passing away. But there are still millions of square miles which +might profitably be planted with forest-trees, and thousands of acres of +parched and barren hillside, within sight of almost every Italian +provincial capital, which might easily and shortly be reclothed with +verdant woods. [Footnote: To one accustomed to the slow vegetation of +less favored climes, the rapidity of growth in young plantations in +Italy seems almost magical. The trees planted along the new drives and +avenues in Florence have attained in three or four years a development +which would require at least ten in our Northern States. This, it is +true, is a special case, for the trees have been planted and tended with +a skill and care which cannot be bestowed upon a forest; but the growth +of trees little cared for is still very rapid in Italy. According to +Toscanelli, Economia rurale nella Provincia di Pisa, p. 8, note--one of +the most complete, curious, and instructive pictures of rural life which +exists in any literature--the white poplar, Populus alba, attains in the +valley of the Serchio a great height, with a mean diameter of two feet, +in twenty years. Solmi states in his Miasma Palustre, p. 115, that the +linden reaches a diameter of sixteen inches in the same period. The +growth of foreign trees is sometimes extremely luxuriant in Italy. Two +Atlas cedars, at the well-known villa of Careggi, near Florence, grown +from seed sown in 1850, measure twenty inches in diameter, above the +swell of the roots, with an estimated height of sixty feet.] + +The denudation of the Central and Southern Apennines and of the Italian +declivity of the Western Alps began at a period of unknown antiquity, +but it does not seem to have been carried to a very dangerous length +until the foreign conquests and extended commerce of Rome created a +greatly increased demand for wood for the construction of ships and for +military material. [Footnote: An interesting example of the collateral +effects of the destruction of the forests in ancient Italy may be found +in old Roman architecture. In the oldest brick constructions of Rome the +bricks are very thin, very thoroughly burnt, and laid with a thick +stratum of mortar between the courses. A few centuries later the bricks +were thicker and less well burnt, and the layers of mortar were thinner. +In the Imperial period the bricks were still thicker, generally +soft-burnt, and with little mortar between the courses. This fact, I +think, is due to the abundance and cheapness of fuel in earlier, and its +growing scarceness and dearness in later, ages. When wood cost little, +constructors could afford to burn their brick thoroughly, and to burn +and use a great quantity of lime. As the price of fire-wood advanced, +they were able to consume less fuel in brick- and lime-kilns, and the +quality and quantity of brick and lime used in building were gradually +reversed in proportion. + +The multitude of geographical designations in Italy which indicate the +former existence of forests show that even in the Middle Ages there were +woods where no forest-trees are now to be found. There are hundreds of +names of mediaeval towns derived from abete, acero, carpino, castagno, +faggio, frassino, pino, quercia, and other names of trees.] The Eastern +Alps, the Western Apennines, and the Maritime Alps retained their +forests much later; but even here the want of wood, and the injury to +the plains and the nagivation of the rivers by sediment brought down by +the torrents, led to legislation for the protection of the forests, by +the Republic of Venice, at various periods between the fifteenth and the +nineteenth centuries, [Footnote: See A. de Bereuger's valuable Saggio +Storico della Legislazione Veneta Forestale. Venezia, 1863. + +We do not find in the Venetian forestal legislation much evidence that +geographical arguments were taken into account by the lawgivers, who +seem to have had an eye only to economical considerations. + +According to Hummel, the desolation of the Karst, the high plateau lying +north of Trieste, now one of the most parched and barren districts in +Europe, is owing to the felling of the woods, centuries ago, to build +the navies of Venice. "Where the miserable peasant of the Karst now sees +nothing but bare rock swept and scoured by the raging Bora, the fury of +this wind was once subdued by mighty firs, which Venice recklessly cut +down to build her fleets."--Physische Geographie, p. 32.] by that of +Genoa as early at least as the seventeenth; and both these Governments, +as well as several others, passed laws requiring the proprietors of +mountain-lands to replant the woods. These, however, seem to have been +little observed, and it is generally true that the present condition of +the forest in Italy is much less due to the want of wise legislation for +its protection than to the laxity of the Governments in enforcing their +laws. + +It is very common in Italy to ascribe to the French occupation under the +first Empire all the improvements and all the abuses of recent times, +according to the political sympathies of the individual; and the French +are often said to have prostrated every forest which has disappeared +within this century. But, however this may be, no energetic system of +repression or restoration was adopted by any of the Italian States after +the downfall of the Empire, and the taxes on forest property in some of +them were so burdensome that rural municipalities sometimes proposed to +cede their common woods to the Government, without any other +compensation than the remission of the taxes imposed on forest-lands. +[Footnote: See the Politecnico for the month of May, 1862, p. 234.] +Under such circumstances, woodlands would soon become disafforested, and +where facilities of transportation and a good demand for timber have +increased the inducements to fell it, as upon the borders of the +Mediterranean, the destruction of the forest and all the evils which +attend it have gone on at a seriously alarming rate. + +Gallenga gives a striking account of the wanton destruction of the +forests in Northern Italy within his personal recollection, [Footnote: +"Far away in the darkest recesses of the mountains a kind of universal +conspiracy seems to have been got up among these Alpine people,--a +destructive mania to hew and sweep down everything that stands on +roots."--Country Life in Piedmont, p. 134. + +"There are huge pyramids of mountains now bare and bleak from base to +summit, which men still living and still young remember seeing richly +mantled with all but primeval forests."--Ibid., p. 135.] and there are +few Italians past middle life whose own memory will not supply similar +reminiscences. The clearing of the mountain valleys of the provinces of +Bergamo and of Bescia is recent, and Lombardini informs us the felling +of the woods in the Valtelline commenced little more than forty years +ago. + +Although no country has produced more able writers on the value of the +forest and the general consequences of its destruction than Italy, yet +the specific geographical importance of the woods, except as a +protection against inundations, has not been so clearly recognized in +that country as in the States bordering it on the north and west. It is +true that the face of nature has been as completely revolutionized by +man, and that the action of torrents has created almost as wide and as +hopeless devastation in Italy as in France; but in the French Empire the +recent desolation produced by clearing the forests is more extensive, +has been more suddenly effected, has occurred in less remote and obscure +localities, and therefore, excites a livelier and more general interest +than in Italy, where public opinion does not so readily connect the +effect with its true cause. Italy, too, from ancient habit, employs +little wood in architectural construction; for generations she has +maintained no military or commercial marine large enough to require +exhaustive quantities of timber, [Footnote: The great naval and +commercial marines of Venice and of Genoa must have occasioned an +immense consumption of lumber in the Middle Ages, and the centuries +immediately succeeding those commonly embraced in that designation. The +marine construction of that period employed larger timbers than the +modern naval architecture of most commercial countries, but apparently +without a proportional increase of strength. The old modes of +ship-building have been, to a considerable extent, handed down to very +recent times in the Mediterranean, and though better models and modes of +construction are now employed in Italian shipyards, an American or an +Englishman looks with astonishment at the huge beams and thick planks so +often employed in the construction of very small vessels navigating that +sea, and not yet old enough to be broken up as unseaworthy.] and the +mildness of her climate makes small demands on the woods for fuel. +Besides these circumstances, it must be remembered that the sciences of +observation did not become knowledges of practical application till +after the mischief was already mainly done and even forgotten in Alpine +Italy, while its evils were just beginning to be sensibly felt in France +when the claims of natural philosophy as a liberal study were first +acknowledged in modern Europe. The former political condition of the +Italian Peninsula would have effectually prevented the adoption of a +general system of forest economy, however clearly the importance of a +wise administration of this great public interest might have been +understood. The woods which controlled and regulated the flow of the +river-sources were very often in one jurisdiction, the plains to be +irrigated, or to be inundated by floods and desolated by torrents, in +another. Concert of action, on such a subject, between a multitude of +jealous petty sovereignties, was obviously impossible, and nothing but +the permanent union of all the Italian States under a single government +can render practicable the establishment of such arrangements for the +conservation and restoration of the forests, and the regulation of the +flow of the waters, as are necessary for the full development of the yet +unexhausted resources of that fairest of lands, and even for the +maintenance of the present condition of its physical geography. + + +The Forests of Germany. + +Germany, including a considerable part of the Austrian Empire, from +character of surface and climate, and from the attention which has long +been paid in all the German States to sylviculture, is in a far better +condition in this respect than its more southern neighbors; and though +in the Alpine provinces of Bavaria and Austria the corresponding +districts of Switzerland, Italy, and France, has produced effects hardly +less disastrous, [Footnote: As an instance of the scarcity of fuel in +some parts of the territory of Bavaria, where, not long since, wood +abounded, I may mention the fact that the water of salt-springs is, in +some instances, conveyed to the distance of sixty miles, in iron pipes, +to reach a supply of fuel for boiling it down. + +In France, the juice of the sugar-beet is sometimes carried three or +four miles in pipes for the same reason. + +Many of my readers may remember that it was not long ago proposed to +manufacture the gas for the supply of London at the mouths of the coal- +mines, and convey it to the city in pipes, thus saving the +transportation of the coal; but as the coke and mineral tar would still +have remained to be disposed of, the operation would probably not have +proved advantageous. + +Great economy in the production of petroleum has resulted from the +application of cast-iron tubes to the wells instead of barrels; the oil +is thus carried over the various inequalities of surface for three or +four miles to the tanks on the railroads, and forced into them by +steam-engines. The price of transport is thus reduced one-fifth.] yet, +as a whole, the German States, as Siemoni well observes, must be +considered as in this respect the model countries of Europe. Not only is +the forest area in general maintained without diminution, but new woods +are planted where they are specially needed, [Footnote: The Austrian +Government is making energetic efforts for the propagation of forests on +the desolate waste of the Karst. The difficulties from drought and from +the violence of the winds, which might prove fatal to young and even to +somewhat advanced plantations, are very serious, but in 1866 upwards of +400,000 trees had been planted and great quantities of seeds sown. Thus +far, the results of this important experiment are said to be +encouraging. See the Chronique Forestiere in the Revue des Eaux et +Forets, Feb. 1870.] and, though the slow growth of forest-trees in those +climates reduces the direct pecuniary returns of woodlands to a minimum, +the governments wisely persevere in encouraging this industry. The +exportation of sawn lumber from Trieste is large, and in fact the +Turkish and Egyptian markets are in great part supplied from this +source. [Footnote: For information respecting the forests of Germany, as +well as other European countries, see, besides the works already cited, +the very valuable Manuale d'Arts Forestale of Siemoni, 2de edizione, +Firenze, 1872.] + + +Forests of Russia. + +Russia, which we habitually consider as substantially a forest +country--which has in fact a large proportion of woodland--is beginning +to suffer seriously for want of wood. Jourdier observes: "Instead of a +vast territory with immense forests, which we expect to meet, one sees +only scattered groves thinned by the wind or by the axe of the moujik, +grounds cut over and more or less recently cleared for cultivation. +There is probably not a single district in Russia which has not to +deplore the ravages of man or of fire, those two great enemies of +Muscovite sylviculture. This is so true, that clear-sighted men already +foresee a crisis which will become terrible, unless the discovery of +great deposits of some new combustible, as pit-coal or anthracite, shall +diminish its evils." [Footnote: Clave, Etudes sur l'Economie Forestiere, +p. 261. Clave adds (p. 262): "The Russian forests are very unequally +distributed through the territory of this vast empire. In the north they +form immense masses, and cover whole provinces, while in the south they +are so completely wanting that the inhabitants have no other fuel than +straw, dung, rushes, and heath." ... "At Moscow, firewood costs thirty +per cent. more than at Paris, while, at the distance of a few leagues, +it sells for a tenth of that price." + +This state of things is partly due to the want of facilities of +transportation, and some parts of the United States are in a similar +condition. During a severe winter, ten or twelve years ago, the sudden +freezing of the canals and rivers, before a large American town had +received its usual supply of fuel, occasioned an enormous rise in the +price of wood and coal, and the poor suffered severely for want of it. +Within a few hours of the city were large forests and an abundant stock +of firewood felled and prepared for burning. + +This might easily have been carried to town by the railroads which +passed through the woods; but the managers of the roads refused to +receive it as freight, because a rival market for wood might raise the +price of the fuel they employed for their locomotives. Truly, our +railways "want a master." + +Hohenstein, who was long professionally employed as a forester in +Russia, describes the consequences of the general war upon the woods in +that country as already most disastrous, and as threatening still more +ruinous evils. The river Volga, the life artery of Russian internal +commerce, is drying up from this cause, and the great Muscovite plains +are fast advancing to a desolation like that of Persia.--Der Wald, p. +223. + +The level of the Caspian Sea is eighty-three feet lower than that of the +Sea of Azoff, and the surface of Lake Aral is fast sinking. Von Baer +maintains that the depression of the Caspian was produced by a sudden +subsidence, from ecological causes, and not gradually by excess of +evaporation over supply. See Kaspische Studien, p. 25. But this +subsidence diminished the area and consequently the evaporation of that +sea, and the rivers which once maintained its ancient equilibrium ought +to have raised it to its former level, if their own flow had not been +diminished. It is, indeed, not proved that the laying bare of a wooded +country diminishes the total annual precipitation upon it; but it is +certain that the summer delivery of water from the surface of a +champaign region, like that through which the Volga, its tributaries, +and the feeders of Lake Aral, flow, is lessened by the removal of its +woods. Hence, though as much rain may still fall in the valleys of those +rivers as when their whole surface was covered with forests, more +moisture may be carried off by evaporation, and a less quantity of water +be discharged by the rivers since their basins were cleared, and +therefore the present condition of the inland waters in question may be +due to the removal of the forests in their valleys and the adjacent +plains.] + + +Forests of United States. + +I greatly doubt whether any one of the American States, except, perhaps, +Oregon, has, at this moment, more woodland than it ought permanently to +preserve, though, no doubt, a different distribution of the forests in +all of them might be highly advantageous. It is, perhaps, a misfortune +to the American Union that the State Governments have so generally +disposed of their original domain to private citizens. It is true that +public property is not sufficiently respected in the United States; and +within the memory of almost every man of mature age, timber was of so +little value in the northernmost States that the owners of private +woodlands submitted, almost without complaint, to what would be regarded +elsewhere as very aggravated trespasses upon them. [Footnote: According +to the maxims of English jurisprudence, the common law consists of +general customs so long established that "the memory of man runneth not +to the contrary." In other words, long custom makes law. In new +countries, the change of circumstances creates new customs, and, in +time, new law, without the aid of legislation. Had the American +colonists observed a more sparing economy in the treatment of their +woods, a new code of customary forest-law would have sprung up and +acquired the force of a statute. Popular habit was fast elaborating the +fundamental principles of such a code, when the rapid increase in the +value of timber, in consequence of the reckless devastation of the +woodlands, made it the interest of the proprietors to interfere with +this incipient system of forest jurisprudence, and appeal to the rules +of English law for the protection of their woods. The courts have +sustained these appeals, and forest property is now legally as +inviolable as any other, though common opinion still combats the course +of judicial decision on such questions.] Persons in want of timber +helped themselves to it wherever they could find it, and a claim for +damages, for so insignificant a wrong as cutting down and carrying off a +few pine or oak trees, was regarded as a mean-spirited act in a +proprietor. The habits formed at this period are not altogether +obsolete, and even now the notion of a common right of property in the +woods still lingers, if not as an opinion at least as a sentiment. Under +such circumstances it has been difficult to protect the forest, whether +it belong to the State or to individuals. Property of this kind is +subject to plunder, as well as to frequent damage by fire. The +destruction from these causes would, indeed, considerably lessen, but +would by no means wholly annihilate the climatic and geographical +influences of the forest, or ruinously diminish its value as a regular +source of supply of fuel and timber. + +It is evidently a matter of the utmost importance that the public, and +especially land-owners, be roused to a sense of the dangers to which the +indiscriminate clearing of the woods may expose not only future +generations, but the very soil itself. Some of the American States, as +well as the Governments of many European colonies, still retain the +ownership of great tracts of primitive woodland. The State of New York, +for example, has, in its north-eastern counties, a vast extent of +territory in which the lumberman has only here and there established his +camp, and where the forest, though interspersed with permanent +settlements, robbed of some of its finest pine groves, and often ravaged +by devastating fires, still covers far the largest proportion of the +surface. Through this territory the soil is generally poor, and even the +new clearings have little of the luxuriance of harvest which +distinguishes them elsewhere. The value of the land for agricultural +uses is therefore very small, and few purchases are made for any other +purpose than to strip the soil of its timber. It has been often proposed +that the State should declare the remaining forest the inalienable +property of the commonwealth, but I believe the motive of the suggestion +has originated rather in poetical than in economical views of the +subject. Both these classes of considerations have a real worth. It is +desirable that some large and easily accessible region of American soil +should remain, as far as possible, in its primitive condition, at once a +museum for the instruction of the student, a garden for the recreation +of the lover of nature, and an asylum where indigenous tree, and humble +plant that loves the shade, and fish and fowl and four-footed beast, may +dwell and perpetuate their kind, in the enjoyment of such imperfect +protection as the laws of a people jealous of restraint can afford them. +The immediate loss to the public treasury from the adoption of this +policy would be inconsiderable, for these lands are sold at low rates. +The forest alone, economically managed, would, without injury, and even +with benefit to its permanence and growth, soon yield a regular income +larger than the present value of the fee. + +The collateral advantages of the preservation of these forests would be +far greater. Nature threw up those mountains and clothed them with lofty +woods, that they might serve as a reservoir to supply with perennial +waters the thousand rivers and rills that are fed by the rains and snows +of the Adirondacks, and as a screen for the fertile plains of the +central counties against the chilling blasts of the north wind, which +meet no other barrier in their sweep from the Arctic pole. The climate +of Northern New York even now presents greater extremes of temperature +than that of Southern France. The long-continued cold of winter is more +intense, the short heats of summer even fiercer than in Provence, and +hence the preservation of every influence that tends to maintain an +equilibrium of temperature and humidity is of cardinal importance. The +felling of the Adirondack woods would ultimately involve for Northern +and Central New York consequences similar to those which have resulted +from the laying bare of the southern and western declivities of the +French Alps and the spurs, ridges, and detached peaks in front of them. + +It is true that the evils to be apprehended from the clearing of the +mountains of New York may be less in degree than those which a similar +cause has produced in Southern France, where the intensity of its action +has been increased by the inclination of the mountain declivities, and +by the peculiar geological constitution of the earth. The degradation of +the soil is, perhaps, not equally promoted by a combination of the same +circumstances, in any of the American Atlantic States, but still they +have rapid slopes and loose and friable soils enough to render +widespread desolation certain, if the further destruction of the woods +is not soon arrested. The effects of clearing are already perceptible in +the comparatively unviolated region of which I am speaking. The rivers +which rise in it flow with diminished currents in dry seasons, and with +augmented volumes of water after heavy rains. They bring down larger +quantities of sediment, and the increasing obstructions to the +navigation of the Hudson, which are extending themselves down the +channel in proportion as the fields are encroaching upon the forest, +give good grounds for the fear of irreparable injury to the commerce of +the important towns on the upper waters of that river, unless measures +are taken to prevent the expansion of "improvements" which have already +been carried beyond the demands of a wise economy. + +In the Eastern United States the general character of the climate, soil, +and surface is such, that for the formation of very destructive torrents +a much longer time is required than would be necessary in the +mountainous provinces of Italy or of France. But the work of desolation +has begun even there, and wherever a rapid mountain-slope has been +stripped of wood, incipient ravines already plough the surface, and +collect the precipitation in channels which threaten serious mischief in +the future. There is a peculiar action of this sort on the sandy surface +of pine-forests and in other soils that unite readily with water, which +has excited the attention of geographers and geologists. Soils of the +first kind are found in all the Eastern States; those of the second are +more frequent in the exhausted counties of Maryland, where tobacco is +cultivated, and in the more southern territories of Georgia and Alabama. +In these localities the ravines which appear after the cutting of the +forest, through some accidental disturbance of the surface, or, in some +formations, through the cracking of the soil in consequence of great +drought or heat, enlarge and extend themselves with fearful rapidity. + +In Georgia and in Alabama, Lyell saw "the beginning of the formation of +hundreds of valleys in places where the primitive forest had been +recently cut down." One of these, in Georgia, in a soil composed of clay +and sand produced by the decomposition in situ of hornblendic gneiss +with layers and veins of quartz, "and which did not exist before the +felling of the forest twenty years previous," he describes as more than +55 feet in depth, 300 yards in length, and from 20 to 180 feet in +breadth. Our author refers to other cases in the same States, "where the +cutting down of the trees, which had prevented the rain from collecting +into torrents and running off in sudden land-floods, has given rise to +ravines from 70 to 80 feet deep." [Footnote: Lyell, Principles of +Geology, 10th ed., vol i., 345-6.] Similar results often follow in the +North-eastern States from cutting the timber on the "pine plains," where +the soil is usually of a sandy composition and loose texture. + + +American Forest-Trees. + +The remaining forests of the Northern States and of Canada no longer +boast the mighty pines which almost rivalled the gigantic sequoia and +redwood of California; and the growth of the larger forest-trees is so +slow, after they have attained to a certain size, that if every pine and +oak were spared for two centuries, the largest now standing would not +reach the stature of hundreds recorded to have been cut within two or +three generations. [Footnote: The growth of the white pine, on good soil +and in open ground, is rather rapid until it reaches the diameter of a +couple of feet, after which it is much slower. The favorite habitat of +this tree is light, sandy earth. On this soil, and in a dense wood, it +requires a century to attain the diameter of a yard. Emerson (Trees of +Massachusetts, p. 65), says that a pine of this species, near Paris, +"thirty years planted, is eighty feet high, with a diameter of three +feet." He also states that ten white pines planted at Cambridge, +Massachusetts in 1809 or 1810, exhibited, in the winter of 1841 and +1842, an average of twenty inches diameter at the ground, the two +largest measuring, at the height of three feet, four feet eight inches +in circumference; and he mentions another pine growing in a rocky swamp, +which at the age of thirty-two years, "gave seven feet in circumference +at the but, with a height of sixty-two feet six inches." This latter I +suppose to be a seedling, the others TRANSPLANTED trees, which might +have been some years old when placed where they finally grew. + +The following case came under my own observation: In 1824 a pine-tree, +so small that a young lady, with the help of a lad, took it up from the +ground and carried it a quarter of a mile, was planted near a house in a +town in Vermont. It was occasionally watered, but received no other +special treatment. I measured this tree in 1860, and found it, at four +feet from the ground, and entirely above the spread of the roots, two +feet and four inches in diameter. A new measurement in 1871 gave a +diameter of two feet eight inches, being an increase of four inches in +eleven years, a slower rate than that of preceding years. It could not +have been more than three inches through when transplanted, and up to +1860 must have increased its diameter at the rate of about seven-tenths +of an inch per year, almost double its later growth. In 1871 the crown +had a diameter of 63 feet. + +In the same neighborhood, elms transplanted in 1803, when they were not +above three or four inches through, had attained, in 1871, a diameter of +from four feet to four feet two inches, with a spread of crown of from +90 to 112 feet. Sugar-maples, transplanted in 1822, at about the same +size, measured two feet three inches through. This growth undoubtedly +considerably exceeds that of trees of the same species in the natural +forest, though the transplanted trees had received no other fertilizing +application than an unlimited supply of light and air.] Dr. Williams, +who wrote about sixty years ago, states the following as the dimensions +of "such trees as are esteemed large ones of their kind in that part of +America" [Vermont], qualifying his account with the remark that his +measurements "do not denote the greatest which nature has produced of +their particular species, but the greatest which are to be found in most +of our towns." + + Diameter. Height. +Pine.......... 6 feet, 247 feet. +Maple......... 5 " 9 inches \ +Buttonwood.... 5 " 6 " | +Elm........... 5 " | +Hemlock....... 4 " 9 " | +Oak........... 4 " > From 100 to 200 feet. +Basswood...... 4 " | +Ash........... 4 " | +Birch......... 4 " / + +He adds a note saying that a white pine was cut in Dunstable, New +Hampshire, in the year 1736, the diameter of which was seven feet and +eight inches. Dr. Dwight says that a fallen pine in Connecticut was +found to measure two hundred and forty-seven feet in height, and adds: +"A few years since, such trees were in great numbers along the northern +parts of Connecticut River." In another letter, he speaks of the white +pine as "frequently six feet in diameter, and two hundred and fifty feet +in height," and states that a pine had been cut in Lancaster, New +Hampshire, which measured two hundred and sixty-four feet, Emerson wrote +in 1846: "Fifty years ago, several trees growing on rather dry land in +Blandford, Massachusetts, measured, after they were felled, two hundred +and twenty-three feet." All these trees are surpassed by a pine felled +at Hanover, New Hampshire, about a hundred years ago, and described as +measuring two hundred and seventy-four feet. [Footnote: Williams, +History of Vermont, ii., p. 53. Dwight s Travels, iv., p. 21, and iii, +p. 36. Emerson, Trees of Massachusetts, p. 61. Parish, Life of +President Wheelock, p. 56.] These descriptions, it will be noticed, +apply to trees cut from seventy to one hundred and forty years since. + +Persons, whom observation has rendered familiar with the present +character of the American forest, will be struck with the smallness of +the diameter which Dr. Williams and Dr. Dwight ascribe to trees of such +extraordinary height. Individuals of the several species mentioned in +Dr. Williams's table are now hardly to be found in the same climate, +exceeding one-half or at most two-thirds of the height which he assigns +to them; but, except in the case of the oak and the pine, the diameter +stated by him would not be thought very extraordinary in trees of far +less height, now standing. Even in the species I have excepted, those +diameters, with half the heights of Dr. Williams, might perhaps be +paralleled at the present time; and many elms, transplanted, at a +diameter of six inches, within the memory of persons still living, +measure four and sometimes even five feet through. For this change in +the growth of forest-trees there are two reasons: the one is, that the +great commercial value of the pine and the oak have caused the +destruction of all the best--that is, the tallest and straightest-- +specimens of both; the other, that the thinning of the woods by the axe +of the lumberman has allowed the access of light and heat and air to +trees of humbler worth and lower stature, which have survived their more +towering brethren. These, consequently, have been able to expand their +crowns and swell their stems to a degree not possible so long as they +were overshadowed and stifled by the lordly oak and pine. While, +therefore, the New England forester must search long before he finds a +pine fit to be the mast Of some great ammiral, beeches and elms and +birches, as sturdy as the mightiest of their progenitors, are still no +rarity. + +[Footnote: The forest-trees of the Northern States do not attain to +extreme longevity in the dense woods. Dr. Williams found that none of +the huge pines, the age of which he ascertained, exceeded three hundred +and fifty or four hundred years, though he quotes a friend who thought +he had noticed trees considerably older. The oak lives longer than the +pine, and the hemlock-spruce is perhaps equally long lived. A tree of +this latter species, cut within my knowledge in a thick wood, counted +four hundred and eighty-six, or, according to another observer, five +hundred annual circles. Great luxuriance of animal and vegetable +production is not commonly accompanied by long duration of the +individual. The oldest men are not found in the crowded city; and in the +tropics, where life is prolific and precocious, it is also short. The +most ancient forest-trees of which we have accounts have not been those +growing in thick woods, but isolated specimens, with no taller neighbor +to intercept the light and heat and air, and no rival to share the +nutriment afforded by the soil. The more rapid growth and greater +dimensions of trees standing near the boundary of the forest, are +matters of familiar observation. "Long experience has shown that trees +growing on the confines of the wood may be cut at sixty years of age as +advantageously as others of the same species, reared in the depth of the +forest, at a hundred and twenty. We have often remarked, in our Alps, +that the trunk of trees upon the border of a grove is most developed or +enlarged upon the outer or open side, where the branches extend +themselves farthest, while the concentric circles of growth are most +uniform in those entirely surrounded by other trees, or standing +entirely alone."--A. and G. Villa, Necessita dei Boschi pp. 17, 18.] + +California fortunately still preserves her magnificent sequoias, which +rise to the height of three hundred feet, and sometimes, as we are +assured, even to three hundred and sixty and four hundred feet, and she +has also pines and cedars of scarcely inferior dimensions. The public +being now convinced of the importance of preserving these colossal +trees, it is very probable that the fear of their total destruction may +prove groundless, and we may still hope that some of them may survive +even till that distant future when the skill of the forester shall have +raised from their seeds a progeny as lofty and as majestic as those +which now exist. [Footnote: California must surrender to Australia the +glory of possessing the tallest trees. According to Dr. Mueller, +Director of the Government Botanic Garden at Melbourne, a Eucalyptus, +near Healesville, measured 480 feet in height. Later accounts speak of +trees of the same species fully 500 feet in height. See Schleiden, Fur +Baum und Wald, p. 21. + +If we may credit late reports, the growth of the eucalyptus is so rapid +in California, that the child is perhaps now born who will see the +tallest sequoia overtopped by this new vegetable emigrant from +Australia.] + + +European and American Trees compared. + +The woods of North America are strikingly distinguished from those of +Europe by the vastly greater variety of species they contain. According +to Clave, there are in "France and in most parts of Europe only about +twenty forest-trees, five or six of which are spike-leaved and resinous, +the remainder broad-leaved." [Footnote: Etudes Forestieres, p. 7.] Our +author, however, doubtless means genera, though he uses the word +especes. Rossmassler enumerates fifty-seven species of forest-trees as +found in Germany, but some of these are mere shrubs, some are fruit and +properly garden trees, and some others are only varieties of familiar +species. The valuable manual of Parade describes about the same number, +including, however, two of American origin--the locust, Robinia +pseudacacia, and the Weymouth or white pine, Pinus Strobus--and the +cedar of Lebanon from Asia, which, or at least a very closely allied +species, is indigenous in Algeria also. We may then safely say that +Europe does not possess above forty or fifty native trees of such +economical value as to be worth the special care of the forester, while +the oak alone numbers more than thirty species in the United +States, [Footnote: For full catalogues of American forest-trees, and +remarks on their geographical distribution, consult papers on the +subject by Dr. J. G. Cooper, in the Report of the Smithsonian +Institution for 1858, and the Report of the United States Patent Office, +Agricultural Division, for 1860.] and some other North American genera +are almost equally diversified. [Footnote: Although Spenser's catalogue +of trees occurs in the first canto of the first book of the "Faery +Queene"--the only canto of that exquisite poem actually read by most +students of English literature--it is not so generally familiar as to +make the quotation of it altogether superfluous: + +VII. + + +Enforst to seeke some covert nigh at hand, +A shadic grove not farr away they spide, +That promist ayde the tempest to withstand; +Whose loftie trees, yclad with sommers pride, +Did spred so broad, that heavens light did hide, +Not perceable with power of any starr: +And all within were pathes and alleies wide, +With footing worne, and leading inward farr; +Faire harbour that them seems; so in they entered ar. + + +VIII. + +And foorth they passe, with pleasure forward led, +Joying to heare the birdes sweete harmony. +Which therein shrouded from the tempest dred, +Seemd in their song to scorne the cruell sky. +Much can they praise the trees so straight and hy, +The sayling pine; the cedar stout and tall; +The vine-propp elm; the poplar never dry; +The builder oake, sole king of forrests all; +The aspine good for staves; the cypresse funerall; + + +IX. + +The laurell, meed of mightie conquerours +And poets sage; the firre that weepeth still; +The willow, worne of forlorn paramours; +The eugh, obedient to the benders will; +The birch for shaftes; the sallow for the mill; +The mirrhe sweete-bleeding in the bitter wound; +The warlike beech; the ash for nothing ill; +The fruitfull olive; and the platane round; +The carver holme; the maple seeldom inward sound. + +Although the number of SPECIES of American forest-trees is much larger +than of European, yet the distinguishable VARIETIES are relatively more +numerous in the Old World, even in the case of trees not generally +receiving special care. This multiplication of varieties is no doubt a +result, though not a foreseen or intended one, of human action; for the +ordinary operations of European forest economy expose young trees to +different conditions from those presented by nature, and new conditions +produce new forms. All European woods, except in the remote North, even +if not technically artificial forests, acquire a more or less artificial +character from the governing hand of man, and the effect of this +interference is seen in the constant deviation of trees from the +original type. The holly, for example, even when growing as absolutely +wild as any tree can ever grow in countries long occupied by man, +produces numerous varieties, and twenty or thirty such, not to mention +intermediate shades, are described and named as recognizably different, +in treatises on the forest-trees of Europe.] + +While the American forest flora has made large contributions to that of +Europe, comparatively few European trees have been naturalized in the +United States, and as a general rule the indigenous trees of Europe do +not succeed well in our climate. The European mountain-ash--which in +beauty, dimensions, and healthfulness of growth is superior to our own +[Footnote: In the Northern Tyrol mountain-ashes fifteen inches in +diameter are not uncommon. The berries are distilled with grain to +flavor the spirit.]--the horse-chestnut, and the abele, or silver +poplar, are valuable additions to the ornamental trees of North America. +The Swiss arve or zirbelkiefer, Pinus cembra, which yields a +well-flavored edible seed and furnishes excellent wood for carving, the +umbrella-pine, [Footnote: The mountain ranges of our extreme West +produce a pine closely resembling the European umbrella-pine.] which +also bears a seed agreeable to the taste, and which, from the color of +its foliage and the beautiful form of its dome-like crown, is among the +most elegant of trees, the white birch of Central Europe, with its +pendulous branches almost rivalling those of the weeping willow in +length, flexibility, and gracefulness of fall, and, especially, the +"cypresse funerall," might be introduced into the United States with +great advantage to the landscape. The European beech and chestnut +furnish timber of far better quality than that of their American +congeners. The fruit of the European chestnut, though inferior to the +American in sweetness and flavor, is larger, and is an important article +of diet among the French and Italian peasantry. The walnut of Europe, +though not equal to some of the American species in beauty of growth or +of wood, or to others in strength and elasticity of fibre, is valuable +for its timber and its oil. [Footnote: The walnut is a more valuable +tree than is generally supposed. It yields one-third of the oil produced +in France, and in this respect occupies an intermediate position between +the olive of the south and the oleaginous seeds of the north. A hectare +(about two and a half acres) will produce nuts to the value of five +hundred francs a year, which cost nothing but the gathering. +Unfortunately, its maturity must be long waited for, and more nut-trees +are felled than planted. The demand for its wood in cabinet-work is the +principal cause of its destruction. See Lavergne, Economie Rurale de la +France, p. 253. + +According to Cosimo Ridolfi (Lezioni Orali, ii., p. 424), France obtains +three times as much oil from the walnut as from the olive, and nearly as +much as from all oleaginous seeds together. He states that the walnut +bears nuts at the age of twenty years, and yields its maximum product at +seventy, and that a hectare of ground, with thirty trees, or twelve to +the acre, is equal to a capital of twenty-five hundred francs. + +The nut of this tree is known in the United States as the "English +walnut." The fruit and the wood much resemble those of the American +black walnut, Juglans nigra, but for cabinet-work the American is the +more beautiful material, especially when the large knots are employed. +The timber or the European species, when straight-grained, and clear, or +free from knots, is, for ordinary purposes, better than that of the +American black walnut, but bears no comparison with the wood of the +hickory, when strength combined with elasticity is required, and its nut +is very inferior in taste to that of the shagbark, as well as to the +butternut, which it somewhat resembles. + +"The chestnut is more valuable still, for it produces on a sterile soil, +which, without it, would yield only ferns and heaths, an abundant +nutriment for man."--Lavergne, Economie Rurale de la France, p. 253. + +I believe the varieties developed by cultivation are less numerous in +the walnut than is the chestnut, which latter tree is often grafted in +Southern Europe. + +The chestnut crop of France was estimated in 1848 at 3,478,000 +hectolitres, or 9,877,520 Winchester bushels, and valued at 13,528,000 +francs, or more than two million and a half dollars. In Tuscany the +annual yield is computed at about 550,000 bushels. + +The Tuscan peasants think the flour of the dried chestnut not less +nutritious than Indian cornmeal, and it sells at the same price, or +about three cents per English pound, in the mountains, and four cents in +the towns.] The maritime pine, which has proved of such immense use in +fixing drifting sands in France, may perhaps be better adapted to this +purpose than any of the pines of the New World, and it is of great +importance for its turpentine, resin, and tar. The epicea, or common +fir, Abies picea, Abies excelsa, Picea excelsa, abundant in the +mountains of France and the contiguous country, is known for its +product, Burgundy pitch, and, as it flourishes in a greater variety of +soil and climate than almost any other spike-leaved tree, it might be +well worth transplantation. [Footnote: This fir is remarkable for its +tendency to cicatrize or heal over its stumps, a property which it +possesses in common with some other firs, the maritime pine, and the +European larch. When these trees grow in thick clumps, their roots are +apt to unite by a species of natural grafting, and if one of them be +felled, although its own proper rootlets die, the stump may continue, +sometimes for a century, to receive nourishment from the radicles of the +surrounding trees, and a dome of wood and bark of considerable thickness +be formed over it. The healing is, however, only apparent, for the +entire stump, except the outside ring of annual growth, soon dies, and +even decays within its covering, without sending out new shoots. See +Monthly Report, Department of Agriculture, for October, 1872.] The cork +oak has been introduced into California and some other parts of the +United States, I believe, and would undoubtedly thrive in the Southern +section of the Union. [Footnote: At the age of twelve or fifteen years, +the cork-tree is stripped of its outer bark for the first time. This +first yield is of inferior quality, and it employed for floats for nets +and buoys, or burnt for lampblack. After this, a new layer of cork, an +inch or an inch and a quarter in thickness, is formed about one in ten +years, and is removed in large sheets without injury to the tree, which +lives a hundred and fifty years or more. According to Clave (p. 252), +the annual product of a forest of cork oaks is calculated at about 660 +kilogrammes, worth 150 frances, to the hectare, which, deducting +expenses, leaves a profit of 100 francs. This is about equal to 250 +pound weight, and eight dollars profit to the acre. The cork oaks of the +national domain in Algeria cover about 500,000 acres, and are let to +individuals at rates which are expected, when the whole is rented, to +yield to the state revenue of about $2,000,000. + +George Sand, in the Histoire de ma Vie, speaks of the cork-forests in +Southern France as among the most profitable of rural possessions, and +states, what I do not remember to have seen noticed elsewhere, that +Russia is the best customer for cork. The large sheets taken from the +trees are slit into thin plates, and used to line the walls of +apartments in that cold climate. On the cultivation and management of +the cork oak, see Des Incendies et de la culture du Chene-liege, in +Revue das Eaux et Forets for February, 1869.] the walnut, the chestnut, +the cork oak, the mulberry, the olive, the orange, the lemon, the fig, +and the multitude of other trees which, by their fruit, or by other +products, yield an annual revenue, nature has provided Southern Europe +with a partial compensation for the loss of the native forest. It is +true that these trees, planted as most of them are at such distances as +to admit of cultivation, or of the growth of grass among them, are but +an inadequate substitute for the thick and shady wood; but they perform +to a certain extent the same offices of absorption and transpiration, +they shade the surface of the ground, they serve to break the force of +the wind, and on many a steep declivity, many a bleak and barren +hillside, the chestnut binds the soil together with its roots, and +prevents tons of earth and gravel from washing down upon the fields and +the gardens. Fruit-trees are not wanting, certainly, north of the Alps. +The apple, the pear, and the prune are important in the economy both of +man and of nature, but they are far less numerous in Switzerland and +Northern France than are the trees I have mentioned in Southern Europe, +both because they are in general less remunerative, and because the +climate, in higher latitudes, does not permit the free introduction of +shade trees into grounds occupied for agricultural purposes. [Footnote: +The walnut, the chestnut, the apple, and the pear are common to the +border between the countries I have mentioned, but the range of the +other trees is bounded by the Alps, and by a well-defined and sharply +drawn line to the west of those mountains. From some peculiarity in the +sky of Europe, cultivated plants will thrive, in Northern Italy, in +Southern France, and even in Switzerland, under a depth of shade where +no crop, not even grass, worth harvesting, would grow in the United +States with an equally high summer temperature. Hence the cultivation of +all these trees is practicable in Europe to a greater extent than would +be supposed reconcilable with the interests of agriculture. Some idea of +the importance of the olive orchards may be formed from the fact that +Sicily alone, an island scarcely exceeding 10,000 square miles in area, +of which one-third at least is absolutely barren, has exported to the +single port of Marseilles more than 2,000,000 pounds weight olive-oil +per year, for the last thirty years. + +According to Cosimo Ridolfi, Lezioni Orali, vol. ii., p. 340, in a +favorable soil and climate the average yield of oil from poorly manured +trees, which compose the great majority, is six English pounds, while +with the best cultivation it rises to twenty-three pounds. The annual +production of olive-oil in the whole of Italy is estimated at upwards of +850,000,000 pounds, and if we allow twelve pounds to the tree, we have +something more than 70,000,000 trees. The real number of trees is, +however, much greater than this estimate, for in Tuscany and many other +parts of Italy the average yield of oil per tree does not exceed two +pounds, and there are many millions of young trees not yet in bearing. +Probably we shall not exaggerate if we estimate the olive trees of Italy +at 100,000,000, and as there are about a hundred trees to the acre, the +quantity of land devoted to the cultivation of the olive may be taken at +a million acres. Although olive-oil is much used in cookery in Italy, +lard is preferred as more nutritious. Much American lard is exported to +South-eastern Italy, and olive-oil is imported in return.] The +multitude of species, intermixed as they are in their spontaneous +growth, gives the American forest landscape a variety of aspect not +often seen in the woods of Europe, and the gorgeous tints, which nature +repeats from the dying dolphin to paint the falling leaf of the American +maples, oaks, and ash trees, clothe the hillsides and fringe the +water-courses with a rainbow splendor of foliage, unsurpassed by the +brightest groupings of the tropical flora. It must be confessed, +however, that both the northern and the southern declivities of the Alps +exhibit a nearer approximation to this rich and multifarious coloring of +autumnal vegetation than most American travellers in Europe are willing +to allow; and, besides, the small deciduous shrubs which often carpet +the forest-glades of these mountains are dyed with a ruddy and orange +glow, which, in the distant landscape, is no mean substitute for the +scarlet and crimson and gold and amber of the transatlantic woodland. +[Footnote: The most gorgeous autumnal coloring I have observed in the +vegetation of Europe has been in the valleys of the Durance and its +tributaries in Dauphiny. I must admit that neither in variety nor in +purity and brilliancy of tint, does this coloring fall much, if at all, +short of that of the New England woods. But there is this difference: in +Dauphiny, it is only in small shrubs that this rich painting is seen, +while in North America the foliage of large trees is dyed in full +splendor. Hence the American woodland has fewer broken lights and more +of what painters call breadth of coloring. Besides this, the arrangement +of the leafage in large globular or conical masses, affords a wider +scale of light and shade, thus aiding now the gradation now the contrast +of tints, and gives the American October landscape a softer and more +harmonious tone than marks the humble shrubbery of the forest hillsides +of Dauphiny. + +Thoreau--who was not, like some very celebrated landscape critics of the +present day, an outside spectator of the action and products of natural +forces, but, in the old religious sense, an OBSERVER of organic nature, +living, more than almost any other descriptive writer, among and with +her children--had a very eloquent paper on the "Autumnal Tints" of the +New England landscape.--See his Excursions, pp. 215 et seqq. + +Few men have personally noticed so many facts in natural history +accessible to unscientific observation as Thoreau, and yet he had never +seen that very common and striking spectacle, the phosphorescence of +decaying wood, until, in the latter years of his life, it caught his +attention in a bivouac in the forests of Maine. He seems to have been +more excited by this phenomenon than by any other described in his +works. It must be a capacious eye that takes in all the visible facts in +the history of the most familiar natural object.--The Maine Woods, p. +184.] + +I admit, though not without reluctance, that the forest-trees of Central +and Southern Europe have a great advantage over our own in the +corresponding latitudes, in density of foliage as well as in depth of +color and persistence of the leaves in deciduous species. An American, +who, after a long absence from the United States, returns in the full +height of summer, is painfully surprised at the thinness and poverty of +the leafage even of the trees which he had habitually regarded as +specially umbrageous, and he must wait for the autumnal frosts before he +can recover his partiality for the glories of his native woods. + +None of our north-eastern evergreens resemble the umbrella pine +sufficiently to be a fair object of comparison with it. A cedar, very +common above the Highlands on the Hudson, and elsewhere, is extremely +like the cypress, straight, slender, with erect, compressed +ramification, and feathered to the ground, but its foliage is neither so +dark nor so dense, the tree does not attain the majestic height of the +cypress, nor has it the lithe flexibility of that tree. [Footnote: The +cold winter, or rather spring, of 1872 proved fatal to many cypresses as +well as olive trees in the Val d'Arno. The cypress, therefore, could be +introduced only into California and our Southern States.] In mere shape, +the Lombardy poplar nearly resembles this latter, but it is almost a +profanation to compare the two, especially when they are agitated by the +wind; for under such circumstances, the one is the most majestic, the +other the most ungraceful, or--if I may apply such an expression to +anything but human affectation of movement--the most awkward of trees. +The poplar trembles before the blast, flutters, struggles wildly, +dishevels its foliage, gropes around with its feeble branches, and +hisses as in impotent passion. The cypress gathers its limbs still more +closely to its stem, bows a gracious salute rather than an humble +obeisance to the tempest, bends to the wind with an elasticity that +assures you of its prompt return to its regal attitude, and sends from +its thick leaflets a murmur like the roar of the far-off ocean. + +The cypress and the umbrella-pine are not merely conventional types of +the Italian landscape. They are essential elements in a field of rural +beauty which can be seen in perfection only in the basin of the +Mediterranean, and they are as characteristic of this class of scenery +as is the date-palm of the oases of the Eastern desert. There is +however, this difference: a single cypress or pine is often enough to +shed beauty over a wide area; the palm is a social tree, and its beauty +is not so much that of the individual as of the group. [Footnote: +European poets, whose knowledge of the date-palm is not founded on +personal observation, often describe its trunk as not only slender, but +particularly STRAIGHT. Nothing can be farther from the truth. When the +Orientals compare the form of a beautiful girl to the stem of the palm, +they do not represent it as rigidly straight, but on the contrary as +made up of graceful curves, which seem less like permanent outlines than +like flowing motion. In a palm grove, the trunks, so far from standing +planted upright like the candles of a chandelier, bend in a vast variety +of curves, now leaning towards, now diverging from, now crossing, each +other, and among a hundred you will hardly see two whose axes are +parallel.] The frequency of the cypress and the pine--combined with the +fact that the other trees of Southern Europe which most interest a +stranger from the north, the orange and the lemon, the cork oak, the +ilex, the myrtle, and the laurel, are evergreens--goes far to explain +the beauty of the winter scenery of Italy. Indeed, it is only in the +winter that a tourist who confines himself to wheel-carriages and high +roads can acquire any notion of the face of the earth, and form any +proper geographical image of that country. At other seasons, not high +walls only, but equally impervious hedges, and now, unhappily, acacias +thickly planted along the railway routes, confine the view so +completely, that the arch of a tunnel, or a night-cap over the +traveller's eyes, is scarcely a more effectual obstacle to the +gratification of his curiosity. [Footnote: Besides this, in a country so +diversified in surface as Italy, with the exception of the champaign +region drained by the Po, every new field of view requires either an +extraordinary coup d'oeil in the spectator, or a long study, in order to +master its relief, its plans, its salient and retreating angles. In +summer, except of course in the bare mountains, the universal greenery +confounds light and shade, distance and foreground; and though the +impression upon a traveller, who journeys for the sake of "sensations," +may be strengthened by the mysterious annihilation of all standards for +the measurement of space, yet the superior intelligibility of the winter +scenery of Italy is more profitable to those who see with a view to +analyze.] + + +The Forest does not furnish Food for Man. + +In a region absolutely covered with trees, human life could not long be +sustained, for want of animal and vegetable food. The depths of the +forest seldom furnish either bulb or fruit suited to the nourishment of +man; and the fowls and beasts on which he feeds are scarcely seen except +upon the margin of the wood, for here only grow the shrubs and grasses, +and here only are found the seeds and insects, which form the sustenance +of the non-carnivorous birds and quadrupeds. [Footnote: Clave, as well as +many earlier writers, supposes that primitive man derived his nutriment +from the spontaneous productions of the wood. "It is to the forests," +says he, "that man was first indebted for the means of subsistence. +Exposed alone, without defence, to the rigor of the seasons, as well as +to the attacks of animals stronger and swifter than himself, he found in +them his first shelter, drew from them his first weapons. In the first +period of humanity, they provided for all his wants: they furnished him +wood for warmth, fruits for food, garments to cover his nakedness, arms +for his defence."--Etudes sur l'Economie Forestiere, p. 13. + +But the history of savage life, as far as it is known to us, presents +man in that condition as inhabiting only the borders of the forest and +the open grounds that skirt the waters and the woods, and as finding +only there the aliments which make up his daily bread. The villages of +the North American Indians were upon the shores of rivers and lakes, and +their weapons and other relics are found only in the narrow open grounds +which they had burned over and cultivated, or in the margin of the woods +around their hamlets. + +Except upon the banks of rivers or of lakes, the woods of the interior +of North America, far from the habitations of man, are almost destitute +of animal life. Dr. Newberry, describing the vast forests of the yellow +pine of the West, Pinus ponderosa, remarks: "In the arid and desert +regions of the interior basin, we made whole days' marches in forests of +yellow pine, of which neither the monotony was broken by other forms of +vegetation, nor its stillness by the flutter of a bird or the hum of an +insect."--Pacific Railroad Report, vol. vi., 1857. Dr. Newberry's Report +on Botany, p. 37. + +Cheadle and Milton's North-west Passage confirms these statements. +Valvasor says, in a paragraph already quoted, "In my many journeys +through this valley, I did never have sight of so much as a single +bird." + +The wild fruit and nut trees, the Canada plum, the cherries, the many +species of walnut, the butternut, the hazel, yield very little, +frequently nothing, so long as they grow in the woods; and it is only +when the trees around them are cut down, or when they grow in pastures, +that they become productive. The berries, too--the strawberry, the +blackberry, the raspberry, the whortleberry, scarcely bear fruit at all +except in cleared ground. + +The rank forests of the tropics are as unproductive of human aliment as +the less luxuriant woods of the temperate zone. In Strain's unfortunate +expedition across the great American isthmus, where the journey lay +principally through thick woods, several of the party died of +starvation, and for many days the survivors were forced to subsist on +the scantiest supplies of unnutritious vegetables perhaps never before +employed for food by man. See the interesting account of that expedition +in Harper's Magazine for March, April, and May, 1855.] + + +First Removal of the Forest. + +When multiplying man had filled the open grounds along the margin of the +rivers, the lakes, and the sea, and sufficiently peopled the natural +meadows and savannas of the interior, where such existed, he could find +room for expansion and further growth only by the removal of a portion +of the forest that hemmed him in. The destruction of the woods, then, +was man's first geographical conquest, his first violation of the +harmonies of inanimate nature. + +Primitive man had little occasion to fell trees for fuel, or for the +construction of dwellings, boats, and the implements of his rude +agriculture and handicrafts. Windfalls would furnish a thin population +with a sufficient supply of such material, and if occasionally a growing +tree was cut, the injury to the forest would be too insignificant to be +at all appreciable. + +The accidental escape and spread of fire or possibly, the combustion of +forests by lightning, must have first suggested the advantages to be +derived from the removal of too abundant and extensive woods, and at the +same time, have pointed out a means by which a large tract of surface +could readily be cleared of much of this natural incumbrance. As soon as +agriculture had commenced at all, it would be observed that the growth +of cultivated plants, as well as of many species of wild vegetation, was +particularly rapid and luxuriant on soils which had been burned over, +and thus a new stimulus would be given to the practice of destroying the +woods by fire, as a means of both extending the open grounds, and making +the acquisition of a yet more productive soil. After a few harvests had +exhausted the first rank fertility of this virgin mould, or when weeds +and briers and the sprouting roots of the trees had begun to choke the +crops of the half-subdued soil, the ground would be abandoned for new +fields won from the forest by the same means, and the deserted plain or +hillock would soon clothe itself anew with shrubs and trees, to be again +subjected to the same destructive process, and again surrendered to the +restorative powers of vegetable nature. [Footnote: In many parts of the +North American States, the first white settlers found extensive tracts +of thin woods, of a very park-like character, called "oak-openings," +from the predominance of different species of that tree upon them. These +were the semi-artificial pasture-grounds of the Indians, brought into +that state, and so kept, by partial clearing, and by the annual burning +of the grass. The object of this operation was to attract the deer to +the fresh herbage which sprang up after the fire. The oaks bore the +annual scorching at least for a certain time; but if it had been +indefinitely continued, they would very probably have been destroyed at +last. The soil would have then been much in the prairie condition, and +would have needed nothing but grazing for a long succession of years to +make the resemblance perfect. That the annual fires alone occasioned the +peculiar character of the oak-openings, is proved by the fact that as +soon as the Indians had left the country, young trees of many species +sprang up and grew luxuriantly upon them. See a very interesting account +of the oak-openings in Dwight s Travels, iv., pp. 58-63. This rude +economy would be continued for generations, and, wasteful as it is, is +still largely pursued in Northern Sweden, Swedish Lapland, and sometimes +even in France and the United States. [Footnote: The practice of burning +over woodland, at once to clear and manure the ground, is called in +Swedieh svedjande, a participial noun from the verb att svedja, to burn +over. Though used in Sweden as a preparation for crops of rye or other +grain, it is employed in Lapland more frequently to secure an abundant +growth of pasturage, which follows in two or three years after the fire; +and it is sometimes resorted to as a mode of driving the Laplanders and +their reindeer from the vicinity of the Swedish backwoodsman's +grass-grounds and hay-stacks, to which they are dangerous neighbors. The +forest, indeed, rapidly recovers itself, but it is a generation or more +before the reindeer-moss grows again. When the forest consists of pine, +tall, the ground, instead of being rendered fertile by this process, +becomes hopelessly barren, and for a long time afterwards produces +nothing but weeds and briers.--Laestadius, Om Uppodlingar i Lappmarken, +p. 15. See also Schubert, Resa i Sverge, ii., p. 375. + +In some parts of France this practice is so general that Clave says: "In +the department of Ardennes it (le sartage) is the basis of agriculture."] + + +Principal Causes of the Destruction of the Forest. + +The needs of agriculture are the most familiar cause of the destruction +of the forest in new countries; for not only does an increasing +population demand additional acres to grow the vegetables which feed it +and its domestic animals, but the slovenly husbandry of the border +settler soon exhausts the luxuriance of his first fields, and compels +him to remove his household gods to a fresher soil. The extent of +cleared ground required for agricultural use depends very much on the +number and kinds of the cattle bred. We have seen, in a former chapter, +that, in the United States, the domestic quadrupeds amount to more than +a hundred millions, or nearly three times the number of the human +population of the Union. In many of the Western States, the swine +subsist more or less on acorns, nuts, and other products of the woods, +and the prairies, or natural meadows of the Mississippi valley, yield a +large amount of food for beast, as well as for man. With these +exceptions, all this vast army of quadrupeds is fed wholly on grass, +grain, pulse, and roots grown on soil reclaimed from the forest by +European settlers. It is true that the flesh of domestic quadrupeds +enters very largely into the aliment of the American people, and greatly +reduces the quantity of vegetable nutriment which they would otherwise +consume, so that a smaller amount of agricultural product is required +for immediate human food, and, of course, a smaller extent of cleared +land is needed for the growth of that product, than if no domestic +animals existed. But the flesh of the horse, the ass, and the mule is +not consumed by man, and the sheep is reared rather for its fleece than +for food. Besides this, the ground required to produce the grass and +grain consumed in rearing and fattening a grazing quadruped, would yield +a far larger amount of nutriment, if devoted to the growing of +breadstuffs, than is furnished by his flesh; and, upon the whole, +whatever advantages may be reaped from the breeding of domestic cattle, +it is plain that the cleared land devoted to their sustenance in the +originally wooded part of the United States, after deducting a quantity +sufficient to produce an amount of aliment equal to their flesh, still +greatly exceeds that cultivated for vegetables, directly consumed by the +people of the same regions; or, to express a nearly equivalent idea in +other words, the meadow and the pasture, taken together, much exceed the +ploughland. [Footnote: The two ideas expressed in the text are not +exactly equivalent, because, though the consumption of animal food +diminishes the amount of vegetable aliment required for human use, yet +the animals themselves consume a great quantity of grain and roots grown +on ground ploughed and cultivated as regularly and as laboriously as any +other. + +The 280,000,000 bushels of oats raised in the United States in 1870, and +fed to the 7,000,000 horses, the potatoes, the turnips, and the maize +employed in fattening the oxen, the sheep, and the swine slaughtered the +same year, occupied an extent of ground which, cultivated by hand-labor +and with Chinese industry and skill, would probably have produced a +quantity of vegetable food equal in alimentary power to the flesh of the +quadrupeds killed for domestic use. Hence, so far as the naked question +of AMOUNT of aliment is concerned, the meadows and the pastures might as +well have remained in the forest condition. It must, however, be borne +in mind that animal labor, if not a necessary, is probably an +economical, force in agricultural occupations, and that without animal +manure many branches of husbandry could hardly be carried on at all. At +the same time, the introduction of machinery into rural industry, and of +artificial, mineral, and fossil manures, is working great revolutions, +and we may find at some future day that the ox is no longer necessary as +a help to the farmer.] + +Governments and military commanders have at different periods +deliberately destroyed forests by fire or the axe, because they afforded +a retreat to robbers, outlaws, or enemies, and this was one of the +hostile measures practised by both Julius Caesar and the Gauls in the +Roman war of conquest against that people. It was also resorted to in +the Mediterranean provinces of France, then much infested by robbers and +deserters, as late as the reign of Napoleon I., and is said to have been +employed by the early American colonists in their exterminating wars +with the native Indians. [Footnote: For many instances of this sort, see +Maury, Les Forets de la Gaule, pp. 3-5, and Becquerel, Des Climats, +etc., pp. 301-303. In 1664 the Swedes made an incursion into Jutland and +felled a considerable extent of forest. After they retired, a survey of +the damage was had, and the report is still extant. The number of trees +cut was found to be 120,000, and as an account was taken of the numbers +of each species of tree, the document is of much interest in the history +of the forest, as showing the relative proportions between the different +trees which at that time composed the wood. See Vaupell, Bogens +Indvandring, p. 35, and Notes, p. 55.] + +In the Middle Ages, as well as in earlier and later centuries, attempts +have been made to protect the woods by law, [Footnote: Stanley, quoting +Selden, De Jure Naturali, lib. vi., and Fabricius, Cod. Psedap., V. T., +i. 874, mentions a noteworthy Hebrew tradition of uncertain date, but +unquestionably very ancient, which is one of the oldest proofs of a +public respect for the woods. + +"A Hebrew tradition attributes to Joshua ten statutes, containing +precise regulations for the protection of the property of every tribe +and of every head of a family against irregular depredations. Small +quadrupeds were allowed to pasture in dense woods, not in thin ones; but +no animal could feed in any forest without the consent of the proprietor +of the soil. Every Hebrew might pick up fallen boughs and twigs, but was +not permitted to cut them. Trees might be pruned for the trimmings, with +the exception of the olive and other fruit-trees, and provided there was +sufficient shade in the place."--Lectures on the History of the Jewish +Church, part i., p. 271. + +Alfred Maury mentions several provisions taken from the laws of the +Indian legislator Manu, on the same subject.--Les Forets de la Gaule, p. +9. + +The very ancient Tables of Heracles contain provisions for the +protection of woods, but whether these referred only to sacred groves, +to public forests, or to leased lands, is not clear.] as necessary for +the breeding of deer, wild boars, and other game, or for the more +reasonable purpose of furnishing a supply of building timber and fuel +for future generations. It was reserved for more advanced ages to +appreciate the geographical importance of the woods, and it is only in +the most recent times, only in a few countries of Europe, that the +general destruction of the forests has been recognized as the most +potent among the many causes of the physical deterioration of the earth. +[Footnote: We must perhaps make an exception in favor of the Emperor +Constantine, who commenced the magnificent series of aqueducts and +cisterns which still supply Constantinople with water, and enacted +strict laws for the protection of the forest of Belgrade, in which rise +the springs that feed the aqueducts. See an article by Mr. H. A. Homes +on the Water-Supply of Constantinople in the Albany Argus of June 6, +1872.] + + +Royal Forests and Game Laws. + +The French authors I have quoted, as well as many other writers of the +same nation, refer to the French Revolution as having given a new +impulse to destructive causes which were already threatening the total +extermination of the woods. [Footnote: Religious intolerance had +produced similar effects in France at an earlier period. "The revocation +of the edict of Nantes and the dragonnades occasioned the sale of the +forests of the unhappy Protestants, who fled to seek in foreign lands +the liberty of conscience which was refused to them in France. The +forests were soon felled by the purchasers, and the soil in part brought +under cultivation."--Becquerel, Des Climats, etc, p. 303.] The general +crusade against the forests, which accompanied that important event, is +to be ascribed, in a considerable degree, to political resentments. The +forest codes of the mediaeval kings, and the local "coutumes" of +feudalism, contained many severe and even inhuman provisions, adopted +rather for the preservation of game than from any enlightened views of +the more important functions of the woods. Ordericus Vitalis informs us +that William the Conqueror destroyed sixty parishes and drove out their +inhabitants, in order that he might turn their lands into a forest, +[Footnote: The American reader must be reminded that, in the language of +the chase and of the English law, a "forest" is not necessarily a wood. +Any large extent of ground, withdrawn from cultivation, reserved for the +pleasures of the chase, and allowed to clothe itself with a spontaneous +growth, serving as what is technically called "cover" for wild animals, +is, in the dialects I have mentioned, a forest. When, therefore, the +Norman kings afforested the grounds referred to in the text, it is not +to be supposed that they planted them with trees, though the protection +afforded to them by the game laws would, if cattle had been kept out, +soon have converted them into real woods.] to be reserved as a +hunting-ground for himself and his posterity, and he punished with death +the killing of a deer, wild boar, or even a hare. His successor, William +Rufus, according to the Histoire des Ducs de Normandie et des Rois +d'Angleterre, p. 67, "was hunting one day in a new forest, which he had +caused to be made out of eighteen parishes that he had destroyed, when, +by mischance, he was killed by an arrow wherewith Tyreus de Rois [Sir +Walter Tyrell] thought to slay a beast, but missed the beast, and slew +the king, who was beyond it. And in this very same forest, his brother +Richard ran so hard against a tree that he died of it. And men commonly +said that these things were because they had so laid waste and taken the +said parishes." + +These barbarous acts, as Bonnemere observes, [Footnote: Histoire des +Paysans, ii., p. 190. The work of Bonnemere is of great value to those +who study the history of mediaeval Europe from a desire to know its real +character, and not in the hope of finding apparent facts to sustain a +false and dangerous theory. Bonnemere is one of the few writers who, +like Michelet, have been honest enough and bold enough to speak the +truth with regard to the relations between the church and the people in +the Middle Ages.] were simply the transfer of the customs of the French +kings, of their vassals, and even of inferior gentlemen, to conquered +England. "The death of a hare," says our author, "was a hanging matter, +the murder of a plover a capital crime. Death was inflicted on those who +spread nets for pigeons; wretches who had drawn a bow upon a stag were +to be tied to the animal alive; and among the seigniors it was a +standing excuse for having killed game on forbidden ground, that they +aimed at a serf." The feudal lords enforced these codes with unrelenting +rigor, and not unfrequently took the law into their own hands. In the +time of Louis IX., according to William of Nangis, "three noble +children, born in Flanders, who were sojourning at the abbey of St. +Nicholas in the Wood, to learn the speech of France, went out into the +forest of the abbey, with their bows and iron-headed arrows, to disport +them in shooting hares, chased the game, which they had started in the +wood of the abbey, into the forest of Enguerrand, lord of Coucy, and +were taken by the sergeants which kept the wood. When the fell and +pitiless Sir Enguerrand knew this, he had the children straightway +hanged without any manner of trial." [Footnote: It is painful to add +that a similar outrage was perpetrated a very few years ago, in one of +the European states, by a prince of a family now dethroned. In this +case, however, the prince killed the trespasser with his own hand, his +sergeants refusing to execute his mandate.] The matter being brought to +the notice of good King Louis, Sir Enguerrand was summoned to appear, +and, finally, after many feudal shifts and dilatory pleas, brought to +trial before Louis himself and a special council. Notwithstanding the +opposition of the other seigniors, who, it is needless to say, spared no +efforts to save a peer, probably not a greater criminal than themselves, +the king was much inclined to inflict the punishment of death on the +proud baron. "If he believed," said he, "that our Lord would be as well +content with hanging as with pardoning, he would hang Sir Enguerrand in +spite of all his barons;" but noble and clerical interests unfortunately +prevailed. The king was persuaded to inflict a milder retribution, and +the murderer was condemned to pay ten thousand livres in coin, and to +"build for the souls of the three children two chapels wherein mass +should be said every day." [Footnote: Guillame De Nangis, as quoted in +the notes to Joinville, Nouvelle Collection des Memoires, etc., par +Michaud et Poujoulat, premiere serie, i., p. 335. Persons acquainted +with the character and influence of the mediaeval clergy will hardly +need to be informed that the ten thousand livres never found their way +to the royal exchequer. It was easy to prove to the simple-minded king +that, as the profits of sin were a monopoly of the church, he ought not +to derive advantage from the commission of a crime by one of his +subjects; and the priests were cunning enough both to secure to +themselves the amount of the fine, and to extort from Louis large +additional grants to carry out the purposes to which they devoted the +money. "And though the king did take the moneys," says the chronicler, +"he put them not into his treasury, but turned them into good works; for +he builded therewith the maison-Dieu of Pontoise, and endowed the same +with rents and lands; also the schools and the dormitory of the friars +preachers of Paris, and the monastery of the Minorite friars."] The hope +of shortening the purgatorial term of the young persons, by the +religious rites to be celebrated in the chapels, was doubtless the +consideration which operated most powerfully on the mind of the king; +and Europe lost a great example for the sake of a mass. + +The desolation and depopulation, resulting from the extension of the +forest and the enforcement of the game laws, induced several of the +French kings to consent to some relaxation of the severity of these +latter. Francis I., however, revived their barbarous provisions, and, +according to Bonnemere, even so good a monarch as Henry IV. re-enacted +them, and "signed the sentence of death upon peasants guilty of having +defended their fields against devastation by wild beasts." "A fine of +twenty livres," he continues, "was imposed on every one shooting at +pigeons, which, at that time, swooped down by thousands upon the +new-sown fields and devoured the seed. But let us count even this a +progress, for we have seen that the murder of a pigeon had been a +capital crime." [Footnote: Histoire des Paysans, ii., p. 200.] + +Not only were the slightest trespasses on the forest domain--the cutting +of an oxgoad, for instance--severely punished, but game animals were +still sacred when they had wandered from their native precincts and were +ravaging the fields of the peasantry. A herd of deer or of wild boars +often consumed or trod down a harvest of grain, the sole hope of the +year for a whole family; and the simple driving out of such animals from +this costly pasturage brought dire vengeance on the head of the rustic, +who had endeavored to save his children's bread from their voracity. "At +all times," says Paul Louis Courier, speaking in the name of the +peasants of Chambord, in the "Simple Discours," "the game has made war +upon us. Paris was blockaded eight hundred years by the deer, and its +environs, now so rich, so fertile, did not yield bread enough to support +the gamekeepers." [Footnote: The following details from Bonnemere will +serve to give a more complete idea of the vexatious and irritating +nature of the game laws of France. The officers of the chase went so far +as to forbid the pulling up of thistles and weeds, or the mowing of any +unenclosed ground before St. John's day (24th June), in order that the +nests of game birds might not be disturbed. It was unlawful to fence-in +any grounds in the plains where royal residences were situated; thorns +were ordered to be planted in all fields of wheat, barley, or oats, to +prevent the use of ground-nets for catching the birds which consumed, or +were believed to consume, the grain, and it was forbidden to cut or pull +stubble before the first of October, lest the partridge and the quail +might be deprived of their cover. For destroying the eggs of the quail, +a fine of one hundred livres was imposed for the first offence, double +that amount for the second, and for the third the culprit was flogged +and banished for five years to a distance of six leagues from the +forest.--Histoire des Paysans, ii., p. 202, text and notes. + +Neither these severe penalties, nor any provisions devised by the +ingenuity of modern legislation, have been able effectually to repress +poaching. "The game laws," says Clave, "have not delivered us from the +poachers, who kill twenty times as much game as the sportsmen. In the +forest of Fontainebleau, as in all those belonging to the state, +poaching is a very common and a very profitable offence. It is in vain +that the gamekeepers are on the alert night and day, they cannot prevent +it. Those who follow the trade begin by carefully studying the habits of +the game. They will lie motionless on the ground, by the roadside or in +thickets, for whole days, watching the paths most frequented by the +animals," etc.--Revue des Deux Mondes, Mai, 1863, p. 160. + +The writer adds many details on this subject, and it appears that, as +there are "beggars on horseback" in South America, there are poachers in +carriages in France.] The Tiers Etat declared, in 1789, "the most +terrible scourge of agriculture is the abundance of wild game, a +consequence of the privileges of the chase; the fields are wasted, the +forests ruined, and the vines gnawed down to the roots." + + +Effects of the French Revolution. + +The abrogation of the game laws and of the harsh provisions of the +forestal code was one of the earliest measures of the revolutionary +government; and the removal of the ancient restrictions on the chase and +of the severe penalties imposed on trespassers upon the public forests, +was immediately followed by unbridled license in the enjoyment of the +newly conceded rights. + +In the popular mind the forest was associated with all the abuses of +feudalism, and the evils the peasantry had suffered from the legislation +which protected both it and the game it sheltered, blinded them to the +still greater physical mischiefs which its destruction was to entail +upon them. No longer under the safeguard of the law, the crown forests +and those of the great lords were attacked with relentless fury, +unscrupulously plundered and wantonly laid waste, and even the rights of +property in small private woods ceased to be respected. [Footnote: +"Whole trees were sacrificed for the most insignificant purposes; the +peasants would cut down two firs to make a single pair of wooden +shoes."--Michelet, as quoted by Clave. Etudes, p. 24. + +A similar wastefulness formerly prevailed in Russia, though not from the +same cause. In St. Pierre's time, the planks brought to St. Petersburg +were not sawn, but hewn with the axe, and a tree furnished but a single +plank.] Various absurd theories, some of which are not even yet +exploded, were propagated with regard to the economical advantages of +converting the forest into pasture and plough-land, the injurious +effects of the woods upon climate, health, facility of internal +communication, and the like. Thus resentful memory of the wrongs +associated with the forest, popular ignorance, and the cupidity of +speculators cunning enough to turn these circumstances to profitable +account, combined to hasten the sacrifice of the remaining woods, and a +waste was produced which hundreds of years and millions of treasure will +hardly repair. + +In the era of savage anarchy which followed the beneficent reforms of +1789, economical science was neglected, and statistical details upon the +amount of the destruction of woods during that period are wanting. But +it is known to have been almost incalculably rapid, and the climatic and +financial evils, which elsewhere have been a more gradual effect of this +cause, began to make themselves felt in France within three or four +years after that memorable epoch. [Footnote: See Becquerel, Memoire sur +les Forets, in the Mem. de l'Academie des Sciences, c. XXXV., p. 411 et +seqq. + +Similar circumstances produced a like result, though on a far smaller +scale, in Italy, at a very recent period. Gallenga says: "The +destruction of the majestic timber [between the Vals Sesia and Sessera] +dates no farther back than 1848, when, on the first proclamation of the +Constitution, the ignorant boor had taken it for granted that all the +old social ties would be loosened, and therefore the old forest-laws +should be at once set at naught."--Country Life in Piedmont, p. 136.] + + +Increased Demand for Lumber. + +With increasing population and the development of new industries, come +new drains upon the forest from the many arts for which wood is the +material. The demands of the near and the distant market for this +product excite the cupidity of the hardy forester, and a few years of +that wild industry of which Springer's "Forest Life and Forest Trees" so +vividly depicts the dangers and the triumphs, suffice to rob the most +inaccessible glens of their fairest ornaments. The value of timber +increases with its dimensions in almost geometrical proportion, and the +tallest, most vigorous, and most symmetrical trees fall the first +sacrifice. This is a fortunate circuinritiinco for the remainder of the +wood; for the impatient lumberman contents himself with felling a few of +the best trees, and then hurries on to take his tithe of still virgin +groves. + +The vast extension of railroads, of manufactures and the mechanical +arts, of military armaments, and especially of the commercial fleets and +navies of Christendom, within the present century, has incredibly +augmented the demand for wood, [Footnote: Let us take the supply of +timber for railroad-ties. According to Clave (p. 248), France had, in +1862, 9,000 kilometres of railway in operation, 7,000 in construction, +half of which is built with a double track. Adding turn-outs and extra +tracks at stations, the number of ties required for a single track is +stated at 1,200 to the kilometre, or, as Clave computes, for the entire +network of France, 58,000,000. This number is too large, for 16,000 + +8,000 for the double track halfway = 24,000, and 24,000 x 1,200 = +28,800,000. In an article in the Revue des Deux Mondes, July, 1863, +Gandy states that 2,000,000 trees had been felled to furnish the ties +for the French railroads, and as the ties must be occasionally renewed, +and new railways have been constructed since 1863, we may probably +double this number. + +The United States had in operation on the first of January, 1872, 61,000 +miles, or about 97,000 kilometres, of railroad. Allowing the same +proportion as in France, the American railroads required 116,400,000 +ties. The Report of the Agricultural Department of the United States for +November and December, 1869, estimates the number of ties annually +required for our railways at 30,000,000, and supposes that 150,000 acres +of the best woodland must be felled to supply this number. This is +evidently an error, perhaps a misprint for 15,000. The same authority +calculates the annual expenditure of the American railroads for lumber +for buildings, repairs, and cars, at $38,000,000, and for locomotive +fuel, at the rate of 10,000 cords of wood per day, at $50,000,000. + +The walnut trees cut in Italy and France to furnish gunstocks to the +American army, during our late civil war, would alone have formed a +considerable forest. A single establishment in Northern Italy used +twenty-eight thousand large walnut trees for that purpose in the years +1862 and 1863. + +The consumption of wood for lucifer matches is enormous, and I have +heard of several instances where tracts of pine forest, hundreds and +even thousands of acres in extent, have been purchased and felled, +solely to supply timber for this purpose. The United States government +tax, at one cent per hundred, produces $2,000,000 per year, which shows +a manufacture of 20,000,000,000 matches. Allowing nothing for waste, +there are about fifty matches to the cubic inch of wood, or 86,400 to +the cubic foot, making in all upwards of 230,000 cubic feet, and, as +only straight-grained wood, free from knots, can be used for this +purpose, the sacrifice of not less than three or four thousand +well-grown pines is required for this purpose. + +If we add to all this the supply of wood for telegraph-posts, wooden +pavements, wooden wall tapestry-paper, shoe-pegs, and even wooden nails, +which have lately come into use--not to speak of numerous other recent +applications of this material which American ingenuity has devised--we +have an amount of consumption, for entirely new purposes, which is +really appalling. + +Wooden field and garden fences are very generally used in America, and +some have estimated the consumption of wood for this purpose as not less +than that for architectural uses. + +Fully one-half our vast population is lodged in wooden houses, and barns +and country out-houses of all descriptions are almost universally of the +same material. + +The consumption of wood in the United States as fuel for domestic +purposes, for charcoal, for brick and lime kilns, for breweries and +distilleries, for steamboats, and many other uses, defies computation, +and is vastly greater than is employed in Europe for the same ends. For +instance, in rural Switzerland, cold as is the winter climate, the whole +supply of wood for domestic fires, dairies, breweries, distilleries, +brick and lime kilns, fences, furniture, tools, and even house-building +and small smitheries, exclusive of the small quantity derived from the +trimmings of fruit-trees, grape-vines, and hedges, and from decayed +fences and buildings, does not exceed TWO HUNDRED AND THIRTY CUBIC FEET, +or less than two cords a year, per household.--See Bericht uber die +Untersuchung der Schweiz Hochgebirgswaldungen, pp. 85-89. In 1789, +Arthur Young estimated the annual consumption of firewood by single +families in France at from two and a half to ten Paris cords of 134 +cubic feet.--Travels, vol. ii., chap. xv. + +The report of the Commissioners on the Forests of Wisconsin, 1867, +allows three cords of wood to each person for household fires alone. +Taking families at an average of five persons, we have eight times the +amount consumed by an equal number of persons in Switzerland for this +and all other purposes to which this material in ordinarily applicable. +I do not think the consumption in the North-eastern States is at all +less than the calculation for Wisconsin. Evergreen trees are often +destroyed in immense numbers in the United States for the purpose of +decoration of churches and on other festive occasions. The New York city +papers reported that 113,000 young evergreen trees, besides 20,000 yards +of small branches twirled into festoons, were sold in the markets of +that city, for this use, at Christmas, in 1869. At the Cincinnati +Industrial Exhibition of 1873, three miles of evergreen festoons were +hung upon the beams and rafters of the "Floral Hall." + +Important statistics on the consumption and supply of wood in the United +States will be found in a valuable paper by the Rev. Frederick Starr, +Jr., in the Transactions of the Agricultural Society for--. + +Of course, there is a vast consumption of ligneous material for all +these uses in Europe, but it is greatly less than at earlier periods. +The waste of wood in European carpentry was formerly enormous, the beams +of houses being both larger and more numerous than permanence or +stability required. In examining the construction of the houses occupied +by the eighty families which inhabit the village of Faucigny, in Savoy, +in 1854, the forest inspector found that FIFTY THOUSAND trees had been +employed in building them. The builders "seemed," says Hudry-Menos, "to +have tried to solve the problem of piling upon the walls the largest +quantity of timber possible without crushing them."--Revue des Deux +Mondes, 1st June, 1864, p. 601. + +European statistics present comparatively few facts on this subject, of +special interest to American readers, but it is worth noting that France +employs 1,500,000 cubic feet of oak per year for brandy and wine casks, +which is about half her annual consumption of that material; and it is +not a wholly insignificant fact that, according to Rentzach, the +quantity of wood used in parts of Germany for small carvings and for +children's toys is so largs, that the export of such objects from the +town of Sonneberg alone, amounted, in 1853, to 60,000 centner, or three +thousand tons' weight.--Der Wald, p. 68. + +In an article in the Revue des Eaux et Forets for November, 1868, it is +stated that 200,000 dozens of drums for boys aro manufactured per month +in Paris. This is equivalent to 28,800,000 per year, for which +56,000,000 drumsticks are required, and the writer supposes that the +annual growth of 50,000 acres of woodland would not more than supply the +material. In the same article the consumption of matches in France is +given at 7,200,000,000, and the quantity of lumber annually required for +this manufacture is computed at 80,000 steres, or cubic +metres--evidently an erroneous calculation.] and but for improvements in +metallurgy and the working of iron, which have facilitated the +substitution of that metal for wood, the last twenty-five years would +have almost stripped Europe of her last remaining tree fit for these +uses. [Footnote: Besides the substitution of iron for wood, a great +saving of consumption of this latter material has been effected by the +revival of ancient methods of increasing its durability, and the +invention of new processes for the same purpose. The most effectual +preservative yet discovered for wood employed on land, is sulphate of +copper, a solution of which is introduced into the pores of the wood +while green, by soaking, by forcing-pumps, or, most economically, by the +simple pressure of a column of the fluid in a small pipe connected with +the end of the piece of timber subjected to the treatment. Clave (Etudes +Forestieres, pp. 240-249) gives an interesting account of the various +processes employed for rendering wood imperishable, and states that +railroad-ties injected with sulphate of copper in 1846, were found +absolutely unaltered in 1855; and telegraphic posts prepared two years +earlier, are now in a state of perfect preservation. + +For many purposes, the method of injection is too expensive, and some +simpler process is much to be desired. The question of the proper time +of felling timber is not settled, and the best modes of air, water, and +steam seasoning are not yet fully ascertained. Experiments on these +subjects would be well worth the patronage of Governments in new +countries, where they can be very easily made, without the necessity of +much waste of valuable material, and without expensive arrangements for +observation. + +The practice of stripping living trees of their bark some years before +they are felled, is as old as the time of Vitruvius, but is much less +followed than it deserves, partly because the timber of trees so treated +inclines to crack and split, and partly because it becomes so hard as to +be wrought with considerable difficulty. + +In America, economy in the consumption of fuel has been much promoted by +the substitution of coal for wood, the general use of stoves both for +wood and coal, and recently by the employment of anthracite in the +furnaces of stationary and locomotive steam-engines. All the objections +to the use of anthracite for this latter purpose appear to have been +overcome, and the improvements in its combustion have been attended with +a great pecuniary saving, and with much advantage to the preservation of +the woods. + +The employment of coal has produced a great reduction in the consumption +of firewood in Paris. In 1815, the supply of firewood for the city +required 1,200,000 steres, or cubic metres; in 1859 it had fallen to +501,805, while, in the meantime, the consumption of coal had risen from +600,000 to 4,320,000 metrical quintals. See Clave, Etudes, p. 212. + +In 1869 Paris consumed 951,157 steres of firewood, 4,902,414 +hectolitres, or more than 13,000,000 bushels, of charcoal, and 6,872,000 +metrical quintals, or more than 7,000,000 tons of mineral +coal.--Annuaire de la Revue des Eaux et Forets for 1872, p. 26. + +The increase in the price of firewood at Paris, within a century, has +been comparatively small, while that of timber and of sawed lumber has +increased enormously.] I have spoken of the foreign demand for American +agricultural products as having occasioned an extension of cultivated +ground, which had led to clearing land not required by the necessities +of home consumption. But the forest itself has become, so to speak, an +article of exportation. England, as we have seen, imported oak and pine +from the Baltic ports more than six hundred years ago. She has since +drawn largely on the forests of Norway, and for many years has received +vast quantities of lumber from her American possessions. + +The unparalleled facilities for internal navigation, afforded by the +numerous rivers of the present and former British colonial possessions +in North America, have proved very fatal to the forests of that +continent. Quebec became many years ago a centre for a lumber trade, +which, in the bulk of its material, and, consequently, in the tonnage +required for its transportation, rivalled the commerce of the greatest +European cities. Immense rafts were collected at Quebec from the great +Lakes, from the Ottawa, and from all the other tributaries which unite +to swell the current of the St. Lawrence and help it to struggle against +its mighty tides. [Footnote: The tide rises at Quebec to the height of +twenty-five feet, and when it is aided by a north-east wind, it flows +with almost irresistible violence. Rafts containing several hundred +thousand cubic feet of timber are often caught by the flood-tide, torn +to pieces, and dispersed for miles along the shores.] Ships, of burden +formerly undreamed of, have been built to convey the timber to the +markets of Europe, and during the summer months the St. Lawrence is +almost as crowded with shipping as the Thames. [Footnote: One of these, +the Baron of Renfrew--so named from one of the titles of the kings of +England--built forty or fifty years ago, measured 5,000 tons. They were +little else than rafts, being almost solid masses of timber designed to +be taken to pieces and sold as lumber on arriving at their port of +destination. + +The lumber trade at Quebec is still very large. According to an article +in the Revue des Deux Mondes, that city exported, in 1860, 30,000,000 +cubic feet of squared timber, and 400,000,000 square feet of "planches." +The thickness of the boards is not stated, but I believe they are +generally cut an inch and a quarter thick for the Quebec trade, and as +they shrink somewhat in drying, we may estimate ten square for one cubic +foot of boards. This gives a total of 70,000,000 cubic feet. The +specific gravity of white pine is .554, and the weight of this quantity +of lumber, very little of which is thoroughly seasoned, would exceed a +million of tons, even supposing it to consist wholly of wood as light as +pine. + +The London Times of Oct. 10, 1871, states the exportation of lumber from +Canada to Europe, in 1870, at 200,000,000 cubic feet, and adds that more +than three times that quantity was sent from the same province to the +United States. A very large proportion of this latter quantity goes to +Burlington, Vermont, whence it is distributed to other parts of the +Union. + +There must, I think, be some error or exaggeration in these figures. +Perhaps instead of cubic feet we should read square feet. Two hundred +millions of cubic feet of timber would require more than half the entire +tonnage of England for its transportation. + +I suppose the quantities in the following estimates, from a carefully +prepared article in the St. Louis Republican, must be understood as +meaning square or superficial feet, board measure, allowing a thickness +of one inch: + +"The lumber trade of Michigan, Wisconsin, and Minnesota, for the year +1869, shows the amount cut as being 2,029,372,255 feet for the State of +Michigan, and 317,400,000 feet for the State of Minnesota, and +964,600,000 feet for the State of Wisconsin. This includes the lake +shore and the whole State of Wisconsin, which heretofore has been +difficult to get a report from. The total amount cut in these States was +3,311,372,255 feet, and that to obtain this quantity there have been +shipped 883,032 acres, or 1,380 square miles of pine have been removed. +It is calculated that 4,000,000 acres of land still remain unstripped in +Michigan, which will yield 15,000,000,000 feet of lumber; while +3,000,000 acres arc still standing in Wisconsin, which will yield +11,250,000,000 feet, and that which remains in Minnesota, taking the +estimate of a few years since of that which was surveyed and unexplored, +after deducting the amount cut the past few years, we find 3,630,000 +acres to be the proper estimate of trees now standing which will yield +32,362,500,000 feet of lumber. This makes a total of 15,630,000 acres of +pine lands, which remain standing in the above States, that will yield +58,612,500,000 feet of lumber, and it is thought that fifteen or twenty +years will be required to cut and send to market the trees now +standing." + +See also Bryant, Forest Trees, chap. iv.] + + +Effects of Forest Fires. + +The operations of the lumberman involve other dangers to the woods +besides the loss of the trees felled by him. The narrow clearings around +his shanties form openings which let in the wind, and thus sometimes +occasion the overthrow of thousands of trees, the fall of which dams up +small streams, and creates bogs by the spreading of the waters, while +the decaying trunks facilitate the multiplication of the insects which +breed in dead wood and are, some of them, injurious to living trees. The +escape and spread of camp-fires, however, is the most devastating of all +the causes of destruction that find their origin in the operations of +the lumberman. The proportion of trees fit for industrial uses is small +in all primitive woods. Only these fall before the forester's axe, but +the fire destroys, almost indiscriminately, every age and every species +of tree. [Footnote: Trees differ in their power of resisting the action +of forest fires. Different woods vary greatly in combustibility, and +even when the bark is scarcely scorched, trees are, partly in +consequence of physiological character, and partly from the greater or +less depth at which their roots habitually lie below the surface, +differently affected by running fires. The white pine, Pinus strobus, as +it is the most valuable, is also perhaps the most delicate tree of the +American forest, while its congener, the Northern pitch-pine, Pinus +rigida, is less injured by fire than any other tree of that country. I +have heard experienced lumbermen maintain that the growth of this pine +was even accelerated by a fire brisk enough to destroy all other trees, +and I have myself seen it still flourishing after a conflagration which +had left not a green leaf but its own in the wood, and actually throwing +out fresh foliage, when the old had been quite burnt off and the bark +almost converted into charcoal. The wood of the pitch-pine is of +comparatively little value for the joiner, but it is useful for very +many purposes. Its rapidity of growth in even poor soils, its hardihood, +and its abundant yield of resinous products, entitle it to much more +consideration, as a plantation tree, than it has hitherto received in +Europe or America.] + +While, then, without fatal injury to the younger growths, the native +forest will bear several "cuttings over" in a generation--for the +increasing value of lumber brings into use, every four or five years, a +quality of timber which had been before rejected as unmarketable--a fire +may render the declivity of a mountain unproductive for a century. +[Footnote: Between sixty and seventy years ago, a steep mountain with +which I am familiar, composed of metamorphic rock, and at that time +covered with a thick coating of soil and a dense primeval forest, was +accidentally burnt over. The fire took place in a very dry season, the +slope of the mountain was too rapid to retain much water, and the +conflagration was of an extraordinarily fierce character, consuming the +wood almost entirely, burning the leaves and combustible portion of the +mould, and in the many places cracking and disintegrating the rock +beneath. The rains of the following autumn carried off much of the +remaining soil, and the mountain-side was nearly bare of wood for two or +three years afterwards. At length a new crop of trees sprang up and grew +vigorously, and the mountain is now thickly covered again. But the depth +of mould and earth is too small to allow the trees to reach maturity. +When they attain to the diameter of about six inches, they uniformly +die, and this they will no doubt continue to do until the decay of +leaves and wood on the surface, and the decomposition of the subjacent +rock, shall have formed, perhaps hundreds of years hence, a stratum of +soil thick enough to support a full-grown forest. Under favorable +conditions, however, as in the case of the fire of Miramichi, a burnt +forest renews itself rapidly and permanently.] + +Aside from the destruction of the trees and the laying bare of the soil, +and consequently the freer admission of sun, rain, and air to the +ground, the fire of itself exerts an important influence on its texture +and condition. It cracks and sometimes even pulverizes the rocks and +stones upon and near the surface; [Footnote: In the burning over of a +hill-forest in the Lower Engadine, in September, 1865, the fire was +intense as to shatter and calcine the rocks on the slope, and their +fragments were precipitated into the valley below.--Ricista Firrestate +del Regna d'Italia, Ottobro, 1865, 1865, p. 474.] it consumes a portion +of the half-decayed vegetable mould which served to hold its mineral +particles together and to retain the water of precipitation, and thus +loosens, pulverizes, and dries the earth; it destroys reptiles, insects, +and worms, with their eggs, and the seeds of trees and of smaller +plants; it supplies, in the ashes which it deposits on the surface, +important elements for the growth of a new forest clothing, as well as +of the usual objects of agricultural industry; and by the changes thus +produced, it fits the ground for the reception of a vegetation different +in character from that which had spontaneously covered it. These new +conditions help to explain the natural succession of forest crops, so +generally observed in all woods cleared by fire and then abandoned. +There is no doubt, however, that other influences contribute to the same +result, because effects more or less analogous follow when the trees are +destroyed by other causes, as by high winds, by the woodman's axe, and +even by natural decay. [Footnote: The remarkable mounds and other +earthworks constructed in the valley of the Ohio and elsewhere in the +territory of the United States, by a people apparently more advanced in +the culture than the modern Indian, were overgrown with a dense clothing +of forest when first discovered by the whites. But though the ground +where they were erected must have been occupied by a large population +for a considerable leagth of time, and therefore entirely cleared, the +trees which grew upon the ancient fortresses and the adjacent lands were +not distinguishable in species, or even in dimensions and character of +growth, from the neighboring forests, where the soil seemed never to +have been disturbed. This apparent exception to the law of change of +crop in natured forest growth was ingeniously explained by General +Harrison's suggestion, that the lapse of time since the era of the +mound-builders was so great as to have embraced several successive +generations of trees, and occasioned, by their rotation, a return to the +original vegetation. + +The succesive changes in the spontaneous growth of the forest, as proved +by the character of the wood found in bogs, are such as to have +suggested the theory of a considerable change of climate during the +human period. But strobus, as it is the most valuable, is also perhaps +the most delicate tree of the American forest, while its congener, the +Northern pitch-pine, Pinus rigida, is less injured by fire than any +other tree of that country. I have heard experienced lumbermen maintain +that the growth of this pine was even accelerated by a fire brisk enough +to destroy all other trees, and I have myself seen it still flourishing +after a conflagration which had left not a green leaf but its own in the +wood, and actually throwing out fresh foliage, when the old had been +quite burnt off and the bark almost converted into charcoal. The wood of +the pitch-pine is of comparatively little value for the joiner, but it +is useful for very many purposes. Its rapidity of growth in even poor +soils, its hardihood, and its abundant yield of resinous products, +entitle it to much more consideration, as a plantation tree, than it has +hitherto received in Europe or America.] without fatal injury to the +younger growths, the native forest will hear several "cuttings over" in +a generation--for the increasing value of lumber brings into use, every +four or five years, a quality of timber which had been before rejected +as unmarketable--a fire may render the declivity of a mountain +unproductive for a century. [Footnote: Between sixty and seventy years +ago, a steep mountain with which I am familiar, composed of metamorphic +rock, and at that time covered with a thick coating of soil and a dense +primeval forest, was accidentally burnt over. The fire took place in a +very dry season, the slope of the mountain was too rapid to retain much +water, and the conflagration was of an extraordinarily fierce character, +consuming the wood almost entirely, burning the leaves and combustible +portion of the mould, and in many places cracking and disintegrating the +rock beneath. The rains of the following autumn carried off much of the +remaining soil, and the mountain-side was nearly bare of wood for two or +three years afterwards. At length a new crop of trees sprang up and grew +vigorously, and the mountain is now thickly covered again. But the depth +of mould and earth is too small to allow the trees to reach maturity. +When they attain to the diameter of about six inches, they uniformly +die, and this they will no doubt continue to do until the decay of +leaves and wood on the surface, and the decomposition of the subjacent +rock, shall have formed, perhaps hundreds of years hence, a stratum of +soil thick enough to support a full-grown forest. Under favorable +conditions, however, as in the case of the fire of Miramichi, a burnt +forest renews itself rapidly and permanently.] + +Aside from the destruction of the trees and the laying bare of the soil, +and consequently the freer admission of sun, rain, and air to the +ground, the fire of itself exerts an important influence on its texture +and condition. It cracks and sometimes even pulverizes the rocks and +stones upon and near the surface; [Footnote: In the burning over of a +hill-forest in the Lower Engadine, in September, 1865, the fire was so +intense as to shatter and calcine the rocks on the slope, and their +fragments were precipitated into the valley below.--Rivista Forestale +del Regno d'Italia, Ottobre, 1865, p. 474.] it consumes a portion of the +half-decayed vegetable mould which served to hold its mineral particles +together and to retain the water of precipitation, and thus loosens, +pulverizes, and dries the earth; it destroys reptiles, insects, and +worms, with their eggs, and the seeds of trees and of smaller plants; it +supplies, in the ashes which it deposits on the surface, important +elements for the growth of a new forest clothing, as well as of the +usual objects of agricultural industry; and by the changes thus +produced, it fits the ground for the reception of a vegetation different +in character from that which had spontaneously covered it. These new +conditions help to explain the natural succession of forest crops, so +generally observed in all woods cleared by fire and then abandoned. +There is no doubt, however, that other influences contribute to the same +result, because effects more or less analogous follow when the trees are +destroyed by other causes, as by high winds, by the woodman's axe, and +even by natural decay. [Footnote: The remarkable mounds and other +earthworks constructed in the valley of the Ohio and elsewhere in the +territory of the United States, by a people apparently more advanced in +culture than the modern Indian, were overgrown with a dense clothing of +forest when first discovered by the whites. But though the ground where +they were erected must have been occupied by a large population for a +considerable length of time, and therefore entirely cleared, the trees +which grew upon the ancient fortresses and the adjacent lands were not +distinguishable in species, or even in dimensions and character of +growth, from the neighboring forests, where the soil seemed never to +have been disturbed. This apparent exception to the law of change of +crop in natural forest growth was ingeniously explained by General +Harrison's suggestion, that the lapse of time since the era of the +mound-builders were so great as to have embraced several successive +generations of trees, and occasioned, by their rotation, a return to the +original vegetation. + +The successive changes in the spontaneous growth of the forest, as +proved by the character of a wood found in bogs, are such as to have +suggested the theory of a considerable change of the climate during the +human period. But this theory cannot be admitted upon the evidence in +question. In fact, the order of succession--for a rotation or +alternation is neither proved nor probable--may be made to move in +opposite directions in different countries with the same climate and at +the same time. Thus in Denmark and in Holland the spike-leaved firs have +given place to the broad-leaved beech, while in Northern Germany the +process has been reversed, and evergreens have supplanted the oaks and +birches of deciduous foliage. The principal determining cause seems to +be the influence of light upon the germination of the seeds and the +growth of the young tree. In a forest of firs, for instance, the +distribution of the light and shade, to the influence of which seeds and +shoots are exposed, is by no means the same as in a wood of beeches or +of oaks, and hence the growth of different species will be stimulated in +the two forests. + +When ground is laid bare both of trees and of vegetable mould, and left +to the action of unaided and unobstructed nature, she first propagates +trees which germinate and grow only under the influence of a full supply +of light and air, and then, in succession, other species, according to +their ability to bear the shade and their demand for more abundant +nutriment. In Northern Europe the large, the white birch, the aspen, +first appear; then follow the maple, the alder, the ash, the fir; then +the oak and the linden; and then the beech. The trees called by these +respective names in the United States are not specifically the same as +their European namesakes, nor are they always even the equivalents of +these latter, and therefore the order of succession in America would not +be precisely as indicated by the foregoing list, but, so far as is +known, it nevertheless very nearly corresponds to it. + +It is thought important to encourage the growth of the beech in Denmark +and Northern Germany, because it upon the whole yields better returns +than other trees, and does not exhaust, but on the contrary enriches, +the soil; for by shedding its leaves it returns to it most of the +nutriment it has drawn from it, and at the same time furnishes a solvent +which aids materially in the decomposition of its mineral constituents. + +When the forest is left to itself, the order of succession is constant, +and its occasional inversion is always explicable by some human +interference. It is curious that the trees which require most light are +content with the poorest soils, and vice versa. The trees which first +appear are also those which propagate themselves farthest to the north. +The birch, the larch, and the fir bear a severer climate than the oak, +the oak than the beech. "These parallelisms," says Vaupell, "are very +interesting, because, though they are entirely independent of each +other," they all prescribe the same order of succession.--Bogens +Indvandring, p. 42. See alo Berg, Das Verdrangen der Laubralder im +Nordlichen Deutschland, 1844. Heyer, Das Verhalten der Waldbaume gegen +Licht und Schatten, 1852. Staring, De Bodem van Nederland, 1856, i., pp. +120-200. Vaupell, De Danske Skove, 1863. Knorr, Studien uber die +Buchen-Wirthschaft, 1863. A. Maury, Les Forets de la Gaule, pp. 73, 74, +377, 384.] + +Another evil, sometimes of serious magnitude, which attends the +operations of the lumberman, is the injury to the banks of rivers from +the practice of floating. I do not here allude to rafts, which, being +under the control of those who navigate them, may be so guided as to +avoid damage to the shore, but to masts, logs, and other pieces of +timber singly entrusted to the streams, to be conveyed by their currents +to sawmill ponds, or to convenient places for collecting them into +rafts. The lumbermen usually haul the timber to the banks of the rivers +in the winter, and when the spring floods swell the streams and break up +the ice, they roll the logs into the water, leaving them to float down +to their destination. If the transporting stream is too small to furnish +a sufficient channel for this rude navigation, it is sometimes dammed +up, and the timber collected in the pond thus formed above the dam. When +the pond is full, a sluice is opened, or the dam is blown up or +otherwise suddenly broken, and the whole mass of lumber above it is +hurried down with the rolling flood. Both of these modes of proceeding +expose the banks of the rivers employed as channels of flotation to +abrasion, [Footnote: Caimi states that "a single flotation in the +Valtelline, in 1830, caused damages appraised at $250,000."--Cenni sulla +Importanza e Coltura dei Boschi, p. 65.] and in some of the American +States it has been found necessary to protect, by special legislation, +the lands through which they flow from the serious injury sometimes +received through the practices I have described. [Footnote: Many +physicists who have investigated the laws of natural hydraulics maintain +that, in consequence of direct obstruction and frictional resistance to +the flow of the water of rivers along their banks, there is both an +increased rapidity of current and an elevation of the water in the +middle of the channel, so that a river presents always a convex surface. +Others have thought that the acknowledged greater swiftness of the +central current must produce a depression in that part of the stream. +The lumbermen affirm that, while rivers are rising, the water is highest +in the middle of the channel, and tends to throw floating objects +shorewards; while they are falling, it is lowest in the middle, and +floating objects incline towards the centre. Logs, they say, rolled into +the water during the rise, are very apt to lodge on the banks, while +those set afloat during the falling of the waters keep in the current, +and are carried without hindrance to their destination, and this law, +which has been a matter of familiar observation among woodmen for +generations, is now admitted as a scientific truth. + +Foresters and lumbermen, like sailors and other persons whose daily +occupations bring them into contact, and often into conflict, with great +natural forces, have many peculiar opinions, not to say superstitious. +In one of these categories we must rank the universal belief of +lumbermen, that with a given head of water, and in a given number of +hours, a sawmill cuts more lumber by night than by day. Having been +personally interested in several sawmills, been assured by them that +their uniform experiences established the fact that, other things being +equal, the action of the machinery of sawmills is more rapid by night +than by day. I am sorry--perhaps I ought to be ashamed--to say that my +skepticism has been too strong to allow me to avail myself of my +ooportunites of testing this question by passing a night, watch in hand, +counting the strokes of a millisaw. More unprejudiced, and, I must add, +very intelligent and credible persons have informed me that they have +done so, and found the report of the sawyers abundantly confirmed. A +land surveyor, who was also an experienced lumberman, sawyer, and +machinist, a good mathematician, and an accurate observer, has +repeatedly told me that he had very often "timed" sawmills, and before +the difference in favor of night-work above thirty per cent. Sed +quaere.] + + +Restoration of the Forest. + +In most countries of Europe--and I fear in many parts of the United +States--the woods are already so nearly extirpated, that the mere +protection of those which now exist is by no means an adequate security +against a great increase of the evils which have already resulted from +the diminution of them. Besides this, experience has shown that where +the destruction of the woods has been carried beyond a certain point, no +coercive legislation can absolutely secure the permanence of the +remainder, especially if it is held by private hands. The creation of +new forests, therefore, is generally recognized, wherever the subject +has received the attention it merits, as an indispensable measure of +sound public economy. Enlightened individuals in some European states, +the Governments in others, have made extensive plantations, and France, +particularly, has now set herself energetically at work to restore the +woods in her southern provinces, and thereby to prevent the utter +depopulation and waste with which that once fertile soil and genial +climate are threatened. + +The objects of the restoration of the forest are as multifarious as the +motives that have led to its destruction, and as the evils which that +destruction has occasioned. It is hoped that the replanting of the +mountain slopes, and of bleak and infertile plains, will diminish the +frequency and violence of river inundations, prevent the formation of +new torrents and check the violence of those already existing, mitigate +the extremes of atmospheric temperature, humidity, and precipitation, +restore dried-up springs, rivulets, and sources of irrigation, shelter +the fields from chilling and from parching winds, arrest the spread of +miasmatic effluvia, and, finally, furnish a self-renewing and +inexhaustible supply of a material indispensable to so many purposes of +domestic comfort, and to the successful exercise of every art of peace, +every destructive energy of war. [Footnote: The preservation of the woods +on the former eastern frontier of France, as a kind of natural abattis, +was recognized by the Government of that country as an important measure +of military defence, though there have been conflicting opinions on the +subject.] + +The Economy of the Forest. + +The legislation of European states upon sylviculture, and the practice +of that art, divide themselves into two great branches--the preservation +of existing forests, and the creation of new. Although there are in +Europe many forests neither planted nor regularly trained by man, yet +from the long operation of causes already set forth, what is understood +in America and other new countries by the "primitive forest," no longer +exists in the territories which were the seats of ancient civilization +and empire, except upon a small scale, and in remote and almost +inaccessible glens quite out of the reach of ordinary observation. The +oldest European woods are indeed native, that is, sprung from self-sown +seed, or from the roots of trees which have been felled for human +purposes; but their growth has been controlled, in a variety of ways, by +man and by domestic animals, and they almost uniformly present more or +less of an artificial character and arrangement. Both they and planted +forests--which, though certainly not few, are of comparatively recent +date in Europe--demand, as well for protection as for promotion of +growth, a treatment different in some respects from that which would be +suited to the character and wants of the virgin wood. + +On this latter branch of the subject, the management of the primitive +wood, experience and observation have not yet collected a sufficient +stock of facts to serve for the construction of a complete system of +this department of sylviculture; but the government of the forest as it +exists in France--the different zones and climates of which country +present many points of analogy with those of the United States and of +some of the British colonies--has been carefully studied, and several +manuals of practice have been prepared for the foresters of that empire. +I believe the Cours Elementaire de Culture des Bois cree a l'Ecole +Forestiere de Nancy, par M. Lorentz, complete et public par A. Parade, +with a supplement under the title of Cours d'Amenagement des Forets, par +Henri Nanquette, has been generally considered the best of these. The +Etudes sur l'Economie Forestiere, par Jules Clave, which I have often +quoted, presents a great number of interesting views on this subject, +but it is not designed as a practical guide, and it does not profess to +be sufficiently specific in its details to serve that purpose. [Footnote: +Among more recent manuals may be mentioned: in French, Les Etudes de +Maitre Pierre, Paris, 1864, 12mo; Bazelaire, Traite de Roboisement, 2d +edition. Paris 1864; Paston, L'Amenagemend des Forets, Paris, 1867; in +English, Gregor, Arboriculture, Edinburgh, 1868: in Italian, Siemoni 's +very valuable Manuale teorico-pratico d'Arte Forestale, 2d ediz., +Firenze, 1872; the excellent work of Cerini, Dei Vantaggi di Societe, +por l'Impianto e Conservazione dei Boschi, Milano, 1844, 8vo; and the +prize essay of Meguscher, Memoria sui Boschi, etc., 2d edizione, Milano, +1859, 8vo. Another very important treatise of the uses of the forest, +though not a manual of sylviculture, is Schleiden, Fur Baum und Wald, +Leipzig, 1870.]Notwithstanding the difference of conditions between the +aboriginal and the trained forest, the judicious observer who aims at +the preservation of the former will reap much instruction from the +treatises I have cited, and I believe he will be convinced that the +sooner a natural wood is brought into the state of an artificially +regulated one, the better it is for all the multiplied interests which +depend on the wise administration of this branch of public economy. + +One consideration bearing on this subject has received less attention +than it merits, because most persons interested in such questions have +not opportunities for the comparison I refer to. I mean the great +general superiority of cultivated timber to that of strictly spontaneous +growth. I say GENERAL superiority, because there are exceptions to the +rule. The white pine, Pinus strobus, for instance, and other trees of +similar character and uses, require, for their perfect growth and best +ligneous texture, a density of forest vegetation around them, which +protects them from too much agitation by wind, and from the persistence +of the lateral branches which fill the wood with knots. A pine which has +grown under those conditions possesses a tall, straight stem, admirably +fitted for masts and spars, and, at the same time, its wood is almost +wholly free from knots, is regular in annular structure, soft and +uniform in texture, and, consequently, superior to almost all other +timber for joinery. If, while a large pine is spared, the broad-leaved +or other smaller trees around it are felled, the swaying of the tree +from the action of the wind mechanically produces separations between +the layers of annual growth, and greatly diminishes the value of the +timber. The same defect is often observed in pines which, from some +accident of growth, have much overtopped their fellows in the virgin +forest. + +The white pine, growing in the fields, or in open glades in the woods, +is totally different from the true forest-tree, both in general aspect +and in quality of wood. Its stem is much shorter, its top less tapering, +its foliage denser and more inclined to gather into tufts, its branches +more numerous and of larger diameter, its wood shows much more +distinctly the divisions of annual growth, is of coarser grain, harder +and more difficult to work into mitre-joints. Intermixed with the most +valuable pines in the American forests, are met many trees of the +character I have just described. The lumbermen call them "saplings," and +generally regard them as different in species from the true white pine, +but botanists are unable to establish a distinction between them, and as +they agree in almost all respects with trees grown in the open grounds +from known white-pine seedlings, I believe their peculiar character is +due to unfavorable circumstances in their early growth. The pine, then, +is an exception to the general rule as to the inferiority of the forest +to the open-ground tree. The pasture oak and pasture beech, on the +contrary, are well known to produce far better timber than those grown +in the woods, and there are few trees to which the remark is not equally +applicable. [Footnote: It is often laid down as a universal law, that the +wood of trees of slow vegetation is superior to that of quick growth. +This is one of those commonplaces by which men love to shield themselves +from the labor of painstaking observation. It has, in fact, so many +exceptions, that it may be doubted in whether it is in any sense true. +Most of the cedars are slow of growth; but while the timber of some of +them is firm and durable, that of others is light, brittle, and +perishable. The hemlock-spruce is slower of growth than the pines, but +its wood is of very little value. The pasture oak and beech show a +breadth of grain--and, of course, an annual increment--twice as great as +trees of the same species grown in the woods; and the American locust, +Robinia pseudacacia, the wood of which is of extreme toughness and +durability, is, of all trees indigenous to North-eastern America, by far +the most rapid in growth. Some of the species of the Australian +Eucalyptus furnish wood of remarkable strength and durability, and yet +the eucalyptus is surpassed by no known tree in rapidity of growth. + +As an illustration of the mutual interdependence of the mechanic arts, I +may mention that in Italy, where stone, brick, and plaster are almost +the only materials used in architecture, and where the "hollow ware" +kitchen implements are of copper or of clay, the ordinary tools for +working wood are of a very inferior description, and the locust timber +is found too hard for their temper. At the same time the work of the +Italian stipettai, or cabinet-makers, and carvers in wood, who take +pains to provide themselves with tools of better metal, is wholly +unsurpassed in finish and in accuracy of adjustment as well as in taste. +When a small quantity of mahogany was brought to England, early in the +last century, the cabinet-makers were unable to use it, from the +defective temper of their tools, until the demand for furniture from the +new wood compelled them to improve the quality of their implements. In +America, the cheapness of wood long made it the preferable material for +almost all purposes to which it could by any possibility be applied. The +mechanical cutlery and artisans' tools of the United States are of +admirable temper, finish, and convenience, and no wood is too hard, or +otherwise too refractory, to be wrought with great facility, both by +hand-tools and by the multitude of ingenious machines which the +Americans have invented for this purpose.] + +Another advantage of the artificially regulated forest is, that it +admits of such grading of the ground as to favor the retention or +discharge of water at will, while the facilities it affords for +selecting and duly proportioning, as well as properly spacing, and in +felling and removing, from time to time, the trees which compose it, are +too obvious to require to be more than hinted at. In conducting these +operations, we must have a diligent eye to the requirements of nature, +and must remember that a wood is not an arbitrary assemblage of trees to +be selected and disposed according to the caprice of its owner. "A +forest," says Clave, "is not, as is often supposed, a simple collection +of trees succeeding each other in long perspective, without bond of +union, and capable of isolation from each other; it is, on the contrary, +a whole, the different parts of which are interdependent upon each +other, and it constitutes, so to speak, a true individuality. Every +forest has a special character, determined by the form of the surface it +grows upon, the kinds of trees that compose it, and the manner in which +they are grouped." The art, or, as the Continental foresters rather +ambitiously call it, the science of sylviculture has been so little +pursued in England and America, that its nomenclature has not been +introduced into the English vocabulary, and it would not be possible to +describe its processes with technical propriety of language, without +occasionally borrowing a word from the forest literature of France and +Germany. A full discussion of the methods of sylviculture would, indeed, +be out of place in a work like the present, but the want of conveniently +accessible means of information on the subject, in the United States, +will justify me in presenting it with somewhat more of detail than would +otherwise be pertinent. + +The two best known methods of treating already existing forests are +those distinguished as the TAILLIS, copse or coppice treatment, +[Footnote: COPSE, or COPPICE, from the French COUPER, to cut, +means properly a wood, the trees of which are cut at certain periods of +immature growth, and allowed to shoot up again from the roots; but it +has come to signify, very commonly, a young wood, grove, or thicket, +without reference to its origin, or to the character of a forest crop.] +and the FUTAIE, for which I find no English equivalent, but which may +not inappropriately be called the FULL-GROWTH system. A TAILLIS, copse, +or coppice, is a wood composed of shoots from the roots of trees +previously cut for fuel and timber. The shoots are thinned out from time +to time, and finally cut, either after a fixed number of years, or after +the young trees have attained to certain dimensions, their roots being +then left to send out a new progeny as before. This is the cheapest +method of management, and therefore the best whenever the price of labor +and of capital bears a high proportion to that of land and of timber; +but it is essentially a wasteful economy. [Footnote: "In America," says +Clave (p. 124, 125), "where there is a vast extent of land almost +without pecuniary value, but where labor is dear and the rate of +interest high, it is profitable to till a large surface at the least +possible cost. EXTENSIVE cultivation is there the most advantageous. In +England, France, and Germany, where every corner of soil is occupied, +and the least bit of ground is sold at a high price, but where labor and +capital are comparatively cheap is wisest to employ INTENSIVE +cultivation. ... All the efforts of the cultivator ought to be directed +to the obtaining of a given result with the least sacrifice, and there +is equally a loss to the commonwealth if the application of improved +agricultural processes be neglected where they are advantageous, or if +they be employed where they are not required. ... In this point of view, +sylviculture must follow the same laws as agriculture, and, like it, be +modified according to the economical conditions of different states. In +countries abounding in good forests, and thinly peopled, elementary and +cheap methods must be pursued; in civilized regions, where a dense +population requires that the soil shall be made to produce all it can +yield, the regular artificial forest, with all the processes that +science teaches, should be cultivated. It would be absurd to apply to +the endless woods of Brazil and of Canada the method of the Spessart by +"double stages," but not less so in our country, where every yard of +ground has a high value, to leave to nature the task of propagating +trees, and to content ourselves with cutting, every twenty or +twenty-five years, the meagre growths that chance may have produced."] +If the woodland is, in the first place, completely cut over as is found +most convenient in practice, the young shoots have neither the shade nor +the protection from wind so important to forest growth, and their +progress is comparatively slow, while at the same time, the thick clumps +they form choke the seedlings that may have sprouted near them. +[Footnote: In ordinary coppices, there are few or no seedlings, because +the young shoots are cut before they are old enough to mature fertile +seed, and this is one of the strongest objections to the system.] The +evergreens, once cut do not shoot up again, [Footnote: It was not long +ago stated, upon the evidence of the Government foresters of Greece, and +of the queen's gardener, that a large wood has been discovered in +Arcadia, consisting of a fir which has the property of sending up both +vertical and lateral shoots from the stump of felled trees and forming a +new crown. It was at first supposed that this forest grew only on the +"mountains," of which the hero of About's most amusing story, Le Roi des +Montagnes, was "king;" but stumps, with the shoots attached, have been +sent to Germany, and recognized by able botanists as true natural +products, and the fact must now be considered as established. Daubeny +refers to Theophrastus as ascribing this faculty of reproduction to the +'Elate [word in greek] or fir, but he does not cite chapter and verse, +and I have not been able to find the passage. The same writer mentions a +case where an entire forest of the common fir in France had been renewed +in this way.--Trees and Shrubs of the Ancients, 1865, pp. 27-28. The +American Northern pitch possesses the same power in a certain degree. + +According to Charles Martins, the cedar of Mount Atlas--which, if not +identical with the cedar of Lebanon, is closely allied to it--possesses +the same power.--Revue des Deux Mondes, July 15, 1864, p. 315.] and the +mixed character of the forest--in many respects an important advantage, +if not an indispensable condition of growth--is lost; [Footnote: Natural +forests are rarely, if ever, composed of trees of a single species, and +experience has shown that oaks and other broad-leaved trees, planted as +artificial woods, require to be mixed, or associated with others of +different habits. + +In the forest of Fontainebleau, "oaks, mingled with beeches in due +proportion," says Clave, "may arrive at the age of five or six hundred +years in full vigor, and attain dimensions which I have never seen +surpassed; when, however, they are wholly unmixed with other trees, they +begin to decay and die at the top, at the age of forty or fifty years, +like men, old before their time, weary of the world, and longing only to +quit it. This has been observed in most of the oak plantations of which +I have spoken, and they have not been able to attain to full growth. +When the vegetation was perceived to languish, they were cut, in the +hope that this operation would restore their vigor, and that the new +shoots would succeed better than the original trees; and, in fact, they +seemed to be recovering for the first few years. But the shoots were +soon attacked by the same decay, and the operation had to be renewed at +shorter and shorter intervals, until at last it was found necessary to +treat as coppices plantations originally designed for the full-growth +system. Nor was this all: the soil, periodically bared by these +cuttings, became impoverished, and less and less suited to the growth of +the oak. ... It was then proposed to introduce the pine and plant with +it the vacancies and glades. + +"... By this means, the forest was saved from the ruin which threatened +it, and now more than 10,000 acres of pines, from fifteen to thirty +years old are disseminated at various points, sometimes intermixed with +broad-leaved trees, sometimes forming groves by themselves"--Revue des +Deux Mondes, Mai, 1863, pp. 153, 154.] and besides this, large wood of +any species cannot be grown in this method because trees which shoot +from decaying stumps and their dying roots, become hollow or otherwise +unsound before they acquire their full dimensions. A more fatal +objection still, is, that the roots of trees will not bear more than two +or three, or at most four cuttings of their shoots before their vitality +is exhausted, and the wood can then be restored only by replanting +entirely. + +The period of cutting coppices varies in Europe from fifteen to forty +years, according to soil, species, and rapidity of growth. In the +futaie, or full-growth system, the trees are allowed to stand as long as +they continue in healthy and vigorous growth. This is a shorter period +than would be at first supposed, when we consider the advanced age and +great dimensions to which, under favorable circumstances, many +forest-trees attain in temperate climates. But, as every observing +person familiar with the forest is aware, these are exceptional cases, +just as are instances of great longevity or of gigantic stature among +men. Able vegetable physiologists have maintained that the tree, like +most fish and reptiles, has no natural limit of life or of growth, and +that the only reason why our oaks and our pines do not reach the age of +twenty centuries and the height of a hundred fathoms, is, that in the +multitude of accidents to which they are exposed, the chances of their +attaining to such a length of years and to such dimensions of growth are +millions to one against them. But another explanation of this fact is +possible. In trees affected by no discoverable external cause of death, +decay begins at the topmost branches, which seem to wither and die for +want of nutriment. The mysterious force by which the sap is carried from +the roots to the utmost twigs, cannot be conceived to be unlimited in +power, and it is probable that it differs in different species, so that +while it may suffice to raise the fluid to the height of five hundred +feet in the eucalyptus, it may not be able to carry it beyond one +hundred and fifty in the oak. The limit may be different, too, in +different trees of the same species, not from defective organization in +those of inferior growth, but from more or less favorable conditions of +soil, nourishment, and exposure. Whenever a tree attains to the limit +beyond which its circulating fluids cannot rise, we may suppose that +decay begins, and death follows from want of nutrition at the +extremities, and from the same causes which bring about the same results +in animals of limited size--such, for example, as the interruption of +functions essential to life, in consequence of the clogging up of ducts +by matter assimilable in the stage of growth, but no longer so when +increment has ceased. In the natural woods we observe that, though, +among the myriads of trees which grow upon a square mile, there are +several vegetable giants, yet the great majority of them begin to decay +long before they have attained their maximum of stature, and this seems +to be still more emphatically true of the artificial forest. In France, +according to Clave, "oaks, in a suitable soil, may stand, without +exhibiting any sign of decay, for two or three hundred years; the pines +hardly exceed one hundred and twenty, and the soft or white woods [bois +blancs], in wet soils, languish, and die before reaching the fiftieth +year." [Footnote: Etudes Forestieres, p. 80.] These ages are certainly +below the average of those of American forest-trees, and are greatly +exceeded in very numerous well-attested instances of isolated trees in +Europe. + +The former mode of treating the futaie, called the garden system, was to +cut the trees individually as they arrived at maturity, but, in the best +regulated forests, this practice has been abandoned for the German +method, which embraces not only the securing of the largest immediate +profit, but the replanting of the forest, and the care of the young +growth. This is effected in the case of a forest, whether natural or +artificial, which is to be subjected to regular management, by three +operations. The first of these consists in felling about one-third of +the trees, in such way as to leave convenient spaces for the growth of +seedlings. The remaining two-thirds are relied upon to replant the +vacancies, by natural sowing, which they seldom or never fail to do. The +seedlings are watched, are thinned out when too dense, and the +ill-formed and sickly, as well as those of species of inferior value, +and the shrubs and thorns which might otherwise choke or too closely +shade them, are pulled up. When they have attained sufficient strength +and development of foliage to require, or at least to bear, more light +and air, the second step is taken, by removing a suitable proportion of +the old trees which had been spared at the first cutting; and when, +finally, the younger trees are hardened enough to bear frost and sun +without other protection than that which they mutually give to each +other, the remainder of the original forest is felled, and the wood now +consists wholly of young and vigorous trees. This result is obtained +after about twenty years. At convenient periods, the unhealthy stocks +and those injured by wind or other accidents are removed, and in some +instances the growth of the remainder is promoted by irrigation or by +fertilizing applications. [Footnote: The grounds which it is most +important to clothe with wood as a conservative influence, and which, +also, can best be spared from agricultural use, are steep hillsides. But +the performance of all the offices of the forester to the tree--seeding, +planting, thinning, trimming, and finally felling and removing for +consumption--is more laborious upon a rapid declivity than on a level +soil, and at the same time it is difficult to apply irrigation or +manures to trees so situated. Experience has shown that there in great +advantage in terracing the face of a hill before planting it, both as +preventing the wash of the earth by checking the flow of water down its +slope, and as presenting a surface favorable for irrigation, as well as +for manuring and cultivating the tree. But even without so expensive a +process, very important results have been obtained by simply ditching +declivities. "In order to hasten the growth of wood on the flanks of a +mountain, Mr. Eugene Chevandier divided the slope into zones forty or +fifty feet wide, by horizontal ditches closed at both ends, and thereby +obtained, from firs of different ages, shoots double the dimensions of +those which grew on a dry soil of the same character, where the water +was allowed to run off without obstruction."--Dumont, Des Travaux +Publics, etc., pp. 94-96. The ditches were about two feet and a half +deep, and three feet and a half wide, and they cost about forty francs +the hectare, or three dollars the acre. This extraordinary growth was +produced wholly by the retention of the rain-water in the ditches, +whence it filtered through the whole soil and supplied moisture to the +roots of the trees. It may be doubted whether in a climate cold enough +to freeze the entire contents of the ditches in winter, it would not be +expedient to draw off the water in the autumn, as the presence of so +large a quantity of ice in the soil might prove injurious to trees too +young and small to shelter the ground effectually against frost. + +Chevandier computes that, if the annual growth of the pine in the marshy +and too humid soil of the Vosges be represented by one, it will equal +two in ordinary dry ground, four or five on slopes so ditched or graded +as to retain the water flowing upon them from roads or steep +declivities, and six where the earth is kept sufficiently moist by +infiltration from running brooks.--Comptes Rendus a l'Academie des +Sciences, t. xix., Juillet, Dec., 1844, p. 167. The effect of accidental +irrigation in well shown in the growth of the trees planted along the +canals of irrigation which traverse the fields in many parts of Italy. +They nourish most luxuriantly, in spite of continual lopping, and yield +a very important contribution to the stock of fuel for domestic use +while trees, situated so far from canals as to be out of the reach of +infiltration from them, are of much slower growth, under circumstances +otherwise equally favorable. In other experiments of Chevandier, under +better conditions, the yield of wood was increased, by judicious +irrigation, in the ratio of seven to one, the profits in that of twelve +to one. At the Exposition of 1855, Chambrelent exhibited young trees, +which, in four years from the seed, had grown to the height of sixteen +and twenty feet, and the circumference of ten and twelve inches. +Chevandier experimented with various manures, and found that some of +them might be profitably applied to young but not to old trees, the +quantity required in the latter case being too great. Wood-ashes and the +refuse of soda factories are particularly recommended. See, on the +manuring of trees, Chevandier, Recherches sur l'emploi de divers +amendements, etc., Paris, 1852, and Koderle, Grundsatze der Kunstlichen +Dungung im Forstculturwesen. Wien, 1865. + +I have seen an extraordinary growth produced in fir-trees by the +application of soapsuds; in a young and sickly cherry-tree, by heaping +the chips and dust from a marble-quarry, to the height of two or three +feet, over the roots and around the stem; and cases have come to my +knowledge where like results followed the planting of vines and trees in +holes half filled with fragments of plaster-castings, and mortar from +old buildings. Chevandier's experiments in the irrigation of the forest +would not have been a "new thing under the sun" to wise King Solomon, +for that monarch saya: "I made me pools of water, to water therewith, +the wood that bringeth forth trees." Eccles. ii. 6.] + +When the forest is approaching maturity, the original processes already +described are repeated; and as, in different parts of an extensive +forest, they would take place at different times in different zones, it +would afford indefinitely an annual crop of small wood, fuel, and +timber. + +The duties of the forester do not end here, for it sometimes happens +that the glades left by felling the older trees are not sufficiently +seeded, or that the species, or essences, as the French oddly call them, +are not duly proportioned in the new crop. In this case, seed must be +artificially sown, or young trees planted in the vacancies. Besides +this, all trees, whether grown for fruit, for fuel, or for timber, +require more or less training in order to yield the best returns. The +experiments of the Vicomte de Courval in sylviculture throw much light +on this subject, and show, in a most interesting way, the importance of +pruning forest-trees. The principal feature of De Courval's very +successful method is a systematical mode of trimming which compels the +tree to develop the stem, by reducing the lateral ramification. +Beginning with young trees, the buds are rubbed off from the stems, and +superfluous lateral shoots are pruned down to the trunk. When large +trees are taken in hand, branches which can be spared, and whose removal +is necessary to obtain a proper length of stem, are very smoothly cut +off quite close to the trunk, and the exposed surface is IMMEDIATELY +brushed over with mineral-coal tar. When thus treated, it is said that +the healing of the wound is perfect, and without any decay of the tree. +Trees trained by De Courval's method, which is now universally approved +and much practised in France, rapidly attained a great height. They grow +with remarkable straightness of stem and of grain, and their timber +commands the highest price. [Footnote: See De Courval, Taille et +conduite des Arbres forestieres et autres arbres de grande dimension. +Paris, 1861. + +The most important part of Viscount de Courval's system will be found in +L'Elagage des Arbres, par le Comte A. Des Cars, an admirable little +treatise, of which numerous editions, at the price of one franc, have +been printed since the first, of 1864, and which ought to be translated +and published without delay in the United States.] + +A system of plantation, specially though not exclusively suited to very +moist soils, recommended by Duhamel a hundred years ago, has been +revived in Germany, within about twenty years, with much success. It is +called hill-planting, and consists in placing the young tree upright on +the greensward with its roots properly spread out, and then covering the +roots and supporting the trunk by thick sods cut so as to form a +circular hillock around it. [Footnote: See Manteuffel, L'Art de Planter, +traduit par Stumper. Paris, 1868.] By this method it is alleged trees +can be grown advantageously both in dry ground and on humid soils, where +they would not strike root if planted in holes after the usual mauner. +If there is any truth in the theory of a desiccating action in evergreen +trees, plantations of this sort might have a value as drainers of lands +not easily laid dry by other processes. There is much ground on the +great prairies of the West, where experiments with this method of +planting are strongly to be recommended. + +It is common in Europe to permit the removal of the fallen leaves and +fragments of bark and branches with which the forest-soil is covered, +and sometimes the cutting of the lower twigs of evergreens. The leaves +and twigs are principally used as litter for cattle, and finally as +manure, the bark and wind-fallen branches as fuel. By long usage, +sometimes by express grant, this privilege has become a vested right of +the population in the neighborhood of many public and even large private +forests; but it is generally regarded as a serious evil. To remove the +leaves and fallen twigs is to withdraw much of the pabulum upon which +the tree was destined to feed. The small branches and leaves are the +parts of the tree which yield the largest proportion of ashes on +combustion, and of course they supply a great amount of nutriment for +the young shoots. "A cubic foot of twigs," says Vaupell, "yields four +times as much ashes as a cubic foot of stem wood. ... For every hundred +weight of dried leaves carried off from a beech forest, we sacrifice a +hundred and sixty cubic feet of wood. The leaves and the mosses are a +substitute, not only for manure, but for ploughing. The carbonic acid +given out by decaying leaves, when taken up by water, serves to dissolve +the mineral constituents of the soil, and is particularly active in +disintegrating feldspar and the clay derived from its decomposition. ... +The leaves belong to the soil. Without them it cannot preserve its +fertility, and cannot furnish nutriment to the beech. The trees +languish, produce seed incapable of germination, and the spontaneous +self-sowing, which is an indispensable element in the best systems of +sylviculture, fails altogether in the bared and impoverished soil." +[Footnote: Vaupell, Bogens Indvandring i de Danske Skove, pp. 29, 46. +Vaupell further observes, on the page last quoted: "The removal of +leaves is injurious to the forest, not only because it retards the +growth of trees, but still more because it disqualifies the soil for the +production of particular species. When the beech languishes, and the +development of its branches is less vigorous and its crown less +spreading, it becomes unable to resist the encroachments of the fir. +This latter tree thrives in an inferior soil, and being no longer +stifled by the thick foliage of the beech, it spreads gradually through +the wood, while the beech retreats before it and finally perishes." + +Schleiden confirms the opinion of Vaupell, and adds many important +observations on this subject.--Fur Baum und Wald, pp. 64, 65.] + +Besides these evils, the removal of the leaves deprives the soil of much +of that spongy character which gives it such immense value as a +reservoir of moisture and a regulator of the flow of springs; and, +finally, it exposes the surface-roots to the drying influence of sun and +wind, to accidental mechanical injury from the tread of animals or men, +and, in cold climates, to the destructive effects of frost. + + +Protection against Wild Animals. + +It is often necessary to take measures for the protection of young trees +against the rabbit, the mole, and other rodent quadrupeds, and of older +ones against the damage done by the larvae of insects hatched upon the +surface or in the tissues of the bark, or even in the wood itself. The +much greater liability of the artificial than of the natural forest to +injury from this cause is perhaps the only point in which the +superiority of the former to the latter is not as marked as that of any +domesticated vegetable to its wild representative. But the better +quality of the wood and the much more rapid growth of the trained and +regulated forest are abundant compensations for the loss thus +occasioned, and the progress of entomological science will, perhaps, +suggest new methods of preventing the ravages of insects. Thus far, +however, the collection and destruction ofthe eggs, by simple but +expensive means, has proved the most effectual remedy. [Footnote: I have +remarked elsewhere that most insects which deposit and hatch their eggs +in the wood of the natural forest confine themselves to dead trees. Not +only is this the fact, but it is also true that many of the borers +attack only freshly-cut timber. Their season of labor is a short one, +and unless the tree is cut during this period, it is safe from them. In +summer you may hear them plying their augers in the wood of a young pine +with soft, green bark, as you sit upon its trunk, within a week after it +has been felled, but the windfalls of the winter lie uninjured by the +worm and even undecayed for centuries. In the pine woods of New England, +after the regular lumberman has removed the standing trees, these old +trunks are hauled out from the mosses and leaves which half cover them, +and often furnish excellent timber. The slow decay of such timber in the +woods, it may be remarked, furnishes another proof of the uniformity of +temperature and humidity in the forest, for the trunk of a tree lying on +grass or ploughland, and of course exposed to all the alternations of +climate, hardly resists complete decomposition for a generation. The +forests of Europe exhibit similar facts. Wessely, in a description of +the primitive wood of Neuwald in Lower Austria, says that the windfalls +required from 150 to 200 years for entire decay.--Die Oesterreichischen +Alpenlander und ihre Forste, p. 312. + +The comparative immunity of the American native forests from attacks by +insects is perhaps in some degree due to the fact that the European +destructive tribes have not yet found their way across the ocean, and +that our native species are less injurious to living trees. On the +European lignivorous insects, see Siemoni, Manuale d'Arte Forestale, 2d +edizione, pp. 369-379.] + + +Exclusion of Domestic Quadrupeds. + +But probably the most important of all rules for the government of the +forest, whether natural or artificial, is that which prescribes the +absolute exclusion of all domestic quadrupeds, except swine, from every +wood which is not destined to be cleared. No growth of young trees is +possible where horned cattle, sheep, or goats, or even horses, are +permitted to pasture at any season of the year, though they are +doubtless most destructive when trees are in leaf. [Footnote: Although +the economy of the forest has received little attention in the United +States, no lover of American nature can have failed to observe a marked +difference between a native wood from which cattle are excluded and one +where they are permitted to browse. A few seasons suffice for the total +extirpation of the "underbrush," including the young trees on which +alone the reproduction of the forest depends, and all the branches of +those of larger growth which hang within reach of the cattle are +stripped of their buds and leaves, and soon wither and fall off. These +effects are observable at a great distance, and a wood-pasture is +recognized, almost as far as it can be seen, by the regularity with +which its lower foliage terminates at what Ruskin somewhere calls the +"cattle-line." This always runs parallel to the surface of the ground, +and is determined by the height to which domestic quadrupeds can reach +to feed upon the leaves. In describing a visit to the grand-ducal farm +of San Rossore near Pisa, where a large herd of camels is kept, +Chateauvieux says: "In passing through a wood of evergreen oaks, I +observed that all the twigs and foliage of the trees were clipped up to +the height of about twelve feet above the ground, without leaving a +single spray below that level. I was informed that the browsing of the +camels had trimmed the trees as high as they could reach." F. Lullin De +Chateuvieux, Lettres sur l'Italie, p. 118. + +Browsing animals, and most of all the goat, are considered by foresters +as more injurious to the growth of young trees, and, therefore, to the +reproduction of the forest, than almost any other destructive cause. +According to Beatson's Saint Helena, introductory chapter, and Darwin's +Journal of Researches in Geology and Natural History, pp. 582, 583, it +was the goats which destroyed the beautiful forests that, three hundred +and fifty years ago, covered a continuous surface of not less than two +thousand acres in the interior of the island [of St. Helena], not to +mention scattered groups of trees. Darwin observes: "During our stay at +Valparaiso, I was most positively assured that sandal-wood formerly grew +in abundance on the island of Juan Fernandez, but that this tree had now +become entirely extinct there, having been extirpated by the goats which +early navigators had introduced. The neighboring islands, to which goats +have not been carried, still abound in sandal-wood." + +In the winter, the deer tribe, especially the great American moose-deer, +subsists much on the buds and young sprouts of trees; yet--though from +the destruction of the wolves or from some not easily explained cause, +these latter animals have recently multiplied so rapidly in some parts +of North America, that, not long since, four hundred of them are said to +have been killed, in one season, on a territory in Maine not comprising +more than one hundred and fifty square miles--the wild browsing +quadrupeds are rarely, if ever, numerous enough in regions uninhabited +by man to produce any sensible effect on the condition of the forest. A +reason why they are less injurious than the goat to young trees may be +that they resort to this nutriment only in the winter, when the grasses +and shrubs are leafless or covered with snow, whereas the goat feeds +upon buds and young shoots principally in the season of growth. However +this may be, the natural law of consumption and supply keeps the forest +growth, and the wild animals which live on its products, in such a state +of equilibrium as to insure the indefinite continuance of both, and the +perpetuity of neither is endangered until man interferes and destroys +the balance. + +When, however, deer are bred and protected in parks, they multiply like +domestic cattle, and become equally injurious to trees. "A few years +ago," says Clave, "there were not less than two thousand deer of +different ages in the forest of Fontainebleau. For want of grass, they +are driven to the trees, and they do not spare them ... It is calculated +that the browsing of these animals, and the consequent retardation of +the growth of the wood, diminishes the annual product of the forest to +the amount of two hundred thousand cubic feet per year, ... and besides +this, the trees thus mutilated are soon exhausted and die. The deer +attack the pines, too, tearing off the bark in long strips, or rubbing +theie heads against them when shedding their horns; and sometimes, in +groves of more than a hundred hectares, not one pine is found uninjured +by them."--Revue des Deux Mondes, Mai, 1863, p. 157. + +Vaupell, though agreeing with other writers as to the injury done to the +forest by most domestic animals and by half-tamed deer--which he +illustrates in an interesting way in his posthumous work, The Danish +Woods--thinks, nonetheless, that at the season when the mast is falling, +swine are rather useful than otherwise to forests of beech and oak, by +treading into the ground and thus sowing beechnuts and acorns, and by +destroying moles and mice.--De Danake Skore, p. 12. Meguschor is of the +same opinion, and adds that swine destroy injurious insects and their +larvae.--Memoria, etc., p. 233. + +Beckstein computes that a park of 2,500 acres, containing 250 acres of +marsh, 250 of fields and meadows, and the remaining 2,000 of wood, mny +keep 364 deer of different species, 47 wild boars, 200 hares, 100 +rabbits, and an indefinite number of pheasants. These animals would +require, in winter, 123,000 pounds of hay, and 22,000 pounds of +potatoes, besides what they would pick up themselves. The natural forest +most thickly peopled with wild animals would not, in temperate climates, +contain, upon the average, one-tenth of these numbers to the same extent +of surface.] + +These animals browse upon the terminal buds and the tender branches, +thereby stunting, if they do not kill, the young trees, and depriving +them of all beauty and vigor of growth. + + +Forest Fires. + +The difficulty of protecting the woods against accidental or incendiary +fires is one of the most discouraging circumstances attending the +preservation of natural and the plantation of artificial +forests. [Footnote: The disappearance of the forests of ancient Gaul and +of mediaeval France has been ascribed by some writers as much to +accidental fires as to the felling of the trees. All the treatises on +sylviculture are full of narratives of forest fires. The woods of +Corsica and Sardinia have suffered incalculable injury from this cause, +and notwithstanding the resistance of the cork-tree to injury from +common fires, the government forests of this valuable tree in Algeria +have been lately often set on fire by the natives and have sustained +immense damage. See an article by Ysabeau in the Annales Forestieres, t. +iii., p. 439; Della Marmora, Voyage en Sardaigne, 2d edition, t. i., p. +426; Rivista Forestale del Regno d'Italia, October, 1865, p. 474. Five +or six years ago I saw in Switzerland a considerable forest, chiefly of +young trees, which had recently been burnt over. I was told that the +poor of the commune had long enjoyed a customary privilege of carrying +off dead wood and windfalls, and that they had set the forest on fire to +kill the trees and so increase the supply of their lawful plunder. The +customary rights of herdsmen, shepherds, and peasants in European +forests are often an insuperable obstacle to the success of attempts to +preserve the woods or to improve their condition. See, on this subject, +Alfred Maury, Les anciens Forets de la Gaule, chap. xxix.] In the +spontaneous wood the spread of fire is somewhat retarded by the general +humidity of the soil and of the beds of leaves which cover it. But in +long droughts the superficial layer of leaves and the dry fallen +branches become as inflammable as tinder, and the fire spreads with +fearful rapidity, until its further progress is arrested by want of +material, or, more rarely, by heavy rains, sometimes caused, as many +meteorologists suppose, by the conflagration itself. + +In the artificial forest the annual removal of fallen or half-dried +trees and the leaves and other droppings of the wood, though otherwise a +very injurious practice, much diminishes the rapid spread of fires; and +the absence of combustible underwood and the greater distance between +the trees are additional safeguards. But, on the other hand, the +comparative dryness of the soil, and of any leaves or twigs which may +remain upon it, and the greater facility for the passage of +wind-currents through a regularly planted and more open wood, are +circumstances unfavorable to the security of the trees against this +formidable danger. The natural forest, unless isolated and of small +extent, can be protected from fire only by a vigilance too costly to be +systematically practised. But the artificial wood may be secured by a +network of ditches and of paths or occasional open glades, which both +check the running of the fire and furnish the means of approaching and +combating it. [Footnote: It is stated that in the pine woods of the +Landes of Gascony a fire has never been known to cross a railway-track +or a common road. See Des Incendies, etc., dans la Region des Maures in +the Revue des Eaux et Forets for February, 1869. Many other important +articles on this subject will be found in other numbers of the same very +valuable periodical.] + +The experience of 1871 ought not to be wholly without value as a lesson. +It is not possible to estimate the damage by forest fires in that +disastrous year, in what were lately the North-western States, and in +Canada, but as the demand for lumber, and consequently, its market +price, are rising at a rate higher than the interest on capital, in a +geometrical ratio, one may almost say it is probable that ten years +hence those fires will be thought to have diminished the national wealth +by a larger amount than even the terrible conflagration at Chicago. + +There is no good reason why insurance companies should not guarantee the +proprietor of a wood as well as the owner of a house against damage by +fire. In Europe there is no conceivable liability to pecuniary loss +which may not be insured against. The American companies might at first +be embarrassed in estimating the risk, but the experience of a few years +would suggest safe principles, and all parties would find advantage in +this extension of security. + + +Forest Legislation. + +I have alleged sufficient reasons for believing that a desolation, like +that which has overwhelmed many once beautiful and fertile regions of +Europe, awaits an important part of the territory of the United States, +and of other comparatively new countries over which European +civilization is now extending its sway, unless prompt measures are taken +to check the action of destructive causes already in operation. It is +almost in vain to expect that mere restrictive legislation can do +anything effectual to arrest the progress of the evil in those +countries, except so far as the state is still the proprietor of +extensive forests. Woodlands which have passed into private hands will +everywhere be managed, in spite of legal restrictions, upon the same +economical principles as other possessions, and every proprietor will, +as a general rule, fell his woods, unless he believes that it will be +for his pecuniary interest to preserve them. Few of the new provinces +which the last three centuries have brought under the control of the +European race, would tolerate any interference by the law-making power +with what they regard as the most sacred of civil rights--the right, +namely, of every man to do what he will with his own. In the Old World, +even in France, whose people, of all European nations, love best to be +governed and are least annoyed by bureaucratic supervision, law has been +found impotent to prevent the destruction, or wasteful economy, of +private forests; and in many of the mountainous departments of that +country, man is at this moment so fast laying waste the face of the +earth, that the most serious fears are entertained, not only of the +depopulation of those districts, but of enormous mischiefs to the +provinces contiguous to them. [Footnote: "The laws against clearing have +never been able to prevent these operations when the proprietor found +his advantage in them, and the long series of royal ordinances and +decrees of parliaments, proclaimed from the days of Charlemagne to our +own, with a view of securing forest property against the improvidence of +its owners, have served only to show the impotence of legislative action +on this subject."--Clave, Etudes sur l'Economie Forestiere, p. 32. + +"A proprietor can always contrive to clear his woods, whatever may be +done to prevent him; it is a mere question of time, and a few imprudent +cuttings, a few abuses of the right of pasturage, suffice to destry a +forest in spite of all regulations to the contrary."--Dunoyer, De la +Liberte du Travail, ii., p. 452, as quoted by Clave, p. 353. + +Both authors agree that the preservation of the forests in France is +practicable only by their transfer to the state, which alone can protect +them and secure their proper treatment. It is much to be feared that +even this measure would be inadequate to preserve the forests of the +American Union. There is little respect for public property in America, +and the Federal Government, certainly, would not be the proper agent of +the nation for this purpose. It proved itself unable to protect the +live-oak woods of Florida, which were intended to be preserved for the +use of the navy, and it more than once paid contractors a high price for +timber stolen from its own forests. The authorities of the individual +States might be more efficient.] The only legal provisions from which +anything is to be hoped, are such as shall make it a matter of private +advantage to the landholder to spare the trees upon his grounds, and +promote the growth of the young wood. Much may be done by exempting +standing forests from taxation, and by imposing taxes on wood felled for +fuel or for timber, something by more stringent provisions against +trespasses on forest property, and something by premiums or honorary +distinctions for judicious management of the woods; and, in short, in +this matter rewards rather than punishments must be the incentives to +obedience even to a policy of enlightened self-interest. It might be +difficult to induce governments, general or local, to make the necessary +appropriations for such purposes, but there can be no doubt that it +would be sound economy in the end. + +In countries where there exist municipalities endowed with an +intelligent public spirit, the purchase and control of forests by such +corporations would often prove advantageous; and in some of the +provinces of Northern Lombardy, experience has shown that such +operations may be conducted with great benefit to all the interests +connected with the proper management of the woods. In Switzerland, on +the other hand, except in some few cases where woods have been preserved +as a defence against avalanches, the forests of the communes have been +of little advantage to the public interests, and have very generally +gone to decay. [Footnote: A better economy has been of late introduced +into the management of the forest in Switzerland. Excellent official +reports on the subject have been published and important legal +provisions adopted.] The rights of pasturage, everywhere destructive to +trees, combined with toleration of trespasses, have so reduced their +value, that there is, too often, nothing left that is worth protecting. +In the canton of Ticino, the peasants have very frequently voted to sell +the town-woods and divide the proceeds among the corporators. The +sometimes considerable sums thus received are squandered in wild +revelry, and the sacrifice of the forests brings not even a momentary +benefit to the proprietors. [Footnote: See in Berlepscu, Die Alpen, +chapter Holzschlager und Flosser, a lively account of the sale of a +communal wood.] + +Fortunately for the immense economical and sanitary interests involved +in this branch of rural and industrial husbandry, public opinion in many +parts of the United States is thoroughly roused to the importance of the +subject. In the Eastern States, plantations of a certain extent have +been made, and a wiser system is pursued in the treatment of the +remaining native woods. [Footnote: When the census of 1860 was taken, +the States of Maine and New York produced and exported lumber in +abundance. Neither of them now has timber enough for domestic use, and +they are both compelled to draw much of their supply from Canada and the +West.] Important experiments have been tried in Massachusetts on the +propagation of forest-trees on seashore bluffs exposed to strong winds. +This had been generally supposed to be impossible, but the experiments +in question afford a gratifying proof that this is an erroneous opinion. +Piper gives an interesting account of Mr. Tudor's success in planting +trees on the bleak and barren shore of Nahant. "Mr. Tudor," observes he, +"has planted more than ten thousand trees at Nahaut, and, by the results +of his experiments, has fully demonstrated that trees, properly cared +for in the beginning, may be made to grow up to the very bounds of the +ocean, exposed to the biting of the wind and the spray of the sea. The +only shelter they require is, at first, some interruption to break the +current of the wind, such as fences, houses, or other trees." [Footnote: +Trees of America, p. 10.] + +Young trees protected against the wind by a fence will somewhat overtop +their shelter, and every tree will serve as a screen to a taller one +behind it. Extensive groves have thus been formed in situations where an +isolated tree would not grow at all. + +The people of the Far West have thrown themselves into the work, we +cannot say of restoration, but rather of creation, of woodland, with +much of the passionate energy which marks their action in reference to +other modes of physical improvement. California has appointed a State +forester with a liberal salary, and made such legal provisions and +appropriations as to render the discharge of his duties effectual. The +hands that built the Pacific Railroad at the rate of miles in a day are +now busy in planting belts of trees to shelter the track from snow- +drifts, and to supply, at a future day, timber for ties and fuel for the +locomotives. The settlers on the open plains, too, are not less actively +engaged in the propagation of the woods, and if we can put faith in the +official statistics on the subject, not thousands but millions of trees +are annually planted on the prairies. + +These experiments are of much scientific as well as economical interest. +The prairies have never been wooded, so far as we know their history, +and it has been contended that successful sylviculture would be +impracticable in those regions from the want of rain. But we are +acquainted with no soil and climate which favor the production of +herbage and forbid the rearing of trees, and, as Bryant well observes, +"it seems certain that where grass will grow trees may be made to grow +also." [Footnote: The origin of our Western treeless prairies and +plains, as of the Russian steppes, which much resemble them, is obscure, +but the want of forests upon them, seems to be due to climatic +conditions and especially to a want of spring and summer rains, which +prevents the spontaneous formation of forests upon them, though not +necessarily the growth of trees artificially planted and cared for. +Climatic conditions more or less resembling those of our Western +territories produce analogous effects in India. Much valuable +information on the relations between climate and forest vegetation will +be found in an article by Dr. Brandis, On the Distribution of Forests in +India, in Ocean Highways for October, 1872. + +In the more eastwardly prairie region fires have done much to prevent +the spread of the native groves, and throughout the whole woodless +plains the pastorage of the buffalo alone would suffice to prevent a +forest growth. The prairies were the proper feeding-grounds of the +bison, and the vast number of those animals is connected, as cause or +consequence, with the existence of these vast pastures. The bison, +indeed, could not convert the forest into a pasture, but he would do +much to prevent the pasture from becoming a forest. + +There is positive evidence that some of the American tribes possessed +large herds of domesticated bisons. See Humboldt, Ansichten der Natur, +i., pp. 71-73. What authorizes us to affirm that this was simply the +wild bison reclaimed, and why may we not, with equal probability, +believe that the migratory prairie-buffalo is the progeny of the +domestic animal run wild? + +There are, both on the prairies, as in Wisconsin, and in deep forests, +as in Ohio, extensive remains of a primitive people, who must have been +more numerous and more advanced in art than the present Indian tribes. +There can be no doubt that the woods where such earthworks are found in +Ohio were cleared by them, and that the vicinity of these fortresses or +temples was inhabited by a large population. Nothing forbids the +supposition that the prairies were cleared by the same or a similar +people, and that the growth of trees upon them has been prevented by +fires and grazing, while the restoration of the woods in Ohio may be due +to the abandonment of that region by its original inhabitants. The +climatic conditions unfavorable to the spontaneous growth of trees on +the prairies may possibly be an effect of too extensive clearings, +rather than a cause of the want of woods. + +It is disputed whether the steppes of Russia were ever wooded. They were +certainly bare of forest growth at a very remote period; for Herodotus +describes the country of the Scythians between the Ister and the Tanais +as woodless, with the exception of the small province of Xylaea between +the Dnieper and the Gulf of Perekop. They are known to have been +occupied by a large nomade and pastoral population down to the sixteenth +century, though these tribes are now much reduced in numbers. The habits +of such races are scarcely less destructive to the forest than those of +civilized life. Pastoral tribes do not employ much wood for fuel or for +construction, but they carelessly or recklessly burn down the forests, +and their cattle effectually check the growth of young trees wherever +their range extends. + +At present, the furious winds which sweep over the plains, the droughts +of summer, and the rights and abuses of pasturage, constitute very +formidable obstacles to the employment of measures which have been +attended with so valuable results on the sand-wastes of France and +Germany. The Russian Government has, however, attempted the wooding of +the steppes, and there are thriving plantations in the neighborhood of +Odessa, where the soil is of a particularly loose and sandy character. +The tree best suited to this locality, and, as there is good reason to +suppose, to sand plains in general, is the Ailanthus glandulosa, or +Japan varnish-tree. The remarkable success which has crowned the +experiments with the ailanthus at Odessa, will, no doubt, stimulate to +similar trials elsewhere, and it seems not improbable that the arundo +and the maritime pine, which have fixed so many thousand acres of +drifting sands in Western Europe, will be, partially at leaat, +superseded by the tamarisk and the varnish-tree. + +According to Hohenstein, Der Wald, pp. 228, 229, an extensive +plantation of pines--a tree new to Southern Russia--was commenced in +1842, on the barren and sandy banks of the Ingula, near Elisabethgrod, +and has met with very flattering success. Other experiments in +sylviculture at different points on the steppes promise valuable +results.] In any case the question will now be subjected to a practical +test, and the plantations are so extensive, and, as is reported, so +thrifty in growth, that one generation will suffice to determine with +certainty and precision how far climate is affected by clothing with +wood a vast territory naturally destitute of that protection. + +I have thus far spoken only of the preservation and training of existing +woods, not of the planting of new forests, because European experience, +to which alone we can appeal, is conversant only with conditions so +different from those of our own climate, soil, and arboreal vegetation, +that precedents drawn from it cannot be relied upon as entirely safe +rules for our guidance in that branch of rural economy. [Footnote: Many +valuable suggestions on this subject will be found in Bryant, Forest +Trees, chap. vi. et seqq.] + +I apprehend that one rule, which is certainly alike applicable to both +sides of the Atlantic--that, namely, of the absolute exclusion of +domestic quadrupeds from all woods, old or young, not destined for the +axe--would be least likely to be observed in our practice. The need of +shade for cattle, and our inveterate habits in this respect, are much +more serious obstacles to compliance with this precept than any inherent +difficulty in the thing itself; for there is no good reason why our +cattle may not be kept out of our woods as well as out of our +wheatfields. When forest-planting is earnestly and perseveringly +practised, means of overcoming this difficulty will be found, and our +husbandry will be modified to meet the exigency. + +The best general advice that can be offered, in the want of an +experimental code, is to make every plantation consist of a great +variety of trees, and this not only because nature favors a diversified +forest-crop, but because the chances of success among a multitude of +species are far greater than if we confine ourselves to one or two. + +It will doubtless be found that in our scorching summer, especially on +bare plains, shade for young plants is even more necessary than in most +parts of Europe, and hence a fair proportion of rapidly growing trees +and shrubs, even if themselves of little intrinsic value, ought to be +regarded as an indispensable feature in every young plantation. These +trees should be of species which bear a full supply of air and light, +and therefore, in the order of nature, precede those which are of +greater value for the permanent wood; and it would be a prudent measure +to seed the ground with a stock of such plants, a year or two before +sowing or transplanting the more valuable varieties. + +More specific rules than these cannot at present well be given, but very +brief experiments, even if not in all respects wisely conducted, will +suffice to determine the main question: whether in a given locality this +or that particular tree can advantageously be propagated or introduced. +The special processes of arboriculture suited to the ends of the planter +may be gathered partly from cautious imitation of European practice, and +partly from an experience which, though not pronouncing definitively in +a single season, will, nevertheless, suggest appropriate methods of +planting and training the wood within a period not disproportioned to +the importance of the object. [Footnote: For very judicious suggestions +on experiments in sylviculture, see the Rev. Frederick Starr's +remarkable paper on the American Forests in the Transactions of the +Agricultural Society for -.] + +The growth of arboreal vegetation is comparatively slow, and we are +often told that, though he who buries an acorn may hope to see it shoot +up to a miniature resemblance of the majestic tree which shall shade his +remote descendants, yet the longest life hardly embraces the seedtime +and the harvest of a forest. The planter of a wood, it is said, must be +actuated by higher motives than those of an investment, the profits of +which consist in direct pecuniary gain to himself or even to his +posterity; for if, in rare cases, an artificial forest may, in a +generation or two, more than repay its original cost, still, in general, +the value of its timber will not return the capital expended and the +interest accrued. [Footnote: According to Clave (Etudes, p. 159), the +net revenue from the forests of the state in France, making no allowance +for interest on the capital represented by the forest, is two dollars +per acre. In Saxony it is about the same, though the cost of +administration is twice as much as in France; in Wurtemberg it is about +a dollar an acre; and in Prussia, where half the income is consumed in +the expenses of administration, it sinks to less than half a dollar. +This low rate in Prussia and other German states is partly explained by +the fact that a considerable proportion of the annual product of the +wood is either conceded to persons claiming prescriptive rights, or +sold, at a very small price, to the poor. Taking into account the +capital invested in forest-land, and adding interest upon it, Pressler +calculates that a pine wood, managed with a view to felling it when +eighty years old, would yield one-eighth of one per cent. annual profit; +a fir wood, at one hundred years, one-sixth of one per cent.; a beech +wood, at one hundred and twenty years, one-fourth of one per cent. The +same author gives the net income of the New Forest in England, over and +above expenses, interest not computed, at twenty-five cents per acre +only. In America, where no expense is bestowed upon the woods, the value +of the annual growth has generally been estimated much higher. +Forest-trees are often planted in Europe for what may be called an early +crop. Thus in Germany acorns are sown and the young seedlings cultivated +like ordinary field-vegetables, and cut at the age of a very few years +for the sake of the bark and young twigs used by tanners. In England, +trees are grown at the rate of two thousand to the acre, and cut for +props in the mines at the diameter of a few inches. Plantations for +hoop-poles, and other special purposes requiring small timber, would, no +doubt, often prove high remunerative.] But the modern improved methods +of sylviculture show vastly more favorable financial results; and when +we consider the immense collateral advantages derived from the presence +of the forest, the terrible evils necessarily resulting from its +destruction, we cannot but admit that the preservation of existing +woods, and the more costly extension and creation of them where they +have been unduly reduced or have never existed, are among the plainest +dictates of self-interest and most obvious of the duties which this age +owes to those that are to come after it. + + +Financial Results of Forest Plantation. + +Upon the whole, I am persuaded that the financial statistics which are +found in French and German authors, as the results of European +experience in forest economy, present the question under a too +unfavorable aspect; and therefore these calculations ought not to +discourage landed proprietors from making experiments on this subject. +These statistics apply to woods whose present condition is, in an +eminent degree, the effect of previous long-continued mismanagement; and +there is much reason to believe that in the propitious climate of the +United States new plantations, regulated substantially according to the +methods of De Courval, Chambrelent, and Chevandier, and accompanied with +the introduction of exotic trees, as, for example, the Australian +caruarina and eucalyptus [Footnote: Although the eucalyptus thrives +admirably in Algeria--where it attains a height of from fifty to sixty +feet, and a diameter of fifteen or sixteen inches, in six years from the +seed--and in some restricted localities in Southern Europe, it will not +bear the winters even of Florence, and consequently cannot be expected +to flourish in any part of the United States except the extreme South +and California. The writer of a somewhat enthusiastic article on this +latter State, in Harper's Monthly for July, 1872, affirms that he saw a +eucalyptus "eight years from a small cutting, which was seventy-five +feet in height, and two feet and a half in diameter at the base." + +The paulownia, which thrives in Northern Italy, has a wood of little +value, but the tree would serve well as a shelter for seedlings and +young plants of more valuable species, and in other cases where a +temporary shade is urgently needed. The young shoots, from a stem polled +the previous season, almost surpass even the eucalyptus in rapidity of +growth. Such a shoot from a tree not six inches in diameter, which I had +an opportunity of daily observing, from the bursting out of the bud from +the bark of the parent stem in April till November of the same year, +acquired in that interval a diameter of between four and five inches and +a height of above twenty feet.] which, latter, it is said, has a growth +at least five, and, according to some, ten times more rapid than that of +the oak--would prove good investments even in an economical aspect. +[Footnote: The economical statistics of Grigor, Arboriculture, +Edinburgh, 1868, are very encouraging. In the preface to that work the +author says: "Having formed several large plantations nearly forty years +ago, which are still standing, in the Highlands of Scotland, I can refer +to them as, after paying every expense, yielding a revenue equal to that +of the finest arable land in the country, where the ground previously to +these formations was not worth a shilling an acre." See also Hartig, +Ueber den Wachsthumsgang und Ertrag der Buche, Eiche und Kiefer, 1869, +and especially Bryant, Forest Trees, chap. ix.] + +There is no doubt that they would pay the expenses of their planting at +no distant period, at least in every case where irrigation is possible, +and in very many situations, terraces, ditches, or even horizontal +furrows upon the hillsides, would answer as a substitute for more +artificial irrigation. Large proprietors would receive important +indirect benefits from the shelter and the moisture which forests +furnish for the lands in their neighborhood, and eventually from the +accumulation of vegetable mould in the woods. [Footnote: The fertility +of newly cleared land is by no means due entirely to the accumulation of +decayed vegetable matter on its surface, and to the decomposition of the +mineral constituents of the soil by the gases emitted by the fallen +leaves. Sachs has shown that the roots of living plants exercise a most +powerful solvent action on rocks, and hence stones are disintegrated and +resolved into elements of vegetable nutrition, by the chemical agency of +the forest, more rapidly than by frost, rain, and other meteorological +influences.] The security of the investment, as in the case of all +real-estate, is a strong argument for undertaking such plantations, and +a moderate amount of government patronage and encouragement would be +sufficient to render the creation of new forests an object of private +interest as well as of public advantage, especially in a country where +the necessity is so urgent and the climate so favorable as in the United +States. + + +Instability of American Life. + +All human institutions, associate arrangements, modes of life, have +their characteristic imperfections. The natural, perhaps the necessary +defect of ours, is their instability, their want of fixedness, not in +form only, but even in spirit. The face of physical nature in the United +States shares this incessant fluctuation, and the landscape is as +variable as the habits of the population. It is time for some abatement +in the restless love of change which characterizes us, and makes us +almost a nomade rather than a sedentary people. [Footnote: It is rare +that a middle-aged American dies in the house where he was born, or an +old man even in that which he has built; and this is scarcely less true +of the rural districts, where every man owns his habitation, than of the +city, where the majority live hired houses. This life of incessant +flitting is unfavorable for the execution of permanent improvements of +every sort, and especially of those which, like the forest, are slow in +repaying any part of the capital expended in them. It requires a very +generous spirit in a landholder to plant a wood on a farm he expects to +sell, or which he knows will pass out of the hands of his descendants at +his death. But the very fact of having begun a plantation would attach +the proprietor more strongly to the soil for which he had made such a +sacrifice; and the paternal acres would have a greater value in the eyes +of a succeeding generation, if thus improved and beautified by the +labors of those from whom they were inherited. Landed property, +therefore, the transfer of which is happily free from every legal +impediment or restriction in the United States, would find, in the +feelings thus prompted, a moral check against a too frequent change of +owners, and would tend to remain long enough in one proprietor or one +family to admit of gradual improvements which would increase its value +both to the possessor and to the state.] We have now felled forest +enough everywhere, in many districts far too much. Let us restore this +one element of material life to its normal proportions, and devise means +of maintaining the permanence of its relations to the fields, the +meadows, and the pastures, to the rain and the dews of heaven, to the +springs and rivulets with which it waters the earth. The establishment +of an approximately fixed ratio between the two most broadly +characterized distinctions of rural surface--woodland and +ploughland--would involve a certain persistence of character in all the +branches of industry, all the occupations and habits of life, which +depend upon or are immediately connected with either, without implying a +rigidity that should exclude flexibility of accommodation to the many +changes of external circumstance which human wisdom can neither prevent +nor foresee, and would thus help us to become, more emphatically, a +well-ordered and stable commonwealth, and, not less conspicuously, a +people of progress. + + + +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. + + +Land artificially won from the Waters. + +Man, as we have seen, has done much to revolutionize the solid surface +of the globe, and to change the distribution and proportions, if not the +essential character, of the organisms which inhabit the land and even +the waters. Besides the influence thus exerted upon the life which +peoples the sea, his action upon the land has involved a certain amount +of indirect encroachment upon the territorial jurisdiction of the ocean. +So far as he has increased the erosion of running waters by the +destruction of the forest or by other operations which lessen the +cohesion of the soil, he has promoted the deposit of solid matter in the +sea, thus reducing the depth of marine estuaries, advancing the +coast-line, and diminishing the area covered by the waters. He has gone +beyond this, and invaded the realm of the ocean by constructing within +its borders wharves, piers, light-houses, breakwaters, fortresses, and +other facilities for his commercial and military operations; and in some +countries he has permanently rescued from tidal overflow, and even from +the very bed of the deep, tracts of ground extensive enough to +constitute valuable additions to his agricultural domain. The quantity +of soil gained from the sea by these different modes of acquisition is, +indeed, too inconsiderable to form an appreciable element in the +comparison of the general proportion between the two great forms of +terrestrial surface, land and water; but the results of such operations, +considered in their physical and their moral bearings, are sufficiently +important to entitle them to special notice in every comprehensive view +of the relations between man and nature. + +There are cases, as on the western shores of the Baltic, where, in +consequence of the secular elevation of the coast, the sea appears to be +retiring; others, where, from the slow sinking of the land, it seems to +be advancing. These movements depend upon geological causes wholly out +of our reach, and man can neither advance nor retard them. [Footnote: It +is possible that the weight of the sediment let fall at the mouths of +great rivers, like the Ganges, the Mississippi, and the Po, may cause +the depression of the strata on which they are deposited, and hence if +man promotes the erosion and transport of earthy material by rivers, he +augments the weight of the sediment they convey into their estuaries, +and consequently his action tends to accelerate such depression. There +are, however, cases where, in spite of great deposits of sediment by +rivers, the coast is rising. Further, the manifestation of the internal +heat of the earth at any given point is conditioned by the thickness of +the crust at such point. The deposits of rivers tend to augment that +thickness at their estuaries. The sediment of slowly-flowing rivers +emptying into shallow seas is spread over so great a surface that we can +hardly imagine the foot or two of slime they let fall over a wide area +in a century to form an element among even the infinitesimal quantities +which compose the terms of the equations of nature. But some swift +rivers, rolling mountains of fine earth, discharge themselves into +deeply scooped gulfs or bays, and in such cases the deposit amounts, in +the course of a few years, to a mass the transfer of which from the +surface of a large basin, and its accumulation at a single point, may be +supposed to produce other effects than those measurable by the +sounding-line. Now, almost all the operations of rural life, as I have +abundantly shown, increase the liability of the soil to erosion by +water. Hence, the clearing of the valley of the Ganges, for example, by +man, must have much augmented the quantity of earth transported by that +river to the sea, and of course have strengthened the effects, whatever +they may be, of thickening the crust of the earth in the Bay of Bengal. +In such cases, then, human action must rank among geological influences. + +To the geological effects of the thickening of the earth's crust in the +Bay of Bengal, are to be added those of thinning it on the highlands +where the Ganges rises. The same action may, as a learned friend +suggests to me, even have a cosmical influence. The great rivers of the +earth, taken as a whole, transport sediment from the polar regions in an +equatorial direction, and hence tend to increase the equatorial +diameter, and at the same time, by their inequality of action, to a +continual displacement of the centre of gravity, of the earth. The +motion of the globe, and of all bodies affected by its attraction, is +modified by every change of its form, and in this case we are not +authorized to say that such effects are in any way compensated.] + +There are also cases where similar apparent effects are produced by +local oceanic currents, by river deposit or erosion, by tidal action, or +by the influence of the wind upon the waves and the sands of the +seabeach. A regular current may drift suspended earth and seaweed along +a coast until they are caught by an eddy and finally deposited out of +the reach of further disturbance, or it may scoop out the bed of the sea +and undermine promontories and headlands; a powerful river, as the wind +changes the direction of its flow at its outlet, may wash away shores +and sandbanks at one point to deposit their material at another; the +tide or waves, stirred to unusual depths by the wind, may gradually wear +down the line of coast, or they may form shoals and coast-dunes by +depositing the sand they have rolled up from the bottom of the ocean. +These latter modes of action are slow in producing effects sufficiently +important to be noticed in general geography, or even to be visible in +the representations of coast-line laid down in ordinary maps; but they +nevertheless form conspicuous features in local topography, and they are +attended with consequences of great moment to the material and the moral +interests of men. The forces which produce these limited results are all +in a considerable degree subject to control, or rather to direction and +resistance, by human power, and it is in guiding, combating, and +compensating them that man has achieved some of his most remarkable and +most honorable conquests over nature. The triumphs in question, or what +we generally call harbor and coast improvements, whether we estimate +their value by the money and labor expended upon them, or by their +bearing upon the interests of commerce and the arts of civilization, +must take a very high rank among the great works of man, and they are +fast assuming a magnitude greatly exceeding their former relative +importance. + +The extension of commerce and of the military marine, and especially the +introduction of vessels of increased burden and deeper draught of water, +have imposed upon engineers tasks of a character which a century ago +would have been pronounced, and, in fact, would have been, +impracticable; but necessity has stimulated au ingenuity which has +contrived means of executing them, and which gives promise of yet +greater performance in time to come. + +Indeed, although man, detached from the solid earth, is almost powerless +to struggle against the sea, he is fast becoming invincible by it so +long as his foot is planted on the shore, or even on the bottom of the +rolling ocean; and though on some battle-fields between the waters and +the land he is obliged slowly to yield his ground, yet he retreats still +facing the foe, and will finally be able to say to the sea, "Thus far +shalt thou come and no farther, and here shall thy proud waves be +stayed!" [Footnote: It is, nevertheless, remarkable that in the +particular branch of coast engineering where great improvements are +most urgently needed, comparatively little has been accomplished. I +refer to the creation of artificial harbors, and of facilities for +loading and discharging ships. The whole coast of Italy is, one may +almost say, harborless and even, wharfless, and there are many thousands +of miles of coast in rich commercial countries in Europe, where vessels +can neither lie in safety for a single day, nor even, in better +protected heavens, ship or land their passengers or cargoes except by +the help of lighters, and other not less clumsy contrivances. It is +strange that such enormous inconveniences are borne with so little +effort to remove them, and especially that break-waters are rarely +constructed by Governments except for the benefit of the military +marine.] + + +Great Works of Material Improvement. + +Men have ceased to admire the vain exercise of power which heaped up the +great pyramid to gratify the pride of a despot with a giant sepulchre; +for many great harbors, many important lines of internal communication, +in the civilized world, now exhibit works which in volume and weight of +material surpass the vastest remains of ancient architectural art, and +demand the exercise of far greater constructive skill and involve a much +heavier pecuniary expenditure than would now be required for the +building of the tomb of Cheops. It is computed that the great pyramid, +the solid contents of which when complete were about 3,000,000 cubic +yards, could be erected for a million of pounds sterling. The breakwater +at Cherbourg, founded in rough water sixty feet deep, at an average +distance of more than two miles from the shore, contains double the mass +of the pyramid, and many a comparatively unimportant canal has been +constructed at twice the cost which would now build that stupendous +monument. + +The description of works of harbor and coast improvement which have only +an economical value, not a true geographical importance, does not come +within the plan of the present volume, and in treating this branch of my +subject, I shall confine myself to such as are designed either to gain +new soil by excluding the waters from grounds which they had permanently +or occasionally covered, or to resist new encroachments of the sea upon +the land. [Footnote: Some notice of great works executed by man in +foreign lands, and probably not generally familiar to my readers, may, +however, prove not uninteresting. + +The desaguadero, or canal constructed by the Viceroy Revillagigedo to +prevent the inundation of the city of Mexico by the lakes in its +vicinity, besides subsidiary works of great extent, has a cutting half a +mile long, 1,000 feet wide, and from 150 to 200 feet deep.--Hoffmann, +Encyclopaedie, art. Mexico. + +The adit which drains the mines of Gwennap in Cornwall, with its +branches, is thirty miles long. Those of the silver mines of Saxony are +scarcely less extensive, and the Ernst-August-Stollen, or great drain of +the mines of the Harz, is fifteen miles long. + +The excavation for the Suez Canal were computed at 75,000,000 cubic +metres, or about 100,000,000 cubic yards, and those of the Ganges Canal, +which, with its branches, had a length of 3,000 miles, amount to nearly +the same quantity. + +The quarries at Maestricht have undermined a space of sixteen miles by +six, or more than two American townships, and the catacombs of Rome, in +part, at least, originally quarries, have a lineal extent of five +hundred and fifty miles. The catacombs of Paris required the excavation +of 13,000,000 cubic yards of stone, or more than four times the volume +of the great pyramid. + +The excavation for the Mt. Cenis tunnel, eight miles in length, wholly +through solid rock, amounted to more than 900,000 cubic yards, and +16,000,000 of brick were employed for the lining. + +In an article on recent internal improvements in England, in the London +Quarterly Review for January, 1858, it is stated that in a single +rock-cutting on the Liverpool and Manchester railway, 480,000 cubic +yards of stone were removed; that the earth excavated in the +construction of English railways up to that date amounted to a hundred +and fifty million cubic yards, and that at the Round Down Cliff, near +Dover, a single blast of nineteen thousand pounds of powder blew down a +thousand million tons of chalk, and covered fifteen acres of land with +the fragments. + +In 1869, a mass of marble equal to one and a half times the cubical +contents of the Duomo at Florence, or about 450,000 cubic yards, was +thrown down at Carrara by one blast, and two hours after, another equal +mass, which had been loosened by the explosion, fell of itself. +Zolfanelli, La Lunigiana, p. 43. + +The coal yearly extracted from the mines of England averages not less +than 100,000,000 tons. The specific gravity of British coal ranges from +1.20 to 1.35, and consequently we may allow a cubic yard to the ton. If +we add the earth and rock removed in order to reach the coal, we shall +have a yearly amount of excavation for this one object equal to more +than thirty times the volume of the pyramid of Cheops. These are +wonderful achievements of human industry; but the rebuilding of Chicago +within a single year after the great fire--not to speak of the +extraordinary material improvements previously executed at that +city--surpasses them all, and it probably involved the expenditure of a +sum of muscular and of moral energy which has never before been exerted +in the accomplishment of a single material object, within a like +period.] + + +Draining of Lincolnshire Fens. + +The draining of the Lincolnshire fens in England, which has converted +about 400,000 acres of marsh, pool, and tide-washed flat into +ploughland and pasturage, is a work, or rather series of works, of great +magnitude, and it possesses much economical, and, indeed, no trifling +geographical, importance. Its plans and methods were, at least in part, +borrowed from the example of like improvements in Holland, and it is, in +difficulty and extent, inferior to works executed for the same purpose +on the opposite coast of the North Sea, by Dutch, Frisie, and Low German +engineers. The space I can devote to such operations will be better +employed in describing the latter, and I content myself with the simple +statement I have already made of the quantity of worthless and even +pestilential land which has been rendered both productive and salubrious +in Lincolnshire, by diking out the sea, and the rivers which traverse +the fens of that country. + +The almost continued prevalence of west winds upon both coasts of the +German Ocean occasions a constant set of the currents of that sea to the +east, and both for this reason and on account of the greater violence of +storms from the former quarter, the English shores of the North Sea are +less exposed to invasion by the waves than those of the Netherlands and +the provinces contiguous to them on the north. The old Netherlandish +chronicles are filled with the most startling accounts of the damage +done by the irruptions of the ocean, from west winds or extraordinarily +high tides, at times long before any considerable extent of seacoast was +diked. Several hundreds of those terrible inundations are recorded, and +in many of them the loss of human lives is estimated as high as one +hundred thousand. It is impossible to doubt that there must be enormous +exaggeration in these numbers; for, with all the reckless hardihood +shown by men in braving the dangers and privations attached by nature to +their birthplace, it is inconceivable that so dense a population as such +wholesale destruction of life supposes could find the means of +subsistence, or content itself to dwell, on a territory liable, a dozen +times in a century, to such fearful devastation. There can be no doubt, +however, that the low continental shores of the German Ocean very +frequently suffered immense injury from inundation by the sea, and it is +natural, therefore, that the various arts of resistance to the +encroachments of the ocean, and, finally, of aggressive warfare upon its +domain, and of permanent conquest of its territory, should have been +earlier studied and carried to higher perfection in the latter +countries, than in England, which had less to lose or to gain by the +incursions or the retreat of the waters. + +Indeed, although the confinement of swelling rivers by artificial +embankments is of great antiquity, I do not know that the defence or +acquisition of land from the sea by diking was ever practised on a large +scale until systematically undertaken by the Netherlanders, a few +centuries after the commencement of the Christian era. The silence of +the Roman historians affords a strong presumption that this art was +unknown to the inhabitants of the Netherlands at the time of the Roman +invasion, and the elder Pliny's description of the mode of life along +the coast which has now been long diked in, applies precisely to the +habits of the people who live on the low islands and mainland flats +lying outside of the chain of dikes, and wholly unprotected by +embankments of any sort. + + +Origin of Sea-dikes. + +It has been conjectured, and not without probability, that the causeways +built by the Romans across the marshes of the Low Countries, in their +campaigns against the Germanic tribes, gave the natives the first hint +of the utility which might be derived from similar constructions applied +to a different purpose. [Footnote: It has often been alleged by eminent +writers that a part of the fens in Lincolnshire was reclaimed by +sea-dikes under the government of the Romans. I have found no ancient +authority in support of this assertion, nor can I refer to any passage +in Roman literature in which sea-dikes are expressly mentioned otherwise +than as walls or piers, except that in Pliny (Hist. Nat. xxxvi. 24), +where it is said that the Tyrrhenian Sea was excluded from the Lucrino +Lake by dikes. Dugdale, whose enthusiasm for his subject led him to +believe that recovering from the sea land subject to be flooded by it, +was of divine appointment, because God said: "Let the waters under the +heavens be gathered together unto one place and let the dry land +appear," unhesitatingly ascribes the reclamation of the Lincolnshire +fens to the Romans, though he is able to cite but one authority, a +passage in Tacitus's Life of Agricola which certainly has no such +meaning, in support of the assertion.--History of Embankment and +Drainage, 2d edition, 1772.] If this is so, it is one of the most +interesting among the many instances in which the arts and enginery of +war have been so modified as to be eminently promotive of the blessings +of peace, thereby in some measure compensating the wrongs and sufferings +they have inflicted on humanity. [Footnote: It is worth mentioning, as +an illustration of the applicability of military instrumentalities to +pacific art, that the sale of gunpowder in the United States was smaller +during the late rebellion than before, because the war caused the +suspension of many public and private improvements, in the execution of +which great quantities of powder were used for blasting. + +The same observation was made in France during the Crimean war, and it +is alleged that, in general, not ten per cent. of the powder +manufactured on either either side of the Atlantic is employed for +military purposes. + +The blasting for the Mount Cenis tunnel consumed gunpowder enough to +fill more than 200,000,000 musket cartridges. It is a fact not +creditable to the moral sense of modern civilization, that very many of +the most important improvements in machinery and the working of metals +have originated in the necessities of war, and that man's highest +ingenuity has been shown, and many of his most remarkable triumphs over +natural forces achieved, in the contrivance of engines for the +destruction of his fellow-man. The military material employed by the +first Napoleon has become, in less than two generations, nearly as +obsolete as the sling and stone of the shepherd, and attack and defence +now begin at distances to which, half a century ago, military +reconnaissances hardly extended. Upon a partial view of the subject, the +human race seems destined to become its own executioner--on the one +hand, exhausting the capacity of the earth to furnish sustenance to her +taskmaster; on the other, compensating diminished production by +inventing more efficient methods of exterminating the consumer. At the +present moment, at an epoch of universal peace, the whole civilized +world with the happy exception of our own country, is devoting its +utmost energies, applying the highest exercise of inventive genius, to +the production of new engines of war; and the last extraordinary rise in +the price of iron and copper is in great part due to the consumption of +these metals in the fabrication of arms and armed vessels. The simple +substitution of sheet-copper for paper and other materials in the +manufacture of cartridges has increased the market-price of copper by a +large percentage on its former cost. + +But war develops great civil virtues, and brings into action a degree +and kind of physical energy which seldom fails to awaken a new +intellectual life in a people that achieves great moral and political +results through great heroism and endurance and perseverance. Domestic +corruption has destroyed more nations than foreign invasion, and a +people is rarely conquered till it has deserved subjugation.] The +Lowlanders are believed to have secured some coast and bay islands by +ring-dikes and to have embanked some fresh-water channels, as early as +the eighth or ninth century; but it does not appear that sea-dikes, +important enough to be noticed in historical records, were constructed +on the mainland before the thirteenth century. The practice of draining +inland accumulations of water, whether fresh or salt, for the purpose of +bringing under cultivation the ground they cover, is of later origin, +and is said not to have been adopted until after the middle of the +fifteenth century. [Footnote: Staring, Voormaals en Thans, p. 150.] + + +Gain and Loss of Land in the Netherlands. + +The total amount of surface gained to the agriculture of the Netherlands +by diking out the sea and by draining shallow bays and lakes, is +estimated by Staring at three hundred and fifty-five thousand bunder or +hectares, equal to eight hundred and seventy-seven thousand two hundred +and forty acres, which is one-tenth of the area of the kingdom. +[Footnote: Idem, p. 163. Much the largest proportion of the lands so +reclaimed, though for the most part lying above low-water tidemark, are +at a lower level than the Lincolnshire fens, and more subject to +inundation from the irruptions of the sea.] In very many instances the +dikes have been partially, in some particularly exposed localities +totally, destroyed by the violence of the sea, and the drained lands +again flooded. In some cases the soil thus painfully won from the ocean +has been entirely lost; in others it has been recovered by repairing or +rebuilding the dikes and pumping out the water. Besides this, the weight +of the dikes gradually sinks them into the soft soil beneath, and this +loss of elevation must be compensated by raising the surface, while the +increased burden thus added tends to sink them still lower. "Tetens +declares," says Kohl, "that in some places the dikes have gradually sunk +to the depth of sixty or even a hundred feet." [Footnote: Die Inseln und +Marschen der Herzogthamer Schleswig und Holstein, iii., p. 151.] For +these reasons, the processes of dike-building have been almost +everywhere again and again repeated, and thus the total expenditure of +money and of labor upon the works in question is much greater than would +appear from an estimate of the actual cost of diking-in a given extent +of coast-land and draining a given area of water-surface. [Footnote: +The purely agricultural island of Pelworm, off the coast of Schleswig, +containing about 10,000 acres, annually expends for the maintenance of +its dikes not less than L6,000 sterling, or nearly $30,000.--J. G. Kohl, +Inseln und Marschen Schleswig's und Holstein's, ii., p. 394. + +The original cost of the dikes of Pelworm is not stated. "The greatest +part of the province of Zeeland is protected by dikes measuring 250 +miles in length, the maintenance of which costs, in ordinary years, more +than a million guilders [above $400,000] ... The annual expenditure for +dikes and hydraulic works in Holland is from five to seven million +guilders" [$2,000,000 to $2,800,000].--Wild, Die Niederlande, i., p. 62. + +One is not sorry to learn that the Spanish tyranny in the Netherlands +had some compensations. The great chain of ring-dikes which surrounds a +large part of Zeeland is due to the energy of Caspar de Robles, the +Spanish governor of that province, who in 1570 ordered the construction +of these works at the public expense, as a substitute for the private +embankments which had previously partially served the same +purpose.--Wild, Die Niederlande, i., p. 62.] + + +Loss of Land by Incursions of Sea. + +On the other hand, by erosion of the coast-line, the drifting of +sand-dunes into the interior, and the drowning of fens and morasses by +incursions of the sea--all caused, or at least greatly aggravated, by +human improvidence--the Netherlands have lost a far larger area of land +since the commencement of the Christian era than they have gained by +diking and draining. Staring despairs of the possibility of calculating +the loss from the first-mentioned two causes of destruction, but he +estimates that not less than six hundred and forty thousand bunder, or +one million five hundred and eighty-one thousand acres, of fen and marsh +have been washed away, or rather deprived of their vegetable surface and +covered by water; and thirty-seven thousand bunder, or ninety-one +thousand four hundred acres, of recovered land, have been lost by the +destruction of the dikes which protected them. [Footnote: Staring, +Voormaals en Thans, p. 163.] The average value of land gained from the +sea is estimated at about nineteen pounds sterling, or ninety dollars, +per acre; while the lost fen and morass was not worth more than one +twenty-fifth part of the same price. The ground buried by the drifting +of the dunes appears to have been almost entirely of this latter +character, and, upon the whole, there is no doubt that the soil added by +human industry to the territory of the Netherlands, within the +historical period, greatly exceeds in pecuniary value that which has +fallen a prey to the waves during the same era. + +Upon most low and shelving coasts, like those of the Netherlands, the +maritime currents are constantly changing, in consequence of the +variability of the winds, and the shifting of the sand-banks, which the +currents themselves now form and now displace. While, therefore, at one +point the sea is advancing landward, and requiring great effort to +prevent the undermining and washing away of the dikes, it is shoaling at +another by its own deposits, and exposing, at low water, a gradually +widening belt of sands and ooze. The coast-lands selected for diking-in +are always at points where the sea is depositing productive soil. The +Eider, the Elbe, the Weser, the Ems, the Rhine, the Maas, and the +Schelde bring down large quantities of fine earth. The prevalence of +west winds prevents the waters from carrying this material far out from +the coast, and it is at last deposited northward or southward from the +mouth of the rivers which contribute it, according to the varying drift +of the currents. + + +Marine Deposits. + +The process of natural deposit which prepares the coast for diking-in is +thus described by Staring: "All sea-deposited soil is composed of the +same constituents. First comes a stratum of sand, with marine shells, or +the shells of mollusks living in brackish water. If there be tides, and, +of course, flowing and ebbing currents, mud is let fall upon the sand +only after the latter has been raised above low-water mark; for then +only, at the change from flood to ebb, is the water still enough to form +a deposit of so light a material. Where mud is found at great depths, +as, for example, in a large proportion of the Ij, it is a proof that at +this point there was never any considerable tidal flow or other current. +... The powerful tidal currents, flowing and ebbing twice a day, drift +sand with them. They scoop out the bottom at one point, raise it at +another, and the sand-banks in the current are continually shifting. As +soon as a bank raises itself above low-water mark, flags and reeds +establish themselves upon it. The mechanical resistance of these plants +checks the retreat of the high water and favors the deposit of the earth +suspended in it, and the formation of land goes on with surprising +rapidity. When it has risen to high-water level, it is soon covered +with grasses, and becomes what is called schor in Zeeland, kwelder in +Friesland. Such grounds are the foundation or starting-point of the +process of diking. When they are once elevated to the flood-tide level, +no more mud is deposited upon them except by extraordinary high tides. +Their further rise is, accordingly, very slow, and it is seldom +advantageous to delay longer the operation of diking." [Footnote: +Voormaals en Thans, pp. 150, 151. According to Reventlov, confercae +first appear at the bottom in shoal water, then, after the deposit has +risen above the surface, Salicornia herbacea. The Salicornia is followed +by various sand-plants, and so the ground rises, by Poa distans and Poa +maritum, and finally common grasses establish themselves.--Om +Markdannelsen poa Vestkyeten of Slesvig, pp. 7, 8.] + + +Sea-dikes of the Netherlands. + +The formation of new banks by the sea is constantly going on at points +favorable for the deposit of sand and earth, and hence opportunity is +continually afforded for enclosure of new land outside of that already +diked in, the coast is fast advancing seaward, and every new embankment +increases the security of former enclosures. The province of Zeeland +consists of islands washed by the sea on their western coasts, and +separated by the many channels through which the Schelde and some other +rivers find their way to the ocean. In the twelfth century these islands +were much smaller and more numerous than at present. They have been +gradually enlarged, and, in several instances, at last connected by the +extension of their system of dikes. Walcheren is formed of ten islets +united into one about the end of the fourteenth century. At the middle +of the fifteenth century, Goeree and Overflakkee consisted of separate +islands, containing altogether about ten thousand acres; by means of +above sixty successive advances of the dikes, they have been brought to +compose a single island, whose area is not less than sixty thousand +acres. [Footnote: Staring, Voormaals en Thans, p, 152. Kohl states that +the peninsula of Diksand on the coast of Holstein consisted, at the +close of the last century, of several islands measuring together less +than five thousand acres. In 1837 they had been connected with the +mainland, and had nearly doubled in area.--Inseln u. Marschen Schlene, +Holst., iii., p. 202] + +In the Netherlands--which the first Napoleon characterized as a deposit +of the Rhine, and as, therefore, by natural law, rightfully the property +of him who controlled the sources of that great river--and on the +adjacent Frisie, Low German, and Danish shores and islands, sea and +river dikes have been constructed on a grander and more imposing scale +than in any other country. The whole economy of the art has been there +most thoroughly studied, and the literature of the subject is very +extensive. For my present aim, which is concerned with results rather +than with processes, it is not worth while to refer to professional +treatises, and I shall content myself with presenting such information +as can be gathered from works of a more popular character. + +The superior strata of the lowlands upon and near the coast are, as we +have seen, principally composed of soil brought down by the great rivers +I have mentioned, and either directly deposited by them upon the sands +of the bottom, or carried out to sea by their currents, and then, after +a shorter or longer exposure to the chemical and mechanical action of +salt-water and marine currents, restored again to the land by tidal +overflow and subsidence from the waters in which it was suspended. At a +very remote period the coast-flats were, at many points, raised so high +by successive alluvious or tidal deposits as to be above ordinary +high-water level, but they were still liable to occasional inundation +from river-floods, and from the seawater also, when heavy or +long-continued west winds drove it landwards. The extraordinary +fertility of this soil and its security as a retreat from hostile +violence attracted to it a considerable population, while its want of +protection against inundation exposed it to the devastations of which +the chroniclers of the Middle Ages have left such highly colored +pictures. The first permanent dwellings on the coast-flats were erected +upon artificial mounds, and many similar precarious habitations still +exist on the unwalled islands and shores beyond the chain of dikes. +River embankments, which, as is familiarly known, have from the earliest +antiquity been employed in many countries where sea-dikes are unknown, +were probably the first works of this character constructed in the Low +Countries, and when two neighboring streams of fresh water had been +embanked, the next step in the process would naturally be to connect the +river-walls together by a transverse dike or raised causeway, which +would serve as a means of communication between different hamlets and at +the same time secure the intermediate ground both against the backwater +of river-floods and against overflow by the sea. The oldest true +sea-dikes described in historical records, however, are those enclosing +islands in the estuaries of the great rivers, and it is not impossible +that the double character they possess as a security against maritime +floods and as a military rampart, led to their adoption upon those +islands before similar constructions had been attempted upon the +mainland. + +At some points of the coast, various contrivances, such as piers, piles, +and, in fact, obstructions of all sorts to the ebb of the current, are +employed to facilitate the deposit of slime, before a regular enclosure +is commenced. Usually, however, the first step is to build low and cheap +embankments, extending from an older dike, or from high ground, around +the parcel of flat intended to be secured. These are called summer +dikes. They are erected when a sufficient extent of ground to repay the +cost has been elevated enough to be covered with coarse vegetation fit +for pasturage. They serve both to secure the ground from overflow by the +ordinary flood-tides of mild weather, and to retain the slime deposited +by very high water, which would otherwise be partly carried off by the +retreating ebb. The elevation of the soil goes on slowly after this; but +when it has at last been sufficiently enriched, and raised high enough +to justify the necessary outlay, permanent dikes are constructed by +which the water is excluded at all seasons. These embankments are +constructed of sand from the coast-dunes or from sand-banks, and of +earth from the mainland or from flats outside the dikes, bound and +strengthened by fascines, and provided with sluices, which are generally +founded on piles and of very expensive construction, for drainage at low +water. The outward slope of the sea-dikes is gentle, experience having +shown that this form is least exposed to injury both from the waves and +from floating ice, and the most modern dikes are even more moderate in +the inclination of the seaward scarp than the older ones. [Footnote: The +inclination varies from one foot rise in four of base to one foot in +fourteen.--Kohl, iii., p. 210.] The crown of the dike, however, for the +last three or four feet of its height, is much steeper, being intended +rather as a protection against the spray than against the waves, and the +inner slope is always comparatively abrupt. + +The height and thickness of dikes varies according to the elevation of +the ground they enclose, the rise of the tides, the direction of the +prevailing winds, and other special causes of exposure, but it may be +said that they are, in general, raised from fifteen to twenty feet above +ordinary high-water mark. The water-slopes of river-dikes are protected +by plantations of willows or strong semi-aquatic shrubs or grasses, but +as these will not grow upon banks exposed to salt-water, sea-dikes must +be faced with stone, fascines, or some other revetement. [Footnote: The +dikes are sometimes founded upon piles, and sometimes protected by one +or more rows of piles driven deeply down into the bed of the sea in +front of them. "Triple rows of piles of Scandinavian pine," says Wild, +"have been driven down along the coast of Friesland, where there are no +dunes, for a distance of one hundred and fifty miles. The piles are +bound together by strong cross-timbers and iron clamps, and the +interstices filled with stones. The ground adjacent to the piling is +secured with fascines, and at exposed points heavy blocks of stone are +heaped up as an additional protection. The earth-dike is built behind +the mighty bulwark of this breakwater, and its foot also is fortified +with stones." ... "The great Helder dike is about five miles long and +forty feet wide at the top, along which runs a good road. It slopes down +two hundred feet into the sea, at an angle of forty degrees. The highest +waves do not reach the summit, the lowest always cover its base. At +certain distances, immense buttresses, of a height and width +proportioned to those of the dike, and even more strongly built, run +several hundred feet out into the rolling sea. This gigantic artificial +coast is entirely composed of Norwegian granite."--Wild, Die +Niederlande, i., pp. 61, 62.] Upon the coast of Schleswig and Holstein, +where the people have less capital at their command, they defend their +embankments against ice and the waves by a coating of twisted straw or +reeds, which must be renewed as often as once, sometimes twice a year. +The inhabitants of these coasts call the chain of dikes "the golden +border," a name it well deserves, whether we suppose it to refer to its +enormous cost, or, as is more probable, to its immense value as a +protection to their fields and their firesides. + +When outlying flats are enclosed by building new embankments the old +interior dikes are suffered to remain, both as an additional security +against the waves, and because the removal of them would be expensive. +They serve, also, as roads or causeways, a purpose for which the +embankments nearest the sea are seldom employed, because the whole +structure might be endangered from the breaking of the turf by wheels +and the hoofs of horses. Where successive rows of dikes have been thus +constructed, it is observed that the ground defended by the more ancient +embankments is lower than that embraced within the newer enclosures, and +this depression of level has been ascribed to a general subsidence of +the coast from geological causes; [Footnote: A similar subsidence of the +surface is observed in the diked ground of the Lincolnshire fens, where +there is no reason to suspect a general depression from geological +causes.] but the better opinion seems to be that it is, in most cases, +due merely to the consolidation and settling of the earth from being +more effectually dried, from the weight of the dikes, from the tread of +men and cattle, and from the movement of the heavy wagons which carry +off the crops. [Footnote: The shaking of the ground, even when loaded +with large buildings, by the passage of heavy carriages or artillery, or +by the march of a body of cavalry or even infantry, shows that such +causes may produce important mechanical effects on the condition of the +soil. The bogs in the Netherlands, as in most other countries, contain +large numbers of fallen trees, buried to a certain depth by earth and +vegetable mould. When the bogs are dry enough to serve as pastures, it +is observed that trunks of these ancient trees rise of themselves to the +surface. Staring ascribes this singular phenomenon to the agitation of +the ground by the tread of cattle. "When roadbeds," observes he, "are +constructed of gravel and pebbles of different sizes, and these latter +are placed at the bottom without being broken and rolled hard together, +they are soon brought to the top by the effect of travel on the road. +Lying loosely, they undergo some motion from the passage of every +wagon-wheel and the tread of every horse that passes over them. This +motion is an oscillation or partial rolling, and as one side of a pebble +is raised, a little fine sand or earth is forced under it, and the +frequent repetition of this process by cattle or carriages moving in +opposite directions brings it at last to the surface. We may suppose +that a similar effect is produced on the stems of trees in the bogs by +the tread of animals."--De Bodem van Nederland, i., pp. 75, 76. + +It is observed in the Northern United States, that when soils containing +pebbles are cleared and cultivated, and the stones removed from the +surface, new pebbles, and even bowlders of many pounds weight, continue +to show themselves above the ground, every spring, for a long series of +years. In clayey soils the fence-posts are thrown up in a similar way, +and it is not uncommon to see the lower rail of a fence thus gradually +raised a foot or even two feet above the ground. This rising of stones +and fences is popularly ascribed to the action of the severe frosts of +that climate. The expansion of the ground, in freezing, it is said, +raises its surface, and, with the surface, objects lying near or +connected with it. When the soil thaws in the spring, it settles back +again to its former level, while the pebbles and posts are prevented +from sinking as low as before by loose earth which has fallen under +them. The fact that the elevation spoken of is observed only in the +spring gives countenance to this theory, which is perhaps applicable +also to the cases stated by Staring, and it is probable that the two +causes above assigned concur in producing the effect. + +The question of the subsidence of the Netherlandish coast has been much +discussed. Not to mention earlier geologists, Venema, in several essays, +and particularly in Het Dalen van de Noordelijke Kuststreken van ons +Land, 1854, adduces many facts and arguments to prove a slow sinking of +the northere provinces of Holland. Laveleye (Affaissement du sol at +envasement des fleuves survenus dans les temps historiques, 1859), upon +a still fuller investigation, arrives at the same conclusion. The +eminent geologist Staring, however, who briefly refers to the subject in +De Bodem van Nederland, i., p. 356 et seqq., does not consider the +evidence sufficient to prove anything more than the sinking of the +surface of the polders from drying and consolidation.--See Elisee +Reclus, La Terre, vol. i., pp. 730, 732.] + +Notwithstanding this slow sinking, most of the land enclosed by dikes is +still above low-water mark, and can, therefore, be wholly or partially +freed from rain-water, and from that received by infiltration from +higher ground, by sluices opened at the ebb of the tide. For this +purpose the land is carefully ditched, and advantage is taken of every +favorable occasion for discharging the water through the sluices. But +the ground cannot be effectually drained by this means, unless it is +elevated four or five feet, at least, above the level of the ebb-tide +because the ditches would not otherwise have a sufficient descent to +carry the water off in the short interval between ebb and flow, and +because the moisture of the saturated sub-soil is always rising by +capillary attraction. Whenever, therefore, the soil has sunk below the +level I have mentioned, and in cases where its surface has never been +raised above it, pumps, worked by wind or some other mechanical power, +must be very frequently employed to keep the land dry enough for +pasturage and cultivation. [Footnote: The elevation of the lands +enclosed by dikes--or polders, as they are called in Holland--above +low-water mark, depends upon the height of the tides or, in other words, +upon the difference between ebb and flood. The tide cannot deposit earth +higher than it flows, and after the ground is once enclosed, the decay +of the vegetables grown upon it and the addition of manures do not +compensate the depression occasional by drying and consolidation. On the +coast of Zeeland and the islands of South Holland, the tides, and of +course the surface of the lands deposited by them, are so high that the +polders can be drained by ditching and sluices, but at other points, as +in the enclosed grounds of North Holland on the Zuiderzee, where the +tide rises but three feet or even less, pumping is necessary from the +beginning.--Staring, Voormaals en Thans, p. 152] + + +DRAINING OF THE LAKE OF HAARLEM. + +The substitution of steam-engines for the feeble and uncertain action of +windmills, in driving pumps, has much facilitated the removal of water +from the polders as well as the draining of lakes, marshes, and shallow +bays, and thus given such an impulse to these enterprises, that not less +than one hundred and ten thousand acres wore reclaimed from the waters, +and added to the agricultural domain of the Netherlands, between 1815 +and 1855. The most important of these undertaking was the draining of +the Lake of Haarlem, and for this purpose some of the most powerful +hydraulic engines over constructed were designed and executed. +[Footnote: The principal engine, of 500 horse-power, drove eleven pumps +with a total delivery of 31,000 cubic yards per hour.--Wild, Die +Netherland, i., p. 87.] The origin of this lake is unknown. It is +supposed by some geographers to be a part of an ancient bed of the +Rhine, the channel of which, as there is good reason to believe, has +undergone great changes since the Roman invasion of the Netherlands; by +others it is thought to have once formed an inland marine channel, +separated from the sea by a chain of low islands, which the sand washed +up by the tides has since connected with the mainland and converted into +a continuous line of coast. The best authorities, however, find +geological evidence that the surface occupied by the lake was originally +a marshy tract containing within its limits little solid ground, but +many ponds and inlets, and much floating as well as fixed fen. + +In consequence of the cutting of turf for fuel, and the destruction of +the few trees and shrubs which held the loose soil together with their +roots, the ponds are supposed to have gradually extended themselves, +until the action of the wind upon their enlarged surface gave their +waves sufficient force to overcome the resistance of the feeble barriers +which separated them, and to unite them all into a single lake. Popular +tradition, it is true, ascribes the formation of the Lake of Haarlem to +a single irruption of the sea, at a remote period, and connects it with +one or another of the destructive inundations of which the Netherland +chronicles describe so many; but on a map of the year 1531, a chain of +four smaller waters occupies nearly the ground afterwards covered by the +Lake of Haarlem, and they have most probably been united by gradual +encroachments resulting from the improvident practices above referred +to, though no doubt the consummation may have been hastened by floods, +and by the neglect to maintain dikes, or the intentional destruction of +them, in the long wars of the sixteenth century. + +The Lake of Haarlem was a body of water not far from fifteen miles in +length, by seven in greatest width, lying between the cities of +Amsterdam and Leyden, running parallel with the coast of Holland at the +distance of about five miles from the sea, and covering an area of about +45,000 acres. By means of the Ij, it communicated with the Zuiderzee, +the Mediterranean of the Netherlands, and its surface was little above +the mean elevation of that of the sea. Whenever, therefore, the waters +of the Zuiderzee were acted upon by strong north-west winds, those of +the Lake of Haarlem were raised proportionally and driven southwards, +while winds from the south tended to create a flow in the opposite +direction. The shores of the lake were everywhere low, and though +between the years 1767 and 1848 more than $1,700,000 had been expended +in checking its encroachments, it often burst its barriers, and produced +destructive inundations. In November, 1836, a south wind brought its +waters to the very gates of Amsterdam, and in December of the same year, +in a north-west gale, they overflowed twenty thousand acres of land at +the southern extremity of the lake, and flooded a part of the city of +Leyden. The depth of water in the lake did not, in general, exceed +fourteen feet, but the bottom was a semi-fluid ooze or slime, which +partook of the agitation of the waves, and added considerably to their +mechanical force. Serious fears were entertained that the lake would +form a junction with the inland waters of the Legmeer and Mijdrecht, +swallow up a vast extent of valuable soil, and finally endanger the +security of a large proportion of the land which the industry of Holland +had gained in the course of centuries from the ocean. + +For this reason, and for the sake of the large addition the bottom of +the lake would make to the cultivable soil of the state, it was resolved +to drain it, and the preliminary steps for that purpose were commenced +in the year 1840. The first operation was to surround the entire lake +with a ring-canal and dike, in order to cut off the communication with +the Ij, and to exclude the water of the streams and morasses which +discharged themselves into it from the land side. The dike was composed +of different materials, according to the means of supply at different +points, such as sand from the coast-dunes, earth and turf excavated from +the line of the ring-canal, and floating turf, [Footnote: In England and +New England, where the marshes have been already drained or are of +comparatively small extent, the existence of large floating islands +seems incredible, and has sometimes been treated as a fable, but no +geographical fact is better established. Kohl (Inseln und Marschen +Schleswig-Holsteins, iii., p. 309) reminds us that Pliny mentions among +the wonders of Germany the floating islands, covered with trees, which +met the Roman fleets at the mouths of the Elbe and the Weser. Our author +speaks also of having visited, in the territory of Bremen, floating +moors, bearing not only houses but whole villages. At low stages of the +water these moors rest upon a bed of sand, but are raised from six to +ten feet by the high water of spring, and remain afloat until, in the +course of the summer, the water beneath is exhausted by evaporation and +drainage, when they sink down upon the sand again. + +Staring explains, in an interesting way, the whole growth, formation, +and functions of floating fens or bogs, in his very valuable work, De +Bodem van Nederland, i., pp. 36-43. The substance of his account is as +follows: The turf and the surface of the fens, is stillness of the +water. Hence they are not found in running streams, nor in pools so +large as to be subject to frequent agitation by the wind. For example, +not a single plant grew in the open part of the Lake of Haarlem, and +fens cease to form in all pools as soon as, by the cutting of the turf +for fuel or other purposes, their area is sufficiently enlarged to be +much acted on by wind. When still water above a yard deep is left +undisturbed, aquatic plants of various genera, such as Nuphar, Nymphaea, +Limnanthemum, Stratiotes, Polygonum, and Potamogeton, fill the bottom +with roots and cover the surface with leaves. Many of the plants die +every year, and prepare at the bottom a soil fit for the growth of a +higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex, +Lythrum, Pedicularis, Spiraea, Polystichum, Comarum, Caltha, etc., etc. +In the course of twenty or thirty years the muddy bottom is filled with +roots of aquatic and marsh plants, which are lighter than water, and if +the depth is great enough to give room for detaching this vegetable +network, a couple of yard for example, it rises to the surface, bearing +with it, of course, the soil formed above it by decay of stems and +leaves. New genera now appear upon the mass, such a Carex, Menyanthes, +and others, and soon thicky cover it. The turf has now acquired a +thickness of from two to four feet, and is called in Groningen lad; in +Friesland, til, tilland, or drifftil; in Overijsse, krag; and in +Holland, rietzod. It floats about as driven by the wind, gradually +increasing in thickness by the decay of its annual crops of vegetation, +and in about half a century reaches the bottom and becomes fixed. If it +has not been invaded in the meantime by men or cattle, trees and +arborescent plants, Alnus, Salix, Myrica, etc., appear, and these +contribute to hasten the attachment of the turf to the bottom, both by +their weight and by sending their roots quite through into the ground." + +This is the regular method employed by nature for the gradual filling up +of shallow lakes and pools, and converting them first into morass and +then into dry land. Whenever, therefore, man removes the peat or turf, +he exerts an injurious geographical agency, and, as I have already said, +there is no doubt that the immense extension of the inland seas of +Holland in modern times is owing to this and other human imprudences. +"Hundreds of hectares of floating pastures," says our author, "which +have nothing in their appearance to distinguish them from grass-lands +resting on solid bog, are found in Overijssel, in North Holland, and +near Utrecht. In short, they occur in all deep bogs, and wherever deep +water is left long undisturbed." + +In one case a floating island, which had attached itself to the shore, +continued to float about for a long time after it was torn off by a +flood, and was solid enough to keep a pond of fresh water upon it sweet, +though the water in which it was swimming had become brackish from the +irruption of the sea. After the hay is cut, cattle are pastured, and +occasionally root-crops grown upon these islands, and they sometimes +have large trees growing upon them. + +When the turf or peat has been cut, leaving water less than a yard deep, +Equisetum limosum grows at once, and is followed by the second class of +marsh plants mentioned above. Their roots do not become detached from +the bottom in such shallow water, but form ordinary turf or peat. These +processes are so rapid that a thickness of from three to six feet of +turf is formed in half a century, and many men have lived to mow grass +where they had fished in their boyhood, and to cut turf twice in the +same spot. In Ireland the growth of peat is said to be much more rapid. +Elisee Reclus, La Terre, i., 591, 592. But see Asbjornsen, Torv og +Torvdrift, ii., 29, 30. + +Captain Gilliss says that before Lake Taguataga in Chili was drained, +there were in it islands composed of dead plants matted together to a +thickness of from four to six feet, and with trees of medium size +growing upon them. These islands floated before the wind "with their +trees and browsing cattle."--United States Naval Astronomical Expedition +to the Southern Hemisphere, i., pp. 16, 17.] fascines being everywhere +used to bind and compact the mass together. This operation was completed +in 1848, and three steam-pumps were then employed for five years in +discharging the water. The whole enterprise was conducted at the expense +of the state, and in 1853 the recovered lands were offered for sale for +its benefit. Up to 1858, forty-two thousand acres had been sold at not +far from sixteen pounds sterling or seventy-seven dollars an acre, +amounting altogether to L661,000 sterling or $3,200,000. The unsold +lands were valued at more than L6,000 or nearly $30,000, and as the +total cost was L764,500 or about $3,700,000, the direct loss to the +state, exclusive of interest on the capital expended, may be stated at +L100,000 or something less than $500,000. + +The success of this operation has encouraged others of like nature in +Holland. The Zuid Plas, which covered 11,500 acres and was two feet +deeper than the Lake of Haarlem, has been drained, and a similar work +now in course of execution on an arm of the Scheld, will recover about +35,000 acres. + +In a country like the United States, of almost boundless extent of +sparsely inhabited territory, such an expenditure for such an object +would be poor economy. But Holland has a narrow domain, great pecuniary +resources, an excessively crowded population, and a consequent need of +enlarged room and opportunity for the exercise of industry. Under such +circumstances, and especially with an exposure to dangers so formidable, +there is no question of the wisdom of the measure. It has already +provided homes and occupation for more than five thousand citizens, and +furnished a profitable investment for a private capital of not less than +L400,000 sterling or $2,000,000, which has been expended in improvements +over and above the purchase money of the soil; and the greater part of +this sum, as well as of the cost of drainage, has been paid as a +compensation for labor. The excess of governmental expenditure over the +receipts, if employed in constructing ships of war or fortifications, +would have added little to the military strength of the kingdom; but the +increase of territory, the multiplication of homes and firesides which +the people have an interest in defending, and the augmentation of +agricultural resources, constitute a stronger bulwark against foreign +invasion than a ship of the line or a fortress armed with a hundred +cannon. + + +Draining of the Zuiderzee. + +I have referred to the draining of the Lake of Haarlem as an operation +of great geographical as well as economical and mechanical interest. A +much more gigantic project, of a similar character, is now engaging the +attention of the Netherlandish engineers. It is proposed to drain the +great salt-water basin called the Zuiderzee. This inland sea covers an +area of not less than two thousand square miles, or about one million +three hundred thousand acres. The seaward half, or that portion lying +north-west of a line drawn from Enkhuizen to Stavoren, is believed to +have been converted from a marsh to an open bay since the fifth century +after Christ, and this change is ascribed, partly if not wholly, to the +interference of man with the order of nature. The Zuiderzee communicates +with the sea by at least six considerable channels, separated from each +other by low islands, and the tide rises within the basin to the height +of three feet. To drain the Zuiderzee, these channels must first be +closed and the passage of the tidal flood through them cut off. If this +be done, the coast currents will be restored approximately to the lines +they followed fourteen or fifteen centuries ago, and thero can be little +doubt that an appreciable effect will thus be produced upon all the +tidal phenomena of that coast, and, of course, upon the maritime +geography of Holland. + +A ring-dike and canal must then be constructed around the landward side +of the basin, to exclude and carry off the freshwater streams which now +empty into it. One of these, the Ijssel, a considerable river, has a +course of eighty miles, and is, in fact, one of the outlets of the +Rhine, though augmented by the waters of several independent +tributaries. These preparations being made, and perhaps transverse dikes +erected at convenient points for dividing the gulf into smaller +portions, the water must be pumped out by machinery, in substantially +the same way as in the case of the Lake of Haarlem. [Footnote: The +dependence of man upon the aid of spontaneous nature, in his most +arduous material works, is curiously illustrated by the fact that one of +the most serious difficulties to be encountered in executing this +gigantic scheme is that of procuring brushwood for the fascines to be +employed in the embankments. See Diggelen's pamphlet, "Groote Werken in +Nederland."] No safe calculations can be made as to the expenditure of +time and money required for the execution of this stupendous enterprise, +but I believe its practicability is not denied by competent judges, +though doubts are entertained as to its financial expediency. [Footnote: +The plan at present most in favor is that which proposes the drainage of +only a portion of the southern half of the Zuiderzee, which covers not +far from 400,000 acres. The project for the construction of a ship-canal +directly from Amsterdam to the North Sea, now in course of execution, +embraces the drainage of the Ij, a nearly land-locked basin +communicating with the Zuiderzee and covering more than 12,000 acres. +See official reports on these projects in Droogmaking vom het zuidelyk +gedeelte der Zuiderzee, te s' Gravenhage, 1868, 4to.] The geographical +results of this improvement would be analogous to those of the draining +of the Lake of Haarlem, but many times multiplied in extent, and its +meteorological effects, though perhaps not perceptible on the coast, +could hardly fail to be appreciable in the interior of Holland. + +The bearing of the works I have noticed, and of others similar in +character, upon the social and moral, as well as the purely economical, +interests of the people of the Netherlands, has induced me to describe +them more in detail than the general purpose of this volume may be +thought to justify; but if we consider them simply from a geographical +point of view, we shall find that they are possessed of no small +importance as modifications of the natural condition of terrestrial +surface. There is good reason to believe that before the establishment +of a partially civilized race upon the territory now occupied by Dutch, +Frisic, and Low German communities, the grounds not exposed to +inundation were overgrown with dense woods; that the lowlands between +these forests and the sea-coasts were marshes, covered and partially +solidified by a thick matting of peat-plants and shrubs interspersed +with trees; and that even the sand-dunes of the shore were protected by +a vegetable growth which, in a great measure, prevented the drifting and +translocation of them. + +The present causes of river and coast erosion existed, indeed, at the +period in question; but some of them must have acted with less +intensity, there were strong natural safeguards against the influence of +marine and fresh-water currents, and the conflicting tendencies had +arrived at a condition of approximate equilibrium, which permitted but +slow and gradual changes in the face of nature. The destruction of the +forests around the sources and along the valleys of the rivers by man +gave them a more torrential character. The felling of the trees, and the +extirpation of the shrubbery upon the fens by domestic cattle, deprived +the surface of its cohesion and consistence, and the cutting of peat for +fuel opened cavities in it, which, filling at once with water, rapidly +extended themselves by abrasion of their borders, and finally enlarged +to pools, lakes, and gulfs, like the Lake of Haarlem and the northern +part of the Zuiderzee. The cutting of the wood and the depasturing of +the grasses upon the sand-dunes converted them from solid bulwarks +against the ocean to loose accumulations of dust, which every sea-breeze +drove farther landward, burying, perhaps, fertile soil and choking up +water-courses on one side, and exposing the coast to erosion by the sea +upon the other. + + +Geographical Effect of Physical Improvements in the Netherlands. + +The changes which human action has produced within twenty centuries in +the Netherlands and the neighboring provinces, are, certainly of no +small geographical importance, considered simply as a direct question of +loss and gain of territory. They have also, as we shall see hereafter, +undoubtedly been attended with some climatic consequences, they have +exercised a great influence on the spontaneous animal and vegetable life +of this region, and they cannot have failed to produce effects upon +tidal and other oceanic currents, the range of which may be very +extensive. The force of the tidal wave, the height to which it rises, +the direction of its currents, and, in fact, all the phenomena which +characterize it, as well as all the effects it produces, depend as much +upon the configuration of the coast it washes, and the depth of water, +and form of bottom near the shore, as upon the attraction which +occasions it. Every one of the terrestrial conditions which affect the +character of tidal and other marine currents has been very sensibly +modified by the operations I have described, and on this coast, at +least, man has acted almost as powerfully on the physical geography of +the sea as on that of the land. [Footnote: See, on the influence of the +artificial modification of the coast-line on tides and other marine +currents, Staring, De Bodem van Nederland, i., p. 279.] + + +Ancient Hydraulic Works. + +The hydraulic works of the Netherlands and of the neighboring states are +of such magnitude that--with the exception of the dikes of the +Mississippi--they quite throw into the shade all other known artificial +arrangements for defending the land against the encroachments of the +rivers and the sea, and for reclaiming to the domain of agriculture and +civilization soil long covered by the waters. But although the recovery +and protection of lands flooded by the sea seems to be an art wholly of +Netherlandish origin, we have abundant evidence that, in ancient as well +as in comparatively modern times, great enterprises more or less +analogous in character have been successfully undertaken, both in inland +Europe and in the less familiar countries of the East. + +In many cases no historical record remains to inform us when or by whom +such works were constructed. The Greeks and Romans, the latter +especially, were more inclined to undertake and carry out stupendous +material enterprises than to boast of them; and many of the grandest and +most important constructions of those nations are absolutely unnoticed +by contemporary annalists, and are first mentioned by writers living +after all knowledge of the epochs of the projectors of these works had +perished. Thus the aqueduct known as the Pont du Gard, near Nimes, +which, though not surpassing in volume or in probable cost other +analogous constructions of ancient and of modern ages, is yet among the +most majestic and imposing remains of ancient civil architecture, is not +so much as spoken of by any Roman author, [Footnote: One reason for the +silence of Roman writers in respect to great material improvements which +had no immediate relation to military or political objects, is doubtless +the contempt in which mechanical operations and mechanical contrivances +were held by that nation of spoilers. Even the engineer, upon whose +skill the attack or defence of a great city depended, was only +praefectus fabrum, the master-artisan, and had no military rank or +command. This prejudice continued to a late period in the Middle Ages, +and the chiefs of artillery were equally without grade or title as +soldiers. + +"The occupations of all artisans," says Cicero, "are base, and the shop +can have nothing of the respectable." De Officiis, 1, i., 42. The +position of the surgeon relatively to the physician, in England, is a +remnant of the same prejudice, which still survives in full vigor in +Italy, with regard to both trade and industry. See p. 6, ante.] and we +are in absolute ignorance of the age or the construction of the +remarkable tunnel cut to drain Lake Copais in Boeotia. This lake, now +reduced by sedimentary deposit and the growth of aquatic and +semi-aquatic vegetation to the condition of a marsh, was originally +partially drained by natural subterranean outlets in the underlying +limestone rock, many of which still exist. But these emissaries, or +katavothra, as they are called in both ancient and modern Greek, were +insufficient for the discharge of the water, and besides, they were +constantly liable to be choked by earth and vegetables, and in such +cases the lake rose to a height which produced much injury. To remedy +this evil and secure a great accession of fertile soil, at some period +anterior to the existence of a written literature in Greece and ages +before the time of any prose author whose works have come down to us, +two tunnels, one of them four miles long, and of course not inferior to +the Torlonian emissary in length, were cut through the solid rock, and +may still be followed throughout their whole extent. They were repaired +in the time of Alexander the Great, in the fourth century before Christ, +and their date was at that time traditionally referred to the reign of +rulers who lived as early as the period of the Trojan war. + +One of the best known hydraulic works of the Romans is the tunnel which +serves to discharge the surplus waters of the Lake of Albano, about +fourteen miles from Rome. This lake, about six miles in circuit, +occupies one of the craters of an extinct volcanic range, and the +surface of its waters is about nine hundred feet above the sea. It is +fed by rivulets and subterranean springs originating in the Alban Mount, +or Monte Cavo, the most elevated peak of the volcanic group just +mentioned, which rises to the height of about three thousand feet. At +present the lake has no discoverable natural outlet, and it is not known +that the water ever stood at such a height as to flow regularly over the +lip of the crater. It seems that at the earliest period of which we have +any authentic memorials, its level was usually kept by evaporation, or +by discharge through subterranean channels, considerably below the rim +of the basin which encompassed it, but in the year 397 B.C., the water, +either from the obstruction of such channels, or in consequence of +increased supplies from unknown sources, rose to such a height as to +flow over the edge of the crater, and threaten inundation to the country +below by bursting through its walls. To obviate this danger, a tunnel +for carrying off the water was pierced at a level much below the height +to which it had risen. This gallery, cut entirely with the chisel +through the rock for a distance of six thousand feet, or nearly a mile +and one-seventh, is still in so good condition as to serve its original +purpose. The fact that this work was contemporaneous with the siege of +Veii, has given to ancient annalists occasion to connect the two events, +but modern critics are inclined to reject Livy's account of the matter, +as one of the many improbable fables which disfigure the pages of that +historian. It is, however, repeated by Cicero and by Dionysius of +Halicarnassus, and it is by no means impossible that, in an age when +priests and soothsayers monopolized both the arts of natural magic and +the little which yet existed of physical science, the Government of +Rome, by their aid, availed itself at once of the superstition and of +the military ardor of its citizens to obtain their sanction to an +enterprise which sounder arguments might not have induced them to +approve. + +Still more remarkable is the tunnel cut by the Emperor Claudius to drain +the Lake Fucinus, now Lago di Celano, in the former Neapolitan +territory, about fifty miles eastward of Rome. This lake, as far as its +history is known, has varied very considerably in its dimensions at +different periods, according to the character of the seasons. It lies +2,200 feet above the sea, and has no visible outlet, but was originally +either drained by natural subterranean conduits, or kept within certain +extreme limits by evaporation. In years of uncommon moisture it spread +over the adjacent soil and destroyed the crops; in dry seasons it +retreated, and produced epidemic disease by poisonous exhalations from +the decay of vegetable and animal matter upon its exposed bed. Julius +Caesar had proposed the construction of a tunnel to lower the bed of the +lake and provide a regular discharge for its waters, but the enterprise +was not actually undertaken until the reign of Claudius, when--after a +temporary failure, from errors in levelling by the engineers, as was +pretended at the time, or, as now appears certain, in consequence of +frauds by the contractors in the execution of the work--it was at least +partially completed. From this imperfect construction, it soon got out +of repair, but was restored by Hadrian, and is said to have answered its +design for some centuries. [Footnote: The fact alluded to in a note on +p. 97, ante, that since the opening of a communication between Lake +Celano and the Garigliano by the works noticed in the text, fish, of +species common in the lake, but not previously found in the river, have +become naturalized in the Garigliano, is a circumstance of some weight +as evidence that the emissary was not actually open in ancient times; +for if the waters had been really connected, the fish of the lake would +naturally have followed the descending current and established +themselves in the river as they have done now.] In the barbarism which +followed the downfall of the empire, it again fell into decay, and +though numerous attempts were made to repair it during the Middle Ages, +no tolerable success seems to have attended any of these efforts until +the present generation. + + +Draining of Lake Celano by Prince Torlonia. + +Works have been some years in progress and are now substantially +completed, at a cost of about six millions of dollars, for restoring, or +rather enlarging and rebuilding, this ancient tunnel, upon a scale of +grandeur which does infinite honor to the liberality and public spirit +of the projectors, and with an ingenuity of design and a constructive +skill which reflect the highest credit upon the professional ability of +the engineers who have planned the works and directed their execution. +The length of the Roman tunnel was 18,634 feet, or rather more than +three miles and a half, but as the new emissary is designed to drain the +lake to the bottom, it must be continued to the lowest part of the +basin. It will consequently have a length of not less than 21,000 feet, +and, of course, is among the longest subterranean galleries in Europe. +Many curious particulars in the design and execution of the original +work have been observed in the course of the restoration, but these +cannot here be noticed. The difference between the lowest and highest +known levels of the surface of the lake is rather more than forty feet +and the difference between the areas covered by water at these levels is +not less than nine thousand acres. The complete drainage of the lake, +including the ground occasionally flooded, will recover, for +agricultural occupation, and permanently secure from inundation, about +forty-two thousand acres of as fertile soil as any in Italy. [Footnote: +Springs rising in the bottom of the lake have materially impeded the +process of drainage, and some engineers believe that they will render +the complete discharge of the waters impossible. It appears that the +earthy and rocky strata underlying the lake are extremely porous, and +that the ground already laid dry on the surface absorbs an abnormally +large proportion of the precipitation upon it. These strata, therefore, +constitute a reservoir which contributes to maintain the spring fed +chiefly, no doubt, by underground channels from the neighboring +mountains. But it is highly probable that, after a certain time, the +process of natural desiccation noticed in note to p. 20, ante, will +drain this reservoir, and the entire removal of the surface-water will +then become practicable.] The ground already dry enough for cultivation +furnishes occupation and a livelihood for a population of 16,000 +persons, and it is thought that this number will be augmented to 40,000 +when the drainage shall be completely effected. + +The new tunnel follows the line of the Claudian emissary--which though +badly executed was admirably engineered--but its axis is at a somewhat +lower level than that of the old gallery, and its cross-section is about +two hundred and fifteen square feet, allowing a discharge of about 2,400 +cubic feet to the second, while the Roman work had a cross-section of +only one hundred and two square feet, with a possible delivery of 424 +cubic feet to the second. + +In consequence of the nature of the rock and of the soil, which had been +loosened and shattered by the falling in of much of the crown and walls +of the old tunnel--every stone of which it was necessary to remove in +the progress of the work--and the great head of water in the lake from +unusually wet seasons, the technical difficulties to be surmounted were +most baffling and discouraging in character, and of such extreme gravity +that it may well be doubted whether the art of engineering has anywhere +triumphed over more serious obstacles. This great "victory of +peace"--probably the grandest work of physical improvement ever effected +by the means, the energy, and the munificence of a single individual--is +of no small geographical and economical, as well as sanitary, +importance, but it has a still higher moral value as an almost unique +example of the exercise of public spirit, courage, and perseverance in +the accomplishment of a noble and beneficent enterprise by a private +citizen. [Footnote: The draining of Lake Celano was undertaken by a +company, but Prince Alessandro Torlonia of Rome bought up the interest +of all the shareholders and has executed the entire work at his own +private expense. Montricher, the celebrated constructor of the great +aqueduct of Marseilles, was the engineer who designed and partly carried +out the plans, and after his lamentable death the work has been directed +with equal ability by Bermont and Brisse.--See Leon De Rothou, +Prosciugamento del Lago Fucino, 8vo. Firenza, 1871.] + +The crater-lake of Nemi, in the same volcanic region as that of Albano, +is also drained by a subterranean tunnel probably of very ancient +construction, and the Valle-Riccia appears to have once been the basin +of a lake long since laid dry, but whether by the bursting of its banks +or by human art we are unable to say. + +The success of the Lake Celano tunnel has suggested other like +improvements in Italy. A gallery has been cut, under circumstances of +great difficulty, to drain Lake Agnano near Naples, and a project for +the execution of a similar operation on the Lake of Perugia, the ancient +Trasimenus, which covers more than 40,000 acres, is under discussion. + +Many similar enterprises have been conceived and executed in modern +times, both for the purpose of reclaiming land covered by water and for +sanitary reasons. [Footnote: A considerable work of this character is +mentioned by Captain Gilliss as having been executed in Chili, a country +to which we should hardly have looked for an improvement of such a +nature. The Lake Taguataga was partially drained by cutting through a +narrow ridge of land, not at the natural outlet, but upon one side of +the lake, and eight thousand acres of land covered by it were gained for +cultivation.--U. S. Naval Astronomical Expedition to the Southern +Hemisphere, i., pp. 16, 17. + +Lake Balaton and the Neusiedler Sea in Hungary have lately been, at +least partially, drained. + +The lakes of Neuchatel, Bienne, and Morat, in Switzerland, have been +connected and the common level of all of them lowered about four feet. +The works now in operation will produce, in the course of the year 1874, +a further depression of four feet, and recover for agricultural use more +than twelve thousand acres of fertile soil.] They are sometimes attended +with wholly unexpected evils, as, for example, in the case of Barton +Pond, in Vermont, and in that of a lake near Ragunda in Sweden, already +mentioned on a former page. Another still less obvious consequence of +the withdrawal of the waters has occasionally been observed in these +operations. The hydrostatic force with which the water, in virtue of its +specific gravity, presses against the banks that confine it, has a +tendency to sustain them whenever their composition and texture are not +such as to expose them to softening and dissolution by the infiltration +of the water. If, then, the slope of the banks is considerable, or if +the earth of which they are composed rests on a smooth and slippery +stratum inclining towards the bed of the lake, they are liable to fall +or slide forward when the mechanical support of the water is removed, +and this sometimes happens on a considerable scale. A few years ago the +surface of the Lake of Lungern, in the Canton of Unterwalden, in +Switzerland, was lowered by driving a tunnel about a quarter of a mile +long through the narrow ridge, called the Kaiserstuhl, which forms a +barrier at the north end of the basin. When the water was drawn off, the +banks, which are steep, cracked and burst, several acres of ground slid +down as low as the water receded, and even the whole village of Lungern +was thought to be in no small danger. [Footnote: In the course of the +year 1864 there were slides of the banks of the Lake of Como, and in one +case the grounds of a villa near the water suffered a considerable +displacement. More important slips occurred at Fesiolo on the shore of +Lago Maggiore in 1867 and 1869, and on the Lake of Orta in 1868. These +occurrences excited some apprehensions in regard to the possible effects +of projects then under discussion for lowering the level of some of the +Italian lakes, to obtain an increased supply of water for irrigation and +as a mechanical power, but as it was not proposed to depress the surface +below the lowest natural low-water level, there seems to have been +little ground for the fears expressed. + +See, for important observations on the character and probable results of +these projects, Tagliasecchi, Nostizie etc. del Canali dell' Alta +Lombardia, Milano, 1871. + +Jacini says: "A large proportion of the water of the lakes, instead of +discharging itself by the Ticino, the Adda, the Oglio, the Mincio, +filters through the silicious strata which underlie the hills, and +follows subterranean channels to the plain, where it collects in the +fontanili, and being thence conducted into the canals of irrigation, +becomes a source of great fertility."--La Proprieta Fondiaria, etc., +p.144. The quantity of water escaping from the lakes by infiltration +depends much on the hydrostatic pressure on the bottom and the walls of +the lake-basins, and consequently the depression of the lake surface, +diminishing this pressure, would diminish the infiltration. Hence it is +possible that the lowering of the level of these lakes would manifest +itself in a decreased supply of water for the springs, fontanili, and +wells of Lombardy.] + + +Mountain Lakes. + +Other inconveniences of a very serious character have often resulted +from the natural wearing down, or, much more frequently, the imprudent +destruction, of the barriers which confine mountain lakes. In their +natural condition, such basins serve both to receive and retain the +rocks and other detritus brought down by the torrents which empty into +them, and to check the impetus of the rushing waters by bringing them to +a temporary pause; but if the outlets are lowered so as to drain the +reservoirs, the torrents continue their rapid flow through the ancient +bed of the basins, and carry down with them the sand and gravel with +which they are charged, instead of depositing their burden as before in +the still waters of the lakes. + +It is a common opinion in America that the river meadows, bottoms, or +intervales, as they are popularly called, are generally the beds of +ancient lakes which have burst their barriers and left running currents +in their place. It was shown by Dr. + +Dwight, many years ago, that this is very far from being universally +true; but there is no doubt that mountain lakes were of much more +frequent occurrence in primitive than in modern geography, and there are +many chains of such still existing in regions where man has yet little +disturbed the original features of the earth. In the long valleys of the +Adirondack range in Northern New York, and in the mountainous parts of +Maine, eight, ten, and even more lakes and lakelets are sometimes found +in succession, each emptying into the next lower pool, and so all at +last into some considerable river. When the mountain slopes which supply +these basins shall be stripped of their woods, the augmented swelling of +the lakes will break down their barriers, their waters will run off, and +the valleys will present successions of flats with rivers running +through them, instead of chains of lakes connected by natural canals. + +A similar state of things seems to have existed in the ancient geography +of France. "Nature," says Lavergne, "has not excavated on the flanks of +our Alps reservoirs as magnificent as those of Lombardy; she had, +however, constructed smaller but more numerous lakes, which the +improvidence of man has permitted to disappear. Auguste de Gasparin +demonstrated more than thirty years ago that many natural dikes formerly +existed in the mountain valleys, which have been swept away by the +waters." [Footnote: Economie Rurale de la France, p. 289.] + +Many Alpine valleys in Switzerland and Italy present unquestionable +evidence of the former existence of chains of lakes in their basins, and +this may be regarded as a general fact in regard to the primitive +topography of mountainous regions. Where the forests have not been +destroyed, the lakes remain as characteristic features of the +geographical surface. But when the woods are felled, these reservoirs +are sooner or later filled up by wash from the shores, and of course +disappear. Geologists have calculated the period when the bottom of the +Lake of Geneva will be levelled up and its outlet worn down. The Rhone +will then flow, in an unbroken current, from its source in the great +Rhone glacier to the Mediterranean Sea. + + +Draining of Swamps. + +The reclamation of bogs and swamps by draining off the surface-water is +doubtless much more ancient than the draining of lakes. The beneficial +results of the former mode of improvement are more unequivocal, and +balanced by fewer disadvantages, and, at the same time, the processes by +which it is effected are much simpler and more obvious. It has +accordingly been practised through the whole historical period, and in +recent times operations for this purpose have assumed a magnitude, and +been attended with economical as well as sanitary and geographical +effects, which entitle them to a high place in the efforts of man to +ameliorate the natural conditions of the soil he occupies. + +The methods by which the draining of marshes is ordinarily accomplished +are too familiar, and examples of their successful employment too +frequent, to require description, and I shall content myself, for the +moment, with a brief notice of some recent operations of this sort which +are less generally known than their importance merits. + +Within the present century more than half a million acres of swamp-land +have been drained and brought under cultivation in Hungary, and works +are in progress which will ultimately recover a still larger area for +human use. The most remarkable feature of these operations, and at the +same time the process which has been most immediately successful and +remunerative, is what is called in Europe the regulation of +water-courses, and especially of the River Theiss, on the lower course +of which stream alone not less than 250,000 acres of pestilential and +wholly unproductive marsh have been converted into a healthful region of +the most exuberant fertility. + +The regulation of a river consists in straightening its channel by +cutting off bends, securing its banks from erosion by floods, and, where +necessary, by constructing embankments to confine the waters and prevent +them from overflowing and stagnating upon the low grounds which skirt +their current. In the course of the Theiss about sixty bends, including +some of considerable length, have been cut off, and dikes sufficient for +securing the land along its banks against inundation have been +constructed. + +Many thousand acres of land have been recently permanently improved in +Italy by the draining of swamps, and extensive operations have been +projected and commenced on the lower Rhone, and elsewhere in France, +with the same object. [Footnote: Very interesting and important +experiments, on the practicability of washing out the salt from seacoast +lands too highly impregnated with that mineral to be fit for +cultivation, are now in progress near the mouth of the Rhone, where +millions of acres of marshy soil can easily be recovered, if these +experiments are successful. + +See Duponchel, Traite d'Hydraulique et de Geologie agricoles. Paris, +1868, chap. xi. and xii. + +In the neighborhood of Ferrara are pools and marshes covering nearly two +hundred square miles, or a surface more than equal to eight American +townships. Centrifugal steam-pumps, of 2,000 horse-power, capable of +discharging more than six hundred and fifty millions of gallons of water +per day have lately been constructed in England for draining these +marshes. This discharge is equal to an area of 640 acres, or a mile +square, with nearly three feet of water.] But there is probably no +country where greater improvements of this sort have either been lately +effected, or are now in course of accomplishment, than in our own. Not +to speak of well-known works on the New Jersey seacoast and the shores +of Lake Michigan, the people of the new State of California are engaging +in this mode of subduing nature with as much enterprise and energy as +they have shown in the search for gold. The Report of the Agricultural +Department of the United States for January, 1872, notices, with more or +less detail, several highly successful experiments in California in the +way of swamp-drainage and securing land from overflow, and it appears +that not far from 200,000 acres have either very recently undergone or +will soon be subjected to this method of improvement. + + +Agricultural Draining. + +I have commenced this chapter with a description of the dikes and other +hydraulic works of the Netherland engineers, because both the immediate +and the remote results of such operations are more obvious and more +easily measured, though certainly not more important, than those of much +older and more widely diffused modes of resisting or directing the flow +of waters, which have been practised from remote antiquity in the +interior of all civilized countries. Draining and irrigation are +habitually regarded as purely agricultural processes, having little or +no relation to technical geography; but we shall find that they exert a +powerful influence on soil, climate, and animal and vegetable life, and +may, therefore, justly claim to be regarded as geographical elements. + +Superficial draining is a necessity in all lands newly reclaimed from +the forest. The face of the ground in the woods is never so regularly +inclined as to permit water to flow freely over it. There are, even on +the hillsides, small ridges depressions, partly belonging to the +original distribution of the soil, and partly occasioned by +irregularities in the growth and deposit of vegetable matter. These, in +the husbandry of nature, serve as dams and reservoirs to collect a +larger supply of moisture than the spongy earth can at once imbibe. +Besides this, the vegetable mould is, even under the most favorable +circumstances, slow in parting with the humidity it has accumulated +under the protection of the woods, and the infiltration from neighboring +forests contributes to keep the soil of small clearings too wet for the +advantageous cultivation of artificial crops. For these reasons, surface +draining must have commenced with agriculture itself, and there is +probably no cultivated district, one may almost say no single field, +which is not provided with artificial arrangements for facilitating the +escape of superficial water, and thus carrying off moisture which, in +the natural condition of the earth, would have been imbibed by the soil. + +All these processes belong to the incipient civilization of the +ante-historical periods, but the construction of subterranean channels +for the removal of infiltrated water marks ages and countries +distinguished by a great advance in agricultural theory and practice, a +great accumulation of pecuniary capital and a density of population +which creates a ready demand and a high price for all products of rural +industry. Under draining, too, would be most advantageous in damp and +cool climates, where evaporation is slow, and upon soils where the +natural inclination of surface does not promote a very rapid flow of the +surface-waters. All the conditions required to make this mode of rural +improvement, if not absolutely necessary, at least profitable, exist in +Great Britain, and it is, therefore, very natural that the wealthy and +intelligent farmers of England should have carried this practice +farther, and reaped a more abundant pecuniary return from it, than those +of any other country. + +Besides superficial and subsoil drains, there is another method of +disposing of superfluous surface-water, which, however, can rarely be +practised, because the necessary conditions for its employment are not +of frequent occurrence. Whenever a tenacious water-holding stratum rests +on a loose, gravelly bed so situated as to admit of a free discharge of +water from or through it by means of the outcropping of the bed at a +lower level, or of deep-lying conduits leading to distant points of +discharge, superficial waters may be carried off by opening a passage +for them through the impervious into the permeable stratum. Thus, +according to Bischof, as early as the time of King Rene, in the first +half of the fifteenth century, when subsoil drainage was scarcely known, +the plain of Paluns, near Marseilles, was laid dry by boring, and +Wittwer informs us that drainage is effected at Munich by conducting the +superfluous water into large excavations, from which it filters through +into a lower stratum of pebble and gravel lying a little above the level +of the river Isar. [Foonote: Physikalische Geographie, p. 288. This +method is now frequently employed in France. Details as to the processes +will be found in Mangon Pratique du Drainage, pp. 78 et seqq. Draining +by driving down stakes mentioned in a note in the chapter on the Woods, +ante, is a process of the same nature. + +In the United States, large tracts of marshy ground, and even shallow +lakes of considerable extent, have been sufficiently drained not only +for pasturage but for cultivation, without resort to any special +measures for effecting that end. The ordinary processes of rural +improvement in the vicinity, such as felling woods upon and around such +grounds, and the construction of roads, the side ditches of which act as +drains, over or near them, aided now and then by the removal of a fallen +tree or other accidental obstruction in the beds of small streams which +flow from them, often suffice to reclaim miles square of unproductive +swamp and water. See notes on p. 20, and on cedar swamps, p. 208, ante.] +So at Washington, in the western part of the city, which lies high above +the rivers Potomac and Rock Creek, many houses are provided with dry +wells for draining their cellars and foundations. These extend through +hard, tenacious earth to the depth of thirty or forty feet, when they +strike a stratum of gravel, through which the water readily passes off. +This practice has been extensively employed at Paris, not merely for +carrying off ordinary surface-water, but for the discharge of offensive +and deleterious fluids from chemical and manufacturing establishments. A +well of this sort received, in the winter of 1832-'33, twenty thousand +gallons per day of the foul water from a starch factory, and the same +process was largely used in other factories. The apprehension of injury +to common and artesian wells and springs led to an investigation on this +subject by Girard and Parent Duchatelet, in the latter year. The report +of these gentlemen, published in the Annales des Ponts et Chaussees for +1833, second half-year, is full of curious and instructive facts +respecting the position and distribution of the subterranean waters +under and near Paris; but it must suffice to say that the report came to +the conclusion that, in consequence of the absolute immobility of these +waters, and the relatively small quantity of noxious fluid to be +conveyed to them, there was no danger of the diffusion of such fluid if +discharged into them. This result will not surprise those who know that, +in another work, Duchatelet maintains analogous opinions as to the +effect of the discharge of the city sewers into the Seine or the waters +of that river. The quantity of matter delivered by them he holds to be +so nearly infinitesimal, as compared with the volume of water of the +river, that it cannot possibly affect it to a sensible degree, and +therefore cannot render the Seine water unfit for drinking. [Foonote: +Coste found, in his experiments on pisciculture, that the fermentation, +which takes place in the water of the Seine in consequence of the +discharge of the drains into the river, destroyed a large proportion of +the eggs of fish in his breeding basins. Analysis of Seine water by +Boussingault in 1855 detected a considerable quantity of ammonia.] + + +Meteorological Effects of Draining. + +The draining of lakes diminishes the water-surface of the soil, and +consequently, in many cases, the evaporation from it, as well as the +refrigeration which attends all evaporation. [Footnote: The relative +evaporating action of earth and water is a very complicated problem, and +the results of observation on the subject are conflicting. Schubler +found that at Geneva the evaporation from bare loose earth, in the +months of December, January, and February, was from two and a half to +nearly six times as great as from a like surface of water in the other +months. The evaporation from water was from about once and a half to six +times as great as from earth. Taking the whole year together, the +evaporation from the two surfaces was 199 lines from earth and 536 lines +from water. Experiments by Van der Steer, at the Helder, in the years +1861 and 1862, showed, for the former year, an evaporation of 602.9 +millimetres from water, 1399.6 millimetres from ground covered with +clover and other grasses; in 1862, the evaporation from water was 584.5 +millimetres, from grassground, 875.5. --Wilhelm, Der Boden und das +Wasser, p. 57; Krecke, Het Klimaat van Nederland, ii., p. 111. + +On the other hand, the evaporation from the Nile in Egypt and Nubia is +stated to be three times as great as that from an equal surface of the +soil which borders it.--Lombardini, Saggio Idrologico sul Nilo, Milano, +1864, and Appendix. The relative thermometrical conditions of land and +water in the same vicinity are constantly varying, and the hygrometrical +state of both is equally unstable. Consequently there is no general +formula to express the proportionate evaporation from fluid and solid +geographical surfaces.] On the other hand, if the volume of water +abstracted is great, its removal deprives its basin of an equalizing and +moderating influence; for large bodies of water take very slowly the +temperature of the air in contact with their surface, and are almost +constantly either sending off heat into the atmosphere or absorbing heat +from it. Besides, as we have seen, lakes in elevated positions discharge +more or less water by infiltration, and contribute it by the same +process to other lakes, to springs, and to rivulets, at lower levels. +Hence the draining of lakes, on a considerable scale, must modify both +the humidity and the temperature of the atmosphere of the neighboring +regions, and the permanent supply of ground-water for the lands lying +below them. + + +Meteorological Action of Marshes. + +The shallow water of marshes, indeed, performs this latter function, +but, under ordinary circumstances, marshes exercise in but a very small +degree the compensating meteorological action which I have ascribed to +large expansions of deeper water. The direct rays of the sun and the +warmth of the atmosphere penetrate to the soil beneath, and raise the +temperature of the water which covers it; and there is usually a much +greater evaporation from marshes than from lakes in the same region +during the warmer half of the year. This evaporation implies +refrigeration, and consequently the diminution of evaporation by the +drainage of swamps tends to prevent the lowering of the atmospheric +temperature, and to lessen the frequency and severity of frosts. +Accordingly it is a fact of experience that, other things being equal, +dry soils, and the air in contact with them, are perceptibly warmer +during the season of vegetation, when evaporation is most rapid, than +moist lands and the atmospheric stratum resting upon them. Instrumental +observation on this special point has not yet been undertaken on a large +scale, but still we have thermometric data sufficient to warrant the +general conclusion, and the influence of drainage in diminishing the +frequency of frost appears to be even better established than a direct +increase of atmospheric temperature. The steep and dry uplands of the +Green Mountain range in New England often escape frosts when the +Indian-corn harvest on moister grounds, five hundred or even a thousand +feet lower, is destroyed or greatly injured by them. The neighborhood of +a marsh is sure to be exposed to late spring and early autumnal frosts, +but they cease to be feared after it is drained, and this is +particularly observable in very cold climates, as, for example, in +Lapland. [Footnote: "The simplest backwoodsman knows by experiences that +all cultivation is impossible in the neighborhood of bogs and marshes. +Why is a crop near the borders of a marsh out off by frost, while a +field upon a hillock, a few stone's throws from it, is spared "--Lars +Levi Laestadius, Om Uppoldingar Lappmarrken, pp. 69, 74.] + +In England, under-drains are not generally laid below the reach of daily +variations of temperature, or below a point from which moisture, if not +carried off by the drains, might be brought to the surface by capillary +attraction, and evaporated by the heat of the sun. They, therefore, like +surface-drains, withdraw from local solar action much moisture which +would otherwise be vaporized by it, and, at the same time, by drying the +soil above them, they increase its effective hygroscopicity, and it +consequently absorbs from the atmosphere a greater quantity of water +than it did when, for want of under-drainage, the subsoil was always +humid, if not saturated. [Footnote: Mangon thinks that the diminution of +evaporation by agricultural drainage corresponds, in certain +circumstances, to five per cent. of the heat received from the sun by +the same surface in a year. He cites observations by Parkes, showing a +difference in temperature of 5.5 degrees (centigrade ) in favor of +drained, as compared with undrained, ground in the same +vicinity.--Instructions pratiques sur le Drainage, pp. 227, 228. + +The diminution of evaporation is not the only mode in which +under-draining affects the temperature. The increased effective +hygroscopicity of the soil increases its absorbent action, and the +condensation of atmospheric vapor thus produced is attended with the +manifestation of heat.] Under-drains, then, contribute to the dryness as +well as to the warmth of the atmosphere, and, as dry ground is more +readily heated by the rays of the sun than wet, they tend also to raise +the mean, and especially the summer, temperature of the soil. + + +Effects of Draining Lake of Haarlem. + +The meteorological influence of the draining of lakes and of humid soils +has not, so far as I know, received much attention from experimental +physicists; but we are not altogether without direct proof in support of +theoretical and a priori conclusions. Thermometrical observations have +been regularly made at Zwanenburg, near the northern extremity of the +Lake of Haarlem, for more than a century; and since 1845 a similiar +registry has been kept at the Helder, forty or fifty miles more to the +north. In comparing these two series of observations, it is found that +towards the end of 1852, when the draining of the lake was finished, and +the following summer had completely dried the newly exposed soil--and, +of course, greatly diminished the water-surface--a change took place in +the relative temperature of those two stations. Taking the mean of each +successive period of five days, from 1845 to 1852, both inclusive, the +temperature of Zwanenburg was thirty-three hundredths of a degree +centigrade LOWER than at the Helder. From the end of 1852 the +thermometer at Zwanenburg has stood, from the 11th of April to the 20th +of September, twenty-two hundredths of a degree HIGHER than that at +Helder; but from the 14th of October to the 17th of March, it has marked +one-tenth of a degree LOWER than its mean between the same dates before +1853. [Footnote: Krecke, Het Klimaat van Nederland, ii., p. 64.] + +There is no reason to doubt that these differences are due to the +draining of the lake. In summer, solar irradiation has acted more +powerfully on the now exposed earth and of course on the air in contact +with it; and there is no longer a large expanse of water still retaining +and of course imparting something of the winter temperature; in winter, +the earth has lost more heat by radiation than when covered by water and +the influence of the lake, as a reservoir of warmth accumulated in +summer and gradually given out in winter, was of course lost by its +drainage. Doubtless the quantity of moisture contained in the atmosphere +has been modified by the same cause, but it does not appear that +observations have been made upon this point. Facts lately observed by +Glaisher tend to prove an elevation of not far from two degrees in the +mean temperature of England during the course of the last hundred years. +For reasons which I have explained elsewhere, the early observations +upon which these conclusions are founded do not deserve entire +confidence; but admitting the fact of the alleged elevation, its most +probable explanation would be found in the more thorough draining of the +soil by superficial and by subterranean conduits. + +So far as respects the immediate improvement of soil and climate, and +the increased abundance of the harvests, the English system of surface +and subsoil drainage has fully justified the eulogiums of its advocates; +but its extensive adoption appears to have been attended with some +altogether unforeseen and undesirable consequences, very analogous to +those which I have described as resulting from the clearing of the +forests. The under-drains carry off very rapidly the water imbibed by +the soil from precipitation, and through infiltration from neighboring +springs or other sources of supply. Consequently, in wet seasons, or +after heavy rains, a river bordered by artificially drained lands +receives in a few hours, from superficial and from subterranean +conduits, an accession of water which, in the natural state of the +earth, would have reached it only by small instalments after percolating +through hidden paths for weeks or even months, and would have furnished +perennial and comparatively regular contributions, instead of swelling +deluges, to its channel. Thus, when human impatience rashly substitutes +swiftly acting artificial contrivances for the slow methods by which +nature drains the surface and superficial strata of a river-basin, the +original equilibrium is disturbed, the waters of the heavens are no +longer stored up in the earth to be gradually given out again, but are +hurried out of man's domain with wasteful haste; and while the +inundations of the river are sudden and disastrous, its current, when +the drains have run dry, is reduced to a rivulet, it ceases to supply +the power to drive the machinery for which it was once amply sufficient, +and scarcely even waters the herds that pasture upon its margin. + +The water of subterranean currents and reservoirs, as well as that of +springs and common wells, is doubtless principally furnished by +infiltration, and hence its quantity must vary with every change of +natural surface which tends to accelerate or to retard the drainage of +the surface-soil. The drainage of marshes, therefore, and all other +methods of drying the superficial strata, whether by open ditches or by +underground tubes or drains, has the same effect as clearing off the +forest in depriving the subterranean waters of accessions which they +would otherwise receive by infiltration, and in proportion as the sphere +of such operation is extended, their influence will make itself felt in +the diminished supply of water in springs and wells. [Footnote: Babinet +condemns the general draining of marshes. "Draining," says he, "has been +much in vogue for some years, and it has been a special object to dry +and fertilize marshy grounds. I believe that excessive dryness is thus +produced, and that other soils in the neighborhood are sterilized in +proportion."--Etudes et Lectures, iv., p. 118. + +"The extent of soil artificially dried by drainage is constantly +increasing, and the water received by the surface from precipitation +flows off by new channels, and is in general carried off more rapidly +than before. Must not this fact exercise an influence on the regime of +springs whose basin of supply thus undergoes a more or less complete +transformation "--Bernhard Cotta, Preface to Paramelle, Quellenkunde, p. +vii., viii. + +The effects of agricultural drainage are perceptible at great depths. It +has been observed in Cornwall that deep mines are more free from water +in well-drained districts than in those where drainage is not generally +practised.--Esquiros, Revue des Deux Mondes, 15 Nov., 1863, p. 430. + +See also Asbjornsen, Torv og Torvdrift, p. 31.] + + +Geographical and Meteorological Effects of Aqueducts, Reservoirs, and +Canals. + +Many of the great processes of internal improvement, such as aqueducts +for the supply of great cities, railroad cuts and embankments, and the +like, divert water from its natural channels and affect its distribution +and ultimate discharge. The collecting of the waters of a considerable +district into reservoirs, to be thence carried off by means of +aqueducts, as, for example, in the forest of Belgrade, near +Constantinople, deprives the grounds originally watered by the springs +and rivulets of the necessary moisture, and reduces them to barrenness. +[Footnote: See a very interesting paper on the Water-Supply of +Constantinople, by Mr. Homes, of the New York State Library, in the +Albany Argus of June 6, 1872. The system of aqueducts for the supply of +water to that city was commenced by Constantine, and the great aqueduct, +frequently ascribed to Justinian, which is 840 feet long and 112 feet +high, is believed to have been constructed during the reign of the +former emperor.] Similar effects must have followed from the +construction of the numerous aqueducts which supplied ancient Rome with +such a profuse abundance of water. [Footnote: The unhealthiness of the +Roman Campagna is ascribed by many mediaeval as well as later writers to +the escape of water from the ancient aqueducts, which had fallen out of +repair from neglect, or been broken down by enemies in the sieges of +Rome.] On the other hand, the filtration of water through the banks or +walls of an aqueduct carried upon a high level across low ground, often +injures the adjacent soil, and is prejudicial to the health of the +neighboring population; and it has been observed in Switzerland and +elsewhere, that fevers have been produced by the stagnation of the water +in excavations from which earth had been taken to form embankments for +railways. + +If we consider only the influence of physical improvements on civilized +life, we shall perhaps ascribe to navigable canals a higher importance, +or at least a more diversified influence, than to aqueducts or to any +other works of man designed to control the waters of the earth, and to +affect their distribution. They bind distant regions together by social +ties, through the agency of the commerce they promote; they facilitate +the transportation of military stores and engines, and of other heavy +material connected with the discharge of the functions of government; +they encourage industry by giving marketable value to raw material and +to objects of artificial elaboration which would otherwise be worthless +on account of the cost of conveyance; they supply from their surplus +waters means of irrigation and of mechanical power; and, in many other +ways, they contribute much to advance the prosperity and civilization of +nations. Nor are they wholly without geographical importance. They +sometimes drain lands by conveying off water which would otherwise +stagnate on the surface, and, on the other hand, like aqueducts, they +render the neighboring soil cold and moist by the percolation of water +through their embankments; [Footnote: Sismondi, speaking of the Tuscan +canals, observes: "But inundations are not the only damage caused by the +waters to the plains of Tuscany. Raised, as the canals are, above the +soil, the water percolates through their banks, penetrates every +obstruction, and, in spite of all the efforts of industry, sterilizes +and turns to morasses fields which nature and the richness of the soil +seemed to have designed for the most abundant harvests. In ground thus +pervaded with moisture, or rendered COLD, as the Tuscans express it, by +the filtration of the canal-water, the vines and the mulberries, after +having for a few years yielded fruit of a saltish taste, rot and perish. +The wheat decays in the ground, or dies as soon as it sprouts. Winter +crops are given up, and summer cultivation tried for a time; but the +increasing humidity, and the saline matter communicated to the +earth--which affects the taste of all its products, even to the grasses, +which the cattle refuse to touch--at last compel the husbandman to +abandon his fields and leave uncultivated a soil that no longer repays +his labor."--Tableau de l'Agriculture Toscane, pp. 11, 12.] they dam up, +check, and divert the course of natural currents, and deliver them at +points opposite to, or distant from, their original outlets; they often +require extensive reservoirs to feed them thus retaining through the +year accumulations of water--which would otherwise run off, or evaporate +in the dry season--and thereby enlarging the evaporable surface of the +country; and we have already seen that they interchange the flora and +the fauna of provinces widely separated by nature. All these modes of +action certainly influence climate and the character of terrestrial +surface, though our means of observation are not yet perfected enough to +enable us to appreciate and measure their effects. + + +Antiquity of Irrigation. + +We know little of the history of the extinct civilizations which +preceded the culture of the classic ages, and no nation has, in modern +times, spontaneously emerged from barbarian and created for itself the +arts of social life. [Footnote: I ought perhaps to except the Mexicans +and the Peruvians, whose arts and institutions are not yet shown to be +historically connected with those of any more ancient people. The +lamentable destruction of so many memorials of these tribes, by the +ignorance and bigotry of the so-called Christian barbarians who +conquered them, has left us much in the dark as to many points of their +civilization; but they seem to have reached that stage where continued +progress in knowledge and in power over nature is secure, and a few more +centuries of independence might have brought them to originate for +themselves most of the great inventions which the last four centuries +have bestowed upon man.] The improvements of the savage races whose +history we can distinctly trace are borrowed and imitative, and our +theories as to the origin and natural development of industrial art are +conjectural. Of course, the relative antiquity of particular branches of +human industry depends much upon the natural character of soil, climate, +and spontaneous vegetable and animal life in different countries; and +while the geographical influence of man would, under given +circumstances, be exerted in one direction, it would, under different +conditions, act in an opposite or a diverging line. I have given some +reasons for thinking that in the climates to which our attention has +been chiefly directed, man's first interference with the natural +arrangement and disposal of the waters was in the way of drainage of +surface. But if we are to judge from existing remains alone, we should +probably conclude that irrigation is older than drainage; for, in the +regions regarded by general tradition as the cradle of the human race, +we find traces of canals evidently constructed for the former purpose at +a period long preceding the ages of which we have any written memorials. +There are, in ancient Armenia, extensive districts which were already +abandoned to desolation at the earliest historical epoch, but which, in +a yet remoter antiquity, had been irrigated by a complicated and highly +artificial system of canals, the lines of which can still be followed; +and there are, in all the highlands where the sources of the Euphrates +rise, in Persia, in Egypt, in India, and in China, works of this sort +which must have been in existence before man had begun to record his own +annals. + +In warm countries, such as most of those just mentioned, the effects I +have described as usually resulting from the clearing of the forests +would very soon follow. In such climates, the rains are inclined to be +periodical; they are also violent, and for these reasons the soil would +be parched in summer and liable to wash in winter. In these countries, +therefore, the necessity for irrigation must soon have been felt, and +its introduction into mountainous regions like Armenia must have been +immediately followed by a system of terracing, or at least scarping the +hillsides. Pasture and meadow, indeed, may be irrigated even when the +surface is both steep and irregular, as may be observed abundantly on +the Swiss as well as on the Piedmontese slope of the Alps; but in dry +climates, ploughland and gardens on hilly grounds require terracing, +both for supporting the soil and for administering water by irrigation, +and it should be remembered that terracing, of itself, even without +special arrangements for controlling the distribution of water, prevents +or at least checks the flow of rain-water, and gives it time to sink +into the ground instead of running off over the surface. + +The summers in Egypt, in Syria, and in Asia Minor and even Rumelia, are +almost rainless. In such climates, the neccssity of irrigation is +obvious, and the loss of the ancient means of furnishing it helps to +explain the diminished fertility of most of the countries in question. +[Footnote: In Egypt, evaporation and absorption by the earth are so +rapid, that all annual crops require irrigation during the whole period +of their growth. As fast as the water retires by the subsidence of the +annual inundation, the seed is sown upon the still moist, uncovered +soil, and irrigation begins at once. Upon the Nile, you hear the +creaking of the water-wheels, and sometimes the movement of steam-pumps, +through the whole night, while the poorer cultivators unceasingly ply +the simple shadoof, or bucket-and-sweep, laboriously raising the water +from trough to trough by as many as six or seven stages when the river +is low. The bucket is of flexible leather, with a stiff rim, and is +emptied into the trough, not by inverting it like a wooden bucket, but +by putting the hand beneath and pushing the bottom up till the water all +runs out over the brim, or, in other words, by turning the vessel inside +out. + +The quantity of water thus withdrawn from the Nile is enormous. Most of +this is evaporated directly from the surface or the superficial strata, +but some moisture percolates down and oozes through the banks into the +river again, while a larger quantity sinks till it joins the slow +current of infiltration by which the Nile water pervades the earth of +the valley to the distance, at some points, of not less than fifty +miles.] The surface of Palestine, for example, is composed, in a great +measure, of rounded limestone hills, once, no doubt, covered with +forests. These were partially removed before the Jewish conquest. +[Footnote: "Forests," "woods," and "groves," are frequently mentioned in +the Old Testament as existing at particular places, and they are often +referred to by way of illustration, as familiar objects. "Wood" is twice +spoken of as a material in the New Testament, but otherwise--at least +according to Cruden--not one of the above words occurs in that volume. +In like manner, while the box, the cedar, the fir, the oak, the pine, +"beams," and "timber," are very frequently mentioned in the Old +Testament, not one of these words is found in the New, EXCEPT the case +of the "beam in the eye," in the parable in Matthew and Luke. + +This interesting fact, were other evidence wanting, would go far to +prove that a great change had taken place in this respect between the +periods when the Old Testament and the New were respectively composed; +for the scriptural writers, and the speakers introduced into their +narratives, are remarkable for their frequent allusions to the natural +objects and the social and industrial habits which characterized their +ages and their country.] When the soil began to suffer from drought, +reservoirs to retain the waters of winter were hewn in the rock near the +tops of the hills, and the declivities were terraced. So long as the +cisterns were in good order, and the terraces kept up, the fertility of +Palestine was unsurpassed, but when misgovernment and foreign and +intestine war occasioned the neglect or destruction of these +works--traces of which still meet the traveller's eye at every +step,--when the reservoirs were broken and the terrace walls had fallen +down, there was no longer water for irrigation in summer, the rains of +winter soon washed away most of the thin layer of earth upon the rocks, +and Palestine was reduced almost to the condition of a desert. + +The course of events has been the same in Idumaea. The observing +traveller discovers everywhere about Petra, particularly if he enters +the city by the route of Wadi Ksheibeh, very extensive traces of ancient +cultivation, and upon the neighboring ridges are the ruins of numerous +cisterns evidently constructed to furnish a supply of water for +irrigation. [Footnote: One of these on Mount Hor, two stories deep, is +in such good preservation, although probably not repaired for many +centuries, that I found ten feet of water in it in June, 1851.] In +primitive ages, the precipitation of winter in these hilly countries +was, in great part, retained for a time in the superficial soil, first +by the vegetable mould of the forests, and then by the artificial +arrangements I have described. The water imbibed by the earth was partly +taken up by direct evaporation, partly absorbed by vegetation, and +partly carried down by infiltration to subjacent strata which gave it +out in springs at lower levels, and thus a fertility of soil and a +condition of the atmosphere were maintained sufficient to admit of the +dense population that once inhabited those now arid wastes. At present, +the rain-water runs immediately off from the surface and is carried down +to the sea, or is drunk up by the sands of the wadis, and the hillsides +which once teemed with plenty are bare of vegetation, and seared by the +scorching winds of the desert. + +In fact, climatic conditions render irrigation a necessity in all the +oriental countries which have any importance in ancient or in modern +history, and there can be no doubt that this diffusion of water over +large surfaces has a certain reaction on climate. Some idea of the +extent of artificially watered soil in India may be formed from the fact +that in fourteen districts of the Presidency of Madras, not less than +43,000 reservoirs, constructed by the ancient native rulers for the +purpose of irrigation, are now in use, and that there are in those +districts at least 10,000 more which are in ruins and useless. These +reservoirs are generally formed by damming the outlets of natural +valleys; and the dams average half a mile in length, though some of them +are thirty miles long and form ponds covering from 37,000 to 50,000 +acres. The areas of these reservoirs alone considerably increase the +water-surface, and each one of them irrigates an extent of cultivated +ground much larger than itself. Hence there is a great augmentation of +humid surface from those constructions. [Footnote: The present +government of India obtains the same result more economically and +advantageously by constructing in many provinces of that vast empire +canals of great length and capacity, which not only furnish a greater +supply of water than the old reservoirs, but so distribute it as to +irrigate a larger area than could be watered by any system of artificial +basins. The excavacations for the Ganges Canal were nearly equal to +those for the Suez Canal, falling little short of 100,000 cubic yards, +without counting feeders and accessory lines amounting to a length of +3,000 miles. This canal, according to a recent article in the London +Times, waters a tract of land 320 miles long by 50 broad. The Jumna +Canal, 130 miles long, with 608 miles of distributing branches, waters a +territory 120 miles long with a breadth of 15 miles. + +Other statements estimate the amount of land actually under irrigation +in British India at 6,000,000 acres, and add that canals now in +construction will water as much more. The Indian irrigation canals are +generally navigable, some of them by boats of large tonnage, and the +canals return a net revenue of from five to twenty per cent. on their +cost.] + +The cultivable area of Egypt, or the space between desert and desert +where cultivation would be possible, is now estimated at ten thousand +square statute miles. [Footnote: The area which the waters of the Nile, +left to themselves, would now cover is greater than it would have been +in ancient times, because the bed of the river has been elevated, and +consequently the lateral spread of the inundation increased. See Smith's +Dictionary of Geography, article "Aegyptus". But the industry of the +Egyptians in the days of the Pharaohs and the Ptolemies carried the +Nile-water to large provinces, which have now been long abandoned and +have relapsed into the condition of desert. "Anciently," observes the +writer of the article "Egypt" in Smith's Dictionary of the Bible, "2,735 +square miles more [about 3,700 square statute miles] may have been +cultivated. In the best days of Egypt, probably all the land was +cultivated that could be made available for agricultural purposes, and +hence we may estimate the ancient arable area of that country at not +less than 11,000 square statute miles, or fully double its present +extent." + +According to an article in the Bollettino della Societa Geografica +Italiana, vol. v., pt. iii., p. 210, the cultivated soil of Egypt in +1869 amounted to 4,500,000 acres, and the remaining soil capable of +cultivation was estimated at 2,000,000 acres.] Much of the surface, +though not out of the reach of irrigation, lies too high to be +economically watered, and irrigation and cultivation are therefore at +present confined to an area of seven thousand square miles, nearly the +whole of which is regularly and constantly watered when not covered by +the inundation, except in the short interval between the harvest and the +rise of the waters. For nearly half of the year, then, irrigation adds +seven thousand square miles to the humid surface of the Nile valley, or, +in other words, more than decuples the area from which an appreciable +quantity of moisture would otherwise be evaporated; for after the Nile +has retired within its banks, its waters by no means cover one-tenth of +the space just mentioned. + +The Nile receives not a single tributary in its course below Khartoum; +there is not so much as one living spring in the whole land, [Footnote: +The so-called spring at Heliopolis is only a thread of water infiltrated +from the Nile or the canals.] and, with the exception of a narrow strip +of coast, where the annual precipitation is said to amount to six +inches, the fall of rain in the territory of the Pharaohs is not two +inches in the year. The subsoil of the whole valley is pervaded with +moisture by infiltration from the Nile, and water can everywhere be +found at the depth of a few feet. Were irrigation suspended, and Egypt +abandoned, as in that case it must be, to the operations of nature, +there is no doubt that trees, the roots of which penetrate deeply, would +in time establish themselves on the deserted soil, fill the valley with +verdure, and perhaps at last temper the climate, and even call down +abundant rain from the heavens. [Footnote: The date and the doum palm, +the sont and many other acacias, the caroub, the sycamore and other +trees grow in Egypt without irrigation, and would doubtless spread +through the entire valley in a few years.] But the immediate effect of +discontinuing irrigation would be, first, an immense reduction of the +evaporation from the valley in the dry season, and then a greatly +augmented dryness and heat of the atmosphere. Even the almost constant +north wind--the strength of which would be increased in consequence of +these changes--would little reduce the temperature of the narrow cleft +between the burning mountains which hem in the channel of the Nile, so +that a single year would transform the most fertile of soils to the most +barren of deserts, and render uninhabitable a territory that irrigation +makes capable of sustaining as dense a population as has ever existed in +any part of the world. [Footnote: Wilkinson states that the total +population, which, two hundred years ago, was estimated at 4,000,000, +amounted till lately to only about 1,800,000 souls, having been reduced +since the year 1800 from 2,500,000 to less than 2,000,000.--Handbook for +Travellers in Egypt. p. 10. The population at the end of the year 1869 +is computed at 5,215,000.--Bollettino della Soc. Geog. Ital., vol. v., +pt. iii., p. 215. This estimate doubtless includes countries bordering +on the upper Nile not embraced in Wilkinson's statistics.] Whether man +found the valley of the Nile a forest, or such a waste as I have just +described, we do not historically know. In either case, he has not +simply converted a wilderness into a garden, but has unquestionably +produced extensive climatic change. [Footnote: Ritter supposes Egypt to +have been a sandy desert when it was first occupied by man. "The first +inhabitant of the sandy valley of the Nile was a desert-dweller, as his +neighbors right and left, the Libyan, the nomade Arab, still are. But +the civilized people of Egypt transformed, by canals, the waste into the +richest granary of the world; they liberated themselves from the +shackles of the rock and sand desert, in the midst of which, by a wise +distribution of the fluid through the solid geographical form, by +irrigation in short, they created a region of culture most rich in +historical monuments."--Einleitung zur allgemeinen vergleichenden +Geographie, pp. 165, 166. + +This view seems to me highly improbable; for great rivers, in warm +climates, are never bordered by sandy plains. A small stream may be +swallowed up by sands, but if the volume of water is too large to be +carried off by evaporation or drank up by absorption, it saturates its +banks with moisture, and unless resisted by art, converts them into +marshes covered with aquatio vegetation. By canals and embankments, man +has done much to modify the natural distribution of the waters of the +Nile; yet the annual inundation is not his work, and the river must have +overflowed its banks and carried spontaneous vegetation with its waters, +as well before as since Egypt was first occupied by the human family. +There is, indeed, some reason to suppose that man lived upon the banks +of the Nile when its channel was much lower, and the spread of its +inundations much narrower, than at present; but wherever its flood +reached, there the forest would propagate itself, and its shores would +certainly have been morasses rather than sands. + +The opinions of Ritter on this subject are not only improbable, but they +are contradictory to the little historical testimony we possess. +Herodotus informs us in Euterpe that except the province of Thebes, all +Egypt, that is to say, the whole of the Delta and of middle Egypt +extending to Hemopolis Magna in N. L. 27 degrees 45 minutes, was +originally a morass. This morass was doubtless in great part covered +with trees, and hence, in the most ancient hieroglyphical records, a +tree is the sign for the cultivated land between the desert and the +channel of the Nile. In all probability, the real change effected by +human art in the superficial geography of Egypt is the conversion of +pools and marshes into dry land, by a system of transverse dikes, which +compelled the flood-water to deposit its sediment on the banks of the +river instead of carrying it to the sea. The colmate of modern Italy +were thus anticipated in ancient Egypt.] + +The fields of Egypt are more regularly watered than those of any other +country bordering on the Mediterranean, except the rice-grounds in +Italy, and perhaps the marcite or winter meadows of Lombardy; but +irrigation is more or less employed throughout almost the entire basin +of that sea, and is everywhere attended with effects which, if less in +degree, are analogous in character, to those resulting from it in Egypt. + +There are few things in European husbandry which surprise English or +American observers so much as the extent to which irrigation is employed +in agriculture, and that, too, on soils, and with a temperature, where +their own experience would have led them to suppose it would be +injurious to vegetation rather than beneficial to it. In Switzerland, +for example, grass-grounds on the very borders of glaciers are freely +irrigated, and on the Italian slope of the Alps water is applied to +meadows at heights exceeding 6,000 feet. The summers in Northern Italy, +though longer, are very often not warmer than in the Northern United +States; and in ordinary years, the summer rains are as frequent and as +abundant in the former country as in the latter. [Footnote: The mean +annual precipitation in Lombardy is thirty-six inches, of which nearly +two-thirds fall during the season of irrigation. The rain-fall is about +the same in Piedmont, though the number of days in the year classed as +"rainy" is said to be but twenty-four in the former province while it is +seventy in the latter.--Baird Smith, Italian Irrigation, vol. i., p. +196. + +The necessity of irrigation in the great alluivial plain of Northern +Italy is partly explained by the fact that the superficial stratum of +fine earth and vegetable mould is very extensively underlaid by beds of +pebbles and gravel brought down by mountain torrents at a remote epoch. +The water of the surface-soil drains rapdily down into these loose beds, +and passes off by subterranean channels to some unknown point of +discharge; but this circumstance alone is not a sufficient solution. It +is not possible that the habits of vegetables, grown in countries where +irrigation has been immemorially employed, have been so changed that +they require water under conditions of soil and climate where their +congeners, which have not been thus indulgently treated, do not It is a +remarkable fact that during the season of irrigation, when large tracts +of surface are almost constantly saturated with water, there is an +extraordinary dryness in the atmosphere of Lombardy, the hygrometer +standing for days together a few degrees only above zero, while in +winter the instrument indicates extreme humidity of the air, approaching +to total saturation.--Baird Smith, Italian Irrigation, i., p. 189. + +There are some atmospheric phenomena in Northern Italy, which an +American finds it hard to reconcile with what he has observed in the +United States. To an American eye, for instance, the sky of Piedmont, +Lombardy, and the northern coast of the Mediterranean, is always whitish +and curdled, and it never has the intensity and fathomless depth of the +blue of his native heavens. And yet the heat of the sun's rays, as +measured by sensation, and, at the same time, the evaporation, are +greater than they would be with the thermometer at the same point in +America. I have frequently felt in Italy, with the mercury below 60 +degrees Fahrenheit, and with a mottled and almost opaque sky, a heat of +solar irradiation which I can compare to nothing but the scorching +sensation experienced in America at a temperature twenty degrees higher, +during the intervals between showers, or before a rain, when the clear +blue of the sky seems infinite in depth and transparency. Such +circumstances may create a necessity for irrigation where it would +otherwise be superfluous, if not absolutely injurious. + +In speaking of the superior apparent clearness of the SKY in America, I +confine myself to the concave vault of the heavens, and do not mean to +assert that terrestrial objects are generally visible at greater +distances in the United States than in Italy. Indeed, I am rather +disposed to maintain the contrary; for though I know that the lower +strata of the atmosphere in Europe never equal in transparency the air +near the earth in New Mexico, Peru, and Chili, yet I think the accidents +of the coast-line of the Riviera, as, for example, between Nice and La +Spezia, and those of the incomparable Alpine panorama seen from Turin, +are distinguishable at greater distances than they would be in the +United States.] Yet in Piedmont and Lombardy irrigation is bestowed upon +almost every crop, while in our Northern States it is never employed at +all in farming husbandry, or indeed for any purpose except in +kitchen-gardens, and possibly, in rare cases, in some other small branch +of agricultural industry. [Footnote: In our comparatively rainless +Western territory, irrigation is extensively and very beneficially +employed. In the Salt Lake valley and in California, hundreds if not +thousands of miles of irrigation canals have been constructed, and there +is little doubt that artificially watering the soil will soon be largely +resorted to in the older States. See valuable observations on this +subject in Hayden, Preliminary Report on Geological Survey of Wyoming, +1870, pp. 194, 195, 258-261.] + +In general, it may be said that irrigation is employed only in the +seasons when the evaporating power of the sun and the capacity of the +air for absorbing humidity are greatest, or, in other words, that the +soil is nowhere artificially watered except when it is so dry that +little moisture would be evaporated from it, and, consequently, every +acre of irrigated ground is so much added to the evaporable surface of +the country. When the supply of water is unlimited, it is allowed, after +serving its purpose on one field, to run into drains, canals, or rivers. +But in most regions where irrigation is regularly employed, it is +necessary to economize the water; after passing over or through one +parcel of ground, it is conducted to another; no more is usually +withdrawn from the canals at anyone point than is absorbed by the soil +it irrigates, or evaporated from it, and, consequently, it is not +restored to liquid circulation, except by infiltration or precipitation. +We are safe, then, in saying that the humidity evaporated from any +artificially watered soil is increased by a quantity bearing a large +proportion to the whole amount distributed over it, for most even of +that which is absorbed by the earth is immediately given out again +either by vegetables or by evaporation; and the hygrometrical and +thermometrical condition of the atmosphere in irrigated countries is +modified proportionally to the extent of the practice. + +It is not easy to ascertain precisely either the extent of surface thus +watered, or the amount of water supplied, in any given country, because +these quantities vary with the character of the season; but there are +not many districts in Southern Europe where the management of the +arrangements for irrigation is not one of the most important branches of +agricultural labor. The eminent engineer Lombardini describes the system +of irrigation in Lombardy as, "every day in summer, diffusing over +550,000 hectares [1,375,000 acres] of land 45,000,000 cubic metres +[nearly 600,000,000 cubic yards] of water, which is equal to the entire +volume of the Seine, at an ordinary flood, or a rise of three metres +above the hydrometer at the bridge of La Tournelle at Paris." [Footnote: +Memorie sui progetti per Pestensions dell' Irrigazione, etc., il +Politecniso, for January, 1868, p. 6.] + +Niel states the quantity of land irrigated in the former kingdom of +Sardinia, including Savoy, in 1856, at 240,000 hectares, or not much +Ices than 600,000 acres. This is about four-thirteenths of the +cultivable soil of the kingdom. According to the same author, the +irrigated lands in Franco did not exceed 100,000 hectares, or 247,000 +acres, while those in Lombardy amounted to 450,000 hectares, more than +1,100,000 acres. [Footnote: Niel, L'Agriculture des Etats Sardes, p. +232. This estimate, it will be observed, is 275,000 acres less than that +of Lombardini.] + +In these three states alone, then, there were more than three thousand +square miles of artificially watered land, and if we add the irrigated +soils of the rest of Italy, [Footnote: In 1865 the total quantity of +irrigated lands in the kingdom of Italy was estimated at 1,357,677 +hectares, or 2,000,000 acres, of which one-half is supplied with water +by artificial canals. The Canal Cavour adds 250,000 acres to the above +amount. The extent of artificially watered ground in Italy is +consequently equal to the entire area of the States of Delaware and +Rhode Island.--See the official report, Sulle Bonificazione, Risaie, ed +Irrigazioni, 1865, p. 269.] of the Mediterranean islands, of the Spanish +peninsula, of Turkey in Europe and in Asia Minor, of Syria, of Egypt and +the remainder of Northern Africa, we shall see that irrigation increases +the evaporable surface of the Mediterranean basin by a quantity bearing +no inconsiderable proportion to the area naturally covered by water +within it. + +Arrangements are concluded, and new plans proposed, for an immense +increase of the lands fertilized by irrigation in France and in Belgium, +as well as in Spain and Italy, and there is every reason to believe that +the artificially watered soil of the latter country will be doubled, +that of France quadrupled, before the end of this century. There can be +no doubt that by these operations man is exercising a powerful influence +on the soil, on vegetable and animal life, and on climate, and hence +that in this, as in many other fields of industry, he is truly a +geographical agency. [Footnote: It belongs rather to agriculture than to +geography to discuss the quality of the crops obtained by irrigation, or +the permanent effects produced by it on the productiveness of the soil. +There is no doubt, however, that all crops which can be raised without +watering are superior in flavor and in nutritive power to those grown by +the aid of irrigation. Garden vegetables, particularly, profusely +watered, are so insipid as to be hardly eatable. Wherever irrigation is +practised, there is an almost irresistible tendency, especially among +ignorant cultivators, to carry it to excess; and in Piedmont and +Lombardy, if the supply of water is abundant, it is so liberally applied +as sometimes not only to injure the quality of the product, but to drown +the plants and diminish the actual weight of the crop. Grass-lands are +perhaps an exception to this remark, as it seems almost impossible to +apply too much water to them, provided it be kept in motion and not +allowed to stagnate on the surface. Protestor Liebig, in his Modern +Agriculture, says: "There is not to be found in chemistry a more +wonderful phenomenon, one which more confounds all human wisdom, than is +presented by the soil of a garden or field. By the simplest experiment, +any one may satisfy himself that rain-water filtered through field or +garden soil does not dissolve out a trace of potash, silicic acid, +ammonia, or phosphoric acid. The soil does not give up to the water one +particle of the food of plants which it contains. The most continuous +rains cannot remove from the field, except mechanically, any of the +essential constituents of ite fertility." "The soil not only retains +firmly all the food of plants which is actually in it, but its power to +preserve all that may be useful to them extends much farther. If rain or +other water holding in solution ammonia, potash, and phosphoric and +silicic acids, be brought in contact with soil, these substances +disappear almost immediately from the solution; the soil withdraws them +from the water. Only such substances are completely withdrawn by the +soil as are indispensable articles of food for plants; all others remain +wholly or in part in solution." + +These opinions were confirmed, soon after their promulgation, by the +experimental researches of other chemists, but are now questioned, and +they are not strictly in accordance with the alleged experience of +agriculturists in those parts of Italy where irrigation is most +successfully applied. They believe that the constituents of vegetable +growth are washed out of the soil by excessive and long-continued +watering. They consider it also established as a fact of observation, +that water which has flowed through or over rich ground is more valuable +for irrigation than water from the same source, which has not been +impregnated with fertilizing substances by passing through soils +containing them; and, on the other hand, that water, rich in the +elements of vegetation, parts with them in serving to irrigate a poor +soil, and is therefore less valuable as a fertilizer of lower grounds to +which it may afterward be conducted. See Baird Smith, Italian +Irrigation, i., p. 25; Scott Moncrieff, Irrigation in Southern Europe, +pp. 34, 87, 89; Lombardini, Sulle Inondazioni etc., p. 73; Mangon, Les +Irrigations, p. 48. + +The practice of irrigation--except in mountainous countries where +springs and rivulets are numerous--is attended with very serious +economical, social, and political evils. The construction of canals and +their immensely ramified branches, and the grading and scarping of the +ground to be watered, are always expensive operations, and they very +often require an amount of capital which can be commanded only by the +state, by moneyed corporations, or by very wealthy proprietors; the +capacity of the canals must be calculated with reference to the area +intended to be irrigated, and when they and their branches are once +constructed, it in very difficult to extend them, or to accommodate any +of their original arrangements to changes in the condition of the soil, +or in the modes or objects of cultivation; the flow of the water being +limited by the abundance of the source or the capacity of the canals, +the individual proprietor cannot be allowed to withdraw water at will, +according to his own private interest or convenience, but both the time +and the quantity of supply must be regulated by a general system +applicable, as far as may be, to the whole area irrigated by the same +canal, and every cultivator must conform his industry to a plan which +may be quite at variance with his special objects or with his views of +good husbandry. The clashing interests and the jealousies of proprietors +depending on the same means of supply are a source of incessant +contention and litigation, and the caprices or partialities of the +officers who control, or of contractors who farm, the canals, lead not +unfrequently to ruinous injustice towards individual landholders. These +circumstances discourage the division of the soil into small properties, +and there is a constant tendency to the accumulation of large estates of +irrigated land in the hands of great capitalists, and consequently to +the dispossession of the small cultivators, who pass from the condition +of owners of the land to that of hireling tillers. + +Though farmers are no longer yeomen, but peasants. Having no interest in +the soil which composes their country, they are virtually expatriated, +and the middle class, which ought to constitute the real physical and +moral strength of the land, ceases to exist as a rural estate, and is +found only among the professional, the mercantile, and the industrial +population of the cities.--See, on the difficulty of regulating +irrigation by law, Negri, Idea su una Legge in materia di Acqua, 1864; +and Agmard, Irrigations du Midi de L'Europe' where curious and +important remarks on the laws and usages of the Spanish Moors and the +Spaniards, in respect to irrigation, will be found. The Moors were so +careful in maintaining the details of their system, that they kept in +publio offices bronze models of their dams and sluices, as guides for +repairs and rebuilding. Some of these models are still preserved. +--Ibidem, pp. 204, 205. For an account of recent irrigation +works in Spain, see Spon, Dictionary of Engineering, article Irrigation. +As near as can be ascertained, the amount of water applied to irrigated +lands is scarcely anywhere less than the total precipitation during the +season of vegetable growth, and in general it much exceeds that +quantity. In grass-grounds and in field-culture it ranges from 27 or 28 +to 60 inches, while in smaller crops, tilled by hand-labor, it is +sometimes carried as high as 300 inches. [Footnote: Niel, Agriculture +des Etata Sardes, p. 237. Lombardini's computation just given allows +eighty-one cubic metres per day to the hectare [two hundred and sixty +cubic yards to the acre], which, supposing the season of irrigation to +be one hundred days, in equal to a precipitation of thirty-two inches. +But in Lombardy, water in applied to some crops during a longer period +than one hundred days; and in the marcite it flows over the ground even +in winter. According to Boussingault (Economie Rurale, ii., p. 240), +grass-grounds ought to receive, in Germany, twenty-one centimetres of +water per week, and with less than half that quantity it is not +advisable to incur the expense of supplying it. The ground is irrigated +twenty-five or thirty times, and if the full quantity of twenty-one +centimetres is applied, it receives more than two hundred inches of +water, or six times the total amount of precipitation. Puvis, quoted by +Boussingault, after much research comes to the conclusion that a proper +quantity is twenty centimetres [eight inches] applied twenty-five or +thirty times, which corresponds with the estimate just stated. Puvis +adds--and, as our author thinks, with reason--that this amount might be +doubled without disadvantage.--Ibidem, ii., p. 248, 249. In some parts +of France this quantity is immensely exceeded, and it is very important +to observe, with reference to the employment of irrigation in our +Northern States, that water is most freely supplied in the COLDER +provinces. Thus, in the Vosges, meadows are literally flooded for weeks +together, and while in the department of Vancluse a meadow may receive, +in five waterings of six and a half hours each, twenty-one inches of +wnter, in the Vosges it might be deluged for twenty-four hundred hours +in six applications, the enormous quantity of thirteen hundred feet of +water flowing over it. See the important work of Herve Mangon, Sur +l'emploi des eaux dans les Irrigations, chap. ix. Boussingault observes +that rain-water is vastly more fertilizing than the water of irrigating +canals, and therefore the supply of the latter must be greater. This is +explained partly by the different character of the substances held in +solution or suspension by the waters of the earth and of the sky, partly +by the higher temperature of the latter, and, possibly, partly also by +the mode of application--the rain being finely divided in its fall or by +striking plants on the ground, river-water flowing in a continuous +sheet. + +The temperature of the water is thought even more important than its +composition. The sources which irrigate the marcite of Lombardy--meadows +so fertile that less than an acre furnishes grass for a cow the whole +year--are very warm. The ground watered by them never freezes, and a +first crop, for soiling, is cut from it in January or February. The +Canal Cavour--which takes its supply chiefly from the Po at Chivasso, +fourteen or fifteen miles below Turin--furnishes water of much higher +fertilizing power than that derived from the Dora Baltea and the Sesia, +both because it is warmer, and because it transports a more abundant and +a richer sediment than the latter streams, which are fed by Alpine +ice-fields and melting snows, and which flow, for long distances, in +channels ground smooth and bare by ancient glaciers and not now +contributing much vegetable mould or fine slime to their waters.] + +The rice-grounds and the marcite of Lombardy are not included in these +estimates of the amount of water applied. [Footnote: About one-seventh +of the water which flows over the marcite is absorbed by the soil of +those meadows or evaporated from their surface, and consequently +six-sevenths of the supply remain for use on ground at lower levels.] +The meteorological effect of irrigation on a large scale, which would +seem prima facie most probable, would be an increase of precipitation in +the region watered. [Footnote: On the pluviometric effect of irrigation, +see Lombardini, Sulle Inondazioni, etc., p. 72, 74; the same author, +Essai Hydrologique sur le Nil, p. 32; Messedaglia, Analisi dell' opera +di Champion, pp. 96, 97, note; and Baird Smith, Italian Irrigation, i., +pp. 189, 190. + +In an article in Aus der Natur, vol. 57, p. 443, it is stated that the +rain on the Isthmus of Suez has increased since the opening of the +canal, and has enlarged the evaporable surface of the country; but this +cannot be accepted as an established fact without further evidence.] +Hitherto scientific observation has recorded no such increase, but in a +question of so purely local a character, we must ascribe very great +importance to a consideration which I have noticed elsewhere, but which, +has been frequently overlooked by meteorologists, namely, that vapors +exhaled in one district may very probably be condensed and precipitated +in another very distant from their source. If then it were proved that +an extension of irrigated soil was not followed by an increase of +rain-fall in the same territory, the probability that the precipitation +was augmented SOMEWHERE would not be in the least diminished. + +But though we cannot show that in the irrigated portions of Italy the +summer rain is more abundant than it was before irrigation was +practised--for we know nothing of the meteorological conditions of that +country at so remote a period--the fact that there is a very +considerable precipitation in the summer months in Lombardy is a strong +argument in favor of such increase. In the otherwise similar climate of +Rumelia and of much of Asia Minor, irrigation is indeed practiced, but +in a relatively small proportion. In those provinces there is little or +no summer rain. Is it not highly probable that the difference between +Italy and Turkey in this respect is to be ascribed, in part at least, to +extensive irrigation in the former country, and the want of it in the +latter It is true that, in its accessible strata, the atmosphere of +Lombardy is extremely dry during the period of irrigation, but it +receives an immense quantity of moisture by the evaporation from the +watered soil, and the rapidity with which the aqueous vapor is carried +up to higher regions--where, if not driven elsewhere by the wind, it +would be condensed by the cold into drops of rain or at least visible +clouds--is the reason why it is so little perceptible in the air near +the ground. [Footnote: Is not the mottled appearance of the upper +atmosphere in Italy, which I have already noticed, perhaps due in part +to the condensation of the aqueous vapor exhaled by watered ground ] + +But the question of an influence on temperature rests on a different +ground; for though the condensation of vapor may not take place within +days of time and degrees of distance from the hour and the place where +it was exhaled from the surface, a local refrigeration must necessarily +accompany a local evaporation. Hence, though the summer temperature of +Lombardy is high, we are warranted in affirming that it must have been +still higher before the introduction of irrigation, and would again +become so if that practice were discontinued. [Footnote: I do not know +that observations have been made on the thermometric influence of +irrigation, but I have often noticed that, on the irrigated plains of +Piedmont ten miles south of Turin, the morning temperature in summer was +several degrees below that marked at the Observatory in the city.] + +The quantity of water artificially withdrawn from running streams for +the purpose of irrigation is such as very sensibly to affect their +volume, and it is, therefore, an important element in the geography of +rivers. Brooks of no trifling current are often wholly diverted from +their natural channels to supply the canals, and their entire mass of +water is completely absorbed or evaporated, so that only such proportion +as is transmitted by infiltration reaches the river they originally fed. +Irrigation, therefore, diminishes great rivers in warm countries by +cutting off their sources of supply as well as by direct abstraction of +water from their main channels. We have just seen that the system of +irrigation in Lombardy deprives the Po of a quantity of water equal to +the total delivery of the Seine at ordinary flood, or, in other words, +of the equivalent of a tributary navigable for hundreds of miles by +vessels of considerable burden. + +The new canals executed and projected will greatly increase the loss. +The water required for irrigation in Egypt is less than would be +supposed from the exceeding rapidity of evaporation in that arid +climate; for the soil is thoroughly saturated during the inundation, and +infiltration from the Nile continues to supply a considerable amount of +humidity in the dryest season. Linant Bey computed that, in the Delta, +fifteen and one-third cubic yards per day sufficed to irrigate an acre. +If we suppose water to be applied for one hundred and fifty days during +the season of growth, this would be equivalent to a total precipitation +of about seventeen inches and one-third. Taking the area of actually +cultivated soil in Egypt at the estimate of 4,500,000 acres, and the +average amount of water daily applied in both Upper and Lower Egypt at +twelve hundredths of an inch in depth, we have an abstraction of about +74,000,000 cubic yards, which--the mean daily delivery of the Nile being +in round numbers 320,000,000 cubic yards--is twenty-three per cent of +the average quantity of water contributed to the Mediterranean by that +river. [Footnote: The proportion of the waters of the Nile withdrawn for +irrigation is greater than this calculation makes it. The quantity +required for an acre is less in the Delta than in Upper Egypt, both +because the soil of the Delta, to which Linant Bey's estimate applies, +lies little higher than the surface of the river, and is partly +saturated by infiltration, and because near the sea, in N. L. 30 +degrees, evaporation is much less rapid than it is several degrees +southwards and in the vicinity of a parched desert.] + +In estimating the effect of this abstraction of water upon the volume of +great rivers, especially in temperate climates and in countries with a +hilly surface, we must remember that all the water thus +withdrawn--except that which is absorbed by vegetation, that which +enters into new inorganic compounds, and that which is carried off by +evaporation--is finally restored to the original current by superficial +flow or by infiltration. It is generally estimated that from one-third +to one-half of the water applied to the fields is absorbed by the earth, +and this, with the deductions just given, is returned to the river by +direct infiltration, or descends through invisible channels to moisten +lower grounds, and thence in part escapes again into the bed of the +river, by similar conduits, or in the form of springs and rivulets. +Interesting observations have lately been made on this subject in France +and important practical results arrived at. It was maintained that +mountain irrigation is not ultimately injurious to that of the plains +below, because lands liberally watered in the spring, when the supply is +abundant, act as reservoirs, storing up by absorption water which +afterwards filters down to lower grounds or escapes into the channel of +the river and keeps up its current in the dry summer months, so as to +compensate for what, during those months, is withdrawn from it for +upland irrigation. Careful investigation showed that though this +proposition is not universally true, it is so in many cases, and there +can be no doubt that the loss in the volume of rivers by the abstraction +of water for irrigation is very considerably less than the measure of +the quantity withdrawn. [Footnote: See Vigan, Etude sur les Irrigations, +Paris, 1867; and Scott Moncrieff, Irrigation in Southern Europe, pp. 89, +90. + +The brook Ain Musa, which runs through the ruined city of Petra and +finally disappears in the sands of Wadi el Araba, is a considerable +stream in winter, and the inhabitants of that town were obliged to +excavate a tunnel through the rock near the right bank, just above the +upper entrance of the narrow Sik, to discharge a part of its swollen +current. The sagacity of Dr. Robinson detected the necessity of this +measure, though the tunnel, the mouth of which was hidden by brushwood, +was not discovered till some time after his visit. I even noticed, near +the arch that crosses the Sik, unequivocal remains of a sluice by which +the water was diverted to the tunnel. Immense labor was also expended in +widening the natural channel at several points below the town, to +prevent the damming up and setting back of the water--a fact I believe +not hitherto noticed by travellers. + +The Fellahheen above Petra still employ the waters of Ain Musa for +irrigation, and in summer the superficial current is wholly diverted +from its natural channel for that purpose. At this season, the bed of +the brook, which is composed of pebbles, gravel, and sand, is dry in the +Sik and through the town; but the infiltration is such that water is +generally found by digging to a small depth in the channel. Observing +these facts in a visit to Petra in the summer, I was curious to know +whether the subterranean waters escaped again to daylight, and I +followed the ravine below the town for a long distance. Not very far +from the upper entrance of the ravine, arborescent vegetation appeared +upon its bottom, and as soon as the ground was well shaded, a thread of +water burst out. This was joined by others a little lower down, and, at +the distance of a mile from the town, a strong current was formed and +ran down towards Wadi el Araba. + +Similar facts are observed in all countries where the superficial +current of water-courses is diverted from their bed for irrigation, but +this case is of special interest because it shows the extent of +absorption and infiltration even in the torrid climate of Arabia. See +Baird Smith, Italian Irrigation, vol. i., pp. 172, 386 and 387.] +Irrigation, as employed for certain special purposes in Europe and +America, is productive of very prejudicial climatic effects. I refer +particularly to the cultivation of rice in the Southern States of the +American Union and in Italy. The climate of the Southern States is in +general not necessarily unhealthy for the white man, but he can scarcely +sleep a single night in the vicinity of the rice-grounds without being +attacked by a dangerous fever. The neighborhood of the rice-fields is +possibly less pestilential in Lombardy and Piedmont than in South +Carolina and Georgia, but still very insalubrious to both man and beast. +"Not only does the population decrease where rice is grown," says +Escourron-Milliago, "but even the flocks are attacked by typhus. In the +rice-grounds the soil is divided into compartments rising in gradual +succession to the level of the irrigating canal, in order that the +water, after having flowed one field, may be drawn off to another, and +thus a single current serve for several compartments, the lowest field, +of course, still being higher than the ditch which at last drains both +it and the adjacent soil. This arrangement gives a certain force of +hydrostatic pressure to the water with which the rice is irrigated, and +the infiltration from these fields is said to extend through neighboring +grounds, sometimes to the distance of not less than a myriametre, or six +English miles, and to be destructive to crops and even trees reached by +it. Land thus affected can no longer be employed for any purpose but +growing rice, and when prepared for that crop, it propagates still +further the evils under which it had itself suffered, and, of course, +the mischief is a growing one." [Footnote: Escourrou-Milliago, D'Italie +a propos de l'Exposition de Paris, 1856, p. 92. According to an article +in the Gazzetto di Torino for the 17th of January, 1869, the deaths from +malarious fever in the Canavese district--which is asserted to have been +altogether free from this disease before the recent introduction of +rice-culture--between the 1st of January and the 15th of October, 1868, +were two thousand two hundred and fifty. The extent of the injurious +influence of this very lucrative branch of rural industry in Italy is +contested by the rice-growers. But see Secondo Laura, Le Risaje, Torino, +1869; Selmi, Il Miasma Palustre, p. 89; and especially Carlo Livi, Della +coltivazione del Riso in Italia, in the Nuova Antologia for July, 1871, +p. 599 et seqq. According to official statistics, the rice-grounds of +Italy, including the islands, amounted in 1866 to 450,000 acres. It is +an interesting fact in relation to geographical and climatic conditions, +that while little rice is cultivated SOUTH of N. L. 44 degrees in Italy, +little is grown in the United States NORTH of 35 degrees. To the +southward of the great alluvial plain of the Po, the surface is in +general too much broken to admit of the formation of level fields of +much extent, and where the ground is suitable, the supply of water is +often insufficient. + +The Moors introduced the cultivation of rice into Spain at an early +period of their dominion in that country. The Spaniards sowed rice in +Lombardy and in the Neapolitan territory in the 16th century; but +besides the want of water and of level ground convenient for irrigation, +rice-husbandry has proved so much more pestilential in Southern than in +Northern Italy that it has long been discouraged by the Neapolitan +government.] + + +Salts deposited by Water of Irrigation. + +The attentive traveller in Egypt and Nubia cannot fail to notice many +localities, generally of small extent, where the soil is rendered +infertile by an excess of saline matter in its composition. In many +cases, perhaps in all, these barren spots lie rather above the level +usually flooded by the inundations of the Nile, and yet they exhibit +traces of former cultivation. Observations in India suggest a possible +explanation of this fact. A saline efflorescence called "Reh" and +"Kuller" is gradually invading many of the most fertile districts of +Northern and Western India, and changing them into sterile deserts. It +consists principally of sulphate of soda (Glauber's salts), with varying +proportions of common salt. These salts (which in small quantities are +favorable to fertility of soil) are said to be the gradual result of +concentration by evaporation of river and canal waters, which contain +them in very minute quantities, and with which the lands are either +irrigated or occasionally overflowed. The river inundations in hot +countries usually take place but once in a year, and, though the banks +remain submerged for days or even weeks, the water at that period, being +derived principally from rains and snows, must be less highly charged +with mineral matter than at lower stages, and besides, it is always in +motion. The water of irrigation, on the other hand, is applied for many +months in succession, it is drawn from rivers and canals at the seasons +when the proportion of salts is greatest, and it either sinks into the +superficial soil, carrying with it the saline substances it holds in +solution, or is evaporated from the surface, leaving them upon it. Hence +irrigation must impart to the soil more salts than natural inundation. +The sterilized grounds in Egypt and Nubia lying above the reach of the +floods, as I have said, we may suppose them to have been first +cultivated in that remote antiquity when the Nile valley received its +earliest inhabitants, and when its lower grounds were in the condition +of morasses. They must have been artificially irrigated from the +beginning; they may have been under cultivation many centuries before +the soil at a lower level was invaded by man, and hence it is natural +that they should be more strongly impregnated with saline matter than +fields which are exposed every year, for some weeks, to the action of +running water so nearly pure that it would be more likely to dissolve +salts than to deposit them. + + +SUBTERRANEAN WATERS. + +I have frequently alluded to a branch of physical geography, the +importance of which is but recently adequately recognized--the +subterranean waters of the earth considered as stationary reservoirs, as +flowing currents, and as filtrating fluids. The earth drinks in moisture +by direct absorption from the atmosphere, by the deposition of dew, by +rain and snow, by percolation from rivers and other superficial bodies +of water, and sometimes by currents flowing into caves or smaller +visible apertures. [Footnote: The great limestone plateau of the Karst +in Carniola is completely honey-combed by caves through which the +drainage of that region is conducted. Rivers of considerable volume pour +into some of these caves and can be traced underground to their exit. +Thus the Recca has been satisfactorily identified with a stream flowing +through the cave of Trebich, and with the Timavo--the Timavus of Virgil +and the ancient geographers--which empties through several mouths into +the Adriatic between Trieste and Aquileia. The city of Trieste is very +insufficiently supplied with fresh water. It has been thought +practicable to supply this want by tunnelling through the wall of the +plateau, which rises abruptly in the rear of the town, until some +subterranean stream is encountered, the current of which can be +conducted to the city. More visionary projectors have gone further, and +imagined that advantage might be taken of the natural tunnels under the +Karst for the passage of roads, railways, and even navigable canals. But +however chimerical these latter schemes may seem, there is every reason +to believe that art might avail itself of these galleries for improving +the imperfect drainage of the champaign country bounded by the Karst, +and that stopping or opening the natural channels might very much modify +the hydrography of an extensive region. See in Aus des Natur, xx., pp. +250-254, 263-266, two interesting articles founded on the researches of +Schmidt. + +The cases are certainly not numerous where marine currents are known to +pour continuously into cavities beneath the surface of the earth, but +there is at least one well-authenticated instance of this sort--that of +the mill-stream at Argostoli in the island of Cephalonia. It had been +long observed that the sea-water flowed into several rifts and cavities +in the limestone rocks of the coast, but the phenomenon has excited +little attention until very recently. In 1833, three of the entrances +were closed, and a regular channel, sixteen feet long and three feet +wide, with a fall of three feet, was cut into the mouth of a larger +cavity. The sea-water flowed into this canal, and could be followed +eighteen or twenty feet beyond its inner terminus, when it disappeared +in holes and clefts in the rock. + +In 1858 the canal had been enlarged to thewidth of five feet and a half, +and a depth of a foot. The water pours rapidly through the canal into an +irregular depression and forms a pool, the surface of which is three or +four feet below the adjacent soil, and about two and a half or three +feet below the level of the sea. From this pool it escapes through +several holes and clefts in the rock, and has not yet been found to +emerge elsewhere. + +There is a tide at Argostoli of about six inches in still weather, but +it is considerably higher with a south wind. I do not find it stated +whether water flows through the canal into the cavity at low tide, but +it distinctly appears that there is no refluent current, as of course +there could not be from a base so much below the sea. Mousson found the +delivery through the canal to be at the rate of 24.88 cubic feet to the +second; at what stage of the tide does not appear. Other mills of the +same sort have been erected, and there appear to be several points on +the coast where the sea flows into the land. + +Various hypotheses have been suggested to explain this phenomenon, some +of which assume that the water descends to a great depth beneath the +crust of the earth; but the supposition of a difference of level in the +surface of the sea on the opposite sides of the island, which seems +confirmed by other circumstances, is the most obvious method of +explaining these singular facts. If we suppose the level of the water on +one side of the island to be raised by the action of currents three or +four feet higher than on the other, the existence of cavities and +channels in the rock would easily account for a subterranean current +beneath the island, and the apertures of escape might be so deep or so +small as to elude observation. See Aus der Natur, vol. xix., pp. 129 et +seqq. I have lately been informed by a resident of the Ionian Islands, +who is familiar with the locality, that the sea flows uninterruptedly +into the sub-insular cavities, at all stages of the tide.] Some of this +humidity is exhaled again by the soil, some is taken up by organic +growths and by inorganic compounds, some poured out upon the surface by +springs and either immediately evaporated or carried down to larger +streams and to the sea, some flows by subterranean courses into the bed +of fresh-water rivers [Footnote: "The affluents received by the Seine +below Rouen are so inconsiderable, that the augmentation of the volume +of that river must be ascribed principally to springs rising in its bed. +This is a point of which engineers now take notice, and M. Belgrand, the +able officer charged with the improvement of the navigation of the Seine +between Paris and Rouen, has devoted much attention to it."--Babinet, +Etudes et Lectures, iii., p. 185. + +On page 232 of the volume just quoted, the same author observes: "In the +lower part of its course, from the falls of the Oise, the Seine receives +so few important affluents, that evaporation alone would suffice to +exhaust all the water which passes under the bridges of Paris." + +This supposes a much greater amount of evaporation than has been usually +computed, but I believe it is well settled that the Seine conveys to the +sea much more water than is discharged into it by all its superficial +branches. Babinet states the evaporation from the surface of water at +Paris to be twice as great as the precipitation. + +Belgrand supposes that the floods of the Seine at Paris are not produced +by the superficial flow of the water of precipitation into its channel, +but from the augmented discharge of its remote mountain sources, when +swollen by the rains and melted snows which percolate through the +permeable strata in its upper course.--Annales des Ponts et Chaussees, +1851, vol. i.] or of the ocean, and some remains, though even here not +in forever motionless repose, to fill deep cavities and underground +channels. In every case the aqueous vapors of the air are the ultimate +source of supply and all these hidden stores are again returned to the +atmosphere by evaporation. + +The proportion of the water of precipitation taken up by direct +evaporation from the surface of the ground seems to have been generally +exaggerated, sufficient allowance not being made for moisture carried +downwards or in a lateral direction by infiltration or by crevices in +the superior rocky or earthy strata. According to Wittwer, Mariotte +found that but one-sixth of the precipitation in the basin of the Seine +was delivered into that sea by the river, "so that five-sixths remained +for evaporation and consumption by the organic world." [Footnote: +Physicalische Geographie, p. 286. It does not appear whether this +inference is Mariotte's or Wittwer's. I suppose it is a conclusion of +the latter. + +According to Valles, the Seine discharges into the sea thirty per cent. +of the precipitation in its valley, while the Po delivers into the +Adriatic two-thirds and perhaps even three-quarters of the total +down-fall of its basin. The differences between the tributaries of the +Mississippi in this respect are remarkable, the Missouri discharging +only fifteen per cent., the Yazoo not less than ninety. The explanation +of these facts is found in the geographical and geological character of +the valleys of these rivers. The Missouri flows with a rapid current +through an irregular country, the Yazoo has a very slow flow through a +low, alluvial region which is kept constantly almost saturated by +infiltration.] Maury estimates the annual amount of precipitation in the +valley of the Mississippi at 620 cubic miles, the discharge of that +river into the sea at 107 cubic miles, and concludes that "this would +leave 513 cubic miles of water to be evaporated from this river-basin +annually." [Footnote: Physical Geography of the Sea. Tenth edition. +London, 1861, Section 274.] In these and other like computations, the +water carried down into the earth by capillary and larger conduits is +wholly lost sight of, and no thought is bestowed upon the supply for +springs, for common and artesian wells, and for underground rivers, like +those in the great caves of Kentucky, which may gush up in fresh-water +currents at the bottom of the Caribbean Sea, or rise to the light of day +in the far-off peninsula of Florida. [Footnote: In the low peninsula of +Florida, rivers, which must have their sources in mountains hundreds of +miles distant, pour forth from the earth with a volume sufficient to +permit steamboats to ascend to their basins of eruption. In January, +1857, a submarine fresh-water river burst from the bottom of the sea not +far from the southern extremity of the peninsula, and for a whole month +discharged a current not inferior in volume to the river Mississippi, or +eleven times the mean delivery of the Po, and more than six times that +of the Nile. We can explain this phenomenon only by supposing that the +bed of the sea was suddenly burst up by the hydrostatic upward pressure +of the water in a deep reservoir communicating with some great +subterranean river or receptacle in the mountains of Georgia or of Cuba, +or perhaps even in the valley of the Mississippi.--Thomassy, Essai sur +l'Hydrologie. Late southern journals inform us that the creek under the +Natural Bridge in Virginia has suddenly disappeared, being swallowed up +by newly formed fissures, of unknown depth, in its channel. It does not +appear that an outlet for the waters thus absorbed has been discovered, +and it is not improbable that they are filling some underground cavity +like that which supplied the submarine river just mentioned.] + +The progress of the emphatically modern science of geology has corrected +these erroneous views, because the observations on which it depends have +demonstrated not only the existence, but the movement, of water in +nearly all geological formations, have collected evidence of the +presence of large reservoirs at greater or less depths beneath surfaces +of almost every character, and have investigated the rationale of the +attendant phenomena. [Footnote: See especially Stoppani, Corso di +Geologia, i., pp. 270 et seqq.] The distribution of these waters has +been minutely studied with reference to a great number of localities, +and though the actual mode and rate of their vertical and horizontal +transmission is still involved in much obscurity, the laws which +determine their aggregation are so well understood, that, when the +geology of a given district is known, it is not difficult to determine +at what depth water will be reached by the borer, and to what height it +will rise. The same principles have been successfully applied to the +discovery of small subterranean collections or currents of water, and +some persons have acquired, by a moderate knowledge of the superficial +structure of the earth combined with long practice, a skill in the +selection of favorable places for digging wells which seems to common +observers little less than miraculous. The Abbe Paramelle--a French +ecclesiastic who devoted himself for some years to this subject and was +extensively employed as a well-finder--states, in his work on Fountains, +that in the course of thirty-four years he had pointed out more than ten +thousand subterranean springs; and though his geological speculations +were often erroneous, high scientific authorities have testified to the +great practical value of his methods, and the general accuracy of his +predictions. [Footnote: Paramelle, Quellenkunde, mit einem Vorwort von +B. Cotta. 1856.] Hydrographical researches have demonstrated the +existence of subterranean currents and reservoirs in many regions where +superficial geology had not indicated their probable presence. Thus, a +much larger proportion of the precipitation in the valley of the Tiber +suddenly disappears than can be accounted for by evaporation and visible +flow into the channel of the river. Castelli suspected that the excess +was received by underground caverns, and slowly conducted by percolation +to the bed of the Tiber. Lombardini--than whom there is no higher +authority--concludes that the quantity of water gradually discharged +into the river by subterranean conduits, is not less than three-quarters +of the total delivery of its basin. [Footnote: See Lombardini, +Importanza degli studi sulla Statistica da Fiumi, p. 27; also, same +author, Sulle Inondazioni avvenute in Francia, etc., p. 29.] What is +true of the hydrology of the Tiber is doubtless more or less true of +that of other rivers, and the immense value of natural arrangements +which diminish the danger of sudden floods by retaining a large +proportion of the precipitation, and of an excessive reduction of river +currents in the droughts of summer, by slowly conducting into their beds +water accumulated and stored up in subterranean reservoirs in rainy +seasons, is too obvious to require to be dwelt upon. The readiness with +which water not obstructed by impermeable strata diffuses itself through +the earth in all directions--and consequently, the importance of keeping +up the supply of subterranaean reservoirs--find a familiar illustration +in the effect of paving the ground about the stems of vines and trees. +The surface-earth around the trunk of a tree may be made almost +impervious to water, by flagstones and cement, for a distance as great +as the spread of the roots; and yet the tree will not suffer for want of +moisture, except in droughts severe enough sensibly to affect the supply +in deep wells and springs. Both forest and fruit trees attain a +considerable age and size in cities where the streets and courts are +closely paved, and where even the lateral access of water to the roots +is more or less obstructed by deep cellars and foundation walls. The +deep-lying veins and sheets of water, supplied by infiltration from +often comparatively distant sources, send up moisture by capillary +attraction, and the pavement prevents the soil beneath it from losing +its humidity by evaporation. Hence, city-grown trees find moisture +enough for their roots, and though plagued with smoke and dust, often +retain their freshness, while those planted in the open fields, where +sun and wind dry up the soil faster than the subterranean fountains can +water it, are withering from drought. [Footnote: The roots of trees +planted in towns do not depend exclusively on infiltration for their +supply of water, for they receive a certain amount of both moisture and +air through the interstices between the paving-stones; but where wide +surfaces of streets and courts are paved with air and water tight +asphaltum, as in Paris, trees suffer from the diminished supply of these +necessary elements.] Without the help of artificial conduit or of +water-carrier, the Thames and the Seine refresh the ornamental trees +that shade the thoroughfares of London and of Paris, and beneath the hot +and reeking mould of Egypt, the Nile sends currents to the extremest +border of its valley. [Footnote: See the interesting observations of +Krieck on this subject, Schriften zur allgemeinen Erdkunde, cap. iii., +Section 6, and especially the passages in Ritter s Erdkunde, vol. i., +there referred to. + +The tenacity with which the parched soil of Egypt retains the supply of +moisture it receives from the Nile is well illustrated by observations +of Girard cited by Lombardini from the Memoires de l'Academie des +Sciences, t. ii., 1817. Girard dug wells at distances of 3,200, 1,800, +and 1,200 metres from the Nile, and after three months of low water in +the river, found water in the most remote well, at 4m. 97, in the next +at 4m. 23, and in that nearest the bank at 3m. 44 above the surface of +the Nile. The fact that the water was highest in the most distant well +appears to show that it was derived from the inundation and not, by +lateral infiltration, from the river. But water is found beneath the +sands at points far above and beyond the reach of the inundations, and +can be accounted for only by subterranean percolation from the Nile. At +high flood, the hydrostatic pressure on the banks, combined with +capillary attribution, sends water to great horizontal distances through +the loose soil; at low water the current is reversed, and the moisture +received from the river is partly returned, and may often be seen oozing +from the banks into the river.--Clot Bey, Apercu sur l'Egypte, i., 128. + +Laurent (Memoires sur le Sahara Oriental, pp. 8, 9), in speaking of a +river at El-Faid, "which, like all those of the desert, is, most of the +time, without water," observes, that many wells are dug in the bed of +the river in the dry season, and that the subterranean supply of water +thus reached extends itself laterally, at about the same level, at least +a kilometre from the river, as water is found by digging to the depth of +twelve or fifteen metres at a village situated at that distance from the +bank. + +Recent experiments, however, have shown that in the case of rivers +flowing through thickly peopled regions, and especially where the refuse +from industrial establishments is discharged into them, the finely +comminuted material received from sewers and factories sometimes clogs +up the interstices between the particles of sand and gravel which +compose the bed and banks, and the water is consequently confined to the +channel and no longer diffuses itself laterally through the adjacent +soil. This obstruction of course acts in both directions, according to +circumstances. In one case, it prevents the escape of river-water and +tends to maintain a full flow of the current; in another it intercepts +the supply the river might otherwise receive by infiltration from the +land, and thus tends to reduce the volume of the stream. In some +instances pits have been sunk along the banks of large rivers and the +water which filters into them pumped up to supply aqueducts. This method +often succeeds, but where the bed of the stream has been rendered +impervious by the discharge of impurities into it, it cannot be depended +upon. + +The tubular wells generally known as the American wells furnish another +proof of the free diffusion and circulation of water through the soil. I +do not know the date of the first employment of these tubes in the +United States, but as early as 1861, the Chevalier Calandra used wooden +tubes for this pose in Piedmont, with complete success. See the +interesting pamphlet, Sulla Estrazione delle Acque Sotterrance, by C. +Calandra. Torino, 1867. + +The most remarkable case of infiltration known to me by personal +observation is the occurrence of fresh water in the beach-sand on the +eastern side of the Gulf of Akaba, the eastern arm of the Red Sea. If +you dig a cavity in the beach near the sea-level, it soon fills with +water so fresh as not to be undrinkable, though the sea-water two or +three yards from it contains even more than the average quantity of +salt. It cannot be maintained that this is sea-water freshed by +filtration through a few feet or inches of sand, for salt-water cannot +be deprived of its salt by that process. It can only come from the +highlands of Arabia, and it would seem that there must exist some large +reservoir in the interior to furnish a supply which, in spite of +evaporation, holds out for months after the last rains of winter, and +perhaps even through the year. I observed the fact in the month of June. +See Robinson, Biblical Researches, 1857, vol i., p. 167. + +The precipitation in the mountains that border the Red Sea is not known +by pluviometric measurement, but the mass of debris brought down the +ravines by the torrents proves that their volume must be large. The +proportion of surface covered by sand and absorbent earth, in Arabia +Petraea and the neighboring countries, is small, and the mountains drain +themselves rapidly into the wadies or ravines where the torrents are +formed; but the beds of earth and disintegrated rock at the bottom of +the valleys are of so loose and porous texture, that a great quantity of +water is absorbed in saturating them before a visible current is formed +on their surface. In a heavy thunder-storm, accompanied by a deluging +rain, which I witnessed at Mount Sinai in the month of May, a large +stream of water poured, in an almost continuous cascade, down the steep +ravine north of the convent, by which travellers sometimes descend from +the plateau between the two peaks, but after reaching the foot of the +mountain, it flowed but a few yards before it was swallowed up in the +sands. + +Fresh-water wells are not unfrequently found upon the borders of ocean +beaches. In the dry summer of 1870, drinkable water was procured in many +places on the coast of Liguria by digging to the depth of a yard in the +beach-sands. Tubular wells reach fresh water at twelve or fifteen feet +below the surface on the sandy plains of Cape Cod. In this latter case, +the supply is more probably derived directly from precipitation than +from lateral infiltration.] + + +Artesian Wells. + +The existence of artesian wells depends upon that of subterranean +reservoirs and rivers, and the supply yielded by borings is regulated by +the abundance of such sources. The waters of the earth are, in many +cases, derived from superficial currents which are seen to pour into +chasms opened, as it were, expressly for their reception; and in others, +where no apertures in the crust of the earth have been detected, their +existence is proved by the fact that artesian wells sometimes bring up +from great depths seeds, leaves, and even living fish, which must have +been carried down through channels large enough to admit a considerable +stream. [Footnote: Charles Martins, Le Sahara, in Revue des Deux Mondes, +Sept. 1, 1864, p. 619; Stoppani, Corso di Geologia, i., 281; Desor, +Die Sahara, Basel, 1871, pp. 50, 51.] But in general, the sheet and +currents of water reached by deep boring appear to be primarily due to +infiltration from highlands where the water is first collected in +superficial or subterranean reservoirs. By means of channels conforming +to the dip of the strata, these reservoirs communicate with the lower +basins, and exert upon them a fluid pressure sufficient to raise a +column to the surface, whenever an orifice is opened. [Footnote: It is +conceivable that in shallow subterranean basins superincumbered mineral +strata may rest upon the water and be partly supported by it. In such +case the weight of such strata would be an additional, if not the sole, +cause of the ascent of the water through the tubes of artesian wells. + +The ascent of petroleum in the artesian oil-wells in Pennsylvania, and, +in many cases, of salt-water in similar tubes, can hardly be ascribed to +hydrostatic pressure, and there is much difficulty in accounting for the +rise of water in artesian wells in many parts of the African desert on +that principle. Perhaps the elasticity of gases, which probably aids in +forcing up petroleum and saline waters, may be, not unfrequently, an +agency in causing the flow of water in common artesian borings. It is +said that artesian wells lately bored in Chicago, some to the depth of +1,600 feet, raise water to the height of 100 feet above the surface. +What is the source of the pressure ] The water delivered by an artesian +well is, therefore, often derived from distant sources, and may be +wholly unaffected by geographical or meteorological changes in its +immediate neighborhood, while the same changes may quite dry up common +wells and springs which are fed only by the local infiltration of their +own narrow basins. + +In most cases, artesian wells have been bored for purely economical or +industrial purposes, such as to obtain good water for domestic use or +for driving light machinery, to reach saline or other mineral springs, +and recently, in America, to open fountains of petroleum or rock-oil. +The geographical and geological effects of such abstraction of fluids +from the bowels of the earth are too remote and uncertain to be here +noticed; [Footnote: Many more or less probable conjectures have been +made on this subject but thus far I am not aware that any of the +apprehended results have been actually shown to have happened. In an +article in the Annales des Ponts et Chaussees for July and August, 1839, +p. 131, it was suggested that the sinking of the piers of a bridge at +Tours in France was occasioned by the abstraction of water from the +earth by artesian wells, and the consequent withdrawal of the mechanical +support it had previously given to the strata containing it. A reply to +this article will be found in Viollet, Theorie des Puits Artesiens, p. +217. + +In some instances the water has rushed up with a force which seemed to +threaten the inundation of the neighborhood, and even the washing away +of much soil; but in those cases the partial exhaustion of the supply, +or the relief of hydrostatic or elastic pressure, has generally produced +a diminution of theflow in a short time, and I do not know that any +serious evil has everbeen occasioned in this way. + +In April, 1866, a case of this sort occurred in boring an artesian well +near the church of St. Agnes at Venice. When the drill reached the depth +of 160 feet, a jet of mud and water was shot up to the height of 130 +feet above the surface, and continued to flow with gradually diminishing +force for about eight hours.] but artesian wells have lately been +employed in Algeria for a purpose which has even now a substantial, and +may hereafter acquire a very great geographical importance. It was +observed by many earlier as well as recent travellers in the East, among +whom Shaw deserves special mention, that the Libyan desert, bordering +upon the cultivated shores of the Mediterranean, appeared in many places +to rest upon a subterranean lake at an accessible distance below the +surface. The Moors are vaguely said to bore artesian wells down to this +reservoir, to obtain water for domestic use and irrigation, and there is +evidence that this art was practised in Northern Africa in the Middle +Ages. But it had been lost by the modern Moors, and the universal +astonishment and incredulity with which the native tribes viewed the +operations of the French engineers sent into the desert for that +purpose, are a sufficient proof that this mode of reaching the +subterranean waters was new to them. They were, however, aware of the +existence of water below the sands, and were dexterous in digging +wells--square shafts lined with a framework of palm-tree stems--to the +level of the sheet. The wells so constructed, though not technically +artesian wells, answer the same purpose; for the water rises to the +surface and flows over it as from a spring. [Footnote: See a very +interesting account of these wells, and of the workmen who clean them +out when obstructed by sand brought up with the water, in Laurent's +memoir on the artesian wells recently bored by the French Government in +the Algerian desert. Mimoire sur le Sahara Oriental, etc., pp. et seqq. +Some of the men remained under water from two minutes to two minutes and +forty seconds. Several officers are quoted as having observed immersions +of three minutes' duration, and M. Berbrugger witnessed ona of six +minutes and five seconds and another of five minutes and fifty-five +seconds. The shortest of these periods is longer than the best +pearl-diver can remain below the surface of salt-water. The wells of the +Sahara are from twenty to eighty metres deep.-Desor, Die Sahara, Basel, +1871, p. 43. + +The ancient Egyptians were acquainted with the art of boring artesian +wells. Ayme, a French engineer in the service of the Pacha of Egypt, +found several of these old wells, a few years ago, in the oases. They +differed little from modern artesian wells, but were provided with +pear-shaped valves of stone for closing them when water was not needed. +When freed from the sand and rubbish with which they were choked, they +flowed freely and threw up fish large enough for the table. The fish +were not blind, as cave-fish often are, but were provided with eyes, and +belonged to species common in the Nile. The sand, too, brought up with +them resembled that of the bed of that river. Hence it is probable that +they were carried to the oases by subterranean channels from the +Nile.--Desor, Die Sahara, Basel, 1871, p. 28; Stoppani, Corso di +Geologia, i., p. 281. Barth speaks of common wells in Northern Africa +from 200 to 360 feet deep.--Reisen in Africa, ii., p. 180. + +It is certain that artesian wells have been common in China from a very +remote antiquity, and the simple method used by the Chinese--where the +drill is raised and let fall by a rope, instead of a rigid rod--has +lately been employed in Europe with advantage. Some of the Chinese wells +are said to be 3,000 feet deep; that of Neusalzwerk in Silesia is 2,300. +A well was bored at St. Louis, in Missouri, a few years ago, to supply a +sugar refinery, to the depth of 2,199 feet. This was executed by a +private firm in three years, at the expense of only $10,000. Four years +since the boring was recommenced in this well and reached a depth of +3,150 feet, but without a satisfactory result. Another artesian well was +sunk at Columbus, in Ohio, to the depth of 2,500 feet, but without +obtaining the desired supply of water. Perhaps, however, the artesian +well of the greatest depth ever executed until very recently, is that +bored within the last six or seven years, for the use of an Insane +Asylum near St. Louis. This well descends to the depth of three thousand +eight hundred and forty-three feet, but the water which it furnishes is +small in quantity and of a quality that cannot be used for ordinary +domestic purposes. The bore has a diameter of six inches to the depth of +425 feet, and after that it is reduced to four inches. For about three +thousand feet the strata penetrated were of carboniferous and magnesian +limestone alternating with sandstone. The remainder of the well passes +through igneous rock. At St. Louis the Missouri and Mississippi rivers +are not more than twenty miles distant from each other, and it is worthy +of note that the waters of neither of those two rivers appear to have +opened for themselves a considerable subterranean passage through the +rocky strata of the peninsula which separates them. + +When in boring an artesian well water is not reached at a moderate +depth, it is not always certain that it will be found by driving the +drill still lower. In certain formations, water diminshes as we descend, +and it seems probable that, except in case of caverns and deep fissures, +the weight of the superincumbent mineral strata so compresses the +underlying ones, at no very great distance below the surface, as to +render them impermeable to water and consequently altogether dry. See +London Quarterly Journal of Science, No. xvii., Jan., 1868, p. 18, 19. + +In the silver mines of Nevada water is scarcely found at depths below +1,000 feet, and at 1,200 feet from the surface the earth is quite +dry.--American Annual of Scientific Discovery for 1870, p. 75. + +Similar facts are observed in Australia. The Pleasant Creek News writes: +"A singular and unaccountable feature in connection with our deep quartz +mines is being developed daily, which must surprise those well +experienced in mining matters. It is the decrease of water as the +greater depths are reached. In the Magdala shaft at 950 ft. the water +has decreased to a MINIMUM; in the Crown Cross Reef Company's shaft, at +800 ft., notwithstanding the two reefs recently struck, no extra water +has been met with; and in the long drive of the Extended Cross Reef +Company, at a depth of over 800 ft., the water is lighter than it was +nearer the surface." + +Boring has been carried to a great depth at Sperenberg near Berlin, +where, in 1871, the drill had descended 5,500 feet below the surface, +passing through a stratum of salt for the last 3,200 feet; but the +drilling was still in progress, the whole thickness of the salt-bed not +having been penetrated.--Aus der Natur, vol. 55, p. 208. + +The facts that there are mines extending two miles under the bed of the +sea, which are not particularly subject to inconvenience from water, +that little water was encountered in the Mt. Cenis tunnel, 3500 feet +below the surface, and that at Scarpa, not far from Tivoli, there is an +ancient well 1700 feet deep with but eighteen feet of water, may also be +cited as proofs that water is not universally diffused at great +distances beneath the surface.] + +These wells, however, are too few and too scanty in supply to serve any +other purposes than the domestic wells of other countries, and it is but +recently that the transformation of desert into cultivable land by this +means has been seriously attempted. The French Government has bored a +large number of artesian wells in the Algerian desert within a few +years, and the native sheikhs are beginning to avail themselves of the +process. Every well becomes the nucleus of a settlement proportioned to +the supply of water, and before the end of the year 1860, several nomade +tribes had abandoned their wandering life, established themselves around +the wells, and planted more than 30,000 palm trees, besides other +perennial vegetables. [Footnote: "In the anticipation of our success at +Oum-Thiour, everything had been prepared to take advantage of this new +source of wealth without a moment's delay. A division of the tribe of +the Selmia, and their sheikh, Aissa ben Sha, laid the foundation of a +village as soon as the water flowed, and planted twelve hundred +date-palms, renouncing their wandering life to attach themselves to the +soil. In this arid spot, life had taken the place of solitude, and +presented itself, with its smiling images, to the astonished traveller. +Young girls were drawing water at the fountain; the flocks, the great +dromedaries with their slow pace, the horses led by the halter, were +moving to the watering trough; the hounds and the falcons enlivened the +group of party-colored tents, and living voices and animated movement +had succeeded to silence and desolation."--Laurent, Memoires sur le +Sahara, p. 85. + +Between 1856 and 1864 the French engineers had bored 83 wells in the +Hodna and the Sahara of the Province of Constantine, yielding, all +together, 9,000 gallons a minute, and irrigating more than 125,000 +date-palms. Reclus, La Terre, i., p. 110.] The water is found at a small +depth, generally from 100 to 200 feet, and though containing too large a +proportion of mineral matter to be acceptable to a European palate, it +answers well for irrigation, and does not prove unwholesome to the +natives. + +The most obvious use of artesian wells in the desert at present is that +of creating stations for the establishment of military posts and +halting-places for the desert traveller; but if the supply of water +shall prove adequate for the indefinite extension of the system, it is +probably destined to produce a greater geographical transformation than +has ever been effected by any scheme of human improvement. + +The most striking contrast of landscape scenery that nature brings near +together in time or place, is that between the greenery of the tropics, +or of a northern summer, and the snowy pall of leafless winter. Next to +this in startling novelty of effect, we must rank the sudden transition +from the shady and verdant oasis of the desert to the bare and burning +party-colored ocean of sand and rock which surrounds it. [Footnote: The +variety of hues and tones in the local color of the desert is, I think, +one of the phenomena which most surprise and interest a stranger to +those regions. In England and the United States, rock is so generally +covered with moss or earth, and earth with vegetation, that untravelled +Englishmen and Americans are not very familiar with naked rock as a +conspicuous element of landscape. Hence, in their conception of a bare +cliff or precipice, they hardly ascribe definite color to it, but depict +it to their imagination as wearing a neutral tint not assimilable to any +of the hues with which nature tinges her atmospheric or paints her +organic creations. There are certainly extensive desert ranges, chiefly +limestone formations, where the surface is either white, or has +weathered down to a dull uniformity of tone which can hardly be called +color at all; and there are sand plains and drifting hills of wearisome +monotony of tint. But the chemistry of the air, though it may tame the +glitter of the limestone to a dusky gray, brings out the green and brown +and purple of the igneous rocks, and the white and red and blue and +violet and yellow of the sandstone. Many a cliff in Arabia Petraea is as +manifold in color as the rainbow, and the veins are so variable in +thickness and inclination, so contorted and involved in arrangement, as +to bewilder the eye of the spectator like a disk of party-colored glass +in rapid evolution. + +In the narrower wadies the mirage is not common; but on broad expanses, +as at many points between Cairo and Suez, and in Wadi el Araba, it mocks +you with lakes and land-locked bays, studded with inlands and fringed +with trees, all painted with an illusory truth of representation +absolutely indistinguishable from the reality. The checkered earth, too, +is canopied with a heaven as variegated as itself. You see, high up in +the sky, rosy clouds at noonday, colored probably by reflection from the +ruddy mountains, while near the horizon float cumuli of a transparent, +ethereal blue, seemingly balled up out of the clear cerulean substance +of the firmament, and detached from the heavenly vault, not by color or +consistence, but solely by the light and shade of their salient and +retreating outlines.] The most sanguine believer in indefinite human +progress hardly expects that man's cunning will accomplish the universal +fulfilment of the prophecy, "the desert shall blossom as the rose," in +its literal sense; but sober geographers have thought the future +conversion of the sand plains of Northern Africa into fruitful gardens, +by means of artesian wells, not an improbable expectation. They have +gone farther, and argued that, if the soil were covered with fields and +forests, vegetation would call down moisture from the Libyan sky, and +that the showers which are now wasted on the sea, or so often deluge +Southern Europe with destructive inundation, would in part be condensed +over the arid wastes of Africa, and thus, without further aid from man, +bestow abundance on regions which nature seems to have condemned to +perpetual desolation. + +An equally bold speculation, founded on the well-known fact that the +temperature of the earth and of its internal waters increases as we +descend beneath the surface, has suggested that artesian wells might +supply heat for industrial and domestic purposes, for hot-house +cultivation, and even for the local amelioration of climate. The success +with which Count Lardarel has employed natural hot springs for the +evaporation of water charged with boracic acid, and other fortunate +applications of the heat of thermal sources, lend some countenance to +the latter project; but both must, for the present, be ranked among the +vague possibilities of science, not regarded as probable future triumphs +of man over nature. + + +Artificial Springs + +A more plausible and inviting scheme is that of the creation of +perennial springs by husbanding rain and snow water, storing it up in +artificial reservoirs of earth, and filtering it through purifying +strata, in analogy with the operations of nature. The sagacious +Palissy--starting from the theory that all springs are primarily derived +from precipitation, and reasoning justly on the accumulation and +movement of water in the earth--proposed to reduce theory to practice, +and to imitate the natural processes by which rain is absorbed by the +earth and given out again in running fountains. "When I had long and +diligently considered the cause of the springing of natural fountains +and the places where they be wont to issue," says he, "I did plainly +perceive, at last, that they do proceed and are engendered of nought but +the rains. And it is this, look you, which hath moved me to enterprise +the gathering together of rain-water after the manner of nature, and the +most closely according to her fashion that I am able; and I am well +assured that by following the formulary of the Supreme Contriver of +fountains, I can make springs, the water whereof shall be as good and +pure and clear as of such which be natural." [Footnote: Oeuvres de +Palissy, Des Eaux et Fontaines, p. 157.] Palissy discusses the subject +of the origin of springs at length and with much ability, dwelling +specially on infiltration, and, among other things, thus explains the +frequency of springs in mountainous regions: "Having well considered the +which, thou mayest plainly see the reason why there be more springs and +rivulets proceeding from the mountains than from the rest of the earth; +which is for no other cause but that the rocks and mountains do retain +the water of the rains like vessels of brass. And the said waters +falling upon the said mountains descend continually through the earth, +and through crevices, and stop not till they find some place that is +bottomed with stone or close and thick rocks; and they rest upon such +bottom until they find some channel or other manner of issue, and then +they flow out in springs or brooks or rivers, according to the greatness +of the reservoirs and of the outlets thereof." [Footnote: Id., p. 166. +Palissy's method has recently been tried with good success in various +parts of France.] + +After a full exposition of his theory, Palissy proceeds to describe his +method of creating springs, which is substantially the same as that +lately proposed by Babinet in the following terms: "Choose a piece of +ground containing four or five acres, with a sandy soil, and with a +gentle slope to determine the flow of the water. Along its upper line, +dig a trench five or six feet deep and six feet wide. Level the bottom +of the trench, and make it impermeable by paving, by macadamizing, by +bitumen, or, more simply and cheaply, by a layer of clay. By the side of +this trench dig another, and throw the earth from it into the first, and +so on until you have rendered the subsoil of the whole parcel +impermeable to rain-water. Build a wall along the lower line with an +aperture in the middle for the water, and plant fruit or other low trees +upon the whole, to shade the ground and check the currents of air which +promote evaporation. This will infallibly give you a good spring which +will flow without intermission, and supply the wants of a whole hamlet +or a large chateau." [Footnote: Babinet, Etudes et Lectures sur les +Sciences d'Observation, ii., p. 225. Our author precedes his account of +his method with a complaint which most men who indulge in thinking have +occasion to repeat many times in the course of their lives. "I will +explain to my readers the construction of artificial fountains according +to the plan of the famous Bernard de Palissy, who, a hundred and fifty +[three hundred] years ago, came and took away from me, a humble +academician of the nineteenth century, this discovery which I had taken +a great deal of pains to make. It is enough to discourage all invention +when one finds plagiarists in the past as well as in the future!" (P. +224.)] Babinet states that the whole amount of precipitation on a +reservoir of the proposed area, in the climate of Paris, would be about +13,000 cubic yards, not above one half of which, he thinks, would be +lost, and, of course, the other half would remain available to supply +the spring. I much doubt whether this expectation would be realized in +practice, in its whole extent; for if Babinet is right in supposing that +the summer rain is wholly evaporated, the winter rains, being much less +in quantity, would hardly suffice to keep the earth saturated and give +off so large a surplus. The method of Palissy, though, as I have said, +similar in principle to that of Babinet, would be cheaper of execution, +and, at the same time, more efficient. He proposes the construction of +relatively small filtering receptacles, into which he would conduct the +rain falling upon a large area of rocky hillside, or other sloping +ground not readily absorbing water. This process would, in all +probability, be a very successful, as well as an inexpensive, mode of +economizing atmospheric precipitation, and compelling the rain and snow +to form perennial fountains at will. + + +Economizing Precipitation. + +The methods suggested by Palissy and by Babinet are of limited +application, and designed only to supply a sufficient quantity of water +for the domestic use of small villages or large private establishments. +Dumas has proposed a much more extensive system for collecting and +retaining the whole precipitation in considerable valleys, and storing +it in reservoirs, whence it is to be drawn for household and mechanical +purposes, for irrigation, and, in short, for all the uses to which the +water of natural springs and brooks is applicable. His plan consists in +draining both surface and subsoil, by means of conduits differing in +construction according to local circumstances, but in the main not +unlike those employed in improved agriculture, collecting the water in a +central channel, securing its proper filterage, checking its too rapid +flow by barriers at convenient points, and finally receiving the whole +in spacious, covered reservoirs, from which it may he discharged in a +constant flow or at intervals as convenience may dictate. [Footnote: M. +G. Dumas, La Science des Fontaines, 1857.] + +There is no reasonable doubt that a very wide employment of these +various contrivances for economizing and supplying water is practicable, +and the expediency of resorting to them is almost purely an economical +question. There appears to be no serious reason to apprehend collateral +evils from them, and in fact all of them, except artesian wells, are +simply indirect methods of returning to the original arrangements of +nature, or, in other words, of restoring the fluid circulation of the +globe; for when the earth was covered with the forest, perennial springs +gushed from the foot of every hill, brooks flowed down the bed of every +valley. The partial recovery of the fountains and rivulets which once +abundantly watered the face of the agricultural world seems practicable +by such means, even without any general replanting of the forests; and +the cost of one year's warfare--or in some countries of that armed peace +which has been called "Platonic war"--if judiciously expended in a +combination of both methods of improvement, would secure, to almost +every country that man has exhausted, an amelioration of climate, a +renovated fertility of soil, and a general physical improvement, which +might almost be characterized as a new creation. + + +Inundations and Torrents. + +In pointing out in a former chapter the evils which have resulted from +the too extensive destruction of the forests, I dwelt at some length on +the increased violence of river inundations, and especially on the +devastations of torrents, in countries improvidently deprived of their +woods, and I spoke of the replanting of the forests as probably the most +effectual method of preventing the frequent recurrence of disastrous +floods. There are many regions where, from the loss of the superficial +soil, from financial considerations, and from other special causes, the +general restoration of the woods is not, under present circumstances, +either possible or desirable. In all inhabited countries, the +necessities of agriculture and other considerations of human convenience +will always require the occupation of much the largest proportion of the +surface for purposes inconsistent with the growth of extensive forests. +Even where large plantations are possible and in actual process of +execution, many years must elapse before the action of the destructive +causes in question can be arrested or perhaps even sensibly mitigated by +their influence; and besides, floods will always occur in years of +excessive precipitation, whether the surface of the soil be generally +cleared or generally wooded. [Footnote: All the arrangements of rural +husbandry, and we might say of civilised occupancy of the earth, are +such as necessarily to increase the danger and the range of floods by +promoting the rapid discharge of the waters of precipitation. +Superficial, if not subterranean, drainage is a necessary condition of +all agriculture. There is no field which has not some artificial +disposition for this purpose, and even the furrows of ploughed land, if +the surface is inclined, and especially when it if frozen, serve rather +to carry off than to retain water. As Bacquerel has observed, common +road and railway ditches are among the most efficient conduits for the +discharge of surface-water which man has yet constructed, and of course +they are powerful agents in causing river inundations. All these +channels are, indeed, necessary for the convenience of man, but this +convenience, like every other interference with the order of nature, +must often be purchased at a heavy cost.] Physical improvement in this +respect, then, cannot be confined to merely preventive measures, but, in +countries subject to damage by inundation, means must be contrived to +obviate dangers and diminish injuries to which human life and all the +works of human industry will occasionally be exposed, in spite of every +effort to lessen the frequency of their recurrence by acting directly on +the causes that produce them. As every civilized country is, in some +degree, subject to inundation by the overflow of rivers, the evil is a +familiar one, and needs no general description. In discussing this +branch of the subject, therefore, I may confine myself chiefly to the +means that have been or may be employed to resist the force and limit +the ravages of floods, which, left wholly unrestrained, would not only +inflict immense injury upon the material interests of man, but produce +geographical revolutions of no little magnitude. + + +Inundations of 1856 in France. + +The month of May, 1856, was remarkable for violent and almost +uninterrupted rains, and most of the river-basins of France were +inundated to an extraordinary height. In the val-leys of the Loire and +its aflluents, about a million of acres, including many towns and +villages, were laid under water, and the amount of pecuniary damage was +almost incalculable. [Footnote: Champion, Les Inondations en France, +iii., p.156, note.] The flood was not less destructive in the valley of +the Rhone, and in fact an invasion by a hostile army could hardly have +been more disastrous to the inhabitants of the plains than was this +terrible deluge. There had been a flood of this latter river in the year +1840, which, for height and quantity of water, was almost as remarkable +as that of 1856, but it took place in the month of November, when the +crops had all been harvested, and the injury inflicted by it upon +agriculturists was, therefore, of a character to be less severely and +less immediately felt than the consequences of the inundation of 1856. +[Footnote: Notwithstanding this favorable circumstance, the damage done +by the inundation of 1840 in the valley of the Rhone was estimated at +seventy-two millions of francs.--Champion, Les Inondations en France, +iv., p. 124. + +Several smaller floods of the Rhone, experienced at a somewhat earlier +season of the year in 1846, occasioned a loss of forty-five millions of +francs. "What if," says Dumont, "instead of happening in October, that +is, between harvest and seedtime, they had occurred before the crops +were secured The damage would have been counted by hundreds of +millions."--Des Travaux Publics, p. 99, note.] + +In the fifteen years between these two great floods, the population and +the rural improvements of the river valleys had much increased, common +roads, bridges, and railways had been multiplied and extended, telegraph +lines had been constructed, all of which shared in the general ruin, and +hence greater and more diversified interests were affected by the +catastrophe of 1856 than by any former like calamity. The great flood of +1840 had excited the attention and roused the sympathies of the French +people, and the subject was invested with new interest by the still more +formidable character of the inundations of 1856. It was felt that these +scourges had ceased to be a matter of merely local concern, for, +although they bore most heavily on those whose homes and fields were +situated within the immediate reach of the swelling waters, yet they +frequently destroyed harvests valuable enough to be a matter of national +interest, endangered the personal security of the population of +important political centres, interrupted communication for days and even +weeks together on great lines of traffic and travel--thus severing, as +it were, all South-western France from the rest of the empire--and +finally threatened to produce great and permanent geographical changes. +The well-being of the whole commonwealth was seen to be involved in +preventing the recurrence and in limiting the range of such +devastations. The Government encouraged scientific investigation of the +phenomena and their laws. Their causes, their history, their immediate +and remote consequences, and the possible safeguards to be employed +against them, have been carefully studied by the most eminent +physicists, as well as by the ablest theoretical and practical engineers +of France. Many hitherto unobserved facts have been collected, many new +hypotheses suggested, and many plans, more or less original in +character, have been devised for combating the evil; but thus far, the +most competent judges are not well agreed as to the mode, or even the +possibility, of applying an effectual remedy. I have noticed in the next +preceding chapter the recent legislation of France upon the preservation +and restoration of the forests, with reference to their utility in +subduing torrents and lessening the frequency and diminishing the +violence of river inundations. The provisions of those laws are +preventive rather than remedial, but most beneficial effects have +already been experienced from the measures adopted in pursuance of them, +though sufficient time has not yet elapsed for the complete execution of +the greater operations of the system. + + +Basins of Reception. + +Destructive inundations of large rivers are seldom, if ever, produced by +precipitation within the limits of the principal valley, but almost +uniformly by sudden thaws or excessive rains on the mountain ranges +where the tributaries take their rise. It is therefore plain that any +measures which shall check the flow of surface-waters into the channels +of the affluents, or which shall retard the delivery of such waters into +the principal stream by its tributaries, will diminish in the same +proportion the dangers and the evils of inundation by great rivers. The +retention of the surface-waters upon or in the soil can hardly be +accomplished except by the methods already mentioned, replanting of +forests, and furrowing or terracing. The current of mountain streams can +be checked by various methods, among which the most familiar and obvious +is the erection of barriers or dams across their channels, at points +convenient for forming reservoirs large enough to retain the superfluous +waters of great rains and thaws. [Footnote: On the construction of +temporary and more permanent barriera to the curreuts of torrents and +rivulets, see Marchand, Les Torrents des Alpes, in Recue des Eaux et +Forets for October and November, 1871.] + +Besides the utility of such basins in preventing floods, the +construction of them is recommended by very strong considerations, such +as the furnishing of a constant supply of water for agricultural and +mechanical purposes, and, also, their value as ponds for breeding and +rearing fish, and, perhaps, for cultivating aquatic vegetables. +[Footnote: In reference to the utilization of artificial as well as +natural reservoirs, see Ackerhof, Die Nutruny der Teiche und Gewasser, +Quadlinburg, 1869.] + +The objections to the general adoption of the system of reservoirs are +these: the expense of their construction and maintenance; the reduction +of cultivable area by the amount of surface they must cover; the +interruption they would occasion to free communication; the probability +that they would soon be filled up with sediment, and the obvious fact +that when full of earth, or even water, they would no longer serve their +principal purpose; the great danger to which they would expose the +country below them in case of the bursting of their barriers; [Footnote: +For accounts of damage from the bursting of reservoirs, see Vallee, +Memoire sur les Reservoir d'Alimentation des Canaux, Annales des Ponts +et Chaussees, 1833, 1er semestre, p.261. + +The dam of the reservoir of Puentes in Spain, which was one hundred and +sixty feet high, after having discharged its functions for eleven years, +burst, in 1802, in consequence of a defect in its foundations, and the +eruption of the water destroyed or seriously injured eight hundred +houses, and produced damage to the amount of more than a million +dollars.--Aynard, Irrigations du Midi d l'Europe, pp. 257-259.] the evil +consequences they would occasion by prolonging the flow of inundations +in proportion as they diminished their height; the injurious effects it +is supposed they would produce upon the salubrity of the neighbouring +districts; and, lastly, the alleged impossibility of constructing +artificial basins sufficient in capacity to prevent, or in any +considerable measure to mitigate, the evils they are intended to guard +against. + +The last argument is more easily reduced to a numerical question than +the others. The mean and extreme annual precipitation of all the basins +where the construction of such works would be seriously proposed is +already approximately known by meteorological tables, and the quantity +of water, delivered by the greatest floods which have occurred within +the memory of man, may be roughly estimated from their visible traces. +From these elements, or from meteorological records, the capacity of the +necessary reservoirs can be calculated. Let us take the case of the +Ardeche. In the inundation of 1857, that river poured into the Rhone +1,305,000,000 cubic yards of water in three days. If we suppose that +half this quantity might have been suffered to flow down its channel +without inconvenience, we shall have about 650,000,000 cubic yards to +provide for by reservoirs. The Ardeche and its principal affluent, the +Chassezae, have, together, about twelve considerable tributaries rising +near the crest of the mountains which bound the basin. If reservoirs of +equal capacity were constructed upon all of them, each reservoir must be +able to contain 54,000,000 cubic yards, or, in other words, must be +equal to a lake 3,000 yards long, 1,000 yards wide, and 18 yards deep, +and besides, in order to render any effectual service, the reservoirs +must all have been empty at the commencement of the rains which produced +the inundation. + +Thus far I have supposed the swelling of the waters to be uniform +throughout the whole basin; but such was by no means the fact in the +inundation of 1857, for the rise of the Chassezae, which is as large as +the Ardeche proper, did not exceed the limits of ordinary floods, and +the dangerous excess came solely from the headwaters of the latter +stream. Hence reservoirs of double the capacity I have supposed would +have been necessary upon the tributaries of that river, to prevent the +injurious effects of the inundation. It is evident that the construction +of reservoirs of such magnitude for such a purpose is financially, if +not physically, impracticable, and when we take into account a point I +have just suggested, namely, that the reservoirs must be empty at all +times of apprehended flood, and, of course, their utility limited almost +solely to the single object of preventing inundations, the total +inapplicability of such a measure in this particular case becomes still +more glaringly manifest. + +Another not less conclusive fact is, that the valleys of all the upland +tributaries of the Ardeche descend so rapidly, and have so little +lateral expansion, as to render the construction of capacious reservoirs +in them quite impracticable. Indeed, engineers have found but two points +in the whole basin suitable for that purpose, and the reservoirs +admissible at these would have only a joint capacity of about 70,000,000 +cubic yards, or less than one-ninth part of what I suppose to be +required. The case of the Ardeche is no doubt an extreme one, both in +the topographical character of its basin and in its exposure to +excessive rains; but all destructive inundations are, in a certain +sense, extreme cases also, and this of the Ardeche serves to show that +the construction of reservoirs is not by any means to be regarded as a +universal panacea against floods. + +Nor, on the other hand, is this measure to be summarily rejected. Nature +has adopted it on a great scale, on both flanks of the Alps, and on a +smaller, on those of the Adirondacks and of many lower chains. The +quantity of water which, in great rains or sudden thaws, rushes down the +steep declivities of the Alps, is so vast that the channels of the Swiss +and Italian rivers would be totally incompetent to carry it off as +rapidly as it would pour into them, were it not absorbed by the +capacious basins which nature has scooped out for its reception, freed +from the transported material which adds immensely both to the volume +and to the force of its current, and then, after some reduction by +evaporation and infiltration, gradually discharged into the beds of the +rivers. In the inundation of 1829 the water discharged into Lake Como +from the 15th to the 20th of September amounted to 2,600 cubic yards the +second, while the outflow from the lake during the same period was only +at the rate of about 1,050 cubic yards to the second. In those five +days, then, the lake accumulated 670,000,000 cubic yards of superfluous +water, and of course diminished by so much the quantity to be disposed +of by the Po. [Footnote: Baird Smith, Italian Irrigation, i., p. 176.] +In the flood of October, 1868, the surface of Lago Maggiore was raised +twenty-five feet above low-water mark in the course of a few hours. +[Footnote: Bollettino della Societa Geog. Italiana, iii., p. 466.] There +can be no doubt that without such detention of water by the Lakes Como, +Maggiore, Garda, and other subalpine basins, almost the whole of +Lombardy would have been irrecoverably desolated, or rather, its great +plain would never have become anything but a vast expanse of river-beds +and marshes; for the annual floods would always have prevented the +possibility of its improvement by man. [Footnote: See, as to the +probable effects of certain proposed hydraulic works at the outlet of +Lake Maggiore on the action of the lake as a regulating reservoir, +Tagliasecchi, Notizie sui Canali dell' Alta Lombardia, Milano, 1869.] + +Lake Bourget in Savoy, once much more extensive than it is at present, +served, and indeed still serves, a similar purpose in the economy of +nature. In a flood of the Rhone, in 1863, this lake received from the +overflow of that river, which does not pass through it, 72,000,000 cubic +yards of water, and of course moderated, to that extent, the effects of +the inundation below. [Footnote: Elisee Recluse, La Terre, i., p. 460.] + +In fact, the alluvial plains which border the course of most +considerable streams, and are overflowed in their inundations, either by +the rise of the water to a higher level than that of their banks, or by +the bursting of their dikes, serve as safety-valves for the escape of +their superfluous waters. The current of the Po, spreading over the +whole space between its widely separated embankments, takes up so much +water in its inundations, that, while a little below the outlet of the +Ticino the discharge of the channel is sometimes not less than 19,500 +cubic yards to the second, it has never exceeded 6,730 yards at Ponte +Lagoscuro, near Ferrara. The currents of the Mississippi, the Rhone, and +of many other large rivers, are modified in the same way. In the flood +of 1858, the delivery of the Mississippi, a little below the month of +the Ohio, was 52,000 cubic yards to the second, but at Baton Rouge, +though of course increased by the waters of the Arkansas, the Yazoo, and +other smaller tributaries, the discharge was reduced to 46,760 cubic +yards. We rarely err when we cautiously imitate the processes of nature, +and there are doubtless many cases where artificial basins of reception +and lateral expansions of river-beds might be employed with advantage. +Many upland streams present points where none of the objections usually +urged against artificial reservoirs, except those of expense and of +danger from the breaking of dams, could have any application. Reservoirs +may be so constructed as to retain the entire precipitation of the +heaviest thaws and rains, leaving only the ordinary quantity to flow +along the channel; they may be raised to such a height as only partially +to obstruct the surface drainage; or they may be provided with sluices +by means of which their whole contents can be discharged in the dry +season and a summer crop be grown upon the ground they cover at high +water. The expediency of employing them and the mode of construction +depend on local conditions, and no rules of universal applicability can +be laid down on the subject. [Footnote: The insufficiency of artificial +basins of reception as a means of averting the evils resulting from the +floods of great rivers has been conclusively shown, in reference to a +most important particular case--that of the Mississippi--by Humphreys +and Abbot, in their admirable monograph of that river.] + +It is remarkable that nations which we, in the inflated pride of our +modern civilization, so generally regard as little less than barbarian, +should have long preceded Christian Europe in the systematic employment +of great artificial basins for the various purposes they are calculated +to subserve. The ancient Peruvians built strong walls, of excellent +workmanship, across the channels of the mountain sources of important +streams, and the Arabs executed immense works of similar description, +both in the great Arabian peninsula and in all the provinces of Spain +which had the good fortune to fall under their sway. The Spaniards of +the fifteenth and sixteenth centuries, who, in many points of true +civilization and culture, were far inferior to the races they subdued, +wantonly destroyed these noble monuments of social and political wisdom, +or suffered them to perish, because they were too ignorant to appreciate +their value, or too unskilful as practical engineers to be able to +maintain them, and some of their most important territories were soon +reduced to sterility and poverty in consequence. + + +Diversion of Rivers. + +Another method of preventing or diminishing the evils of inundation by +torrents and mountain rivers, analogous to that employed for the +drainage of lakes, consists in the permanent or occasional diversion of +their surplus waters, or of their entire currents, from their natural +courses, by tunnels or open channels cut through their banks. Nature, in +many cases, resorts to a similar process. Most great rivers divide +themselves into several arms in their lower course, and enter the sea by +different mouths. There are also cases where rivers send off lateral +branches to convey a part of their waters into the channel of other +streams. [Footnote: Some geographical writers apply the term bifurcation +exclusively to this intercommunication of rivers; others, with more +etymological propriety, use it to express the division of great rivers +into branches at the head of their deltas. A technical word is wanting +to designate the phenomenon mentioned in the text, and there is no valid +objection to the employment of the anatomical term anastomosis for this +purpose.] The most remarkable of these is the junction between the +Amazon and the Orinoco by the natural canal of the Cassiquiare and the +Rio Negro. In India, the Cambodja and the Menam are connected by the +Anam; the Saluen and the Irawaddi by the Panlaun. There are similar +examples, though on a much smaller scale, in Europe. The Tornea, and the +Calix rivers in Lapland communicate by the Tarando, and in Westphalia, +the Else, an arm of the Haase, falls into the Weser. [Footnote: The +division of the currents of rivers, as a means of preventing the +overflow of their banks, is by no means a remedy capable of general +application, even when local conditions are favorable to the +construction of an emissary. The velocity of a stream, and consequently +its delivery in a given time, are frequently diminished in proportion to +the diminution of the volume by diversion; and on the other hand, the +increase of volume by the admission of a new tributary increases +proportionally the velocity and the quantity of water delivered. +Emissaries may, nevertheless, often be useful in carrying off water +which has already escaped from the channel and which would otherwise +become stagnant and prevent further lateral discharge from the main +current, and it is upon this principle that Humphreys and Abbot think a +canal of diversion at Lake Providence might be advisable. Emissaries +serve an important purpose in the lower course of rivers where the bed +is nearly a dead level and the water moves from previously acquired +momentum and the pressure of the current above, rather than by the force +of gravitation, and it is, in general, only under such circumstances, as +for example in the deltas at the mouths of great rivers, that nature +employs them.] + +The change of bed in rivers by gradual erosion of their banks is +familiar to all, but instances of the sudden abandonment of a primitive +channel are by no means wanting. At a period of unknown antiquity, the +Ardeche pierced a tunnel 200 feet wide and 100 high, through a rock, and +sent its whole current through it, deserting its former bed, which +gradually filled up, though its course remained traceable. In the great +inundation of 1827, the tunnel proved insufficient for the discharge of +the water, and the river burst through the obstructions which had now +choked up its ancient channel, and resumed its original course. +[Footnote: Mardigny, Memoire sur les Inondations de l'Ardeche, p. 13.] + +It was probably such facts as these that suggested to ancient engineers +the possibility of like artificial operations, and there are numerous +instances of the execution of works for this purpose in very remote +ages. The Bahr Jusef, the great stream which supplies the Fayoum with +water from the Nile, has been supposed, by some writers, to be a natural +channel; but both it and the Bahr el Wady are almost certainly +artificial canals constructed to water that basin, to regulate the level +of Lake Meeris, and possibly, also, to diminish the dangers resulting +from excessive inundations of the Nile, by serving as waste-weirs to +discharge a part of its overflowing waters. [Footnote: The +starting-points of these anals were far up the Nile, and of course at a +comparatively high level, and it is probable that they received water +only during the inundation. Linant Bey calculates the capacity of Lake +Moeris at 3,686,667 cubic yards and the water received by it at high +Nile at 465 cubic yards the second.] Several of the seven ancient mouths +of the Nile are believed to be artificial channels, and Herodotus even +asserts that King Menes diverted the entire course of that river from +the Libyan to the Arabian side of the valley. There are traces of an +ancient river-bed along the western mountains, which give eome +countenance to this statement. But it is much more probable that the +works of Menes were designed rather to prevent a natural, than to +produce an artificial, change in the channel of the river. + +Two of the most celebrated cascades in Europe, those of the Teverone at +Tivoli and of the Velino at Terni, owe, if not their existence, at least +their position and character, to the diversion of their waters from +their natural beds into new channels, in order to obviate the evils +produced by their frequent floods. Remarkable works of the same sort +have been executed in Switzerland, in very recent times. Until the year +1714, the Kander, which drains several large Alpine valleys, ran, for a +considerable distance, parallel with the Lake of Thun, and a few miles +below the city of that name emptied into the river Aar. It frequently +flooded the flats along the lower part of its course, and it was +determined to divert it into the Lake of Thun. For this purpose, two +parallel tunnels were cut through the intervening rock, and the river +turned into them. The violence of the current burst up the roof of the +tunnels, and, in a very short time, wore the new channel down not less +than one hundred feet, and even deepened the former bed at least fifty +feet, for a distance of two or three miles above the tunnel. The lake +was two hundred feet deep at the point where the river was conducted +into it, but the gravel and sand carried down by the Kander has formed +at its mouth a delta containing more than a hundred acres, which is +still advancing at the rate of several yards a year. The Linth, which +formerly sent its waters directly to the Lake of Zurich, and often +produced very destructive inundations, was turned into the Wallensee +about fifty years ago, and in both these cases a great quantity of +valuable land was rescued both from flood and from insalubrity. + + +Glacier Lakes. + +In Switzerland, the most terrible inundations often result from the +damming up of deep valleys by ice-slips or by the gradual advance of +glaciers, and the accumulation of great masses of water above the +obstructions. The ice is finally dissolved by the heat of summer or the +flow of warm waters, and when it bursts, the lake formed above is +discharged almost in an instant, and all below is swept down to certain +destruction. In 1595, about a hundred and fifty lives and a great amount +of property were lost by the eruption of a lake formed by the descent of +a glacier into the valley of the Drance, and a similar calamity laid +waste a considerable extent of soil in the year 1818. On this latter +occasion, the barrier of ice and snow was 3,000 feet long, 600 thick, +and 400 high, and the lake which had formed above it contained not less +than 800,000,000 cubic feet. A tunnel was driven through the ice, and +about 300,000,000 cubic feet of water safely drawn off by it, but the +thawing of the walls of the tunnel rapidly enlarged it, and before the +lake was half drained, the barrier gave way and the remaining +500,000,000 cubic feet of water were discharged in half an hour. The +recurrence of these floods has since been prevented by directing streams +of water, warmed by the sun, upon the ice in the bed of the valley, and +thus thawing it before it accumulates in sufficient mass to form a new +barrier and threaten serious danger. [Footnote: In 1845 a similar lake +was formed by the extension of the Vernagt glacier. When the ice barrier +gave way, 3,000,000 cubic yards of water were discharged in an +hour.--Sonklar, Die Oetzthaler Gebirgsgruppe, section 167.] In the cases +of diversion of streams above mentioned, important geographical changes +have been directly produced by those operations. By the rarer process of +draining glacier lakes, natural eruptions of water, which would have +occasioned not less important changes in the face of the earth, have +been prevented by human agency. River Embankments. The most obvious and +doubtless earliest method of preventing the escape of river-waters from +their natural channels, and the overflow of fields and towns by their +spread, is that of raised embankments along their course. [Footnote: +Riparian embankments are a real, if not a conscious, imitation of a +natural process. The waters of rivers which flow down planes of gentle +inclination deposit, in their inundations, the largest proportion of +their sediment as soon as, by overflowing their banks, they escape from +the swift current of the channel. The immediate borders of such rivers +consequently become higher than the grounds lying further from the +stream, and constitute, of themselves, a sort of natural dike of small +elevation. In the "intervales" or "bottoms" of the great North American +rivers the alluvial banks are elevated and dry, the flats more remote +from the river lower and swampy. This is generally observable in Egypt +(see Figari Bey, Studi Scientifici sull' Egitto, i, p. 87), though less +so than in the valley of the Mississippi, where the alluvial banks form +natural glacis, descending as you recede from the river, and in some +places, as below Cape Girardeau, at the rate of seven feet in the first +mile. Humphreys and Abbott, Report, pp. 96, 97. + +In fact, rivers, like mountain torrents, often run for a long distance +on the summit of a ridge built up by their own deposits. The delta of +the Mississippi is a regular cone, or rather mountain, of dejection, +extending far out into the Gulf of Mexico, along the crest of which the +river flows, sending off here and there, as it approaches the sea, a +system of lateral streams resembling the fan-shaped discharge of a +torrent.] The necessity of such embankments usually arises from the +gradual elevation of the bed of running streams in consequence of the +deposit of the earth and gravel they are charged with in high water; +and, as we have seen, this elevation is rapidly accelerated when the +highlands around the headwaters of rivers are cleared of their forests. +When a river is embanked at a given point, and, consequently, the water +of its floods, which would otherwise spread over a wide surface, is +confined within narrow limits, the velocity of the current and its +transporting power are augmented, and its burden of sand and gravel is +deposited at some lower point, where the rapidity of its flow is checked +by a dam or other artificial obstruction, by a diminution in the +inclination of the bed, by a wider channel, or finally by a lacustrine +or marine basin which receives its waters. Wherever it lets fall solid +material, its channel is raised in consequence, and the declivity of the +whole bed between the head of the embankment and the slack of the stream +is reduced. Hence the current, at first accelerated by confinement, is +afterwards checked by the mechanical resistance of the matter deposited, +and by the diminished inclination of its channel, and then begins again +to let fall the earth it holds in suspension, and to raise its bed at +the point where its overflow had been before prevented by embankment. +[Footnote: In proportion as the dikes are improved, and breaches and the +escape of the water through them are less frequent, the height of the +annual inundations is increased. Some towns on the banks of the Po, and +of course within the system of parallel embankments, were formerly +secure from flood by the height of the artificial mounds on which they +were built; but they have recently been obliged to construct ring-dikes +for their protection. + +Lombardini lays down the following general statement of the effects of +river embankments: + +"The immediate effect of embanking a river is generally an increase in +the height of its floods, but, at the same time, a depression of its +bed, by reason of the increased force, and consequently excavating +action, of the current. + +"It is true that coarser material may hence be carried further, and at +the same time deposit itself on a reduced slope. + +"The embankment of the upper branches of a river increases the volume, +and therefore the height of the floods in the lower course, in +consequence of the more rapid discharge of its affluents into it. + +"When, in consequence of the flow of a river channel through an alluvial +soil not yet REGULATED, or, in other words, which has not acquired its +normal inclination, the course of the river has not become established, +it is natural that its bed should rise more rapidly after its +embankment. ... + +"The embankment of the lower course of a river, near its discharge into +the sea, causes the elevation of the bed of the next reach above, both +because the swelling of the current, in consequence of its lateral +confinement, occasions eddies, and of course deposits, and because the +prolongation of the course of the stream, or the advance of its delta +into the sea, is accelerated."--Dei congiamenti cia soggiacque +l'idraulica condizione del Po, etc., pp. 41, 42. + +Del Noce states that in the levellings for the proposed Leopolda +railway, he found that the bed of the Sieue had been permanently +elevated two yards between 1708 and 1844, and that of the Fosso di San +Gaudenzio more than a yard and a half between 1752 and 1845. Those, +indeed, are not rivers of the rank of the Po; but neither are they what +are technically called torrents or mountain streams, whose flow is only +an occasional effect of heavy rains or melting snow.--Trattato delle +Macchie e Foreste di Tuscana, Firenze, 1857, p. 29.] The bank must now +be raised in proportion, and these processes would be repeated and +repeated indefinitely, had not nature provided a remedy in floods, which +sweep out recent deposits, burst the bonds of the river and overwhelm +the adjacent country with final desolation, or divert the current into a +new channel, destined to become, in its turn, the scene of a similar +struggle between man and the waters. [Footnote: The Noang-ho has +repeatedly burst its dikes and changed the channel of its lower course, +sometimes delivering its waters into the sea to the north, sometimes to +the south of the peninsula of Chan-tung, thus varying its point of +discharge by a distance of 220 miles.--Elisee Reclus, La Terre, t. i, p. +477. + +Sec interesting notices of the lower course of the Noang-ho in Nature, +Nov. 25, 1869. + +The frequent changes of channel and mouth in the deltas of great rivers +are by no means always an effect of diking. The mere accumulation of +deposits in the beds of rivers which transport much sediment compels +them continually to seek new outlets, and it is only by great effort +that art can keep their points of discharge pproximately constant. The +common delta of the Ganges and the Brahmapootra is in a state of +incessant change, and the latter river is said to have shifted its main +channel 200 miles to the west since 1785, the revolution having been +principally accomplished between 1810 and 1830.] + +But here, as in so many other fields where nature is brought into +conflict with man, she first resists his attempts at interference with +her operations, then, finding him the stronger, quietly submits to his +rule, and ends by contributing her aid to strengthen the walls and +shackles by which he essays to confine her. If, by assiduous repair of +his dikes, he, for a considerable time, restrains the floods of a river +within new bounds, nature, by a series of ingenious compensations, +brings the fluctuating bed of the stream to a substantially constant +level, and when his ramparts have been, by his toil, raised to a certain +height and widened to a certain thickness, she, by her laws of +gravitation and cohesion, consolidates their material until it becomes +almost as hard, as indissoluble, and as impervious as the rock. + +But, though man may press the forces of nature into his service, there +is a limit to the extent of his dominion over them, and unless future +generations shall discover new modes of controlling those forces, or new +remedies against their action, he must at last succumb in the struggle. +When the marine estuaries and other basins of reception shall be filled +up with the sedimentary debris of the mountains, or when the lower +course of the rivers shall be raised or prolonged by their own deposits +until they have, no longer, such a descent that gravitation and the +momentum of the current can overcome the frictional resistance of the +bed and banks, the water will, in spite of all obstacles, diffuse itself +laterally and for a time raise the level of the champaign land upon its +borders, and at last convert it into morasses. It is for this reason +that Lombardini advises that a considerable space along the lower course +of rivers be left undiked, and the water allowed to spread itself over +its banks and gradually raise them by its deposits. [Footnote: This +method has been adopted on the lower course of the Lamone, and a +considerable extent of low ground adjacent to that river has been raised +by spontaneous deposit to a sufficient height to admit of profitable +cultivation.] This would, indeed, be a palliative, but only a +palliative. For the present, however, we have nothing better, and here, +as often in political economy, we must content ourselves with "apres +nous le deluge," allowing posterity to suffer the penalty of our +improvidence and our ignorance, or to devise means for itself to ward +off the consequences of them. + +The deposit of slime by rivers upon the flats along their banks not only +contributes greatly to the fertility of the soil thus flowed, but it +subserves a still more important purpose in the general economy of +nature. All running streams begin with excavating channels for +themselves, or deepening the natural depressions in which they flow; +[Footnote: I do not mean to say that all rivers excavate their own +valleys, for I have no doubt that in the majority of cases such +depressions of the surface originate in higher geological causes, such +as the fissures and other irregularities of surface which could not fail +to accompany upheaval, and hence the valley makes the river, not the +river the valley. But even if we suppose a basin of the hardest rock to +be elevated at once, completely formed, from the submarine abyss where +it was fashioned, the first shower of rain that falls upon it, after it +rises to the air, will discharge its waters along the lowest lines of +the surface, and cut those lines deeper, and so on with every successive +rain. The disintegrated rock from the upper part of the basin forms the +lower by alluvial deposit, which is constantly transported farther and +farther until the resistance of gravitation and cohesion balances the +mechanical force of the running water. Thus plains, more or less steeply +inclined, are formed, in which the river is constantly changing its bed, +according to the perpetually varying force and direction of its +currents, modified as they are by ever-fluctuating conditions. Thus the +Po is said to have long inclined to move its channel southwards, at +certain points, in consequence of the mechanical force of its northern +affluents. A diversion of these tributaries from their present beds, so +that they should enter the main stream at other points and in different +directions, might modify the whole course of that great river. But the +mechanical force of the tributary is not the only element of its +influence on the course of the principal stream. The deposits it lodges +in the bed of the latter, acting as simple obstructions or causes of +diversion, are not less important agents of change.] but in proportion +as their outlets are raised by the solid material transported by their +currents, their velocity is diminished, they deposit gravel and sand at +constantly higher and higher points, and so at last elevate, in the +middle and lower part of their course, the beds they had previously +scooped out. [Footnote: The distance to which a new obstruction to the +flow of a river, whether by a dam or by a deposit in its channel, will +retard its current, or, in popular phrase, "set back the water," is a +problem of more difficult practical solution than almost any other in +hydraulics. The elements--such as straightness or crookedness of +channel, character of bottom and banks, volume and previous velocity of +current, mass of water far above the obstruction, extraordinary drought +or humidity of seasons, relative extent to which the river may be +affected by the precipitation in its own basin, and by supplies received +through subterranean channels from sources so distant as to be exposed +to very different meteorological influences, effects of clearing and +other improvements always going on in new countries--are all extremely +difficult, and some of them impossible, to be known and measured. In the +American States, very numerous water-mills have been erected within a +few years, and there is scarcely a stream in the settled portion of the +country which has not several mill-dams upon it. When a dam is raised--a +process which the gradual diminution of the summer currents renders +frequently necessary--or when a new dam is built, it often happens that +the meadows above are flowed, or that the retardation of the stream +extends back to the dam next above. This leads to frequent law-suits. +From the great uncertainty of the facts, the testimony is more +conflicting in these than in any other class of cases, and the obstinacy +with which "water causes" are disputed has become proverbial.] The +raising of the channels is compensated in part by the simultaneous +elevation of their banks and the flats adjoining them, from the deposit +of the finer particles of earth and vegetable mould brought down from +the mountains, without which elevation the low grounds bordering all +rivers would be, as in many cases they in fact are, mere morasses. + +All arrangements which tend to obstruct this process of raising the +flats adjacent to the channel, whether consisting in dikes which confine +the waters, and, at the same time, augment the velocity of the current, +or in other means of producing the last-mentioned effect, interfere with +the restorative economy of nature, and at last occasion the formation of +marshes where, if left to herself, she might have accumulated +inexhaustible stores of the richest soil, and spread them out in plains +above the reach of ordinary floods. [Footnote: The sediment of the Po +has filled up some lagoons and swamps in its delta, and converted them +into comparatively dry land; but, on the other hand, the retardation of +the current from the lengthening of its course, and the diminution of +its velocity by the deposits at its mouth, have forced its waters at +some higher points to spread in spite of embankments, and thus fertile +fields have been turned into unhealthy and unproductive marshes.--See +Botter, Sulla condizione dei Terreni Maremmani nel Ferraress. Annali di +Agricoltura, etc., Fasc. v., 1863.] + +Dikes, which, as we have seen, are the means most frequently employed to +prevent damage by inundation, are generally parallel to each other and +separated by a distance not very much greater than the natural width of +the bed. [Footnote: In the case of rivers flowing through wide alluvial +plains and much inclined to shift their beds, like the Po, the +embankments often leave a very wide space between them. The dikes of the +Po are sometimes three or four miles apart.] If such walls are high +enough to confine the water and strong enough to resist its pressure, +they secure the lands behind them from all the evils of inundation +except those resulting from filtration; but such ramparts are enormously +costly in original construction and in maintenance, and, as has been +already shown, the filling up of the bed of the river in its lower +course, by sand and gravel, often involves the necessity of incurring +new expenditures in increasing the height of the banks. [Footnote: It +appears from the investigations of Lombardini that the rate of elevation +of the bed of the Po has been much exaggerated by earlier writers, and +in some parts of its course the change is so slow that its level may be +regarded as nearly constant. Observation has established a similar +constancy in the bed of the Rhone and of many other important rivers, +while, on the other hand, the beds of the Adige and the Brenta, streams +of a more torrential character, are raised considerably above the level +of the adjacent fields. + +The length of the lower course of the Po having been considerably +increased by the filling up of the Adriatic with its deposits, the +velocity of the current ought, prima facie, to have been diminished and +its bed raised in proportion. There are abundant grounds for believing +that this has happened in the case of the Nile, and one reason why the +same effect has not been more sensibly perceptible in the Po is, that +the confinement of the current by continuous embankements gives it a +high-water velocity sufficient to sweep out deposits let fall at lower +stages and slower movements of the water. Torrential streams tend to +excavate or to raise their beds according to the inclination, and to the +character of the material they transport. No general law on this point +can be laid down in relation to the middle and lower courses of rivers. +The conditions which determine the question of the depression or +elevation of a river-bed are too multifarious, variable, and complex, to +be subjected to formulae, and they can scarcely even be enumerated. + +The following observation, however, though apparently too +unconditionally stated, is too important to be omitted. + +Rivers which transport sand, gravel, pebbles, heavy mineral matter in +short, tend to raise their own beds; those charged only with fine, light +earth, to cut them deeper. The prairie rivers of the western United +States have deep channels, because the mineral matter they carry down is +not heavy enough to resist the impulse of even a moderate current, and +those tributaries of the Po which deposit their sediment in the +lakes--the Ticino, the Adda, the Oglio, and the Mincio--flow in deep +cuts, for the same reason.--Baumgarten, p. 132. + +In regard to the level of the bed of the Po, there is another weighty +consideration which does not seem to have received the attention it +deserves. refer to the secular depression of the western coast of the +Adriatic, which is computed at the rate of fifteen or twenty centimetres +in a century, and which of course increases the inclination of the bed, +and the velocity and transporting power of the current of the Po, UNLESS +we assume that the whole course of the river, from the sea to its +sources, shares in the depression. Of this assumption there is no proof, +and the probability is to the contrary. For the evidence, though not +conclusive, perhaps, tends to show an elevation of the Tuscan coast, and +even of the Ligurian shore at points lying farther west than the sources +of the Po. The level of certain parts of the bed of the river referred +to by Lombardini as constant, is not their elevation as compared with +points nearer the sea, but relatively to the adjacent plains, and there +is every reason to believe that the depression of the Adriatic coast, +whether, as is conceivable, occasioned by the mere weight of the +fluviatile deposits or by more general geological causes, has increased +the slope of the bed of the river between the points in question and the +sea. In this instance, then, the relative permanency of the river level +at certain points may be, not the ordinary case of a natural +equilibrium, but the negative effect of an increased velocity of current +which prevents deposits where they would otherwise have happened.] They +are attended, too, with some collateral disadvantages. They deprive the +earth of the fertilizing deposits of the waters, which are powerful +natural restoratives of soils exhausted by cultivation; they accelerate +the rapidity and transporting power of the current at high water by +confining it to a narrower channel, and it consequently conveys to the +sea the earthy matter it holds in suspension, and chokes up harbors with +a deposit which it would otherwise have spread over a wider surface; +they interfere with roads and the convenience of river navigation, and +no amount of cost or care can secure them from occasional rupture, in +case of which the rush of the waters through the breach is more +destructive than the natural flow of the highest inundation. [Footnote: +To secure the city of Sacramento, in California, from the inundations to +which it is subject, a dike or levee was built upon the bank of the +river and raised to an elevation above that of the highest known floods, +and it was connected, below the town, with grounds lying considerably +above the river. On one occasion a breach in the dike occurred above the +town at a very high stage of the flood. The water poured in behind it, +and overflowed the lower part of the city, which remained submerged for +some time after the river had retired to its ordinary level, because the +dike, which had been built to keep the water OUT, now kept it IN. + +According to Arthur Young, on the lower Po, where the surface of the +river at high water has been elevated considerably above the level of +the adjacent fields by diking, the peasants in his time frequently +endeavored to secure their grounds against threatened devastation +through the bursting of the dikes, by crossing the river when the danger +became imminent and opening a cut in the opposite bank, thus saving +their own property by flooding their neighbors'. He adds, that at high +water the navigation of the river was absolutely interdicted, except to +mail and passenger boats, and that the guards fired upon all others; the +object of the prohibition being to prevent the peasants from resorting +to this measure of self-defence.--Travels in Italy and Spain, Nov. 7, +1789. + +In a flood of the Po in 1839, a breach of the embankment took place at +Bonizzo. The water poured through and inundated 116,000 acres, or 181 +square miles, of the plain to the depth of from twenty to twenty-three +feet, in the lower parts. The inundation of May, 1872, a giant breach +occurred in the dike near Ferrara, and 170,000 acres of cultivated land +were overflowed, and a population of 30,000 souls driven from their +homes. In the flood of October in the same year, in consequence of a +breach of the dike at Revere, 250,000 acres of cultivated soil were +overflowed, and 60,000 persons were made homeless. The dikes were +seriously injured at more than forty points. See page 279, ante. In the +flood of 1856, the Loire made seventy-three breaches in its dikes, and +thus, instead of a comparatively gradual rise and gentle expansion of +its waters, it created seventy-three impetuous torrents, which inflicted +infinitely greater mischief than a simply natural overflow would have +done. The dikes or levees of the Mississippi, being of more recent +construction than those of the Po, are not yet well consolidated and +fortified, and for this reason crevasses which occasion destructive +inundations are of very frequent occurrence.] + +For these reasons, many experienced engineers are of opinion that the +system of longitudinal dikes is fundamentally wrong, and it has been +argued that if the Po, the Adige, and the Brenta had been left +unconfined, as the Nile formerly was, and allowed to spread their muddy +waters at will, according to the laws of nature, the sediment they have +carried to the coast would have been chiefly distributed over the plains +of Lombardy. Their banks, it is supposed, would have risen as fast as +their beds, the coast-line would not have been extended so far into the +Adriatic, and, the current of the streams being consequently shorter, +the inclination of their channel and the rapidity of their flow would +not have been so greatly diminished. Had man, too, spared a reasonable +proportion of the forests of the Alps, and not attempted to control the +natural drainage of the surface, the Po, it has been said, would +resemble the Nile in all its essential characteristics, and, in spite of +the difference of climate, perhaps be regarded as the friend and ally, +not the enemy and the invader, of the population which dwells upon its +banks. + +But it has been shown by Humphreys and Abbot that the system of +longitudinal dikes is the only one susceptible of advantageous +application to the Mississippi, and if we knew the primitive geography +and hydrography of the basin of the Po as well as wo do those of the +valley of the great American river, we should very probably find that +the condemnation of the plan pursued by the ancient inhabitants of +Lombardy is a too hasty generalization, and that the case of the Nile is +an exception, not an example of the normal regime and condition of a +great river. [Footnote: Embankments have been employed on the lower +course of the Po for at least two thousand years, and for some centuries +they have been connected in a continuous chain from the sea to the +vicinity of Cremona. From early ages the Italian hydrographers have +stood in the front rank of their profession, and the Italian literature +of this branch of material improvement is exceedingly voluminous, +exhaustive, and complete. + +"The science of rivers after the barbarous ages," says Mengotti, "may be +said to have been born and perfected in Italy." The eminent Italian +engineer Lombardini published in 1870, under the title of Guida allo +studio dell' idrologia fluviale e dell' Idraulica practica, which serves +both as a summary of the recent progress of that science and as an index +to the literature of the subject. The professional student, therefore, +as well as the geographer, will have very frequent occasion to consult +Italian authorities, and in the very valuable Report of Humphreys and +Abbot on the Mississippi, America has lately made a contribution to our +potamological knowledge, which, in scientific interest and practical +utility, does not fall short of the ablest European productions in the +same branch of inquiry.] + +But in any event, these theoretical objections are counsels apres coup. +The dikes of the Po and probably of some of its tributaries were begun +before we have any trustworthy physical or political annals of the +provinces they water. The civilization of the valley has accommodated +itself to these arrangements, and the interests which might be +sacrificed by a change of system are too vast to be hazarded by what, in +the present state of our knowledge, can be only considered as a doubtful +experiment. [Footnote: Dupenchel advised a resort to the "heroic remedy" +of sacrificing, or converting into cellars, the lower storeys of houses +in cities exposed to river inundation, filling up the streets, and +admitting the water of floods freely over the adjacent country, and thus +allowing it to raise the level of the soil to that of the highest +inundations.--Traite d'Hydraulique et de Geologie Agricole, Paris, 1868, +p. 241.] + +The embankments of the Po, though they are of vast extent and have +employed centuries in their construction, are inferior in magnitude to +the dikes or levees of the Mississippi, which are the work of scarcely a +hundred years, and of a comparatively sparse population. On the right or +western bank of the river, the levee extends, with only occasional +interruptions from high bluffs and the mouths of rivers, for a distance +of more than eleven hundred miles. The left bank is, in general, higher +than the right, and upon that side a continuous embankment is not +needed; but the total length of the dikes of the Mississippi, including +those of the lower course of its tributaries and of its bayous or +natural emissaries, is not less than 2,500 miles. They constitute, +therefore, not only one of the greatest material achievements of the +American people, but one of the most remarkable systems of physical +improvement which has been anywhere accomplished in modern times. + +Those who condemn the system of longitudinal embankments have often +advised that, in cases where that system cannot be abandoned without +involving too great a sacrifice of existing interests, the elevation of +the dikes should be much reduced, so as to present no obstruction to the +lateral spread of extraordinary floods, and that they should be provided +with sluices to admit the water without violence whenever they are +likely to be overflowed. Where dikes have not been erected, or where +they have been reduced in height, it is proposed to construct, at +convenient intervals, transverse embankments of moderate height running +from the banks of the river across the plains to the hills which bound +them. These measures, it is argued, will diminish the violence of +inundations by permitting the waters to extend themselves over a greater +surface, and by thus retarding the flow of the river currents, will, at +the same time, secure the deposit of fertilizing slime upon all the soil +covered by the flood. [Footnote: The system described in the text is +substantially the Egyptian method, the ancient Nile dikes having been +constructed rather to retain than to exclude the water.] + +Rozet, an eminent French engineer, has proposed a method of diminishing +the ravages of inundations, which aims to combine the advantages of all +other systems, and at the same time to obviate the objections to which +they are all more or less liable. [Footnote: Moyens de forcer les +Torrents de rendre une partie du sol qu'ils ravagent, et d'empecher les +grandes Inondations.] The plan of Rozet is recommended by its simplicity +and cheapness as well as its facility and rapidity of execution, and is +looked upon with favor by many persons very competent to judge in such +matters. It is, however, by no means capable of universal application, +though it would often doubtless prove highly useful in connection with +the measures now employed in South-eastern France. He proposes to +commence with the amphitheatres in which mountain torrents so often +rise, by covering their slopes and filling their beds with loose blocks +of rock, and by constructing at their outlets, and at other narrow +points in the channels of the torrents, permeable barriers of the same +material promiscuously heaped up, much according to the method employed +by the ancient Romans in their northern provinces for a similar purpose. +By this means, he supposes, the rapidity of the current would be +checked, and the quantity of transported pebbles and gravel--which, by +increasing the mechanical force of the water, greatly aggravate the +damage by floods--much diminished. When the stream has reached that part +of its course where it is bordered by soil capable of cultivation, and +worth the expense of protection, he proposes to place along one or both +banks, according to circumstances, a line of cubical blocks of stone or +pillars of masonry three or four feet high and wide, and at the distance +of about eleven yards from each other. The space between the two lines, +or between a line and the opposite high bank, would, of course, be +determined by observation of the width of the swift-water current at +high floods. As an auxiliary measure, small ditches and banks, or low +walls of pebbles, should be constructed from the line of blocks across +the grounds to be protected, nearly at right angles to the current, but +slightly inclining downwards, and at convenient distances from each +other. Rozet thinks the proper interval would be 300 yards, and it is +evident that, if he is right in his main principle, hedges, rows of +trees, or even common fences, would in many cases answer as good a +purpose as banks and trenches or low walls. The blocks or pillars of +stone would, he contends, check the lateral currents so as to compel +them to let fall all their pebbles and gravel in the main channel--where +they would be rolled along until ground down to sand or silt--and the +transverse obstructions would detain the water upon the soil long enough +to secure the deposit of its fertilizing slime. Numerous facts are cited +in support of the author's views, and I imagine there are few residents +of rural districts whose own observation will not furnish testimony +confirmatory of their soundness. [Footnote: The effect of trees and +other detached obstructions in checking the flow of water is +particularly noticed by Palissy in his essay on Waters and Fountains, p. +173, edition of 1844. "There be," says he, "in divers parts of France, +and specially at Nantes, wooden bridges, where, to break the force of +the waters and of the floating ice, which might endamage the piers of +the said bridges, they have driven upright timbers into the bed of the +rivers above the said piers, without the which they should abide but +little. And in like wise, the trees which be planted along the mountains +do much deaden the violence of the waters that flow from them." + +Lombardini attaches great importance to the planting of rows of trees +transversely to the current on grounds subject to overflow.--Esame degli +Studi sul Tevere, Section 53, and Appendice, Sections 33, 34.] + + +Removal of Obstructions. + +The removal of obstructions in the beds of rivers dredging the bottom or +blasting rocks, the washing out of deposits and locally increasing the +depth of water by narrowing the channel by moans of spurs or other +constructions projecting from the banks, and, finally, the cutting off +of bends and thus shortening the course of the stream, diminishing the +resistance of its shores and bottom and giving the bed a more rapid +declivity, have all been employed not only to facilitate navigation, but +as auxiliaries to more effectual modes of preventing inundations. But a +bar removed from one point is almost sure to re-form at the same or +another, spurs occasion injurious eddies and unforeseen diversions of +the current, [Footnote: The introduction of a new system of spurs with +parabolic curves has been attended with giant advantage in +France.--Annales du Genie Civil, Mai, 1863.] and the cutting off of +bends, though occasionally effected by nature herself, and sometimes +advantageous in torrential streams whose banks are secured by solid +walls of stone or other artificial constructions, seldom establishes a +permanent channel, and besides, the increased rapidity of the flow +through the new cut often injuriously affects the regime of the river +for a considerable distance below. [Footnote: This practice has +sometimes been resorted to on the Mississippi with advantage to +navigation, but it is quite another question whether that advantage has +not been too dearly purchased by the injury to the banks at lower +points. If we suppose a river to have a navigable course of 1,600 miles +as measured by its natural channel, with a descent of 800 feet, we shall +have a fall of six inches to the mile. If the length of channel be +reduced to 1,200 miles by cutting off bends, the fall is increased to +eight inches per mile. The augmentation of velocity consequent upon this +increase of inclination is not computable without taking into account +other elements, such as depth and volume of water, diminution of direct +resistance, and the like, but in almost any supposable case, it would be +sufficient to produce great effects on the height of floods, the deposit +of sediment in the channel, on the shores, and at the outlet, the +erosion of banks and other points of much geographical importance. + +The Po, in those parts of its course where the embankments leave a wide +space between, often cuts off bends in its channel and straightens its +course. These short cuts are called salti, or leaps, and sometimes +abridge the distance between their termini by several miles. In 1777, +the salto of Cottaro shortened a distance of 7,000 metres by 5,000, or, +in other words, reduced the length of the river by five kilometres, or +about three miles, and in 1807 and 1810 the two salti of Mozzanone +effected a still greater reduction.] + + +Combination of Methods. + +Upon the whole, it is obvious that no one of the methods heretofore +practised or proposed for averting the evils resulting from river +inundations is capable of universal application. Each of them is +specially suited to a special case. But the hydrography of almost every +considerable river and its tributaries will be found to embrace most +special cases, most known forms of superficial fluid circulation. For +rivers, in general, begin in the mountains, traverse the plains, and end +in the sea; they are torrents at their sources, swelling streams in +their middle course, placid currents, flowing molli flumine, at their +termination. Hence in the different parts of their course the different +methods of controlling and utilizing them may successively find +application, and there is every reason to believe that by a judicious +application of all, every great river may, in a considerable degree, be +deprived of its powers of evil and rendered subservient to the use, the +convenience, and the dominion of man. [Footnote: On the remedies against +inundation, see the valuable paper of Lombardini, Sulle Inondazioni +avvenute in questi ultimi tempi in Francia. Milano, 1858. + +There can be no doubt that in the case of rivers which receive their +supply in a large measure from mountain streams, the methods described +in a former chapter as recently employed in South-eastern France to +arrest the formation and lessen the force of torrents, would prove +equally useful as a preventive remedy against inundations. They would +both retard the delivery of surface-water and diminish the discharge of +sediment into rivers, thus operating at once against the two most +efficient causes of destructive floods. See Chapter III., pp. 316 at +seqq.] + + +Dikes of the Nile. + +"History tells us," says Mengotti, "that the Nile became terrible and +destructive to ancient Egypt, in consequence of being confined within +elevated dikes, from the borders of Nubia to the sea. It being +impossible for these barriers to resist the pressure of its waters at +such a height, its floods burst its ramparts, sometimes on one side, +sometimes on the other, and deluged the plains, which lay far below the +level of its current. . . . In one of its formidable inundations the +Nile overwhelmed and drowned a large part of the population. The +Egyptians then perceived that they were struggling against nature in +vain, and they resolved to remove the dikes, and permit the river to +expand itself laterally and raise by its deposits the surface of the +fields which border its channel." [Footnote: Idraulica Fisica e +Sperimentale. 2d edizione, vol. i., pp. 131, 133.] + +The original texts of the passages cited by Mengotti, from Latin +translations of Diodorus Siculus and Plutarch and from Pliny the Elder, +do not by any means confirm this statement, though the most important of +them, that from Diodorus Siculus, is, perhaps, not irreconcilable with +it. Not one of them speaks of the removal of the dikes, and I understand +them all as relating to the mixed system of embankments, reservoirs, and +canals which have been employed in Egypt through the whole period +concerning which we have clear information. I suppose that the +disastrous inundations referred to by the authors in question were +simply extraordinary floods of the same character as those which have +been frequent at later periods of Egyptian history, and I find nothing +in support of the proposition that continuous embankments along the +banks of the Nile ever existed until such were constructed by Mehemet +Ali. [Footnote: The gradual elevation of the bed of the Nile from +sedimentary deposit, from the prolongation of the Delta and consequent +reduction of the inclination of the river-bed, or, as has been supposed +by some, though without probability, from a secular rise of the coast, +rendered necessary some change in the hydraulic arrangements of Egypt. +Mehemet Ali was advised to adopt a system of longitudinal levees, and he +embanked the river from Jebel Silsileh to the sea with dikes six or +seven feet high and twenty feet thick. Similar embankments were made +around the Delta. These dikes are provided with transverse embankments, +with sluices for admitting and canals for distributing the water, and +they serve rather to retain the water and control its flow than to +exclude it. Clot Bey, Apercu sur l'Egypte, ii., 437.] + +The object of the dikes of the Po, and, with few exceptions, of those of +other European rivers, has always been to confine the waters of floods +and the solid material transported by them within as narrow a channel as +possible, and entirely to prevent them from flowing over the adjacent +plains. The object of the Egyptian dikes and canals is the reverse, +namely, to diffuse the swelling waters and their sediment over as wide a +surface as possible, to store them up until the soil they cover has them +thoroughly saturated and enriched, and then to conduct them over other +grounds requiring a longer or a second submersion, and, in general, to +suffer none of the precious fluid to escape except by evaporation and +infiltration. + +Lake Moeris, whether wholly an artificial excavation, or a natural basin +converted by embankments into a reservoir, was designed chiefly for the +same purpose as the barrage built by Mougel Bey across the two great +arms which enclose the Delta, namely, as a magazine to furnish a +perennial supply of water to the thirsty soil. But these artificial +arrangements alone did not suffice. Canals were dug to receive the water +at lower stages of the river and conduct it far into the interior, and +as all this was still not enough, hundreds of thousands of wells were +sunk to bring up from the subsoil, and spread over the surface, the +water which, by means of infiltration from the river-bed, pervades the +inferior strata of the whole valley. [Footnote: It is said that in the +Delta alone 50,000 wells are employed for irrigation.] + +If a system of lofty continuous dikes, like those of the Po, had really +been adopted in Egypt, in the early dynasties when the power and the +will to undertake the most stupendous material enterprises were so +eminently characteristic of the government of that country, and +persevered in through later ages, and the waters of the annual +inundation had thus been permanently prevented from flooding the land, +it is conceivable that the productiveness of the small area of +cultivable soil in the Nile valley might have been long kept up by +artificial irrigation and the application of manures. But nature would +have rebelled at last, and centuries before our time the mighty river +would have burst the fetters by which impotent man had vainly striven to +bind his swelling floods, the fertile fields of Egypt would have been +converted into dank morasses, and then, perhaps, in some distant future, +when the expulsion of man should have allowed the gradual restoration of +the primitive equilibrium, would be again transformed into luxuriant +garden and plough land. Fortunately, the sapientia AEgyptiorum, the +wisdom of the Egyptians, taught them better things. They invited and +welcomed, not repulsed, the slimy embraces of Nilus, and his favors have +been, from the hoariest antiquity, the greatest material blessing that +nature ever bestowed upon a people. [Footnote: Deep borings have not +detected any essential difference in the quantity or quality of the +deposits of the Nile for forty or fifty, or, as some compute, for a +hundred centuries. From what vast store of rich earth does this river +derive the three or four inches of fertilizing material which it spreads +over the soil of Egypt every hundred years Not from the White Nile, for +that river drops nearly all its suspended matter in the broad expansions +and slow current of its channel south of the tenth degree of north +latitude. Nor does it appear that much sediment is contributed by the +Bahr-el-Azrek, which flows through forests for a great part of its +course. I have been informed by an old European resident of Egypt who is +very familiar with the Upper Nile, that almost the whole of the earth +with which its waters are charged is brought down by the Takazze.] + + +Deposits of the Nile. + +The Nile is larger than all the rivers of Lombardy together, [Footnote: +From daily measurements during a period of fourteen years--1827 to +1840--the mean delivery of the Po at Ponte Lagoscuro, below the entrance +of its last tributary, is found to be 1,720 cubic metres, or 60,745 +cubic feet, per second. Its smallest delivery is 186 cubic metres, or +6,569 cubic feet, its greatest 5,156 cubic metres, or 152,094 cubic +feet. The average delivery of the Nile being 101,000 cubic feet per +second, it follows that the Po contributes to the Adriatic rather more +than six-tenths as much water as the Nile to the Mediterranean--a result +which will surprise most readers. + +It is worth remembering that the mean delivery of the Rhone is almost +identical with that of the Po, and that of the Rhine is very nearly the +same. Though the Po receives four-tenths of its water from lakes, in +which the streams that empty into them let fall the solid material they +bring down from the mountains, its deposits in the Adriatic are at least +sixty or seventy per cent. greater than those transported to the +Mediterranean by the Rhone, which derives most of its supply from +mountain and torrential tributaries. Those tributaries lodge much +sediment in the Lake of Geneva and the Lac de Bourget, but the total +erosion of the Po and its affluents must be considerably greater than +that of the Rhone system. The Rhine conveys to the sea much less +sediment than either of the other two rivers.--Lombardini, Cargiamenti +nella condizione del Po, pp. 29, 39. + +The mean discharge of the Mississippi is 675,000 cubic feet per second, +and, accordingly, that river contributes to the sea about eleven times +as much water as the Po, and more than six and a half times as much as +the Nile. The discharge of the Mississippi is estimated at one-fourth of +the precipitation in its basin--certainly a very large proportion, when +we consider the rapidity of evaporation in many parts of the basin, and +the probable loss by infiltration.--Humphreys and Abbott'S Report, p. +93. + +The basin of the Mississippi has an area forty-six times as large as +that of the Po, with a mean annual precipitation of thirty inches, while +that of the Po, at least according to official statistics, has a +precipitation of forty inches. Hence the down-fall in the former is +one-fourth less than in the latter. Besides this, the Mississippi loses +little or nothing by the diversion of its waters for irrigation. +Consequently the measured discharge of the Mississippi is proportionally +much less than that of the Po, and we are authorized to conclude that +the difference is partly due to the escape of water from the bed, or at +least the basin of the Mississippi, by subterranean channels. + +These comparisons are interesting in reference to the supply received by +the sea directly from great rivers, but they fail to give a true idea of +the real volume of the latter. To take the case of the Nile and the Po: +we have reason to suppose that comparatively little water is diverted +from the tributaries of the former for irrigation, but enormous +quantities are drawn from its main trunk for that purpose, below the +point where it receives its last affluent. This quantity is now +increasing in so rapid a proportion, that Elisee Reclus foresees the day +when the entire low-water current will be absorbed by new arrangements +to meet the needs of extended and improved agriculture. On the other +hand, while the affluents of the Po send off a great quantity of water +into canals of irrigation, the main trunk loses little or nothing in +that way except at Chivasso. Trustworthy data are wanting to enable us +to estimate how far these different modes of utilizing the water balance +each other in the case under consideration. Perhaps the Canal Cavour, +and other irrigating canals now proposed, may one day intercept as large +a proportion of the supply of the lower Po as Egyptian dikes, canals, +shadoofs, and steam-pumps do of that of the Nile. + +Another circumstance is important to be considered in comparing the +character of these three rivers. The Po runs nearly east and west, and +it and its tributaries are exposed to no other difference of +meterological conditions than those which always subsist between the +mountains and the plains. The course of the Nile and the Mississippi is +mainly north and south. The sources of the Nile are in a very humid +region, its lower course for many hundred miles in almost rainless +latitudes with enormous evaporating power, while the precipitation is +large throughout the Mississippi system, except in the basins of some of +its western affluents.] it drains a basin fifty, possibly even a +hundred, times as extensive, its banks have been occupied by man +probably twice as long. But its geographical character has not been much +changed in the whole period of recorded history, and, though its outlets +have somewhat fluctuated in number and position, its historically known +encroachments upon the sea are trifling compared with those of the Po +and the neighboring streams. The deposits of the Nile are naturally +greater in Upper than in Lower Egypt. They are found to have raised the +soil at Thebes about seven feet within the last seventeen hundred years, +and in the Delta the rise has been certainly more than half as great. + +We shall, therefore, probably not exceed the truth if we suppose the +annually inundated surface of Egypt to have been elevated, upon an +average, ten feet, [Footnote: Fraas and Eyth maintain that we have no +trustworthy data for calculating the annual or secular elevation of the +soil of Egypt by the sediment of the Nile. The deposit, they say, is +variable from irregularity of current, and especially from the +interference of man with the operations of nature, to a degree which +renders any probable computation of the amount quite impossible.--Fraas, +Aus dem Orient, pp. 212, 213. + +The sedimentary matter transported by the Nile might doubtless be +estimated with approximate precision by careful observation of the +proportion of suspended slime and water at different stations and +seasons for a few successive years. Figari Bey states that at low stages +the water of the Nile contains little or no sediment, and that the +greatest proportion occurs about the end of July, and of course, while +the river is still rising. Experiments at Khartum at that season showed +solid matter in the proportion of one to a thousand by weight. The +quantity is relatively greater at Cairo, a fact which shows that the +river receives more earth from the erosion of its banks than it deposits +at its own bottom, and it must consequently widen its channel unless we +suppose a secular depression of the coast at the mouth of the Nile which +produces an increased inclination of the bed of the river, and +consequently an augmented velocity of flow sufficient to sweep out earth +from the bottom and mix it with the current. + +Herschell states the Nile sediment at 1 in 633 by weight, and computes +the entire annual quantity at 140 millions of tons.--Physical Geography, +p. 231. + +The mean proportion of sedimentary material in the waters of the +Mississippi is calculated at 1 to 1,500 by weight, and 1 to 2,900 in +volume, and the total annual quantity at 812,500,000,000 pounds, which +would cover one square mile to the depth of 214 feet.--Humphreys and +Abbott, Report, p. 140.] within the last 5,000 years, or twice and a +half the period during which the history of the Po is known to us. +[Footnote: We are quite safe in supposing that the valley of the Nile +has been occupied by man at least 5,000 years. The dates of Egyptian +chronology are uncertain, but I believe no inquirer estimates the age of +the great pyramids at less than forty centuries, and the construction of +such works implies an already ancient civilization. + +It is an interesting fact that the old Egyptian system of embankments +and canals is probably more ancient than the geological changes which +have converted the Mississippi from a limpid to a turbid stream, and +occasioned the formation of the vast delta at the mouth of that river. +Humphreys and Abbot conclude that the delta of the Mississippi began its +encroachments on the Gulf of Mexico not more than 4,400 years ago, +before which period they suppose the Mississippi to have been "a +comparatively clear stream," conveying very little sediment to the sea. +The present rate of advance of the delta is 262 feet a year, and there +are reasons for thinking that the amount of deposit has long been +approximately constant.--Report, pp. 435, 436.] + +As I have observed, the area of cultivated soil is much less extensive +now than under the dynasties of the Pharaohs and the Ptolemies; +for--though, in consequence of the elevation of the river-bed, the +inundations now have a wider NATURAL spread--the industry of the ancient +Egyptians conducted the Nile water over a great surface which it does +not now reach. + +Had the Nile been banked in, like the Po, all this deposit, except that +contained in the water diverted by canals or otherwise drawn from the +river for irrigation and other purposes, would have soon carried out to +sea. This would have been a considerable quantity; for the Nile holds +some earth in suspension at all seasons except at the very lowest water, +a much larger proportion during the flood, and irrigation must have been +carried on during the whole year. The precise amount of sediment which +would have been thus distributed over the soil is matter of conjecture, +but though large, it would have been much less than the inundations have +deposited, and continuous longitudinal embankments would have compelled +the Nile to transport to the Mediterranean an immense quantity over and +above what it has actually deposited in that sea. The Mediterranean is +shoal for some miles out to sea along the whole coast of the Delta, and +the large bays or lagoons within the coast-line, which communicate both +with the river and the sea, have little depth of water. These lagoons +the river deposits would have filled up, and there would still have been +surplus earth enough to extend the Delta far into the Mediterranean. + +[Footnote: The present annual extension of the Delta is, if perceptible, +at all events very small. According to some authorities, a few hectares +are added every year at each Nile mouth. Others, among whom I may +mention Fraas, deny that there is any extension at all, the deposit +being balanced by a secular depression of the coast. + +Elisee Reclus states that the Delta advances about 40 inches per +year.--La Terre, i., p. 500.] + +Obstruction of River Mouths. + +The mouths of a large proportion of the streams known to ancient +navigation are already blocked up by sand-bars or fluviatile deposits, +and the maritime approaches to river harbors frequented by the ships of +Phenicia and Carthage and Greece and Rome are shoaled to a considerable +distance out to sea. The inclination of the lower course of almost every +known river bed has been considerably reduced within the historical +period, and nothing but great volume of water, or exceptional rapidity +of flow, now enables a few large streams like the Amazon, the La Plata, +the Ganges, and, in a loss degree, the Mississippi, to carry their own +deposits far enough out into deep water to prevent the formation of +serious obstructions to navigation. But the degradation of their banks, +and the transportation of earthy matter to the sea by their currents, +are gradually filling up the estuaries even of those mighty floods, and +unless the threatened evil shall be averted by the action of geological +forces, or by artificial contrivances more efficient than +dredging-machines, the destruction of every harbor in the world which +receives a considerable river must inevitably take place at no very +distant date. + +This result would, perhaps, have followed in some incalculably distant +future, if man had not come to inhabit the earth as soon as the natural +forces which had formed its surface had arrived at such an approximate +equilibrium that his existence on the globe was possible; but the +general effect of his industrial operations has been to accelerate it +immensely. Rivers, in countries planted by nature with forests and never +inhabited by man, employ the little earth and gravel they transport +chiefly to raise their own beds and to form plains in their basins. In +their upper course, where the current is swiftest, they are most heavily +charged with coarse rolled or suspended matter, and this, in floods, +they deposit on their shores in the mountain valleys where they rise; in +their middle course, a lighter earth is spread over the bottom of their +widening basins, and forms plains of moderate extent; the fine silt +which floats farther is deposited over a still broader area, or, if +carried out to sea, is in great part quickly swept far off by marine +currents and dropped at last in deep water. Man's "improvement" of the +soil increased the erosion from its surface; his arrangements for +confining the lateral spread of the water in floods compel the rivers to +transport to their mouths the earth derived from that erosion even in +their upper course; and, consequently, the sediment they deposit at +their outlets is not only much larger in quantity, but composed of +heavier materials, which sink more readily to the bottom of the sea and +are less easily removed by marine currents. + +The tidal movement of the ocean, deep-sea currents, and the agitation of +inland waters by the wind, lift up the sands strewn over the bottom by +diluvial streams or sent down by mountain torrents, and throw them up on +dry land, or deposit them in sheltered bays and nooks of the coast--for +the flowing is stronger than the ebbing tide, the affluent than the +refluent wave. This cause of injury to harbors it is not in man's power +to resist by any means at present available; but, as we have seen, +something can be done to prevent the degradation of high grounds, and to +diminish the quantity of earth which is annually abstracted from the +mountains, from table-lands, and from river-banks, to raise the bottom +of the sea. + +This latter cause of harbor obstruction, though an active agent, is, +nevertheless, in many cases, the less powerful of the two. The earth +suspended in the lower course of fluviatile currents is lighter than +sea-sand, river water lighter than sea water, and hence, if a land +stream enters the sea with a considerable volume, its water flows over +that of the sea, and bears its slime with it until it lets it fall far +from shore, or, as is more frequently the case, mingles with some marine +current and transports its sediment to a remote point of deposit. The +earth borne out of the mouths of the Nile is in part carried over the +waves which throw up sea-sand on the beach, and deposited in deep +water, in part drifted by the current, which sweeps east and north along +the coasts of Egypt and Syria, and lodged in every nook along the +shore--and among others, to the great detriment of the Suez Canal, in +the artificial harbor at its northern terminus--and in part borne along +until it finds a final resting-place in the north-eastern angle of the +Mediterranean. [Footnote: "The stream carries this mud, etc., at first +farther to the east, and only lets it fall where the force of the +current becomes weakened. This explains the continual advance of the +land seaward along the Syrian coast, in consequence of which Tyre and +Sideon no longer lie on the shore, but some distance inland. That the +Nile contributes to this deposit may easily be seen, even by the +unscientific observer, from the stained and turbid character of the +water for many miles from its mouths. Ships often encounter floating +masses of Nile mud, and Dr. Clarke thus describes a case of this sort: + +"While we were at table, we heard the sailors who were throwing the lead +suddenly cry out: 'Three and a half!' The ship slackened her way, and +veered about. As she came round, the whole surface of the water was seen +to be covered with thick, black mud, which extended so far that it +appeared like an island. At the same time, actual land was nowhere to be +seen--not even from the mast-head--nor was any notice of such a shoal to +be found or any chart on board. The fact is, as we learned afterwards, +that a stratum of mud, stretching from the mouths of the Nile for many +miles out into the open sea, forms a movable deposit along the Egyptian +coast. If this deposit is driven forwards by powerful currents, it +sometimes rises to the surface, and disturbs the mariner by the sudden +appearance of shoals where the charts lead him to expect a considerable +depth of water. But these strata of mud are, in reality, not in the +least dangerous. As soon as a ship strikes them they break up at once, +and a frigate may hold her course in perfect safety where an +inexperienced pilot, misled by his soundings, would every moment expect +to be stranded."--Bottger, Das Mittchneer, pp. 188, 189. + +This phenomenon is not peculiar to the locality in question, and it is +frequently observed in the Gulf of Bengal, and other great marine +estuaries.] + +Thus the earth loosened by the rude Abyssinian ploughshare, and washed +down by the rain from the hills of Ethiopia which man has stripped of +their protecting forests, contributes to raise the plains of Egypt, to +shoal the maritime channels which lead to the city built by Alexander +near the mouth of the Nile, to obstruct the artificial communication +between the Mediterranean and the Red Sea, and to fill up the harbors +made famous by Phenician commerce. + + + +Deposits of the Tuscan Rivers. + +The Arno, and all the rivers rising on the western slopes and spurs of +the Apennines, carry down immense quantities of mud to the +Mediterranean. There can be no doubt that the volume of earth so +transported is very much greater than it would have been had the soil +about the headwaters of those rivers continued to be protected from wash +by forests; and there is as little question that the quantity borne out +to sea by the rivers of Western Italy is much increased by artificial +embankments, because they are thereby prevented from spreading over the +surface the sedimentary matter with which they are charged. The western +coast of Tuscany has advanced some miles seawards within a very few +centuries. The bed of the sea, for a long distance, has been raised, and +of course the relative elevation of the land above it lessened; harbors +have been filled up and destroyed; long lines of coast dunes have been +formed, and the diminished inclination of the beds of the rivers near +their outlets has caused their waters to overflow their banks and +convert them into pestilential marshes. The territorial extent of +Western Italy has thus been considerably increased, but the amount of +soil habitable and cultivable by man has been, in a still higher +proportion, diminished. The coast of ancient Etruria was filled with +great commercial towns, and their rural environs were occupied by a +large and prosperous population. But maritime Tuscany has long been one +of the most unhealthy districts in Christendom; the famous Etruscan mart +of Populonia has scarcely an inhabitant; the coast is almost absolutely +depopulated, and the malarious fevers have extended their ravages far +into the interior. + +These results are certainly not to be ascribed wholly to human action. +They are, in a large proportion, due to geological causes over which man +has no control. The soil of much of Tuscany becomes pasty, almost fluid +even, as soon as it is moistened, and when thoroughly saturated with +water, it flows like a river. Such a soil as this would not be +completely protected by woods, and, indeed, it would now be difficult to +confine it long enough to allow it to cover itself with forest +vegetation. Nevertheless, it certainly was once chiefly wooded, and the +rivers which flow through it must then have been much less charged with +earthy matter than at present, and they must have carried into the sea a +smaller proportion of their sediment when they were free to deposit it +on their banks than since they have been confined by dikes. + +It is, in general, true, that the intervention of man has hitherto +seemed to insure the final exhaustion, ruin, and desolation of every +province of nature which he has reduced to his dominion. Attila was only +giving an energetic and picturesque expression to the tendencies of +human action, as personified in himself, when he said that "no grass +grew where his horse's hoofs had trod." The instances are few, where a +second civilization has flourished upon the ruins of an ancient culture, +and lands once rendered uninhabitable by human acts or neglect have +generally been forever abandoned as hopelessly irreclaimable. It is, as +I have before remarked, a question of vast importance, how far it is +practicable to restore the garden we have wasted, and it is a problem on +which experience throws little light, because few deliberate attempts +have yet been made at the work of physical regeneration, on a scale +large enough to warrant general conclusions in any one class of cases. + +The valleys and shores of Tuscany form, however, a striking exception to +this remark. The succcess with which human guidance has made the +operations of nature herself available for the restoration of her +disturbed harmonies, in the Val di Chiana and the Tuscan Maremma, is +among the noblest, if not the most brilliant achievements of modern +engineering, and, regarded in all its bearings on the great question of +which I have just spoken, it is, as an example, of more importance to +the general interests of humanity than the proudest work of internal +improvement that mechanical means have yet constructed. The operations +in the Val di Chiana have consisted chiefly in so regulating the flow of +the surface-waters into and through it, as to compel them to deposit +their sedimentary matter at the will of the engineers, and thereby to +raise grounds rendered insalubrious and unfit for agricultural use by +stagnating water; the improvements in the Maremma have embraced both +this method of elevating the level of the soil, and the prevention of +the mixture of salt-water with fresh in the coast marshes and shallow +bays, which is regarded as a very active cause of the development of +malarious influences. [Footnote: The fact that the mixing of salt and +fresh water in coast marshes and lagoons is deleterious to the sanitary +condition of the vicinity, has been generally admitted, though the +precise reason why a mixture of both should be more injurious than +either alone, is not altogether clear. It has been suggested that the +admission of salt-water to the lagoons and rivers kills many fresh-water +plants and animals, while the fresh water is equally fatal to many +marine organisms, and that the decomposition of the remains originates +poisonous minsmata. Other theories, however, have been proposed. The +whole subject is fully and ably discussed by Dr. Salvagnoli Marchetti in +the appendix to his valuable Rapporto aul Bonificamento delle Maremme +Toscane. See also the Memorie Economico-Statistiche sulle Maremme +Toscane, of the same author. A different view of this subject is taken +by Raffanini and Orlandini in Analisi, Storico-Fisico-Economica sulli +insolubrita nelle Maremme Toscane, Firenze, 1869. See also the important +memoir of D. Pantaleoni, Del miasma vegetale e delle Malattie +Miasmatiche, in which the views of Salvagnoli on this point are +combated.] + + +Improvements in the Tuscan Maremma. + +In the improvements of the Tuscan Maremma, formidable difficulties have +been encountered. The territory to be reclaimed was extensive; the +salubrious places of retreat for laborers and inspectors were remote; +the courses of the rivers to be controlled were long and their natural +inclination not rapid; some of them, rising in wooded regions, +transported comparatively little earthy matter, [Footnote: This +difficulty has been remedied--though with doubtful general advantage--as +to one important river of the Maremma, the Pecora, by clearings recently +executed along its upper course. "The condition of this marsh and of its +affluents are now, November, 1859, much changed, and it is advisable to +prosecute its improvement by deposits. In consequence of the extensive +felling of the woods upon the plains, hills, and mountains of the +territory of Massa and Scarlino, within the last ten years, the Pecora +and other affluents of the marsh receive, during the rains, water +abundantly charged with slime, so that the deposits within the first +division of the marsh are already considerable, and we may now hope to +see the whole marsh and pond filled up in a much shorter time than we +had a right to expect before 1850. This circumstance totally changes the +terms of the question, because the filling of the marsh and pond, which +then seemed almost impossible on account of the small amount of sediment +deposited by the Pecora, has now become practicable."--Salvagnoli, +Rapporto sul Bonificamento delle Maremme Toscane, pp.li., lii. + +Between 1830 and 1859 more than 36,000,000 cubic yards of sediment were +deposited in the marsh and shoal-water lake of Castiglione +alone.--Salvagnoli, Raccolta di Documenti, pp. 74, 75.] and above all, +the coast, which is a recent deposit of the waters, is little elevated +above the sea, and admits into its lagoons and the mouths of its rivers +floods of salt-water with every western wind, every rising tide. +[Footnote: The tide rises ten inches on the coast of Tuscany. See Memoir +by Fantoni, in the appendix to Salvagnoli, Rapporto, p. 189. + +On the tides of the Mediterranean, see Bottger, Das Mittelmeer, p. 190.] + +The western coast of Tuscany is not supposed to have been an unhealthy +region before the conquest of Etruria by the Romans, but it certainly +became so within a few centuries after that event. This was a natural +consequence of the neglect or wanton destruction of the public +improvements, and especially the hydraulic works in which the Etruscans +were so skilful, and of the felling of the upland forests, to satisfy +the demand for wood at Rome for domestic, industrial, and military +purposes. After the downfall of the Roman empire, the incursions of the +barbarians, and then feudalism, foreign domination, intestine wars, and +temporal and spiritual tyrannies, aggravated still more cruelly the +moral and physical evils which Tuscany and the other Italian States were +doomed to suffer, and from which they have enjoyed but brief respites +during the whole period of modern history. The Maremma was already +proverbially unhealthy in the time of Dante, who refers to the fact in +several familiar passages, and the petty tyrants upon its borders often +sent criminals to places of confinement in its territory, as a slow but +certain mode of execution. Ignorance of the causes of the insalubrity, +and often the interference of private rights, [Footnote: In Catholic +countries, the discipline of the church requires a meagre diet at +certain seasons, and as fish is not flesh, there is a great demand for +that article of food at those periods. For the convenience of +monasteries and their patrons, and as a source of pecuniary emolument to +ecclesiastical establishments and sometimes to lay proprietors, great +numbers of artificial fish-ponds were created during the Middle Ages. +They were generally shallow pools formed by damming up the outlet of +marshes, and they were among the most fruitful sources of endemic +disease, and of the peculiar malignity of the epidemics which so often +ravaged Europe in those centuries. These ponds, in religious hands, were +too sacred to be infringed upon for sanitary purposes, and when +belonging to powerful lay lords they were almost an inviolable. The +rights of fishery were a standing obstacle to every proposal of hydralic +improvement, and to this day large and fertile districts in Southern +Europe remain sickly and almost unimproved and uninhabited, because the +draining of the ponds upon them would reduce the income of proprietors +who derive large profits by supplying the faithful, in Lent, with fish, +and with various species of waterfowl which, though very fat, are, +ecclesiastically speaking, meagre.]prevented the adoption of measures to +remove it, and the growing political and commercial importance of the +large towns in more healthful localities absorbed the attention of +Government, and deprived the Maremma of its just share in the systems of +physical improvement which were successfully adopted in interior and +Northern Italy. + +Before any serious attempts were made to drain or fill up the marshes of +the Maremma, various other sanitary experiments were tried. It was +generally believed that the insalubrity of the province was the +consequence, not the cause, of its depopulation, and that, if it were +once densely inhabited, the ordinary operations of agriculture, and +especially the maintenance of numerous domestic fires, would restore it +to its ancient healthfulness. [Footnote: Macchiavelli advised the +Government of Tuscany "to provide that men should restore the +wholesomeness of the soil by cultivation, and purify the air by +fires."--Salvagnoli, Memorie, p. 111.] In accordance with these views, +settlers were invited from various parts of Italy, from Greece, and, +after the accession of the Lorraine princes, from that country also, and +colonized in the Maremma. To strangers coming from soils and skies so +unlike those of the Tuscan marshes, the climate was more fatal than to +the inhabitants of the neighboring districts, whose constitutions had +become in some degree inured to the local influences, or who at least +knew better how to guard against them. The consequence very naturally +was that the experiment totally failed to produce the desired effects, +and was attended with a great sacrifice of life and a heavy loss to the +treasury of the state. + +The territory known as the Tuscan Maremma, ora maritime, or Maremme--for +the plural form is most generally used--lies upon and near the western +coast of Tuscany, and comprises about 1,900 square miles English, of +which 500 square miles, or 320,000 acres, are plain and marsh including +45,500 acres of water surface, and about 290,000 acres are forest. One +of the mountain peaks, that of Mount Amiata, rises to the height of +6,280 feet. The mountains of the Maremma are healthy, the lower hills +much less so, as the malaria is felt at some points at the height of +1,000 feet, and the plains, with the exception of a few localities +favorably situated on the seacoast, are in a high degree pestilential. +The fixed population is about 80,000, of whom one-sixth live on the +plains in the winter and about one-tenth in the summer. Nine or ten +thousand laborers come down from the mountains of the Maremma and the +neighboring provinces into the plain, during the latter season, to +cultivate and gather the crops. + +Out of this small number of inhabitants and strangers, 35,619 were ill +enough to require medical treatment between the 1st of June, 1840, and +the 1st of June, 1841, and more than one-half the cases were of +intermittent, malignant, gastric, or catarrhal fever. Very few +agricultural laborers escaped fever, though the disease did not always +manifest itself until they had returned to the mountains. In the +province of Grosseto, which embraces nearly the whole of the Maremma, +the annual mortality was 3.92 per cent., the average duration of life +but 23.18 years, and 75 per cent. of the deaths were among persons +engaged in agriculture. + +The filling up of the low grounds and the partial separation of the +waters of the sea and the land, which had been in progress since the +year 1827, now began to show very decided effects upon the sanitary +condition of the population. In the year ending June 1st, 1842, the +number of the sick was reduced by more than 2,000, and the cases of +fever by more than 4,000. The next year the cases of fever fell to +10,500, and in that ending June 1st, 1844, to 9,200. The political +events of 1848, and the preceding and following years, occasioned the +suspension of the works of improvement in the Maremma, but they were +resumed after the revolution of 1859. I have spoken with some detail of +the improvements in the Tuscan Maremma, because of their great relative +importance, and because their history is well known; but like operations +have been executed in the territory of Pisa and upon the coast of the +duchy of Lucca. In the latter case they were confined principally to +prevention of the intermixing of fresh water with that of the sea. In +1741 sluices or lock-gates were constructed for this purpose, and the +following year the fevers, which had been destructive to the coast +population for a long time previous, disappeared altogether. In 1768 and +1769, the works having fallen to decay, the fevers returned in a very +malignant form, but the rebuilding of the gates again restored the +healthfulness of the shore. Similar facts recurred in 1784 and 1785, and +again from 1804 to 1821. This long and repeated experience has at last +impressed upon the people the necessity of vigilant attention to the +sluices, which are now kept in constant repair. The health of the coast +is uninterrupted, and Viareggio, the capital town of the district, is +now much frequented for its sea-baths and its general salubrity, at a +season when formerly it was justly shunned as the abode of disease and +death. [Footnote: Giorgini, Sur les causes de l'Insalubrite de l'air +dans le voisinage des marais, etc., lue a l'Academie des Sciences a +Paris, le 12 Juillet, 1825. Reprinted in Salvagnoli, Rapporto, etc., +appendice, p. 5, et seqq.] + + +Improvements in the Val di Chiana. + +For twenty miles or more after the remotest headwaters of the Arno have +united to form a considerable stream, this river flows south-eastwards +to the vicinity of Arezzo. It here sweeps round to the north-west, and +follows that course to near its junction with the Sieve, a few miles +above Florence, from which point its general direction is westward to +the sea. From the bend at Arezzo, a depression called the Val di Chiana +runs south-eastwards until it strikes into the valley of the Paglia, a +tributary of the Tiber, and thus connects the basin of the latter river +with that of the Arno. In the Middle Ages, and down to the eighteenth +century, the Val di Chiana was often overflowed and devastated by the +torrents which poured down from the highlands, transporting great +quantities of slime with their currents, stagnating upon its surface, +and gradually converting it into a marshy and unhealthy district, which +was at last very greatly reduced in population and productiveness. It +had, in fact, become so desolate that even the swallow had deserted +it. [Footnote: This curious fact is thus stated in the preface to +Fossombroni (Memorie sopra la Val di Chiana, edition of 1835, p. xiii.), +from which also I borrow most of the data hereafter given with respect +to that valley: "It is perhaps not universally known, that the swallows, +which come from the north [south] to spend the summer in our climate, do +not frequent marshy districts with a malarious atmosphere. A proof of +the restoration of salubrity in the Val di Chiana is furnished by these +aerial visitors, which had never before been seen in those low grounds, +but which have appeared within a few years at Forano and other points +similarly situated." + +Is the air of swamps destructive to the swallows, or is their absence in +such localities merely due to the want of human habitations, near which +this half-domestic bird loves to breed, perhaps because the house-fly +and other insects which follow man are found only in the vicinity of his +dwellings In almoust all European countries the swallow is protected, by +popular opinion or superstition, from the persecution to which almost +all other birds are subject. It is possible that this respect for the +swallow is founded upon ancient observation of the fact just stated on +the authority of Fossombroni. Ignorance mistakes the effect for the +cause, and the absence of this bird may have been supposed to be the +occasion, not the consequence, of the unhealthiness of particular +localities. This opinion once adopted, the swallow would become a sacred +bird, and in process of time fables and legends would be invented to +give additional sanction to the prejudices which protected it. The +Romans considered the swallow as consecrated to the Penates, or +household gods, and according to Peretti (Le Serate del Villaggio, p. +168) the Lombard peasantry think it a sin to kill them, because they are +le gallinelle del Signore, the chickens of the Lord.] + +The bed of the Arno near Arezzo and that of the Paglia at the southern +extremity of the Val di Chiana did not differ much in level. The general +inclination of the valley was therefore small; it does not appear to +have ever been divided into opposite slopes by a true watershed, and the +position of the summit seems to have shifted according to the varying +amount and place of deposit of the sediment brought down by the lateral +streams which emptied into it. The length of its principal channel of +drainage, and even the direction of its flow at any given point, were +therefore fluctuating. Hence, much difference of opinion was entertained +at different times with regard to the normal course of this stream, and, +consequently, to the question whether it was to be regarded as properly +an affluent of the Tiber or of the Arno. + +The bed of the latter river at the bend has been eroded to the depth of +thirty or forty feet, and that, apparently, at no very remote +period. [Footnote: Able geologists infer from recent investigations, +that, although the Arno flowed to the south within the pliocenic period, +the direction of its course was changed at an earlier epoch than that +supposed in the text.] If it were elevated to what was evidently +original height, the current of the Arno would be so much above that of +the Paglia as to allow of a regular flow from its channel to the latter +stream, through the Val di Chiana, provided the bed of the valley had +remained at the level which excavations prove it to have had a few +centuries ago, before it was raised by the deposits I have mentioned. +These facts, together with the testimony of ancient geographers which +scarcely admits of any other explanation, are thought to prove that all +the waters of the Upper Arno were originally discharged through the Val +di Chiana into the Tiber, and that a part of them still continued to +flow, at least occasionally, in that direction down to the days of the +Roman empire, and perhaps for some time later. The depression of the bed +of the Arno, and the raising of that of the valley by the deposits of +the lateral torrents, finally cut off the branch of the river which had +flowed to the Tiber, and all its waters were turned into its present +channel, though the drainage of the principal part of the Val di Chiana +appears to have been in a south-eastwardly direction until within a +comparatively recent period. + +In the sixteenth century the elevation of the bed of the valley had +become so considerable, that in 1551, at a point about ten miles south +of the Arno, it was found to be not less than one hundred and thirty +feet above that river; then followed a level of ten miles, and then a +continuous descent to the Paglia. Along the level portion of the valley +was a boatable channel, and lakes, sometimes a mile or even two miles in +breadth, had formed at various points farther south. At this period the +drainage of the summit level might easily have been determined in either +direction, and the opposite descents of the valley made to culminate at +the north or at the south end of the level. In the former case, the +watershed would have been ten miles south of the Arno; in the latter, +twenty miles, and the division of the valley into two opposite slopes +would have been not very unequal. + +Various schemes were suggested at this time for drawing off the stagnant +waters, as well as for the future regular drainage of the valley, and +small operations for those purposes were undertaken with partial +success; but it was feared that the discharge of the accumulated waters +into the Tiber would produce a dangerous inundation, while the diversion +of the drainage into the Arno would increase the violence of the floods +to which that river was very subject, and no decisive steps were taken. +In 1606 an engineer, whose name has not been preserved, proposed, as the +only possible method of improvement, the piercing of a tunnel through +the hills bounding the valley on the west to convey its waters to the +Ombrone, but the expense and other objections prevented the adoption of +this scheme. [Footnote: Morozzi, Dello stato dell' Arno, ii., pp. 39, +40.] The fears of the Roman Government for the safety of the basin of +the Tiber had induced it to construct embankments across the portion of +the valley lying within its territory, and these obstructions, though +not specifically intended for that purpose, naturally promoted the +deposit of sediment and the elevation of the bed of the valley in their +neighborhood. The effect of this measure and of the continued +spontaneous action of the torrents was, that the northern slope, which +in 1551 had commenced at the distance of ten miles from the Arno, was +found in 1605 to begin nearly thirty miles south of that river, and in +1645 it had been removed about six miles farther in the same direction. +[Footnote: Morozzi, Dello stato, etc., dell' Arno, ii., pp. 39, 40.] + +In the seventeenth century the Tuscan and Papal Governments consulted +Galileo, Torricelli, Castelli, Cassini, Viviani, and other distinguished +philosophers and engineers, on the possibility of reclaiming the valley +by a regular artificial drainage. Most of these eminent physicists were +of opinion that the measure was impracticable, though not altogether for +the same reasons; but they seem to have agreed in thinking that the +opening of such channels, in either direction, as would give the current +a flow sufficiently rapid to drain the lands properly, would dangerously +augment the inundations of the river--whether the Tiber or the +Arno--into which the waters should be turned. The general improvement of +the valley was now for a long time abandoned, and the waters were +allowed to spread and stagnate until carried off by partial drainage, +infiltration, and evaporation. Torricelli had contended that the slope +of a large part of the valley was too small to allow it to be drained by +ordinary methods, and that no practicable depth and width of canal would +suffice for that purpose. It could be laid dry, he thought, only by +converting its surface into an inclined plane, and he suggested that +this might be accomplished by controlling the flow of the numerous +torrents which pour into it, so as to force them to deposit their +sediment at the pleasure of the engineer, and, consequently, to elevate +the level of the area over which it should be spread. [Footnote: +Torricelli thus expressed himself on this point: "If we content +ourselves with what nature has made practicable to human industry, we +shall endeavor to control, as far as possible, the outlets of these +streams, which, by raising the bed of the valley with their deposits, +will realize the fable of the Tagus and the Pactolus, and truly roll +golden sands for him that is wise enough to avail himself of +them."--Fossombroni, Memoris sopra la Val di China, p. 219.] This plan +did not meet with immediate general acceptance, but it was soon adopted +for local purposes at some points in the southern part of the valley, +and it gradually grew in public favor and was extended in application +until its final triumph a hundred years later. + +In spite of these encouraging successes, however, the fear of danger to +the valley of the Arno and the Tiber, and the difficulty of an agreement +between Tuscany and Rome--the boundary between which states crossed the +Val di Chiana not far from the half-way point between the two +rivers--and of reconciling other conflicting interests, prevented the +resumption of the projects for the general drainage of the valley until +after the middle of the eighteenth century. In the meantime the science +of hydraulics had become better understood, and the establishment of the +natural law according to which the velocity of a current of water, and +of course the proportional quantity discharged by it in a given time, +are increased by increasing its mass, had diminished if not dissipated +the fear of exposing the banks of the Arno to greater danger from +inundations by draining the Val di China into it. The suggestion of +Torricelli was finally adopted as the basis of a comprehensive system of +improvement, and it was decided to continue and extend the inversion of +the original flow of the waters, and to turn them into the Arno from a +point as far to the south as should be found practicable. The conduct of +the works was committed to a succession of able engineers who, for a +long series of years, were under the general direction of the celebrated +philosopher and statesman Fossombroni, and the success has fully +justified the expectations of the most sanguine advocates of the scheme. +The plan of improvement embraced two branches: the one, the removal of +obstructions in the bed of the Arno, and, consequently, the further +depression of the channel of that river, in certain places, with the +view of increasing the rapidity of its current; the other, the gradual +filling up of the ponds and swamps, and raising of the lower grounds of +the Val di Chiana, by directing to convenient points the flow of the +streams which pour down into it, and there confining their waters by +temporary dams until the sediment was deposited where it was needed. The +economical result of these operations has been, that in 1835 an area of +more than four hundred and fifty square miles of pond, marsh, and damp, +sickly low grounds had been converted into fertile, healthy, and +well-drained soil, and, consequently, that so much territory has been +added to the agricultural domain of Tuscany. But in our present view of +the subject, the geographical revolution which has been accomplished is +still more interesting. The climatic influence of the elevation and +draining of the soil must have been considerable, though I do not know +that an increase or a diminution of the mean temperature or +precipitation in the valley has been established by meteorological +observation. There is, however, in the improvement of the sanitary +condition of the Val di Chiana, which was formerly extremely unhealthy, +satisfactory proof of a beneficial climatic change. The fevers, which +not only decimated the population of the low grounds but infested the +adjacent hills, have ceased their ravages, and are now not more frequent +than in other parts of Tuscany. The strictly topographical effect of the +operations in question, besides the conversion of marsh into dry +surface, has been the inversion of the inclination of the valley for a +distance of thirty-five miles, so that this great plain which, within a +comparatively short period, sloped and drained its waters to the south, +now inclines and sends its drainage to the north. The reversal of the +currents of the valley has added to the Arno a new tributary equal to +the largest of its former affluents, and a most important circumstance +connected with this latter fact is, that the increase of the volume of +its waters has accelerated their velocity in a still greater proportion, +and, instead of augmenting the danger from its inundations, has almost +wholly obviated that source of apprehension. [Footnote: Arrian observes +that at the junction of the Hydaspes and the Acesines, both of which are +described as wide streams, "one very narrow river is formed of two +confluents, and its current is very swift."--Arrian, Alex. Anab., vi., +4. + +A like example is observed in the Anapus near Syracuse, which, below the +junction of its two branches, is narrower, though swifter than either of +them, and such cases are by no means unfrequent. The immediate effect of +the confluence of two rivers upon the current below depends upon local +circumstances, and especially upon the angle of incidence. If the two +nearly coincide in direction, so as to include a small angle, the join +current will have a greater velocity than the slower confluent, perhaps +even than either of them. If the two rivers run in transverse, still +more if they flow in more or less opposite, directions, the velocity of +the principal branch will be retarded both above and below the junction, +and at high water it may even set back the current of the affluent. + +On the other hand, the diversion of a considerable branch from a river +retards its velocity below the point of separation, and here a deposit +of earth in its channel immediately begins, which has a tendency to turn +the whole stream into the new bed. "Theory and the authority of all +hydrographical writers combine to show that the channels of rivers +undergo an elevation of bed below a canal of diversion."--Letter of +Fossombroni, in Salvagnoli, Raccolta di Documenti, p. 32. See the early +authorities and discussions on the principle stated in the text, in +Frisi, Del modo di regolare i Fiumi e i Torrenti, libro iii., capit. i., +and Mongotti, Idraulica, ii., pp. 88 et seqq., and see p. 498, note, +ante. + +In my account of these improvements I have chiefly followed Fossombroni, +under whose direction they were principally executed. Many of +Fossombroni's statements and opinions have been controverted, and in +comparatively unimportant particulars they have been shown to be +erroneous.--See Lombardini, Guida allo studio dell' Idrologia, cap. +xviii., and same author, Esame degli Studi sul Tevere, Section 33.] + +Between the beginning of the fifteenth century and the year 1761, +thirty-one destructive floods of the Arno are recorded; between 1761, +when the principal streams of the Val di Chiana were diverted into that +river, and 1835, not one. [Footnote: Fossombroni, Memorie +Idraulico-storiche, Introduzione, p. xvi. Between the years 1700 and +1799 the chroniclers record seventeen floods of the Arno, and twenty +between 1800 and 1870, but none of these were of a properly destructive +character except those in 1844, 1864, and 1870, and the ravages of this +latter were chiefly confined to Pisa, and were occasioned by the +bursting of a dike or wall. They are all three generally ascribed to +extraordinary, if not unprecedented, rains and snows, but many inquirers +attribute them to the felling of the woods in the valleys of the upper +tributaries of the Arno since 1835. See a paper by Griffini, in the +Italia Nuova, 18 Marzo, 1871.] + + +Results of Operations. + +It is now a hundred years since the commencement of the improvements in +the Val di Chiana, and those of the Maremma have been in more or less +continued operation for above a generation. They have, as we have seen, +produced important geographical changes in the surface of the earth and +in the flow of considerable rivers, and their effects have been not less +conspicuous in preventing other changes, of a more or less deleterious +character, which would infallibly have taken place if they had not been +arrested by the improvements in question. + +The sediment washed into the marshes of the Maremma is not less than +12,000,000 cubic yards per annum. The escape of this quantity into the +sea, which, is now almost wholly prevented, would be sufficient to +advance the coast-line fourteen yards per year, for a distance of forty +miles, computing the mean depth of the sea near the shore at twelve +yards. It is true that in this case, as well as in that of other rivers, +the sedimentary matter would not be distributed equally along the shore, +and much of it would be carried out into deep water, or perhaps +transported by the currents to distant coasts. The immediate effects of +the deposit in the sea, therefore, would not be so palpable as they +appear in this numerical form, but they would be equally certain, and +would infallibly manifest themselves, first, perhaps, at some remote +point, and afterwards more energetically at or near the outlets of the +rivers which produced them. The elevation of the bottom of the sea would +diminish the inclination of the beds of the rivers discharging +themselves into it on that coast, and of course their tendency to +overflow their banks and extend still further the domain of the marshes +which border them would be increased in proportion. + +It has been already stated that, in order to prevent the overflow of the +valley of the Tiber by freely draining the Val di Chiana into it, the +Papal authorities, long before the commencement of the Tuscan works, +constructed strong barriers near the southern end of the valley, which +detained the waters of the wet season until they could be gradually +drawn off into the Paglia. They consequently deposited most of their +sediment in the Val di Chiana and carried down comparatively little +earth to the Tiber. The lateral streams contributing the largest +quantities of sedimentary matter to the Val di Chiana originally flowed +into that valley near its northern end; and the change of their channels +and outlets in a southern direction, so as to raise that part of the +valley by their deposits and thereby reverse its drainage, was one of +the principal steps in the process of improvement. + +We have seen that the north end of the Val di Chiana near the Arno had +been raised by spontaneous deposit of sediment to such a height as to +interpose a sufficient obstacle to all flow in that direction. If, then, +the Roman dam had not been erected, or the works of the Tuscan +Government undertaken, the whole of the earth, which has been arrested +by those works and employed to raise the bed and reverse the declivity +of the valley, would have been carried down to the Tiber and thence into +the sea. The deposit thus created would, of course, have contributed to +increase the advance of the shore at the mouth of that river, which has +long been going on at the rate of three metres and nine-tenths (twelve +feet and nine inches) per annum. [Footnote: See the careful estimates of +Rozet, Moyens de forcer les Torrents, etc., pp. 42, 44.] It is evident +that a quantity of earth, sufficient to effect the immense changes I +have described in a wide valley more than thirty miles long, if +deposited at the outlet of the Tiber, would have very considerably +modified the outline of the coast, and have exerted no unimportant +influence on the flow of that river, by raising its point of discharge +and lengthening its channel. + +The Coast of the Netherlands. It has been shown in a former section that +the dikes of the Netherlands and the adjacent states have protected a +considerable extent of coast from the encroachments of the sea, an have +won a large tract of cultivable land from the dominion of the ocean +waters. The immense results obtained from the operations of the Tuscan +engineers in the Val di Chiana, and the Maremma have suggested the +question, whether a different method of accomplishing these objects +might not have been adopted with advantage. It has been argued, as in +the case of the Po, that a system of transverse inland dikes and canals, +upon the principle of those which have been so successfully employed in +the Val di Chiana and in Egypt, might have elevated the low grounds +above the ocean tides, by spreading over them the sediment brought down +by the Rhine, the Maes, and the Scheld. If this process had been +introduced in the Middle Ages, and constantly pursued to our times, the +superficial and coast geography, as well as the hydrography of the +countries in question, would undoubtedly have presented an aspect very +different from their present condition; and by combining the process +with a system of maritime dikes, which would have been necessary, both +to resist the advance of the sea and to retain the slime deposited by +river overflows, it is, indeed, possible that the territory of those +states would have been as extensive as it now is, and, at the same time, +somewhat elevated above its natural level. + +The argument in favor of that method rests on the assumption that all +the sea-washed earth, which the tides have let fall upon the shallow +coast of the Netherlands, has been brought down by the rivers which +empty upon those shores, and could have been secured by allowing those +rivers to spread over the flats and deposit their sediment in +still-water pools formed by cross-dikes like those of Egypt. + +But we are ignorant of the proportions in which the marine deposits that +form the soil of the polders have been derived from materials brought +down by these rivers, or from other more remote sources. Much of the +river slime has, no doubt, been transported by marine currents quite +beyond the reach of returning streams, and it is uncertain how far this +loss has been balanced by earth washed by the sea from distant shores +and let fall on the coasts of the Netherlands and other neighboring +countries. + +We know little or nothing of the quantity of solid matter brought down +by the rivers of Western Europe in early ages, but, as the banks of +those rivers are now generally better secured against wash and abrasion +than in former centuries, the sediment transported by them must be less +than at periods nearer the removal of the primitive forests of their +valleys, though certainly greater than it was before those forests were +felled. Kladen informs us that the sedimentary matter transported to the +sea by the Rhine would amount to a cubic geographical mile in five +thousand years. [Footnote: Erdhunde, vol. i, p. 384. The Mississippi--a +river "undercharged with sediment"--with a mean discharge of about ten +times that of the Rhine, deposits a cubic geographical mile in +thirty-three years.] The proportion of this suspended matter which, with +our present means, could be arrested and precipitated upon the ground, +is almost infinitesimal, for only the surface-water, which carries much +less sediment than that at the bottom of the channel, would flow over +the banks, and as the movement of this water, if not checked altogether, +would be greatly retarded by the proposed cross-dikes, the quantity of +solid matter which would be conveyed to a given portion of land during a +single inundation would be extremely small. Inundations of the Rhine +occur but once or twice a year, and high water continues but a few days, +or even hours; the flood-tide of the sea happens seven hundred times in +a year, and at the turn of the tide the water is brought to almost +absolute rest. Hence, small as is the proportion of suspended matter in +the tide-water, the deposit probably amounts to far more in a year than +would be let fall upon the same area by the Rhine. + +This argument, except as to the comparison between river and tide water, +applies to the Mississippi, the Po, and most other great rivers. Hence, +until that distant day when man shall devise means of extracting from +rivers at flood, the whole volume of their suspended material and of +depositing it at the same time on their banks, the system of cross-dikes +and COLMATAGE must be limited to torrential streams transporting large +proportions of sediment, and to the rivers of hot countries, like the +Nile, where the saturation of the soil with water, and the securing of a +supply for irrigation afterwards, are the main objects, while raising +the level of the banks is a secondary consideration. + + + +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. + + + + +Origin of Sand. + +Sand, which is found in beds or strata at the bottom of the sea or in +the channels of rivers, as well as in extensive deposits upon or beneath +the surface of the dry land, appears to consist essentially of the +detritus of rocks. It is not always by any means clear through what +agency the solid rock has been reduced to a granular condition; for +there are beds of quartzose sand, where the sharp, angular shape of the +particles renders it highly improbable that they have been formed by +gradual abrasion and attrition, and where the supposition of a crushing +mechanical force seems equally inadmissible. In common sand, the quartz +grains are the most numerous; but this is not a proof that the rocks +from which these particles were derived were wholly, or even chiefly, +quartzose in character; for, in many composite rocks, as, for example, +in the granitic group, the mica, feldspar, and hornblende are more +easily decomposed by chemical action, or disintegrated, comminuted, and +reduced to an impalpable state by mechanical force, than the quartz. In +the destruction of such rocks, therefore, the quartz would survive the +other ingredients, and remain unmixed, when they had been decomposed and +recomposed into new mineralogical or chemical combinations, or been +ground to slime and washed away by water currents. + +The greater or less specific gravity of the different constituents of +rock doubtless aids in separating them into distinct masses when once +disintegrated, though there are veined and stratified beds of sand where +the difference between the upper and lower layers, in this respect, is +too slight to be supposed capable of effecting a complete +separation. [Footnote: In the curiously variegated sandstone of Arabia +Petraea--which is certainly a reaggregation of loose sand derived from +disaggregation of older rocks--the continuous veins frequently differ +very widely in color, but not sensibly in specific gravity or in +texture; and the singular way in which they are now alternated, now +confusedly intermixed, must be explained otherwise than by the weight of +the respective grains which compose them. They seem, in fact, to have +been let fall by water in violent ebullition or tumultuous mechanical +agitation, or deposited by a succession of sudden aquatic or aerial +currents flowing in different directions and charged with differently +colored matter.] In cases where rock has been reduced to sandy fragments +by heat, or by obscure chemical and other molecular forces, the +sand-beds may remain undisturbed, and represent, in the series of +geological strata, the solid formations from which they were derived. +The large masses of sand not found in place have been transported and +accumulated by water or by wind, the former being generally considered +the most important of these agencies; for the extensive deposits of the +Sahara, of the Arabian peninsulas, of the Llano Estacado and other North +and South American deserts, of the deserts of Persia, and of that of +Gobi, are supposed to have been swept together or distributed by marine +currents, and to have been elevated above the ocean by the same means as +other upheaved strata. Meteoric and mechanical influences are still +active in the reduction of rocks to a fragmentary state; [Footnote: A +good account of the agencies now operative in the reduction of rock to +sand will be found in Winkler, Zand en Duinen, Dockarm, 1865, pp. 4-20. +I take this occasion to acknowledge my obligations to this author for +assuming the responsibility of many of the errors I may have committed +in this chapter, by translating a large part of it from a former edition +of the present work and publishing it as his own.] but the quantity of +sand now transported to the sea seems to be comparatively +inconsiderable, because--not to speak of the absence of diluvial +action--the number of torrents emptying directly into the sea is much +less than it was at earlier periods. The formation of alluvial plains in +maritime bays, by the sedimentary matter brought down from the +mountains, has lengthened the flow of such streams and converted them +very generally into rivers, or rather affluents of rivers of later +geographical origin than themselves. The filling up of the estuaries has +so reduced the slope of all large and many small rivers, and, +consequently, so checked the current of what the Germans call their +Unterlauf, or lower course, that they are much less able to transport +heavy material than at earlier epochs. The slime deposited by rivers at +their junction with the sea, is usually found to be composed of material +too finely ground and too light to be denominated sand, and it can be +abundantly shown that the sand-banks at the outlet of most large streams +are of tidal, not of fluviatile, accumulation, or, in lakes and tideless +seas, a result of the concurrent action of waves and of wind. Large +deposits of sand, therefore, must in general be considered as of +ancient, not of recent formation, and many eminent geologists ascribe +them to diluvial action. Staring has discussed this question very fully, +with special reference to the sands of the North Sea, the Zuiderzee, and +the bays and channels of the Dutch coast. [Footnote: De Bodem van +Nederland, i., pp. 243, 246-377, et seqq. See also the arguments of +Bremontier as to the origin of the dune-sands of Gascony, Annales des +Ponts et Chaussees, 1833, 1er semestre, pp. 158, 161. Bremontier +estimates the sand anually thrown up on that coast at five cubic toises +and two feet to the running toise (ubi supra, p. 162), or rather more +than two hundred and twenty cubic feet to the running foot. Laval, upon +observations continued through seven years, found the quantity to be +twenty-five metres per running metre, which is equal to two hundred and +sixty-eight cubic feet to the running foot.--Annales des Ponts et +Chaussees, 1842, 2me semestre, p. 229. These computations make the +proportion of sand deposited on the coast of Gascony three or four times +as great as that observed by Andresen on the shores of Jutland. Laval +estimates the total quantity of sand annually thrown up on the coast of +Gascony at 6,000,000 cubic metres, or more than 7,800,000 cubic yards.] +His general conclusion is, that the rivers of the Netherlands "move sand +only by a very slow displacement of sand-banks, and do not carry it with +them as a suspended or floating material." The sands of the German Ocean +he holds to be a product of the "great North German drift," deposited +where they now lie before the commencement of the present geological +period, and he maintains similar opinions with regard to the sands +thrown up by the Mediterranean at the mouths of the Nile and on the +Barbary coast. [Footnote: De Bodem van Nederland, i., p. 339.] + + +Sand now carried to the Sea. + +There are, however, cases where mountain streams still bear to the sea +perhaps relatively small, but certainly absolutely large, amounts of +disintegrated rock. [Footnote: The conditions favorable to the +production of sand from disintegrated rock, by causes now in action, are +perhaps nowhere more perfectly realized than in the Sinaitic Peninsula. +The mountains are steep and lofty, unprotected by vegetation or even by +a coating of earth, and the rocks which compose them are in a shattered +and fragmentary condition. They are furrowed by deep and precipitous +ravines, with beds sufficiently inclined for the rapid flow of water, +and generally without basins in which the larger blocks of stone rolled +by the torrents can be dropped and left in repose; there are severe +frosts and much snow on the higher summits and ridges, and the winter +rains are abundant and heavy. The mountains are principally of igneous +formation, but many of the less elevated peaks are capped with +sandstone, and on the eastern slope of the peninsula you may sometimes +see, at a single glance, several lofty pyramids of granite, separated by +considerable intervals, and all surmounted by horizontally stratified +deposits of sandstone often only a few yards square, which correspond to +each other in height, are evidently contemporaneous in origin, and were +once connected in continuous beds. The degradation of the rock on which +this formation rests is constantly bringing down masses of it, and +mingling them with the basaltic, porphyritic, granitic, and calcareous +fragments which the torrents carry down to the valleys, and, through +them, in a state of greater or less disintegration, to the sea. The +quantity of sand annually washed into the Red Sea by the larger torrents +of the Lesser Peninsula, is probably at least equal to that contributed +to the ocean by any streams draining basins of no greater extent. +Absolutely considered, then, the mass may be said to be large, but it is +apparently very small as compared with the sand thrown up by the German +Ocean and the Atlantic on the coasts of Denmark and of France. There +are, indeed, in Arabia Petraea, many torrents with very short courses, +for the sea-waves in many parts of the peninsular coast wash the base of +the mountains. In these cases, the debris of the rocks do not reach the +sea in a sufficiently comminuted condition to be entitled to the +appellation of sand, or even in the form of well-rounded pebbles. The +fragments retain their annular shape, and, at some points on the coast, +they become cemented together by lime or other binding substances held +in solution or mechanical suspension in the sea-water, and are so +rapidly converted into a singularly heterogeneous conglomerate, that one +deposit seems to be consolidated into a breccia before the next winter's +torrents cover it with another. + +In the northern part of the peninsula there are extensive deposits of +sand intermingled with agate pebbles and petrified wood, but these are +evidently neither derived from the Sinaitic group, nor products of local +causes known to be now in action. + +I may here notice the often repeated but mistaken assertion, that the +petrified wood of the Western Arabian desert consists wholly of the +stems of palms, or at least of endogenous vegetables. This is an error. +I have myself picked up in that desert, within the space of a very few +square yards, fragments apparently of fossil palms, and of at least two +petrified trees distinctly marked as of exogenous growth both by annular +structure and by knots. In ligneous character, one of these almost +precisely resembles the grain of the extant beech, and this specimen was +worm-eaten before it was converted into silex.] + +The quantity of sand and gravel carried into the Mediterranean by the +torrents of the Maritime Alps, the Ligurian Apennines, the islands of +Corsica, Sardinia, and Sicily, and the mountains of Calabria, is +apparently great. In mere mass, it is possible, if not probable, that as +much rocky material, more or less comminuted, is contributed to the +basin of the Mediterranean by Europe, even excluding the shores of the +Adriatic and the Euxine, as is washed up from it upon the coasts of +Northern Africa and Syria. A great part of this material is thrown out +again by the waves on the European shores of that sea. The harbors of +Luni, Albenga, San Remo, and Savona west of Genoa, and of Porto Fino on +the other side, are filling up, and the coast near Carrara and Massa is +said to have advanced upon the sea to a distance of 475 feet in +thirty-three years. [Footnote: Bottger, Das Mittelmeer, p. 128.] Besides +this, we have no evidence of the existence of deep-water currents in the +Mediterranean, extensive enough and strong enough to transport quartzose +sand across the sea. It may be added that much of the rock from which +the torrent sands of Southern Europe are derived contains little quartz, +and hence the general character of these sands is such that they must be +decomposed or ground down to an impalpable slime, long before they could +be swept over to the African shore. + + +Sands of Northern Africa. + +The torrents of Europe, then, do not at present furnish the material +which composes the beach sands of Northern Africa, and it is equally +certain that those sands are not brought down by the rivers of the +latter continent. They belong to a remote geological period, and have +been accumulated by causes which we cannot at present assign. The wind +does not stir water to great depths with sufficient force to disturb the +bottom, [Footnote: The testimony of divers and of other observers on +this point is conflicting, as might be expected from the infinite +variety of conditions by which the movement of water is affected. It is +generally believed that the action of the wind upon the water is not +perceptible at greater depths than from fifteen feet in ordinary to +eighty or ninety in extreme cases; but these estimates are probably very +considerably below the truth. Andresen quotes Bremontier as stating that +the movement of the waves sometimes extends to the depth of five hundred +feet, and he adds that others think it may reach to six or even seven +hundred feet below the surface.--Andresen, Om Klitformationen, p. 20. + +Many physicists now suppose that the undulations of great bodies of +water reach even deeper. But a movement of undulation is not necessarily +a movement of translation, and besides, there is very frequently an +undertow, which tends to carry suspended bodies out to sea as powerfully +as the superficial waves to throw them on shore. Sand-banks sometimes +recede from the coast, instead of rolling towards it. Reclus informs us +that the Mauvaise, a sand-bank near the Point de Grave, on the Atlantic +coast of France, has moved five miles to the west in less than a +century.--Revue des Deux Mondes for December, 1862, p. 905. + +The action of currents may, in some cases, have been confounded with +that of the waves. Sea-currents, strong enough, possibly, to transport +sand for some distance, flow far below the surface in parts of the open +ocean, and in narrow straits they have great force and velocity. The +divers employed at Constantinople in 1853 found in the Bosphorus, at the +depth of twenty-five fathoms and at a point much exposed to the wash +from Galata and Pera, a number of bronze guns supposed to have belonged +to a ship-of-war blown up about a hundred and fifty years before. These +guns were not covered by sand or slime, though a crust of earthy matter, +an inch in thickness, adhered to their upper surfaces, and the bottom of +the strait appeared to be wholly free from sediment. The current was so +powerful at this depth that the divers were hardly able to stand, and a +keg of nails, purposely dropped into the water, in order that its +movements might serve as a guide in the search for a bag of coin +accidentally lost overboard from a ship in the harbor, was rolled by the +stream several hundred yards before it stopped.] and the sand thrown +upon the coast in question must be derived from a narrow belt of sea. It +must hence, in time, become exhausted, and the formation of new +sand-banks and dunes upon the southern shores of the Mediterranean will +cease at last for want of material. [Footnote: Few seas have thrown up +so much sand as the shallow German Ocean; but there is some reason to +think that the amount of this material now cast upon its northern shores +is less than at some former periods, though no extensive series of +observations on this subject has been recorded. On the Spit of Agger, at +the present outlet of the Liimfjord, Andresen found the quantity during +ten years, on a beach about five hundred and seventy feet broad, equal +to an annual deposit of an inch and a half over the whole surface.--Om +Klitformationen, p. 56. This gives seventy-one and a quarter cubic feet +to the running foot--a quantity certainly much smaller than that cast up +by the same sea on the shores of the Dano-German duchies and of Holland, +and, as we have seen, scarcely one-fourth of that deposited by the +Atlantic on the coast of Gascony.] + +But even in the cases where the accumulations of sand in extensive +deserts appear to be of marine formation, or rather aggregation, and to +have been brought to their present position by upheaval, they are not +wholly composed of material collected or distributed by the currents of +the sea; for, in all such regions, they continue to receive some small +contributions from the disintegration of the rocks which underlie, or +crop out through, the superficial deposits. [Footnote: See, on this +subject, an article in Aus der Natur, vol. xxx., p. 590. + +The Florentine Frescobaldi, who visited the Sinaitic peninsula five +hundred years ago, observed the powerful action of the solar heat in the +disintegration of the desert rocks. "This place," says he, "was a ridge +of rocks burnt to powder by the sun, and this powder is blown away from +the rock by the wind and is the sand of the desert; and there be many +hills which are pure bare rock, and when the sun parcheth them, the wind +carries off the dust, and other sand is there none in that +land,"--Viaggio, pp. 69, 70. In Arabia Petraea, when a wind, powerful +enough to scour down below the ordinary surface of the desert and lay +bare a fresh bed of stones, is followed by a sudden burst of sunshine, +the dark agate pebbles are often cracked and broken by the heat; and +this is the true explanation of the occurrence of the fragments in +situations where the action of fire is not probable. If the fragments +are small enough to be rolled by the winds, they are in time ground down +to sand and contribute to the stock of that material which covers the +face of the desert, though the sand thus formed is but an infinitesimal +proportion of the whole.] In some instances, too, as in Northern Africa, +additions are constantly made to the mass by the prevalence of +sea-winds, which transport, or, to speak more precisely, roll the finer +beach-sand to considerable distances into the interior. But this is a +very slow process, and the exaggerations of travellers have diffused a +vast deal of popular error on the subject. + + +Sands of Egypt. + +In the narrow valley of the Nile--which, above its bifurcation near +Cairo, is, throughout Egypt and Nubia, generally bounded by precipitous +cliffs--wherever a ravine or other considerable depression occurs in the +wall of rock, one sees what seems a stream of desert sand pouring down, +and common observers have hence concluded that the whole valley is in +danger of being buried under a stratum of infertile soil. The ancient +Egyptians apprehended this, and erected walls, often of unburnt brick, +across the outlet of gorges and lateral valleys, to check the flow of +the sand-streams. In later ages, these walls have mostly fallen into +decay, and no preventive measures against such encroachments are now +resorted to. But the extent of the mischief to the soil of Egypt, and +the future danger from this source, have been much overrated. The sand +on the borders of the Nile is neither elevated so high by the wind, nor +transported by that agency in so great masses, as is popularly supposed; +and of that which is actually lifted or rolled and finally deposited by +air-currents, a considerable proportion is either calcareous, and, +therefore, readily decomposable, or in the state of a very fine dust, +and so, in neither case, injurious to the soil. There are, indeed, both +in Africa and in Arabia, considerable tracts of fine, silicious sand, +which may be carried far by high winds, but these are exceptional cases, +and in general the progress of the desert sand is by a rolling motion +along the surface. [Footnote: Sand heaps, three and even six hundred +feet high, are indeed formed by the wind, but this is effected by +driving the particles up an inclined plane, not by lifting them. +Bremontier, speaking of the sand-hills on the western coast of France, +says: "The particles of sand composing them are not large enough to +resist wind of a certain force, nor small enough to be taken up by it, +like dust; they only roll along the surface from which they are +detached, and, though moving with great velocity, they rarely rise to a +greater height than three or four inches."--Memoirs sur les Dunes, +Annales des Ponts et Chaussecs, 1833, ler semestre, p, 148. + +Andresen says that a wind, having a velocity of forty feet per second, +is strong enough to raise particles of sand as high as the face and eyes +of a man, but that, in general, it rolls along the ground, and is +scarcely ever thrown more than to the height of a couple of yards from +the surface. Even in these cases, it is carried forward by a hopping, +not a continuous, motion; for a very narrow sheet or channel of water +stops the drift entirely, all the sand dropping into it until it is +filled up. + +Blake observes, Pacific Railroad Report, vol. v., p. 242, that the sand +of the Colorado desert does not rise high in the air, but bounds along +on the surface or only a few inches above it. + +The character of the motion of sand drifts is well illustrated by an +interesting fact not much noticed hitherto by travellers in the East. In +situations where the sand is driven through depressions in rock-beds, or +over deposits of silicious pebbles, the surface of the stone is worn and +smoothed much more effectually than it could be by running water, and I +have picked up, in such localities, rounded, irregularly broken +fragments of agate, which had received from the attrition of the sand as +fine a polish as could be given them by the wheel of the lapidary. + +Very interesting observations, by Blake, on the polishing of hard stones +by drifting sand will be found in the Pacific Railroad Report, vol. v., +pp. 92, 230, 231. The grinding and polishing power of sand has lately +received a new and most ingenious application in America. Jets of sand, +and even of small particles of softer substances, thrown with a certain +force, are found capable of cutting the hardest minerals and metals. A +block of corundum, some inches thick, has been bored through in a few +minutes by this process, and it promises to be highly useful in +glass-cutting and other similar operations.] So little is it lifted, and +so inconsiderable is the quantity yet remaining on the borders of Egypt, +that a wall four or five feet high suffices for centuries to check its +encroachments. This is obvious to the eye of every observer who prefers +the true to the marvellous; but the old-world fable of the overwhelming +of caravans by the fearful simoom--which even the Arabs no longer +repeat, if indeed they are the authors of it--is so thoroughly rooted in +the imagination of Christendom that most desert travellers, of the +tourist class, think they shall disappoint the readers of their journals +if they do not recount the particulars of their escape from being buried +alive by a sand-storm, and the popular demand for a "sensation" must be +gratified accordingly. [Footnote: Wilkinson says that, in much +experience in the most sandy parts of the Libyan desert, and much +inquiry of the best native sources, he never saw or heard of any +instance of danger to man or beast from the mere accumulation of sand +transported by the wind. Chesney's observations in Arabia, and the +testimony of the Bedouins he consulted, are to the same purpose. The +dangers of the simoom are of a different character, though they are +certainly aggravated by the blinding effects of the light particles of +dust and sand borne along by it, and by that of the inhalation of them +upon the respiration. ] + +Another circumstance is necessary to be considered in estimating the +danger to which the arable lands of Egypt are exposed. The prevailing +wind in the valley of the Nile and its borders is from the north, and it +may be said without exaggeration that the north wind blows for +three-quarters of the year. [Footnote: In the narrow valley of the Nile, +bounded as it is, above the Delta, by high cliffs, all air-currents from +the northern quarter become north winds, though of course varying in +partial direction, in conformity with the sinuosities of the valley. +Upon the desert plateau they incline westwards, and have already borne +into the valley the sands of the eastern banks, and driven those of the +western quite out of the Egyptian portion of the Nile basin.] The effect +of winds blowing up the valley is to drive the sands of the desert +plateau which border it, in a direction parallel with the axis of the +valley, not transversely to it; and if it ran in a straight line, the +north wind would carry no desert sand into it. There are, however, both +curves and angles in its course, and hence, wherever its direction +deviates from that of the wind, it might receive sand-drifts from the +desert plain through which it runs. But, in the course of ages, the +winds have, in a great measure, bared the projecting points of their +ancient deposits, and no great accumulations remain in situations from +which either a north or a south wind would carry them into the valley. +[Footnote: These considerations apply, with equal force, to the supposed +danger of the obstruction of the Suez Canal by the drifting of the +desert sands. The winds across the isthmus are almost uniformly from the +north, and they swept it comparatively clean of flying sands long ages +since. The traces of the ancient canal between the Red Sea and the Nile +are easily followed for a considerable distance from Suez. Had the +drifts upon the isthmus been as formidable as some have feared and +others have hoped, those traces would have been obliterated, and Lake +Timsah and the Bitter Lakes filled up, many centuries ago. The few +particles driven by the rare east and west winds towards the line of the +canal, will easily be arrested by plantations or other simple methods, +or removed by dredging. The real dangers and difficulties of this +magnificent enterprise--and they have been great--consisted in the +nature of the soil to be removed in order to form the line, and +especially in the constantly increasing accumulation of sea-sand at the +southern terminus by the tides of the Red Sea, and of sand and Nile +slime at the northern, by the action of the winds and currents. Both +seas are shallow for miles from the shore, and the excavation and +maintenance of deep channels, and of capacious harbors with easy and +secure entrances, in such localities, is doubtless one of the hardest +problems offered to modern engineers for practical solution. See post, +Geological Importance of Dunes, note.] + +The sand let fall in Egypt by the north wind is derived, not from the +desert, but from a very different source--the sea. Considerable +quantities of sand are thrown up by the Mediterranean, at and between +the mouths of the Nile, and indeed along almost the whole southern coast +of that sea, and drifted into the interior to distances varying +according to the force of the wind and the abundance and quality of the +material. The sand so transported contributes to the gradual elevation +of the Delta, and of the banks and bed of the river itself. But just in +proportion as the bed of the stream is elevated, the height of the water +in the annual inundations is increased also, and as the inclination of +the channel is diminished, the rapidity of the current is checked, and +the deposition of the slime it holds in suspension consequently +promoted. Thus the winds and the water, moving in contrary directions, +join in producing a common effect. + +The sand, blown over the Delta and the cultivated land higher up the +stream during the inundation, is covered or mixed with the fertile earth +brought down by the river, and no serious injury is sustained from it. +That spread over the same ground after the water has subsided, and +during the short period when the soil is not stirred by cultivation or +covered by the flood, forms a thin pellicle over the surface as far as +it extends, and serves to divide and distinguish the successive layers +of slime deposited by the annual inundations. The particles taken up by +the wind on the sea-beach are borne onward, by a hopping motion, or +rolled along the surface, until they are arrested by the temporary +cessation of the wind, by vegetation, or by some other obstruction, and +they may, in process of time, accumulate in large masses, under the lee +of +rocky projections, buildings, or other barriers which break the force of +the wind. + +In these facts we find an important element in the explanation of the +sand drifts, which have half buried the Sphinx and so many other ancient +monuments in that part of Egypt. These drifts, as I have said, are not +wholly from the desert, but in largo proportion from the sea; and, as +might be supposed from the distance they have travelled, they have been +long in gathering. While Egypt was a great and flourishing kingdom, +measures were taken to protect its territory against the encroachment of +sand, whether from the desert or from the Mediterranean; but the foreign +conquerors, who destroyed so many of its religious monuments, did not +spare its public works, and the process of physical degradation +undoubtedly began as early as the Persian invasion. The urgent +necessity, which has compelled all the successive tyrannies of Egypt to +keep up some of the canals and other arrangements for irrigation, was +not felt with respect to the advancement of the sands; for their +progress was so slow as hardly to be perceptible in the course of a +single reign, and long experience has shown that, from the natural +effect of the inundations, the cultivable soil of the valley is, on the +whole, trenching upon the domain of the desert, not retreating before +it. + +The oases of the Libyan, as well as of many Asiatic deserts, have no +such safeguards. The sands are fast encroaching upon them, and threaten +soon to engulf them, unless man shall resort to artesian wells and +plantations, or to some other efficient means of checking the advance of +this formidable enemy, in time to save these islands of the waste from +final destruction. + +Accumulations of sand are, in certain cases, beneficial as a protection +against the ravages of the sea; but, in general, the vicinity, and +especially the shifting of bodies of this material, are destructive to +human industry, and hence, in civilized countries, measures are taken to +prevent its spread. This, however, can be done only where the population +is large and enlightened, and the value of the soil, or of the +artificial erections and improvements upon it, is considerable. Hence in +the deserts of Africa and of Asia, and thee inhabited lands which border +on them, no pains are usually taken to check the drifts, and when once +the fields, the houses, the springs, or the canals of irrigation are +covered or choked, the district is abandoned without a struggle, and +surrendered to perpetual desolation. [Footnote: In parts of the Algerian +desert, some efforts are made to retard the advance of sand dunes which +threaten to overwhelm villages. "At Debila," says Laurent, "the lower +parts of the lofty dunes are planted with palms, ... but they are +constantly menaced with burial by the sands. The only remedy employed by +the natives consists in little dry walls of crystallized gypsum, built +on the crests of the dunes, together with hedges of dead palm-leaves. +These defensive measures are aided by incessant labor; for every day the +people take up in baskets the sand blown over to them the night before +and carry it back to the other side of the dune."--Memoires sur le +Sahara, p. 14.] + + +Sand Dunes and Sand Plains. + +Two forms of sand deposit are specially important in European and +American geography. The one is that of dune or shifting hillock upon the +coast, the other that of barren plain in the interior. The coast-dunes +are composed of sand washed up from the depths of the sea by the waves, +and heaped in more or less rounded knolls and undulating ridges by the +winds. The sand with which many plains are covered appears sometimes to +have been deposited upon them while they were yet submerged beneath the +sea, sometimes to have been drifted from the seacoast, and scattered +over them by wind-currents, sometimes to have been washed upon them by +running water. In these latter cases, the deposit, though in itself +considerable, is comparatively narrow in extent and irregular in +distribution, while, in the former, it is often evenly spread over a +very wide surface. In all great bodies of either sort, the silicious +grains are the principal constituent, though, when not resulting from +the disintegration of silicious rock and still remaining in place, they +are generally accompanied with a greater or less admixture of other +mineral particles, and of animal and vegetable remains, [Footnote: +Organic constituents, such as comminuted shells, and silicious and +calcareous exuviae of infusorial animals and plants, are sometimes found +mingled in considerable quantities with mineral sands. These are usually +the remains of aquatic vegetables or animals, but not uniformly so, for +the microscopic organisms, whose flinty cases enter so largely into the +sand-beds of the Mark of Brandenburg, are still living and prolific in +the dry earth. See Wittwer, Physikalische Geographic, p. 142. The desert +on both sides of the Nile is inhabited by a land-snail--of which I have +counted eighty, in estimation, on a single shrub barely a foot high--and +thousands of its shells are swept along and finally buried in the drifts +by every wind. Every handful of the sand contains fragments of them. +Forchhammer, in Leonhard und Bronn s Jahrbuch, 1841, p. 8, says of the +sand-hills of the Danish coast: "It is not rare to find, high in the +knolls, marine shells, and especially those of the oyster. They are due +to the oyster-eater [Haemalopus ostralegus], which carries his prey to +the top of the dunes to devour it." See also Staring, De Bodem van +Nederland, i., p. 821.] and they are also, usually somewhat changed in +consistence by the ever-varying conditions of temperature and moisture +to which they have been exposed since their deposit. Unless the +proportion of these latter ingredients is so large as to create a +considerable adhesiveness in the mass--in which case it can no longer +properly be called sand--it is infertile, and, if not charged with +water, partially agglutinated by iron, lime, or other cement, or +confined by alluvion resting upon it, it is much inclined to drift, +whenever, by any chance, the vegetable network which, in most cases, +thinly clothes and at the same time confines it, is broken. Human +industry has not only fixed the flying dunes by plantations, but, by +mixing clay and other tenacious earths with the superficial stratum of +extensive sand plains, and by the application of fertilizing substances, +it has made them abundantly productive of vegetable life. These latter +processes belong to agriculture and not to geography, and, therefore, +are not embraced within the scope of the present subject. But the +preliminary steps, whereby wastes of loose, drifting barren sands are +transformed into wooded knolls and plains, and finally, through the +accummulation of vegetable mould, into arable ground, constitute a +conquest over nature which precedes agriculture--a geographical +revolution--and, therefore, an account of the means by which the change +has been effected belongs properly to the history of man's influence on +the great features of terrestrial surface. I proceed, then, to examine +the structure of dunes, and to describe the warfare man wages with the +sand-hills, striving on the one hand to maintain and even extend them, +as a natural barrier against encroachments of the sea, and, on the +other, to check their moving and wandering propensities, and prevent +them from trespassing upon the fields he has planted and the habitations +in which he dwells. + + +COAST DUNES. + +Coast dunes are oblong ridges or round hillocks, formed by the action of +the wind upon sands thrown up by the waves on the low beaches of seas, +and sometimes of fresh-water lakes. On most coasts, the supply of sand +for the formation of dunes is derived from tidal waves. The flow of the +tide is more rapid, and consequently its transporting power greater, +than that of the ebb; the momentum, acquired by the heavy particles in +rolling in with the water, tends to carry them even beyond the flow of +the waves; and at the turn of the tide, the water is in a state of +repose long enough to allow it to let fall much of the solid matter it +holds in suspension. Hence, on all low, tide-washed coasts of seas with +sandy bottoms, there exist several conditions favorable to the formation +of sand deposits along high-water mark. [Footnote: There are various +reasons why the formation of dunes is confined to low shores, and this +law is so universal, that when bluffs are surmounted by them, there is +always cause to suspect upheaval, or the removal of a sloping beach in +front of the bluff, after the dunes were formed. Bold shores are usually +without a sufficient beach for the accumulation of large deposits; they +are commonly washed by a sea too deep to bring up sand from its bottom; +their abrupt elevation, even if moderate in amount, would still be too +great to allow ordinary winds to lift the sand above them; and their +influence in deadening the wind which blows towards them would even more +effectually prevent the raising of sand from the beach at their foot. +Forchhammer, describing the coast of Jutland, says that, in high winds, +"one can hardly stand upon the dunes, except when they are near the +water line and have been cut down perpendicularly by the waves. Then the +wind is little or not at all felt--a fact of experience very common on +our coasts, observed on all the steep shore bluffs of 200 feet height, +and, in the Faroe Islands, on precipices 2,000 feet high. In heavy gales +in those islands, the cattle fly to the very edge of the cliffs for +shelter, and frequently fall over. The wind, impinging against the +vertical wall, creates an ascending current which shoots somewhat past +the crest of the rock, and thus the observer or the animal is protected +against the tempest by a barrier of air."-Leonhard und Bronn, Jahrbuch, +1841, p. 3. The calming, or rather diversion, of the wind by cliffs +extends to a considerable distance in front of them, and no wind would +have sufficient force to raise the sand vertically, parallel to the face +of a bluff, even to the height of twenty feet.] If the land-winds are of +greater frequency, duration, or strength than the sea-winds, the sands +left by the retreating wave will be constantly blown back into the +water; but if the prevailing air-currents are in the opposite direction, +the sands will soon be carried out of the reach of the highest waves, +and transported continually farther and farther into the interior of the +land, unless obstructed by high grounds, vegetation, or other obstacles. + +The laws which govern the formation of dunes are substantially these. We +have seen that, under certain conditions, sand is accumulated above +high-water mark on low sea and lake shores. So long as the sand is kept +wet by the spray or by capillary attraction, it is not disturbed by +air-currents, but as soon as the waves retire sufficiently to allow it +to dry, it becomes the sport of the wind, and is driven up the gently +sloping beach until it is arrested by stones, vegetables, or other +obstructions, and thus an accumulation is formed which constitutes the +foundation of a dune. However slight the elevation thus created, it +serves to stop or retard the progress of the sand-grains which are +driven against its shoreward face, and to protect from the further +influence of the wind the particles which are borne beyond it, or rolled +over its crest, and fall down behind it. If the shore above the beach +line were perfectly level and straight, the grass or bushes upon it of +equal height, the sand thrown up by the waves uniform in size and weight +of particles as well as in distribution, and if the action of the wind +were steady and regular, a continuous bank would be formed, everywhere +alike in height and cross section. But no such constant conditions +anywhere exist. The banks are curved, broken, unequal in elevation; they +are sometimes bare, sometimes clothed with vegetables of different +structure and dimensions; the sand thrown up is variable in quantity and +character; and the winds are shifting, gusty, vertical, and often +blowing in very narrow currents. From all these causes, instead of +uniform hills, there rise irregular rows of sand-heaps, and these, as +would naturally be expected, are of a pyramidal, or rather conical +shape, and connected at bottom by more or less continuous ridges of the +same material. + + +Elisee Reclus, in describing the coast dunes of Gascony, observes that +when, as sometimes happens, the sands are not heaped in a continuous, +irregular bulwark, but deposited in isolated hillocks, they have a +tendency to assume a crescent shape, the convexity being turned +seawards, or towards the direction from which the prevailing winds +proceed. This fact, the geological bearing of which is obvious, is not +noticed by previous French writers or even by Andresen, though a +semi-lunar outline has been long generally ascribed to inland dunes. It +is, however evident that such a form would naturally be produced by the +action of a wind blowing long in a given direction upon a mass of loose +sand with a fixed centre--such as is constituted by the shrub or stone +around which the sand is first deposited--and free extremities. On a +receding coast, dunes will not attain so great a height as on more +secure shores, because they are undermined and carried off before they +have time to reach their greatest dimensions. Hence, while at sheltered +points in South-western France, there are dunes three hundred feet or +more in height, those on the Frisic Islands and the exposed parts of the +coast of Schleswig-Holstein range only from twenty to one hundred feet. +On the western shores of Africa, it is said that they sometimes attain +an elevation of six hundred feet. This is one of the very few points +known to geographers where desert sands are advancing seawards, +[Footnote: "On the west coast of Africa the dunes are drifting seawards, +and always receiving new accessions from the Sahara. They are constantly +advancing out into the sea."--Naumann, Geognosie, ii., p.1172.] and here +they rise to the greatest altitude to which sand-grains can be carried +by the wind. The hillocks, once deposited, are held together and kept in +shape, partly by mere gravity, and partly by the slight cohesion of the +lime, clay, and organic matter mixed with the sand; and it is observed +that, from capillary attraction, evaporation from lower strata, and +retention of rain-water, they are always moist a little below the +surface. [Footnote: "Dunes are always full of water, from the action of +capillary attraction. Upon the summits, one seldom needs to dig more +than a foot to find the sand moist, and in the depressions, fresh water +is met with near the surface."--Forchhammer, in Leonhard and Bronx, for +1841, p.5, note. On the other hand, Andresen, who has very carefully +investigated this as well as all other dune phenomena, maintains that +the humidity of the sand ridges cannot be derived from capillary +attraction. He found by experiment that a heap of drift-sand was not +moistened to a greater height than eight and a half inches, after +standing with its base a whole night in water. He states the minimum of +water contained by the sand of the dunes, one foot below the surface, +after a long drought, at two per cent, the maximum, after a rainy month, +at four per cent. At greater depths the quantity is larger. The +hygroscopicity of the sand of the coast of Jutland he found to be +thirty-three per cent, by measure, or 21.5 by weight. The annual +precipitation on that coast is twenty-seven inches, and as the +evaporation is about the same, he argues that rain-water does not +penetrate far beneath the surface of the dunes, and concludes that their +humidity can be explained only by evaporation from below.--Om +Klitformationen, pp. 106-110. In the dunes of Algeria, water in so +abundant that wells are constantly dug in them at high points on their +surface. They are sunk to the depth of three or four inches only, and +the water rises to the height of a metre in them.--Laurent, Memoire sur +le Sahara, pp. 11, 12, 13. The same writer observes (p. 14) that the +'hollows in the dunes are planted with palms which find moisture enough +a little below the surface. It would hence seem that proposal to fix the +dunes which are supposed to threaten the Suez Canal, by planting the +maratime pine and other trees upon them, is not altogether so absurd as +it has been thought to be by some of those disinterested philanthropists +of other nations who were distressed with fears that French capitalists +would lose the money they had invested in that great undertaking. Ponds +of water are often found in the depression between the sand-hills of the +dune chains in the North American desert.] + +By successive accumulations, they gradually rise to the height of +thirty, fifty, sixty, or a hundred feet, and sometimes even much higher. +Strong winds, instead of adding to their elevation, sweep off loose +particles from their surface, and these, with others blown over or +between them, build up a second row of dunes, and so on according to the +character of the wind, the supply and consistence of the sand, and the +face of the country. In this way is formed a belt of sand-dunes, +irregularly dispersed and varying much in height and dimensions, and +sometimes many miles in breadth. On the Island of Sylt, in the German +Sea, where there are several rows, the width of the belt is from half a +mile to a mile. There are similar ranges on the coast of Holland, +exceeding two miles in breadth, while at the mouths of the Nile they +form a zone not less than ten miles wide. The base of some of the dunes +in the Delta of the Nile is reached by the river during the annual +inundation, and the infiltration of the water, which contains lime, has +converted the lower strata into a silicious limestone, or rather a +calcarous sandstone, and thus afforded an opportunity of studying the +structure of that rock in a locality where its origin and mode of +aggregation and solidification are known. + +The tide, though a usual, is by no means a necessary condition for the +accumulations of sand out of which dunes are formed. The Baltic and the +Mediterranean are almost tideless seas, but there are vast ranges of +dunes on the Russian and Prussian coasts of the Baltic and at the mouths +of the Nile and many other points on the shores of the Mediterranean. +The vast shoals in the latter sea, known to the ancients as the Greater +and Lesser Syrtis, are of marine origin. They are still filling up with +sand, washed up from greater depths, or sometimes drifted from the coast +in small quantities, and will probably be converted, at some future +period, into dry land covered with sand-hills. There are also extensive +ranges of dunes upon the eastern shores of the Caspian, and at the +southern, or rather south-eastern, extremity of Lake Michigan. +[Footnote: The careful observations of Colonel J. D. Graham, of the +United States Army, show a tide of about three inches in Lake Michigan. +See "A Lunar Tidal Wave in the North American Lakes," demonstrated by +Lieut.-Colonel J. D. Graham, in the fourteenth volume of the Proceedings +of the American Association for the Advancement of Science.] There is no +doubt that this latter lake formerly extended much farther in that +direction, but its southern portion has gradually shoaled and at last +been converted into solid land, in consequence of the prevalence of the +north-west winds. These blow over the lake a large part of the year, and +create a southwardly set of the currents, which wash up sand from the +bed of the lake and throw it on shore. Sand is taken up from the beach +at Michigan City by every wind from that quarter, and, after a heavy +blow of some hours' duration, sand ridges may be observed on the north +side of the fences, like the snow wreaths deposited by a drifting wind +in winter. Some of the particles are carried back by contrary winds, but +most of them lodge on or behind the dunes, or in the moist soil near the +lake, or are entangled by vegetables, and tend permanently to elevate +the level. Like effects are produced by constant sea-winds, and dunes +will generally be formed on all low coasts where such prevail, whether +in tideless or in tidal waters. + +Jobard thus describes the modus operandi, under ordinary circumstances, +at the mouths of the Nile, where a tide can scarcely be detected: "When +a wave breaks, it deposits an almost imperceptible line of fine sand. +The next wave brings also its contribution, and shoves the preceding +line a little higher. As soon as the particles are fairly out of the +reach of the water they are dried by the heat of the burning sun, and +immediately seized by the wind and rolled or borne farther inland. The +gravel is not thrown out by the waves, but rolls backwards and forwards +until it is worn down to the state of fine sand, when it, in its turn, +is cast upon the land and taken up by the wind." [Footnote: Staring, De +Bodun van Nederland, i., p. 327, note.] This description applies only to +the common every-day action of wind and water; but just in proportion to +the increasing force of the wind and the waves, there is an increase in +the quantity of sand, and in the magnitude of the particles carried off +from the beach by it, and, of course, every storm in a landward +direction adds sensibly to the accumulation upon the shore. + + +Sand Banks. + +Although dunes, properly so called, are found only on dry land and above +ordinary high-water mark, and owe their elevation and structure to the +action of the wind, yet, upon many shelving coasts, accumulations of +sand much resembling dunes are formed under water at some distance from +the shore by the oscillations of the waves, and are well known by the +name of sand banks. They are usually rather ridges than banks, of +moderate inclination, and with the steepest slope seawards, [Footnote: +Kohl, Inseln und Marschen Schleswig Holsteins, ii., p. 33. From a +drawing in Andresen, Om Klitformationen, p. 24, it would appear that on +the Schleswig coast the surf-formed banks have the steepest slope +landwards, those farther from the shore, as stated in the text.] and +their form differs little from that of dunes except in this last +particular and in being lower and more continuous. Upon the western +coast of the island of Amrum, for example, there are three rows of such +banks, the summits of which are at a distance of perhaps a couple of +miles from each other; so that, including the width of the banks +themselves, the spaces between them, and the breadth of the zone of +dunes upon the land, the belt of moving sands on that coast is probably +not less than eight miles wide. + +Under ordinary circumstances, sand banks are always rolling, landwards, +and they compose the magazine from which the material for the dunes is +derived. [Footnote: Sand banks sometimes connect themselves with the +coast at both ends, and thus cut off a portion of the sea. In this case, +as well as when salt water is enclosed by sea-dikes, the water thus +separated from the ocean gradually becomes fresh, or at least brackish. +The Haffs, or large expanses of fresh water in Eastern Prussia--which +are divided from the Baltic by narrow sand banks called Nehrungen, or, +at sheltered points of the coast, by fluviatile deposits called +Werders--all have one or more open passages, through which the water of +the rivers that supply them at last finds its way to the sea.] The +dunes, in fact, are but aquatic sand banks transferred to dry land. The +laws of their formation are closely analogous, because the action of the +two fluids, by which they are respectively accumulated and built up, is +very similar when brought to bear upon loose particles of solid matter. +It would, indeed, seem that the slow and comparatively regular movements +of the heavy, unelastic water ought to affect such particles very +differently from the sudden and fitful impulses of the light and elastic +air. But the velocity of the wind currents gives them a mechanical force +approximating to that of the slower waves, and, however difficult it may +be to explain all the phenomena that characterize the structure of the +dunes, observation has proved that it is nearly identical with that of +submerged sand banks. [Footnote: Forchhammer ascribes the resemblance +between the furrowing of the dune sands and the beach ripples, not to +the similarity of the effect of wind and water upon sand, but wholly to +the action of the wind; in the first instance, directly, in the latter, +through the water. "The wind-ripples on the surface of the dunes +precisely resemble the water-ripples of sand flats occasionally +overflowed by the sea; and with the closest scrutiny, I have never been +able to detect the slightest difference between them. This is easily +explained by the fact, that the water-ripples are produced by the action +of light wind on the water which only transmits the air-waves to the +sand."--Leonhard und Bronn, 1841, pp. 7, 8.] The differences of form are +generally ascribable to the greater number and variety of surface +accidents of the ground on which the sand hills of the land are built +up, and to the more frequent changes, and wider variety of direction, in +the courses of the wind. + + +CHARACTER OF DUNE SAND. + +"Dune sand," says Staring, "consists of well-rounded grains of quartz, +more or less colored by iron, and often mingled with fragments of +shells, small indeed, but still visible to the naked eye. [Footnote: +According to the French authorities, the dunes of France are not always +composed of quartzose sand. "The dune sands" of different characters, +says Bremontier, "partake of the nature of the different materials which +compose them. At certain points on the coast of Normandy they are found +to be purely calcareous; they are of mixed composition on the shores of +Brittany and Saintonge, and generally quartzose between the mouth of the +Gironde and that of the Adour."--Memoire sur les Dunes, Annales des +Ponts et Chaussees, t. vii., 1833, 1er semestre, p. 146. + +In the dunes of Long Island and of Jutland, there are considerable veins +composed almost wholly of garnet. For a very full examination of the +mechanical and chemical composition of the dune sands of Jutland, see +Andresen, Om Klitformationen, p. 110. Fraas informs us, Aus dem Orient, +pp. 176, 177, that the dune sands of the Egyptian coast arise from the +disintegration of the calcareous sandstone of the same region. This +sandstone, composed in a large proportion of detritus of both land and +sea shells mingled with quartz sand, appears to have been consolidated +under water during an ancient period of subsidence. A later upheaval +brought it to or near the surface, when it was more or less +disintegrated by the action of the waves and by meteoric influences--a +process still going on--and it is now again subsiding with the coast it +rests on. + +The calcareous sand arising from the comminution of corals forms dunes +on some of the West India Islands.--Agassiz, Bulletin of the Museum of +Comparative Zoology, vol. i.] These fragments are not constant +constituents of dune sand. They are sometimes found at the very summits +of the hillocks, as at Overveen; in the King's Dune, near Egmond, they +form a coarse, calcareous gravel very largely distributed through the +sand, while the interior dunes between Haarlem and Warmond exhibit no +trace of them. It is yet undecided whether the presence or absence of +these fragments is determined by the period of the formation of the +dunes, or whether it depends on a difference in the process by which +different dunes have been accumulated. Land shells, such as snails, for +example, are found on the surface of the dunes in abundance, and many of +the shelly fragments in the interior of the hillocks may be derived from +the same source." [Footnote: De Bodem van Nederland, i., p. 323.] + +Sand concretions form within the dunes and especially in the depressions +between them. These are sometimes so extensive and impervious as to +retain a sufficient supply of water to feed perennial springs, and to +form small permanent ponds, and they are a great impediment to the +penetration of roots, and consequently to the growth of trees planted, +or germinating from self-sown seeds, upon the dunes. [Footnote: Staring, +De Bodem van Nederland, i., p.317. See also Bergsoe, Reventlov's +Virksomhed, ii., p. 11. + +"In the sand-hill ponds mentioned in the text, there is a vigourous +growth of bog plants accompanied with the formation of peat, which goes +on regularly as long as the dune sand does not drift. But if the surface +of the dunes is broken, the sand blows into the ponds, covers the peat, +and puts and end to its formation. When, in the course of time, marine +currents cut away the coast, the dunes move landwards and fill up the +ponds and thus are formed the remarkable strata of fossile peat called +Martorv, which appears to be unknown to the geologists of other parts of +Europe." -- Forchhammer, in Leonhard und Bronn, 1841, p. 18. Martorv has +a specific gravity thrice as great as that of ordinary peat in +consequence of the pressure of the sand.--Asbjornsen, Torv og Torvdrift, +p.26.] + + +Interior Structure of Dunes. + +The interior structure of the dunes, the arrangement of their particles, +is not, as might be expected, that of an unorganized, confused heap, but +they show a strong tendency to stratification. This is a point of much +geological interest, because it indicates that sandstone may owe its +stratified character to the action of other forces as well as of water. +The origin and peculiar character of these layers are due to a variety +of causes. + +For example, a south-west wind and current may deposit upon a dune a +stratum of a given color and mineral composition, and this may be +succeeded by a north-west wind and current, bringing with them particles +of a different hue, constitution, and origin. Again, if we suppose a +violent tempest to strew the beach with sand-grains very different in +magnitude and specific gravity, and, after the sand is dry, to be +succeeded by a gentle breeze, it is evident that only the lighter +particles will be taken up and carried to the dunes. If, after some +time, the wind freshens, heavier grains will be transported and +deposited on the former, and a still stronger succeeding gale will roll +up yet larger kernels. Each of these deposits will form a stratum. If we +suppose the tempest to be followed, after the sand is dry, not by a +gentle breeze, but by a wind powerful enough to lift at the same time +particles of very various magnitudes and weights, the heaviest will +often lodge on the dune while the lighter will be carried farther. This +would produce a stratum of coarse sand, and the same effect might result +from the blowing away of light particles out of a mixed layer, while the +heavier remained undisturbed. [Footnote: The lower strata must be older +than the superficial layers, and the particles which compose them may in +time become more disintegrated, and therefore finer than those deposited +later and above them. + +Hull ingeniously suggests that, besides other changes, fine sand +intermixed with or deposited above a coarser stratum, as well as the +minute particles resulting from the disintegration of the grains of the +latter, may be carried by rain in the case of dunes, or by the ordinary +action or sea-water in that of sand-banks, down through the interstices +in the coarser layer, and thus the relative position of sand and gravel +may be changed.--Oorsprong der Hollandsche Duinen, p. 103.] + +Still another cause of apparent stratification may be found in the +occasional interposition of a thin layer of leaves or other vegetable +remains between successive deposits, and this I imagine to be more +frequent than has been generally supposed. Some geologists have thought +that the sand strata of dunes are of annual formation; [Footnote: +Schomann, Geologische Wanderungen durch die Preussischen Ost-See +Provinzen, 1869, p. 81.] but the autumnal deposit of foliage from +neighboring trees and shrubs furnishes a more probable explanation of +the division of the sand-heaps into regular layers. + +A late distinguished American admiral communicated to me an interesting +observation made by him at San Francisco, which has an important bearing +on the arrangement of the particles of sand in dunes and other irregular +accumulations of that substance. In laying out a navy-yard at that port, +a large quantity of earthy material was removed from the dunes and other +hillocks and carted to a low piece of ground which required filling up. +Sand of various characters, fine and coarse gravel, and common earth +were dropped promiscuously by the carts as accident or convenience +dictated, and of course they were all confusedly intermixed. Some time +after, when the new ground was consolidated, various excavations were +made in it, and the different materials of which the filling was +composed were found to be stratified with considerable regularity, +according to their specific gravity. + +Two explanations of this remarkable fact suggest themselves to me, +which, however, do not perhaps exclude others. San Francisco is subject +to earthquakes, and though violent or even sensible shocks are not very +frequent, it is highly probable that, as is shown to be the case in many +other countries, by late seismological observations, there are, in the +course of the year, a great number of slight shocks which escape +unscientific observation. A frequent repetition of slight tremblings of +the earth would, like any other moderate mechanical agitation, probably +produce the separation of a miscellaneous mass, like that described, +into distinct layers. Again, the Pacific coast, like all others upon an +open sea, is exposed to incessant concussion from the shock of the +waves, which is repeated many thousand times a day. This concussion is +often sensibly felt by the observer, and it seems not in the least +improbable that the agitation may have tended to produce a stratified +arrangement in the case at San Francisco, as well as in all coast dunes +and other accumulations of loose mineral material in similar situations. +Kohl observes that the shore on the landward side of the files of dunes +often trembles from the shock of the waves on the beach, [Footnote: +Inseln und Marschen, etc., ii., p. 34.] and Villeneuve established by +careful experiment that at Dunkerque the ground is sensibly agitated by +the same cause, in stormy weather, to a distance of more than a mile +from the sea. + +The eddies of strong winds between the hillocks must also occasion +disturbances and re-arrangements of the sand layers, and it seems +possible that the irregular thickness and the strange contortions of the +strata of the sandstone at Petra may be due to some such cause. A +curious observation of Professor Forchhammer suggests an explanation of +another peculiarity in the structure of the sandstone of Mount Seir. He +describes dunes in Jutland, composed of yellow quartzose sand intermixed +with black titanian iron. When the wind blows over the surface of the +dunes, it furrows the sand with alternate ridges and depressions, +ripples, in short, like those of water. The swells, the dividing ridges +of the system of sand ripples, are composed of the light grains of +quartz, while the heavier iron rolls into the depressions between, and +thus the whole surface of the dune appears as if covered with a fine +black network. + +The sea side of dunes, being more exposed to the caprices of the wind, +is more irregular in form than the lee or land side, where the +arrangement of the particles is affected by fewer disturbing and +conflicting influences. Hence, the stratification of the windward slope +is somewhat confused, while the sand on the lee side is found to be +disposed in more regular beds, inclining landwards, and with the largest +particles lowest, where their greater weight would naturally carry them. +The lee side of the dunes, being thus formed of sand deposited according +to the laws of gravity, is very uniform in its slope, which, according +to Forchhammer, varies little from an angle of 30 degrees with the +horizon, while the more exposed and irregular weather side lies at an +inclination of from 5 degrees to 10 degrees. When, however, the outer +tier of dunes is formed so near the waterline as to be exposed to the +immediate action of the waves, it is undermined, and the face of the +hill is very steep and sometimes nearly perpendicular. + + +Geological Importance of Dunes. + +These observations, and other facts which a more attentive study on the +spot would detect, might furnish the means of determining interesting +and important questions concerning geological formations in localities +very unlike those where dunes are now thrown up. For example, Studer +supposes that the drifting sand-hills of the African desert were +originally coast dunes, and that they have been transported to their +present position far in the interior, by the rolling and shifting +leeward movement to which all dunes not covered with vegetation are +subject. The present general drift of the sands of that desert appears +to be to the south-west and west, the prevailing winds blowing from the +north-east and east; but it has been doubted whether the shoals of the +western coast of Northern Africa, and the sands upon that shore, are +derived from the bottom of the Atlantic, in the usual manner, or, by an +inverse process, from those of the Sahara. The latter, as has been +before remarked, is probably the truth, though observations are wanting +to decide the question. [Footnote: "The North African desert falls into +two divisions: the Sahel, or western, and the Sahar, or eastern. The +sands of the Sahar were, at a remote period, drifted to the west. In the +Sahel, the prevailing east winds drive the sand-ocean with a progressive +westward motion. The eastern half of the desert is swept +clean."--Naumann, Geognosie, ii., p. 1173.] There would be nothing +violently improbable in the a priori supposition that they may have been +in part first thrown up by the Mediterranean on its Libyan coast, and +thence blown south and west over the vast space they now cover. But +inasmuch as it is now geologically certain that the Sahara is an +uplifted bed of an ancient sea, we may suppose that, while submerged, it +was, like other sea-bottoms, strewn with sand, and that its present +supply of that material was, in great proportion, brought up with it. +Laurent observed, some years ago, that marine shells of still extinct +species were found in the Sahara, far from the sea, and even at +considerable depths below the surface. [Footnote: Memoires sur le Sahara +Oriental p. 62] These observations have been confirmed past all question +by Desor, Martins, and others, and the facts and the obvious conclusion +they suggest are at present not disputed. But whatever has been the +source and movement of these sands, they can hardly fail to have left on +their route some sandstone monuments to mark their progress, such, for +example, as we have seen are formed from the dune sand at the mouth of +the Nile; and it is conceivable that the character of the drifting sands +themselves, and of the conglomerates and sandstones to whose formation +they have contributed, might furnish satisfactory evidence as to their +origin, their starting-point, and the course by which they have wandered +so far from the sea. [Footnote: Forchhammer, after pointing out the +coincidence between the inclined stratification of dunes and the +structure of ancient tilted rocks, says: "But I am not able to point out +a sandstone formation corresponding to the dunes. Probably most ancient +dunes have been destroyed by submersion before the loose sand became +cemented to solid stone, but we may suppose that circumstances have +existed somewhere which have preserved the characteristics of this +formation."--Leonhard und Bronn, 1841, p. 8, 9. Such formations, +however, certainly exist. Laurent (Memoire sur le Sahara, etc., p. 12) +tells us that in the Algerian desert there are "sandstone formation" not +only "corresponding to the dunes," but, actually consolidated within +them. "A place called El-Mouia-Tadjer presents a repetition of what we +saw at El-Baya; one of the funnels formed in the middle of the dunes +contains wells from two metres to two and a half in depth, dug in a sand +which pressure, and probably the presence of certain salts, have +cemented so as to form true sandstone, soft indeed, but which does not +yield except to the pickaxe. These sandstones exhibit an inclination +which seems to be the effect of wind; for they conform to the direction +of the sands which roll down a scarp occasioned by the primitive +obstacle." + +"At New Quay the dune sands are converted to stone by an oxide of iron +held in solution by the water which pervades them. This stone, which is +formed, so to speak, under our eye, has been found solid enough to be +employed for building."-Esquiros, L'Angleterre, etc., in Revue des Deux +Mondes, 1864, pp. 44, 45. + +The dunes near the mouth of the Nile, the lower sands of which have been +cemented together by the infiltration of Nile water, would probably show +a similar stratification in the sandstone which now forms their base. + +Dana describes a laminated rook often formed by the infiltration of +water into the sand dunes on the Hawaian islands.--Corals and Coral +Islands, 1872, p.155.] + +If the sand of coast dunes is, as Staring describes it, composed chiefly +of well-rounded, quartzose grains, fragments of shells, and other +constant ingredients, it would often be recognizable as coast sand, in +its agglutinate state of sandstone. The texture of this rock varies from +an almost imperceptible fineness of grain to great coarseness, and +affords good facilities for microscopic observation of its structure. +There are sandstones, such, for example, as are used for grindstones, +where the grit, as it is called, is of exceeding sharpness; others where +the angles of the grains are so obtuse that they scarcely act at all on +hard metals. The former may be composed of grains of rock, disintegrated +indeed, and re-cemented together, but not, in the meanwhile, much +rolled; the latter, of sands long washed by the sea, and drifted by +land-winds. There is, indeed, so much resemblance between the effects of +driving winds and of rolling water upon light bodies, that there might +be difficulty in distinguishing them; but after all, it is not probable +that sandstone, composed of grains thrown up from the salt sea, and long +tossed by the winds, would be identical in its structure with that +formed from fragments of rock crushed by mechanical force, or +disintegrated by heat, and again agglutinated without much exposure to +the action of moving water. + + +Dunes of American Coasts. + +Upon the Atlantic coast of the United States, the prevalence of western +or off-shore winds is unfavorable to the formation of dunes, and, though +marine currents lodge vast quantities of sand, in the form of banks, on +that coast, its shores are proportionally more free from sand-hills than +some others of lesser extent. There are, however, very important +exceptions. The action of the tide throws much sand upon some points of +the New England coast, as well as upon the Beaches of Long Island and +other more southern shores, and here dunes resembling those of Europe +are formed. There are also extensive ranges of dunes on the Pacific +coast of the United States, and at San Francisco they border some of the +streets of the city. + +The dunes of America are far older than her civilization, and the soil +they threaten or protect possesses, in general, too little value to +justify any great expenditure in measures for arresting their progress +or preventing their destruction. Hence, great as is their extent and +their geographical importance, they have, at present, no such intimate +relations to human life as to render them objects of special interest in +the point of view I am taking, and I do not know that the laws of their +formation and motion have been made a subject of original investigation +by any American observer. + + +Dunes of Western Europe. + +Upon the western coast of Europe, on the contrary, the ravages +occasioned by the movement of sand dunes, and the serious consequences +often resulting from the destruction of them, have long engaged the +earnest attention of Governments and of scientific men, and for nearly a +century persevering and systematic effort has been made to bring them +under human control. The subject has been carefully studied in Denmark +and the adjacent duchies, in Western Prussia, in the Netherlands, and in +France; and the experiments in the way of arresting the drifting of the +dunes, and of securing them, and the lands they shelter, from the +encroachments of the sea, have resulted in the adoption of a system of +coast improvement substantially the same in all these countries. The +sands, like the forests, have now their special literature, and the +volumes and memoirs, which describe them and the processes employed to +subdue them, are full of scientific interest and of practical +instruction. + + +Dunes of Gascony. + +In the small kingdom of Denmark, inclusive of the duchies of Schleswig +and Holstein, the dunes cover an area of more than two hundred and sixty +square miles. The breadth of the chain is very various, and in some +places it consists only of a single row of sand-hills, while in others, +it is more than six miles wide. [Footnote: Andersen, Om Klitformationen, +pp. 78, 202, 275.] The dunes of the Prussian coast are vaguely estimated +to cover from eighty-five to one hundred and ten thousand acres; those +of Holland one hundred and forty thousand acres; and those of Gascony +more than two hundred thousand acres. I do not find any estimate of +their extent in other provinces of France, or in the Baltic provinces of +Russia, but it is probable that the entire quantity of dune land upon +the Atlantic and Baltic shores of Europe does not fall much short of a +million of acres. [Footnote: In an article on the dunes of Europe, in +vol. 29 (1864) of Aus der Natur, p. 590, the dunes are estimated to +cover, on the islands and coasts of Schleswig Holstein, in North-west +Germany, Denmark, Holland, and France, one hundred and eighty-one +German, or nearly four thousand English square miles; in Scotland, about +ten German, or two hundred and ten English miles; in Ireland, twenty +German, or four hundred and twenty English miles; and in England, one +hundred and twenty German, or more than twenty-five hundred English +miles. Pannewitz (Anleitung zum Anbau der Sandfluchen), as cited by +Andresen (Om Klitformationen, p. 45), states that the drifting sands of +Europe, including, of course, sand plains as well as dunes, cover an +extent of 21,000 square miles. This is, perhaps, an exaggeration, though +there is, undoubtedly, much more desert-land of this description on the +European continent than has been generally supposed. There is no +question that most of this waste is capable of reclamation by simple +planting, and no mode of physical improvement is better worth the +attention of civilized Governments than this. + +There are often serious objections to extensive forest planting on soils +capable of being otherwise made productive, but they do not apply to +sand wastes, which, until covered by woods, are not only a useless +incumbrance, but a source of serious danger to all human improvements in +the neighborhood of them.] This vast deposit of sea-sand extends along +the coasts for a distance of several hundred miles, and from the time of +the destruction of the forests which covered it, to the year 1789, the +whole line was rolling inwards and burying the soil beneath it, or +rendering the fields unproductive by the sand which drifted from it. At +the same time, as the sand-hills moved landwards, the ocean was closely +following their retreat and swallowing up the ground they had covered, +as fast as their movement left it bare. + + +Age, Character, and Permanence of Dunes. + +The origin of most great lines of dunes goes back past all history. +There are on many coasts several distinct ranges of sand-hills which +seem to be of very different ages, and to have been formed under +different relative conditions of land and water. [Footnote: Krause, +speaking of the dunes on the coast of Prussia, says: "Their origin +belongs to three different periods, in which important changes in the +relative level of sea and land have unquestionably taken place.... +Except in the deep depressions between them, the dunes are everywhere +sprinkled, to a considerable height, with brown oxydulated iron, which +has penetrated into the sand to the depth of from three to eighteen +inches, and colored it red. ... Above the iron is a stratum of sand +differing in composition from ordinary sea-sand, and on this, growing +woods are always found.... The gradually accumulated forest soil occurs +in beds of from one to three feet thick, and changes, proceeding upward, +from gray sand to black humus." + +Even on the third or seaward range, the sand grasses appear and thrive +luxuriantly, at least on the west coast, though Krause doubts whether +the dunes of the east coast were ever thus protected.--Der Dunenbau, pp. +8, 11.] In some cases there has been an upheaval of the coast line since +the formation of the oldest hillocks, and these have become inland +dunes, while younger rows have been thrown up on the new beach laid bare +by elevation of the sea-bed. Our knowledge of the mode of their first +accumulation is derived from observation of the action of wind and water +in the few instances where, with or without the aid of man, new coast +dunes have been accumulated, and of the influence of wind alone in +elevating new sand-heaps inland of the coast tier, when the outer rows +are destroyed by the sea, as also when the sodded surface of ancient +sands has been broken, and the subjacent strata laid open to the air. + +It is a question of much interest, in what degree the naked condition of +most dunes is to be ascribed to the improvidence and indiscretion of +man. There are, in Western France, extensive ranges of dunes covered +with ancient and dense forests, while the recently formed sand-hills +between them and the sea are bare of vegetation, and in some cases are +rapidly advancing upon the wooded dunes, which they threaten to bury +beneath their drifts. Between the old dunes and the new there is no +discoverable difference in material or in structure; but the modern +sand-hills are naked and shifting, the ancient, clothed with vegetation +and fixed. It has been conjectured that artificial methods of +confinement and plantation were employed by the primitive inhabitants of +Gaul; and Laval, basing his calculations on the rate of annual movement +of the shifting dunes, assigns the fifth century of the Christian era as +the period when those processes wore abandoned. [Footnote: Laval, +Memoire sur les Dunes de Gascogne, Annales des Ponts et Chaussees, 1847, +2me semestre, p. 231. The same opinion had been expressed by Bremontier, +Annales des Ponts et Chaussees, 1833, 1er semestre, p. 185.] + +There is no historical evidence that the Gauls were acquainted with +artificial methods of fixing the sands of the coast, and we have little +reason to suppose that they were advanced enough in civilization to be +likely to resort to such processes, especially at a period when land +could have had but a moderate value. + +In other countries, dunes have spontaneously clothed themselves with +forests, and the rapidity with which their surface is covered by various +species of sand-plants, and finally by trees, where man and cattle and +burrowing animals are excluded from them, renders it highly probable +that they would, as a general rule, protect themselves, if left to the +undisturbed action of natural causes. The sand-hills of the Frische +Nehrung, on the coast of Prussia, were formerly wooded down to the +water's edge, and it was only in the last century that, in consequence +of the destruction of their forests, they became moving sands. +[Footnote: "In the Middle Ages," says Willibald Alexis, as quoted by +Muller, Das Buch der Pflanzenwelt, i., p. 16, "the Nebrung was extending +itself further, and the narrow opening near Lochstadt had filled itself +up with sand. A great pine forest bound with its roots the dune sand and +the heath uninterruptedly from Danzig to Pillau. King Frederick William +I. was once in want of money. A certain Herr von Korff promised to +procure it for him, without loan or taxes, if he could be allowed to +remove something quite useless. He thinned out the forests of Prussia, +which then, indeed, possessed little pecuniary value; but he felled the +entire woods of the Frische Nebrung, so far as they lay within the +Prussian territory. The financial operation was a success. The king had +money, but in the material effects which resulted from it, the state +received irreparable injury. The sea-winds rush over the bared hills; +the Frische Haff is half-choked with sand; the channel between Elbing, +the sea, and Konigsberg is endangered, and the fisheries in the Haff +injured. The operation of Herr von Korff brought the king 200,000 +thalers. The state would now willingly expend millions to restore the +forests again."] There is every reason to believe that the dunes of the +Netherlands were clothed with trees until after the Roman invasion. The +old geographers, in describing these countries, speak of vast forests +extending to the very brink of the sea; but drifting coast dunes are +first mentioned by the chroniclers of the Middle Ages, and so far as we +know they have assumed a destructive character in consequence of the +improvidence of man. [Footnote: Staring, Voormaals en Thans, p. 231. +Had the dunes of the Netherlandish and French coasts, at the period of +the Roman invasion, resembled the moving sand-hills of the present day, +it is inconceivable that they could have escaped the notice of so acute +a physical geographer as Strabo; and the absolute silence of Caesar, +Ptolemy, and the encyclopaedic Pliny, respecting them, would be not less +inexplicable.] The history of the dunes of Michigan, so far as I have +been able to learn from my own observation, or that of others, is the +same. Thirty years ago, when that region was scarcely inhabited, they +were generally covered with a thick growth of trees, chiefly pines, and +underwood, and there was little appearance of undermining and wash on +the lake side, or of shifting of the sands, except where the trees had +been cut or turned up by the roots. [Footnote: The sands of Cape Cod were +partially, if not completely, covered with vegetation by nature. Dr. +Dwight, describing the dunes as they were in 1800, says: "Some of them +are covered with beach grass; some fringed with whortleberry bushes; and +some tufted with a small and singular growth of oaks. ... The parts of +this barrier which are covered with whortleberry bushes and with oaks, +have been either not at all or very little blown. The oaks, +particularly, appear to be the continuation of the forests originally +formed on this spot. ... They wore all the marks of extreme age; were, +in some instances, already decayed, and in others decaying; were hoary +with moss and were deformed by branches, broken and wasted, not by +violence, but by time."--Travels, iii., p. 91] + +Nature, as she builds up dunes for the protection of the seashore, +provides, with similar conservatism, for the preservation of the dunes +themselves; so that, without the interference of man, these hillocks +would be, not perhaps absolutely perpetual, but very lasting in +duration, and very slowly altered in form or position. When once covered +with the trees, shrubs, and herbaceous growths adapted to such +localities, dunes undergo no apparent change, except the slow occasional +undermining of the outer tier, and accidental destruction by the +exposure of the interior, from the burrowing of animals, or the +upturning of trees with their roots, and all these causes of +displacement are very much less destructive when a vegetable covering +exists in the immediate neighborhood of the breach. + + +Protection of Dunes. + +Before the occupation of the coasts by man, dunes, at all points where +they have been observed, seem to have been protected in their rear by +forests, which served to break the force of the winds in both +directions, [Footnote: Bergsoe (Reventlovs Virksomhed, ii., 3) states +that the dunes on the west coast of Jutland were stationary before the +destruction of the forests to the east of them. The felling of the tall +trees removed the resistance to the lower currents of the westerly +winds, and the sands have since buried a great extent of fertile soil. +See also same work, ii., p. 124.] and to have spontaneously clothed +themselves with a dense growth of the various plants, grasses, shrubs, +and trees, which nature has assigned to such soils. It is observed in +Europe that dunes, though now without the shelter of a forest country +behind them, begin to protect themselves as soon as human trespassers +are excluded, and grazing animals denied access to them. Herbaceous and +arborescent plants spring up almost at once, first in the depressions, +and then upon the surface of the sand-hills. Every seed that sprouts, +binds together a certain amount of sand by its roots, shades a little +ground with its leaves, and furnishes food and shelter for still younger +or smaller growths. A succession of a very few favorable seasons +suffices to bind the whole surface together with a vegetable network, +and the power of resistance possessed by the dunes themselves, and the +protection they afford to the fields behind them, are just in proportion +to the abundance and density of the plants they support. + +The growth of the vegetable covering can, of course, be much accelerated +by judicious planting and watchful care, and this species of improvement +is now carried on upon a vast scale on the sandy coasts of Western +Europe, wherever the value of land is considerable and the population +dense. + + +Use of Dunes as a Barrier against the Sea. + +Although the sea throws up large quantities of sand on flat lee-shores, +there are many cases where it continually encroaches on those same +shores and washes them away. At all points of the shallow North Sea +where the agitation of the waves extends to the bottom, banks are +forming and rolling eastwards. Hence the sea-sand tends to accumulate +upon the coast of Schleswig-Holstein and Jutland, and were there no +conflicting influences, the shore would rapidly extend itself westwards. +But the same waves which wash the sand to the coast undermine the beach +they cover, and still more rapidly degrade the shore at points where it +is too high to receive partial protection by the formation of dunes upon +it. The earth of the coast is generally composed of particles finer, +lighter, and more transportable by water than the sea-sand. While, +therefore, the billows raised by a heavy west wind may roll up and +deposit along the beach thousands of tons of sand, the same waves may +swallow up even a larger quantity of fine shore-earth. This earth, with +a portion of the sand, is swept off by northwardly and southwardly +currents, and let fall at other points of the coast, or carried off, +altogether, out of the reach of causes which might bring it back to its +former position. + +Although, then, the eastern shore of the German Ocean here and there +advances into the sea, it in general retreats before it, and but for the +protection afforded it by natural arrangements seconded by the art and +industry of man, whole provinces would soon be engulfed by the waters. +This protection consists in an almost unbroken chain of sand banks and +dunes, extending from the northernmost point of Jutland to the Elbe, a +distance of not much less than three hundred miles, and from the Elbe +again, though with more frequent and wider interruptions, to the +Atlantic borders of France and Spain. So long as the dunes are +maintained by nature or by human art, they serve, like any other +embankment or dike, as a partial or a complete protection against the +encroachments of the sea; and on the other hand, when their drifts are +not checked by natural processes, or by the industry of man, they become +a cause of as certain, if not of as sudden, destruction as the ocean +itself whose advance they retard. On the whole, the dunes on the coast +of the German Sea, notwithstanding the great quantity of often fertile +land they cover, and the evils which result from their movement, are a +protective and beneficial agent, and their maintenance is an object of +solicitude with the Governments and people of the shores they defend. +[Footnote: "We must, therefore, not be surprised to see the people here +deal as gingerly with their dunes as if treading among eggs. He who is +lucky enough to own a molehill of dune pets it affectionately, and +spends his substance in cherishing and fattening it. That fair, fertile, +rich province, the peninsula of Eiderstadt in the south of Friesland, +has, on the point towards the sea, only a tiny row of dunes, some six +miles long or so; but the people talk of their fringe of sand hills, as +if it were a border set with pearls. They look upon it as their best +defence against Neptune. They have connected it with their system of +dikes, and for years have kept sentries posted to protect it against +wanton injury."--J. G. Kohl, Die Inseln u. Marschen Schleswig-Holsteins, +ii., p. 115.] + +The eastward progress of the sea on the Danish, Netherlandish, and +French coasts depends so much on local geological structure, on the +force and direction of tidal and other marine currents, on the volume +and rapidity of coast rivers, on the contingencies of the weather and on +other varying circumstances, that no general rate can be assigned to it. + +At Agger, near the western end of the Liimfjord, in Jutland, the coast +was washed away, between the years 1815 and 1839, at the rate of more +than eighteen feet a year. The advance of the sea appears to have been +something less rapid for a century before; but from 1840 to 1857, it +gained upon the land no less than thirty feet a year. At other points of +the shore of Jutland the loss is smaller, but the sea is encroaching +generally upon the whole line of the coast. [Footnote: Andersen, "Om +Klitformationen," pp. 68-72.] + + +The Liimfjord. + +The irruption of the sea into the fresh-water lagoon of Liimfjord in +Jutland, in 1825--one of the most remarkable encroachments of the ocean +in modern times--is expressly ascribed to "mismanagement of the dunes" +on the narrow neck of land which separated the fjord from the North Sea. +At earlier periods the sea had swept across the isthmus, and even burst +through it, but the channel had been filled up again, sometimes by +artificial means, sometimes by the operation of natural causes, and on +all these occasions effects were produced very similar to those +resulting from the formation of the new channel in 1825, which still +remains open. [Footnote: Id., pp. 231, 232. Andresen's work, though +printed in 1861, was finished in 1859. Lyell (Antiquity of Man, 1863, p. +14) says: "Even in the course of the present century, the salt-waters +have made one eruption into the Baltic by the Liimfjord, although they +have been now again excluded."] Within comparatively recent historical +ages, the Liimfjord has thus been several times alternately filled with +fresh and with salt water, and man has produced, by neglecting the +dunes, or at least might have prevented by maintaining them, changes +identical with those which are usually ascribed to the action of great +geological causes, and sometimes supposed to have required vast periods +of time for their accomplishment. + +"This breach," says Forchhammer, "which converted the Liimfjord into a +sound, and the northern part of Jutland into an island, occasioned +remarkable changes. The first and most striking phenomenon was the +sudden destruction of almost all the fresh-water fish previously +inhabiting this lagoon, which was famous for its abundant fisheries. +Millions of fresh-water fish were thrown on shore, partly dead and +partly dying, and were carted off by the people. A few only survived, +and still frequent the shores at the mouth of the brooks. The eel, +however, has gradually accommodated itself to the change of +circumstances, and is found in all parts of the fjord, while to all +other fresh-water fish, the salt-water of the ocean seems to have been +fatal. It is more than probable that the sand washed in by the irruption +covers, in many places, a layer of dead fish, and has thus prepared the +way for a petrified stratum similar to those observed in so many older +formations. + +"As it seems to be a law of nature that animals whose life is suddenly +extinguished while yet in full vigor, are the most likely to be +preserved by petrification, we find here one of the conditions favorable +to the formation of such a petrified stratum. The bottom of the +Liimfjord was covered with a vigorous growth of aquatic plants, +belonging both to fresh and to salt water, especially Zostera marina. +This vegetation totally disappeared after the irruption, and, in some +instances, was buried by the sand; and here again we have a familiar +phenomenon often observed in ancient strata--the indication of a given +formation by a particular vegetable species--and when the strata +deposited at the time of the breach shall be accessible by upheaval, the +period of eruption will be marked by a stratum of Zostera, and probably +by impressions of fresh-water fishes. + +"It is very remarkable that the Zostera marina, a sea-plant, was +destroyed even where no sand was deposited. This was probably in +consequence of the sudden change from brackish to salt water ... It is +well established that the Liimfjord communicated with the German Ocean +at some former period. + +To that era belong the deep beds of oyster shells and Cardium edule, +which are still found at the bottom of the fjord. And now, after an +interval of centuries, during which the lagoon contained no salt-water +shell fish, it again produces great numbers of Mytilus edulis. Could we +obtain a deep section of the bottom, we should find beds of Ostrea +edulis and Cardium edule, then a layer of Zostera marina with +fresh-water fish, and then a bed of Mytilus edulis. If, in course of +time, the new channel should be closed, the brooks would fill the lagoon +again with fresh water; fresh-water fish and shell fish would reappear, +and thus we should have a repeated alternation of organic inhabitants of +the sea and of the waters of the land. + +"These events have been accompanied with but a comparatively +insignificant change of land surface, while the formations in the bed of +this inland sea have been totally revolutionized in character." +[Footnote: Forchhammer, Geognostiche Studien am Meeres-Ufer, Leonhard +und Bronn, Jahrbuch, 1841, pp. 11, 13.] Coasts of Schleswig-Holstein, +Holland, and France. On the islands on the coast of Schleswig-Holstein, +the advance of the sea has been more unequivocal and more rapid. Near +the beginning of the last century, the dunes which had protected the +western coast of the island of Sylt began to roll to the east, and the +sea followed closely as they retired. In 1757, the church of Rantum, a +village upon that island, was obliged to be taken down in consequence of +the advance of the sand-hills; in 1791, these hills had passed beyond +its site, the waves had swallowed up its foundations, and the sea gained +so rapidly, that, fifty years later, the spot where they lay was seven +hundred feet from the shore. [Footnote: Andresen, Om Klitformationen, pp. +68, 72.] The most prominent geological landmark on the coast of Holland +is the Huis te Britten, Arx Britannica, a fortress built by the Romans, +in the time of Caligula, on the main land near the mouth of the Rhine. +At the close of the seventeenth century, the sea had advanced sixteen +hundred paces beyond it. The older Dutch annalists record, with much +parade of numerical accuracy, frequent encroachments of the sea upon +many parts of the Netherlandish coast. But though the general fact of an +advance of the ocean upon the land is established beyond dispute, the +precision of the measurements which have been given is open to question. +Staring, however, who thinks the erosion of the coast much exaggerated +by popular geographers, admits a loss of more than a million and a half +acres, chiefly worthless morass; [Footnote: Voormaals en Thans, pp. 126, +170.] and it is certain that but for the resistance of man, but for his +erection of dikes and protection of dunes, there would now be left of +Holland little but the name. It is, as has been already seen, still a +debated question among geologists whether the coast of Holland now is, +and for centuries has been, subsiding. I believe most investigators +maintain the affirmative; and if the fact is so, the advance of the sea +upon the land is, in part, due to this cause. But the rate of subsidence +is at all events very small, and therefore the encroachments of the +ocean upon the coast are mainly to be ascribed to the erosion and +transportation of the soil by marine waves and currents. + +The sea is fast advancing at several points of the western coast of +France, and unknown causes have given a new impulse to its ravages since +the commencement of the present century. Between 1830 and 1842, the +Point de Grave, on the north side of the Girondo, retreated one hundred +and eighty metres, or fifty feet per year; from the latter year to 1846, +the rate was increased to more than three times that quantity, and the +loss in those four years was about six hundred feet. All the buildings +at the extremity of the peninsula have been taken down and rebuilt +farther landwards, and the lighthouse of the Grave now occupies its +third position. The sea attacked the base of the peninsula also, and the +Point de Grave and the adjacent coasts have been for thirty years the +scene of one of the most obstinately contested struggles between man and +the ocean recorded in the annals of modern engineering. + + +Movement of Dunes. + +Besides their importance as a barrier against the inroads of the ocean, +dunes are useful by sheltering the cultivated ground behind them from +the violence of the sea-wind, from salt spray, and from the drifts of +beach sand which would otherwise overwhelm them. But the dunes +themselves, unless their surface sands are kept moist, and confined by +the growth of plants, or at least by a crust of vegetable earth, are +constantly rolling inwards, and thus, while, on one side, they lay bare +the traces of ancient human habitations or other evidences of the social +life of primitive man, they are, on the other, burying fields, houses, +churches, and converting populous districts into barren and deserted +wastes. + +Especially destructive are they when, by any accident, a cavity is +opened into them to a considerable depth, thereby giving the wind access +to the interior, where the sand is thus first dried, and then scooped +out and scattered far over the neighboring soil. The dune is now a +magazine of sand, no longer a rampart against it, and mischief from this +source seems more difficult to resist than from almost any other drift, +because the supply of material at the command of the wind is more +abundant and more concentrated than in its original thin and widespread +deposits on the beach. The burrowing of conies in the dunes is, in this +way, not unfreqnently a cause of their destruction and of great injury +to the fields behind them. Drifts, and even inland sand-hills, sometimes +result from breaking the surface of more level sand deposits, far within +the range of the coast dunes. Thus we learn from Staring, that one of +the highest inland dunes in Friesland owes its origin to the opening of +the drift sand by the uprooting of a large Oak. [Footnote: De Bodem van +Nederland, i. p. 425.] + +Great as are the ravages produced by the encroachment of the sea upon +the western shores of continental Europe, they have been in some degree +compensated by spontaneous marine deposits at other points of the coast, +and we have seen in a former chapter that the industry of man has +reclaimed a large territory from the bosom of the ocean. These latter +triumphs are not of recent origin, and the incipient victories which +paved the way for them date back perhaps as far as ten centuries. In the +meantime, the dunes had been left to the operation of the laws of +nature, or rather freed, by human imprudence, from the fetters with +which nature had bound them, and it is scarcely three generations since +man first attempted to check their destructive movements. As they +advanced, he unresistingly yielded and retreated before them, and they +have buried under their sandy billows many hundreds of square miles of +luxuriant cornfields and vineyards and forests. + +On the west coast of France a belt of dunes, varying in width from a +quarter of a mile to five miles, extends from the Adour to the estuary +of the Gironde, and covers an area of nine hundred and seventy square +kilometres, or two hundred and forty thousand acres. When not fixed by +vegetable growths, these dunes advance eastwards at a mean rate of about +one rod, or sixteen and a half feet, a year. Wo do not know historically +when they began to drift, but if we suppose their motion to have been +always the same as at present, they would have passed over the space +between the sea coast and their present eastern border, and covered the +large area above mentioned, in fourteen hundred years. We know, from +written records, that they have buried extensive fields and forests and +thriving villages, and changed the courses of rivers, and that the +lighter particles carried from them by the winds, even where not +transported in sufficient quantities to form sand-hills, have rendered +sterile much land formerly fertile. [Footnote: The movement of the dunes +has been hardly less destructive on the north side of the Gironde. See +the valuable articles of Elisee Reclus in the Revue des Deux Mondes for +December 1862, and several later numbers, entitled "Le Littoral de la +France."] They have also injuriously obstructed the natural drainage of +the maritime districts by choking up the beds of the streams, and +forming lakes and pestilential swamps of no inconsiderable extent. In +fact, so completely do they embank the coast, that between the Gironde +and the village of Mimizan, a distance of one hundred miles, there are +but two outlets for the discharge of all the waters which flow from the +land to the sea; and the eastern front of the dunes is bordered by a +succession of stagnant pools, some of which are more than six miles in +length and breadth. [Footnote: Laval, Memoire sur les Dunes du Golfe de +Gascongne, Annales des Ponte et Chaussees, 1847, p. 223. The author +adds, as a curious and unexplained fact, that some of these pools, +though evidently not original formations but mere accumulations of water +dammed up by the dunes, have, along their western shore, near the base +of the sand-hills, a depth of more than one hundred and thirty feet, and +hence their bottoms are not less than eighty feet below the level of the +lowest tides. Their western banks descend steeply, conforming nearly to +the slope of the dunes, while on the north-east and south the +inclination of their beds is very gradual. The greatest depth of these +pools corresponds to that of the sea ten miles from the shore. Is it +possible that the weight of the sands has pressed together the soil on +which they rest, and thus occasioned a subsidence of the surface +extending beyond their base? + +A more probable explanation of the fact stated in the note is suggested +by Elisee Reclus, in an article entitled Le Littoral de la France, in +the Revue des Deux Mondes for September 1, 1864, pp. 193, 194. This able +writer believes such pools to be the remains of ancient maritime bays, +which have been cut off from the ocean by gradually accumulated sand +banks raised by the waves and winds to the character of dunes.] A range +of dunes extends along the whole western coast of Jutland and +Schleswig-Holstein, and the movement of these sand-hills was formerly, +and at some points still is, very destructive. The rate of eastward +movement of the drifting dunes varies from three to twenty-four feet per +annum. If we adopt the mean of thirteen feet and a half for the annual +motion, these dunes have traversed the widest part of the belt in about +twenty-five hundred years. Historical data are wanting as to the period +of the formation of these dunes and of the commencement of their +drifting; but there is recorded evidence that they have buried a vast +extent of valuable land within three or four centuries, and further +proof is found in the fact that the movement of the sands is constantly +uncovering ruins of ancient buildings, and other evidences of human +occupation, at points far within the present limits of the uninhabitable +desert. Andresen estimates the average depth of the sand deposited over +this area at thirty feet, which would give a cubic mile and a half for +the total quantity. [Footnote: Andresen, On Klitformationen, pp. 56, 79, +82] + +The drifting of the dunes on the coast of Prussia commenced not much +more than a hundred years ago. The Frische Nehrung is separated from the +mainland by the Frische Haff, and there is but a narrow strip of arable +land along its eastern borders. Hence its rolling sands have covered a +comparatively small extent of dry land, but fields and villages have +been buried and valuable forests laid waste by them. The loose coast-row +has drifted over the inland ranges, which, as was noticed in the +description of these dunes on a former page, were protected by a surface +of different composition, and the sand has thus been raised to a height +which it could not have reached upon level ground. This elevation has +enabled it to advance upon and overwhelm woods, which, upon a plain, +would have checked its progress, and, in one instance, a forest of many +hundred acres of tall pines was destroyed by the drifts between 1804 and +1827. + + +Control of Dunes by Man. + +There are three principal modes in which the industry of man is brought +to bear upon the dunes. First, the creation of them, at points where, +from changes in the currents or other causes, new encroachments of the +sea are threatened; second, the maintenance and protection of them where +they have been naturally formed; and third, the removal of the inner +rows where the belt is so broad that no danger is to be apprehended from +the loss of them. + +In describing the natural formation of dunes, it was said that they +began with an accumulation of sand around some vegetable or other +accidental obstruction to the drifting of the particles. A high, +perpendicular cliff, which deadens the wind altogether, prevents all +accumulation of sand; but, up to a certain point, the higher and broader +the obstruction, the more sand will heap up in front of it, and the more +will that which falls behind it be protected from drifting further. This +familiar observation has taught the inhabitants of the coast that an +artificial wall or dike will, in many situations, give rise to a broad +belt of dunes. Thus a sand dike or wall, of three or four miles in +length, thrown in 1610 across the Koegras, a tide-washed flat between +the Zuiderzee and the North Sea, has occasioned the formation of rows of +dunes a mile in breadth, and thus excluded the sea altogether from the +Koegras. A similar dike, called the Zijperzeedijk, has produced another +scarcely less extensive belt in the course of two centuries. A few years +since, the sea was threatening to cut through the island of Ameland, +and, by encroachment on the southern side and the blowing off of the +sand from a low flat which connected the two higher parts of the island, +it had made such progress, that in heavy storms the waves sometimes +rolled quite across the isthmus. The construction of a breakwater and a +sand dike have already checked the advance of the sea, and a large +number of sand-hills has been formed, the rapid growth of which promises +complete future security against both wind and wave. Similar effects +have been produced by the erection of plank fences, and even of simple +screens of wattling and reeds. [Footnote: Staring, De Bodem van +Nederland, i., pp. 329-331. Id., Voormaals en Thans, p. 163. Andresen, +Om Klitformationen, pp. 280, 295. + +The creation of new dunes, by the processes mentioned in the text, seems +to be much older in Europe than the adoption of measures for securing +them by planting. Dr. Dwight mentions a case in Massachusetts, where a +beach was restored, and new dunes formed, by planting beach grass. +"Within the memory of my informant, the sea broke over the beach which +connects Truro with Province Town, and swept the body of it away for +some distance. The beach grass was immediately planted on the spot; in +consequence of which the beach was again raised to a sufficient height, +and in various places into hills."--Travels, iii., p. 93.] + +The dunes of Holland are sometimes protected from the dashing of the +waves by a revetement of stone, or by piles; and the lateral high-water +currents, which wash away their base, are occasionally checked by +transverse walls running from the foot of the dunes to low-water mark; +but the great expense of such constructions has prevented their adoption +on a large scale. [Footnote: Staring, i., pp. 310, 332.] The principal +means relied on for the protection of the sand-hills are the planting of +their surfaces and the exclusion of burrowing and grazing animals. There +are grasses, creeping plants, and shrubs of spontaneous growth, which +flourish in loose sand, and, if protected, spread over considerable +tracts, and finally convert their face into a soil capable of +cultivation, or, at least, of producing forest trees. Krause enumerates +one hundred and seventy-one plants as native to the coast sands of +Prussia, and the observations of Andresen in Jutland carry the number of +these vegetables up to two hundred and thirty-four. + +Some of these plants, especially the Arundo arenaria or arenosa, or +Psamma or Psammophila arenaria--Klittetag, or Hjelme in Danish, helm in +Dutch, Dunenhalm, Sandschilf, or Hugelrohr in German, gourbet in French, +and marram in English--are exclusively confined to sandy soils, and +thrive well only in a saline atmosphere. [Footnote: There is some +confusion in the popular use of these names, and in the scientific +designations of sand-plants, and they are possibly applied to different +plants in different places. Some writers style the gourbet Calamagrostis +arenaria, and distinguish it from the Danish Klittetag or Hjelme.] The +arundo grows to the height of about twenty-four inches, but sends its +strong roots with their many rootlets to a distance of forty or fifty +feet. It has the peculiar property of flourishing best in the loosest +soil, and a sand-shower seems to refresh it as the rain revives the +thirsty plants of the common earth. Its roots bind together the dunes, +and its leaves protect their surface. When the sand ceases to drift, the +arundo dies, its decaying roots fertilizing the sand, and the +decomposition of its leaves forming a layer of vegetable earth over it. +Then follows a succession of other plants which gradually fit the +sand-hills by growth and decay, for forest planting, for pasturage, and +sometimes for ordinary agricultural use. + +But the protection and gradual transformation of the dunes is not the +only service rendered by this valuable plant. Its leaves are nutritious +food for sheep and cattle, its seeds for poultry; [Footnote: Bread, not +indeed very palatable, has been made of the seeds of the arundo, but the +quantity which can be gathered is not sufficient to form an important +economical resource.--Andresen, Om Klitformationen, p. 160.] cordage and +netting twine are manufactured from its fibres, it makes a good material +for thatching, and its dried roots furnish excellent fuel. These useful +qualities, unfortunately, are too often prejudicial to its growth. The +peasants feed it down with their cattle, cut it for rope-making, or dig +if up for fuel, and it has been found necessary to resort to severe +legislation to prevent them from bringing ruin upon themselves by thus +improvidently sacrificing their most effectual safeguard against the +drifting of the sands. [Footnote: Bergsoe, Reventlovs Virksomhed, ii., +p. 4.] + +In 1539 a decree of Christian III., king of Denmark, imposed a fine upon +persons convicted of destroying certain species of sand-plants upon the +west coast of Jutland. This ordinance was renewed and made more +comprehensive in 1558, and in 1569 the inhabitants of several districts +were required, by royal rescript, to do their best to check the +sand-drifts, though the specific measures to be adopted for that purpose +are not indicated. Various laws against stripping the dunes of their +vegetation were enacted in the following century, but no active measures +were taken for the subjugation of the sand-drifts until 1779, when a +preliminary system of operation for that purpose was adopted. This +consisted in little more than the planting of the Arundo arenaria, and +other sand-plants, and the exclusion of animals destructive to those +vegetables. [Footnote: Measures were taken for the protection of the +dunes of Cape Cod, in Massachusetts, during the colonial period, though +I believe they are now substantially abandoned. A hundred years ago, +before the valley of the Mississippi, or even the rich plains of Central +and Western New York, were opened to the white settler, the value of +land was relatively much greater in New England than it is at present, +and consequently some rural improvements were then worth making, which +would not now yield sufficient returns to tempt the investment of +capital. The money and the time required to subdue and render productive +twenty acres of sea-sand on Cape Cod, would buy a "section" and rear a +family in Illinois. The son of the Pilgrim, therefore, abandons the +sea-hills, and seeks a better fortune on the fertile prairies of the +West. See Dwight, Travels, i., pp. 92, 93.] Ten years later, plantations +of forest trees, which have since proved so valuable a means of fixing +the dunes and rendering them productive, were commenced, and have been +continued ever since. [Footnote: Andresen, Om Klitformationen, pp. 237, +240.] During this latter period, Bremontier, without any knowledge of +what was doing in Denmark, experimented upon the cultivation of forest +trees on the dunes of Gascony, and perfected a system, which, with some +improvements in matters of detail, is still largely pursued on those +shores. + +The example of Denmark was soon followed in the neighboring kingdom of +Prussia, and in the Netherlands; and, as we shall see hereafter, these +improvements have been everywhere crowned with most flattering success. + +Under the administration of Reventlov, a little before the close of the +last century, the Danish Government organized a regular system of +improvement in the economy of the dunes. They were planted with the +arundo and other vegetables of similar habits, protected against +trespassers, and at last partly covered with forest trees. By these +means much waste soil has been converted into arable ground, a large +growth of valuable timber obtained, and the further spread of the +drifts, which threatened to lay waste the whole peninsula of Jutland, to +a considerable extent arrested. + +In France, the operations for fixing and reclaiming the dunes--which +began under the direction of Bremontier about the same time as in +Denmark, and which are, in principle and in many of their details, +similar to those employed in the latter kingdom--have been conducted on +a far larger scale, and with greater success, than in any other country. +This is partly owing to a climate more favorable to the growth of +suitable forest trees than that of Northern Europe, and partly to the +liberality of the Government, which, having more important landed +interests to protect, has put larger means at the disposal of the +engineers than Denmark and Prussia have found it convenient to +appropriate to that purpose. The area of the dunes already secured from +drifting, and planted by the processes invented by Bremontier and +perfected by his successors, is about 100,000 acres. [Footnote: "These +plantations, perseveringly continued from the time of Bremontier, now +cover more than 40,000 hectares, and compose forests which are not only +the salvation of the department, but constitute its wealth." --Clave, +Etudes Forestieres, p. 254. Other authors have stated the plantations of +the French dunes to be much more extensive.] This amount of productive +soil, then, has been added to the resources of France, and a still +greater quantity of valuable land has been thereby rescued from the +otherwise certain destruction with which it was threatened by the +advance of the rolling sand-hills. + +The improvements of the dunes on the coast of West Prussia began in +1795, under Soren Bjorn, a native of Denmark, and, with the exception of +the ten years between 1807 and 1817, they have been prosecuted ever +since. The methods do not differ essentially from those employed in +Denmark and France, though they are modified by local circumstances, +and, with respect to the trees selected for planting, by climate. In +1850, between the mouth of the Vistula and Kahlberg, 6,300 acres, +including about 1,900 acres planted with pines and birches, had been +secured from drifting; between Kahlberg and the eastern boundary of West +Prussia, 8,000 acres; and important preliminary operations had been +carried on for subduing the dunes on the west coast. [Footnote: Kruse, +Dunenbau, pp. 34, 38, 40.] + +The tree which has been fonnd to thrive best upon the sand-hills of the +French coast, and at the same time to confine the sand most firmly and +yield the largest pecuniary returns, is the maritime pine, Pinus +maritima, a species valuable both for its timber and for its resinous +products. It is always grown from seed, and the young shoots require to +be protected for several seasons, by the branches of other trees, +planted in rows, or spread over the surface and staked down, by the +growth of the Arundo arenaria and other small sand-plants, or by wattled +hedges. The beach, from which the sand is derived, has been generally +planted with the arundo, because the pine does not thrive well so near +the sea; but it is thought that a species of tamarisk is likely to +succeed in that latitude even better than the arundo. The shade and the +protection offered by the branching top of this pine are favorable to +the growth of deciduous trees, and, while still young, of shrubs and +smaller plants, which contribute more rapidly to the formation of +vegetable mould, and thus, when the pine has once taken root, the +redemption of the waste is considered as effectually secured. + +In France, the maritime pine is planted on the sands of the interior as +well as on the dunes of the seacoast, and with equal advantage. This +tree resembles the pitch pine of the Southern American States in its +habits, and is applied to the same uses. The extraction of turpentine +from it begins at the age of about twenty years, or when it has attained +a diameter of from nine to twelve inches. Incisions are made up and down +the trunk, to the depth of about half an inch in the wood, and it is +insisted that if not more than two such slits are cut, the tree is not +sensibly injured by the process. The growth, indeed, is somewhat +checked, but the wood becomes superior to that of trees from which the +turpentine is not extracted. Thus treated, the pine continues to +flourish to the age of one hundred or one hundred and twenty years, and +up to this age the trees on an acre yield annually 300 pounds of essence +of turpentine, and 250 pounds of resin, worth together not far from ten +dollars. The expense of extraction and distillation is calculated at +about four dollars, and a clear profit of more than five dollars per +acre is left. [Footnote: These processes are substantially similar to +those employed in the pineries of the Carolinas, but they are better +systematized and more economically conducted in France. In the latter +country, all the products of the pine, even to the cones, find a +remunerating market, while, in America, the price of resin is so low, +that in the fierce steamboat races on the great rivers, large quantities +of it are thrown into the furnaces to increase the intensity of the +fires. In a carefully prepared article on the Southern pineries +published in an American magazine--I think Harper's--a few years ago, it +was stated that the resin from the turpentine distilleries was sometimes +allowed to run to waste; and the writer, in one instance, observed a +mass, thus rejected as rubbish, which was estimated to amount to two +thousand barrels. Olmsted saw, near a distillery which had been in +operation but a single year, a pool of resin estimated to contain three +thousand barrels, which had been allowed to run off as waste.--A Journey +in the seaboard Slave States, 1863, p. 345.] This is exclusive of the +value of the timber, when finally cut, which, of course, amounts to a +very considerable sum. In Denmark, where the climate is much colder, +hardier conifers, as well as the birch and other northern trees, are +found to answer a better purpose than the maritime pine, and it is +doubtful whether this tree would be able to resist the winter on the +dunes of Massachusetts. Probably the pitch-pine of the Northern States, +in conjunction with some of the American oaks, birches, and poplars, and +especially the robinia or locust, would prove very suitable to be +employed on the sand-hills of Cape Cod and Long Island. The ailanthus, +now coming into notice as a sand-loving tree, some species of tamarisk, +and perhaps the Aspressus macrocarpa, already found useful on the dunes +in California, may prove valuable auxiliaries in resisting the +encroachment of drifting sands, whether in America or in Europe, and the +intermixing of different species would doubtless be attended with as +valuable results in this as in other branches of forest economy. It +cannot, indeed, be affirmed that human power is able to arrest +altogether the incursions of the waves on sandy coasts, by planting the +beach, and clothing the dunes with wood. On the contrary, both in +Holland and on the French coast, it has been found necessary to protect +the dunes themselves by piling and by piers and sea-walls of heavy +masonry. But experience has amply shown that the processes referred to +are entirely successful in preventing the movement of the dunes, and the +drifting of their sands over cultivated lands behind them; and that, at +the same time, the plantations very much retard the landward progress of +the waters. [Footnote: See a very interesting article entitled "Le +Littoral de la France," by Elisee Reclus, in the Revue des Deux Mondes +for December, 1862, pp. 901, 936.] + +Besides the special office of dune plantations already noticed, these +forests have the same general uses as other woods, and they have +sometimes formed by their droppings so thick a layer of vegetable mould +that the sand beneath has become sufficiently secured to allow the wood +to be felled, and the surface to be ploughed and cultivated with +ordinary field crops. + +In some cases it has been found possible to confine and cultivate coast +sand-hills, even without preliminary forestal plantation. Thus, in the +vicinity of Cap Breton in France, a peculiar process is successfully +employed, both for preventing the drifting of dunes, and for rendering +the sands themselves immediately productive; but this method is +applicable only in exceptional cases of favorable climate and exposure. +It consists in planting vineyards upon the dunes, and protecting them by +hedges of broom, Erica scoparia, so disposed as to form rectangles about +thirty feet by forty. The vines planted in these enclosures thrive +admirably, and the grapes produced by them are among the best grown in +France. The dunes are so far from being an unfavorable soil for the +vine, that fresh sea-sand is regularly employed as a fertilizer for it, +alternating every other season with ordinary manure. The quantity of +sand thus applied every second year, raises the surface of the vineyard +about four or five inches. The vines are cut down every year to three or +four shoots, and the raising of the soil rapidly covers the old stocks. +As fast as buried, they send out new roots near the surface, and thus +the vineyard is constantly renewed, and has always a youthful +appearance, though it may have been already planted a couple of +generations. This practice is ascertained to have been followed for two +centuries, and is among the oldest well-authenticated attempts of man to +resist and vanquish the dunes. [Footnote: Boitel, Mise en valeur des +Terres pauvres, pp. 212, 218.] + +The artificial removal of dunes, no longer necessary as a protection, +does not appear to have been practiced upon a large scale except in the +Netherlands, where the numerous canals furnish an easy and economical +means of transporting the sand, and where the construction and +maintenance of sea and river dikes, and of causeways and other +embankments and fillings, create a great demand for that material. Sand +is also employed in Holland, in large quantities, for improving the +consistence of the tough clay bordering upon or underlying diluvial +deposits, and for forming an artificial soil for the growth of certain +garden and ornamental vegetables. When the dunes are removed, the ground +they covered is restored to the domain of industry; and the quantity of +land recovered in the Netherlands by the removal of the barren sands +which encumbered it, amounts to hundreds and perhaps thousands of acres. + +Inland Dunes. + +Vast deposits of sand, both in the form of dunes and of plains, are +found far in the interior of continents, in the Old World and in the +New. The deserts of Gobi, of Arabia, and of Africa have been rendered +familiar by the narratives of travellers, but the sandy wilderness of +America, and even of Europe, have not yet been generally recognized as +important elements in the geography of the regions where they occur. +There are immense wastes of drifting sands in Poland and other interior +parts of Europe, in Peru, and in the less known regions of our own +Western territory, where their extent is greater than that of all the +coast dunes together which have hitherto been described by European and +American geographers. [Footnote: On the Niobrara river alone, the dunes +cover a surface of twenty thousand square miles.--Hayden, Report on +Geological Survey of Wyoming, 1870, p. 108.] The inland sand-hills of +both hemispheres are composed of substantially the same material and +aggregated by the action of the same natural forces as the dunes of the +coast. There is, therefore, a general resemblance between them, but they +appear, nevertheless, to be distinguished by certain differences which a +more attentive study may perhaps enable geologists to recognize in the +sandstone formed by them. The sand of which they are composed comes in +both principally from the bed of the sea being brought to the surface in +one case by the action of the wind and the waves, in the other by +geological upheaval. [Footnote: American observers do not agree in their +descriptions of the form and character of the sand-grains which compose +the interior dunes of the North American desert. C. C. Parry, geologist +to the Mexican Boundary Commission, in describing the dunes near the +station at a spring thirty-two miles west from the Rio Grande at El +Paso, says: "The separate grains of the sand composing the sand-hills +are seen under a lens to be angular, and not rounded, as would be the +case in regular beach deposits."--U. S. Mexican Boundary Survey, Report +of, vol i., Geological Report of C. C. Parry, p. 10. + +In the general description of the country traversed, same volume, p. 47, +Colonel Emory says that on an "examination of the sand with a microscope +of sufficient power," the grains are seen to be angular, not rounded by +rolling in water. + +On the other hand, Blake, in Geological Report, Pacific Railroad Rep., +vol. v., p. 119, observes that the grains of the dune sand, consisting +of quartz, chalcedony, carnelian, agate, rose quartz, and probably +chrysolite, were much rounded; and on page 241, he says that many of the +sand grains of the Colorado desert are perfect spheres. On page 20 of a +report in vol. ii. of the Pacific Railroad Report, by the same observer, +it is said that an examination of dunes brought from the Llano Estacado +by Captain Pope, showed the grains to be "much rounded by attrition." +The sands described by Mr. Parry and Colonel Emory are not from the same +localities as those examined by Mr. Blake, and the difference in their +character may be due to a difference of origin or of age. In New Mexico, +sixty miles south of Fort Stanton, there are island dunes composed of +finely granulated gypsum.--American Naturalist, Jan. 1871, p. 695.] The +sand of the coast dunes is rendered, to a certain extent, cohesive by +moisture and by the saline and other binding ingredients of sea-water, +while long exposure to meteoric influences has in a great measure +deprived the inland sands of these constituents, though there are not +wanting examples of large accumulations of sand far from the sea, and +yet agglutinated by saline material. Hence, as might be expected, inland +dunes, when not confined by a fixed nucleus, are generally more movable +than those of the coast, and the form of such dunes is more or less +modified by their want of consistence. Thus, the crescent or falciform +shape is described by all observers as more constant and conspicuous in +these sandhills than in those of littoral origin; they tend less to +unite in continuous ridges, and they rarely attain the height or other +dimensions of the dunes of the seashore. Meyer describes the sand-hills +of the Peruvian desert as perfectly falciform in shape and from seven to +fifteen feet high, the chord of their arc measuring from twenty to +seventy paces. The slope of the convex face is described as very small, +that of the concave as high as 70 degrees or 80 degrees, and their +surfaces were rippled. No smaller dunes were observed, nor any in the +process of formation. The concave side uniformly faced the north-west, +except towards the centre of the desert, where, for a distance of one or +two hundred paces, they gradually opened to the west, and then again +gradually resumed the former position. Tschudi observed, in the same +desert, two species of dunes, fixed and movable, and he ascribes a +falciform shape to the movable, a conical to the fixed dunes, or +medanos. "The medanos," he observes, "are hillock-like elevations of +sand, some having a firm, others a loose base. The former [latter], +which are always crescent-shaped, are from ten to twenty feet high, and +have an acute crest. The inner side is perpendicular, and the outer or +bow side forms an angle with a steep inclination downwards. [Footnote: +The dunes of the plains between Bokhara and the Oxus are all horse-shoe +shaped, convex towards the north, from which the prevailing wind blows. +On this side they are sloping, inside precipitous, and from fifteen to +twenty feet high.--Burnes, Journal in Bokhara, ii., pp. 1, 2.] When +driven by violent winds, the medanos pass rapidly over the plains. The +smaller and lighter ones move quickly forward, before the larger; but +the latter soon overtake and crush them, whilst they are themselves +shivered by the collision. These medanos assume all sorts of +extraordinary figures, and sometimes move along the plain in rows +forming most intricate labyrinths.... A plain often appears to be +covered with a row of medanos, and some days afterwards it is again +restored to its level and uniform aspect.... "The medanos with immovable +bases are formed on the blocks of rocks which are scattered about the +plain. The sand is driven against them by the wind, and as soon as it +reaches the top point, it descends on the other side until that is +likewise covered; thus gradually arises a conical-formed hill. [Footnote: +The sand-hills observed by Desor in the Algerian desert were fixed, +changing their form only on the surface as sand was blown to and from +them.--Sahara und Atlas, 1865, p. 21.] Entire hillock chains with acute +crests are formed in a similar manner.... On their southern declivities +are found vast masses of sand, drifted thither by the mid-day gales. The +northern declivity, though not steeper than the southern, is only +sparingly covered with sand. If a hillock chain somewhat distant from +the sea extends in a line parallel with the Andes, namely, from S. S. E. +to N. N. W., the western declivity is almost entirely free of sand, as +it is driven to the plain below by the south-east wind, which constantly +alternates with the wind from the south." [Footnote: Travels in Peru, +New York, 1848, chap. ix.] It is difficult to reconcile this description +with that of Meyen, but if confidence is to be reposed in the accuracy +of either observer, the formation of the sand-hills in question must be +governed by very different laws from those which determine the structure +of coast dunes. Captain Gilliss, of the American navy, found the +sand-hills of the Peruvian desert to be in general crescent-shaped, as +described by Meyen, and a similar structure is said to characterize the +inland dunes of the Llano Estacado and other plateaus of the North +American desert, though those latter are of greater height and other +dimensions than those described by Meyen. There is no very obvious +explanation of this difference in form between maritime and inland +sand-hills, and the subject merits investigation. It is, however, +probable that the great mobility of the flying dunes of the Peruvian +desert is an effect of their dryness, no rain falling in that desert, +and of the want of salt or other binding material to hold their +particles together. + +Inland Sand Plains. + +The inland sand plains of Europe are either derived from the drifting of +dunes or other beach sands, or consist of diluvial deposits, or are +ancient sea-beds uplifted by geological upheaval. As we have seen, when +once the interior of a dune is laid open to the wind, its contents ars +soon scattered far and wide over the adjacent country, and the beach +sands, no longer checked by the rampart which nature had constrained +them to build against their own encroachments, are also carried to +considerable distances from the coast. Few regions have suffered so much +from this cause, in proportion to their extent, as the peninsula of +Jutland. So long as the woods, with which nature had planted the Danish +dunes, were spared, they seem to have been stationary, and we have no +historical evidence, of an earlier date than the sixteenth century, that +they had become in any way injurious. From that period there are +frequent notices of the invasions of cultivated grounds by the sands; +and excavations are constantly bringing to light proof of human +habitation and of agricultural industry, in former ages, on soils now +buried beneath deep drifts from the dunes and beaches of the seacoast. +[Footnote: For details, consult Andresen, Om Klitformationen, pp. 223, +236.] + +Extensive tracts of valuable plain land in the Netherlands and in France +have been covered in the same way with a layer of sand deep enough to +render them infertile, and they can be restored to cultivation only by +processes analogous to those employed for fixing and improving the +dunes. [Footnote: When the deposit is not very deep, and the adjacent +land lying to the leeward of the prevailing winds is covered with water, +or otherwise worthless, the surface is sometimes freed from the drifts +by repeated harrowings, which loosen the sand, so that the wind takes it +up and transports it to grounds where accumulations of it are less +injurious.] Diluvial sand plains, also, have been reclaimed by these +methods in the Duchy of Austria, between Vienna and the Semmering ridge, +in Jutland, and in the great champaign country of Northern Germany, +especially the Mark Brandenburg, where artificial forests can be +propagated with great ease, and where, consequently, this branch of +industry has been pursued on a great scale, and with highly beneficial +results, both as respects the supply of forest products and the +preparation of the soil for agricultural use. + +As has been already observed, inland sands are generally looser, dryer, +and more inclined to drift, than those of the seacoast, where the moist +and saline atmosphere of the ocean keeps them always more or less humid +and cohesive. The sands of the valley of the Lower Euphrates--themselves +probably of submarine origin, and not derived from dunes are advancing +to the north-west with a rapidity which seems fabulous when compared +with the slow movement of the sand-hills of Gascony and the Low German +coasts. Loftus, speaking of Niliyya, an old Arab town a few miles east +of the ruins of Babylon, says that, "in 1848, the sand began to +accumulate around it, and in six years, the desert, within a radius of +six miles, was covered with little, undulating domes, while the ruins of +the city were so buried that it is now impossible to trace their +original form or extent." [Footnote: Travels and Researchs in Chaldaea, +chap. ix. + +Dwight mentions (Travels, vol. iii, p. 101) an instance of great +mischief from the depasturing of the beach grass which had been planted +on a sand plain in Cape Cod: "Here, about one thousand acres were +entirely blown away to the depth, in many places, of ten feet.... Not a +green thing was visible except the whortleberries, which tufted a few +lonely hillocks rising to the height of the original surface and +prevented by this defence from being blown away also. These, although +they varied the prospect, added to the gloom by their strongly +picturesque appearance, by marking exactly the original level of the +plain, and by showing us in this manner the immensity of the mass which +had been thus carried away by the wind. The beach grass had been planted +here, and the ground had been formerly enclosed; but the gates had been +left open, and the cattle had destroyed this invaluable plant."] Loftus +considers this sand-flood as the "vanguard of those vast drifts which +advancing from the south-east, threaten eventually to overwhelm Babylon +and Baghdad." An observation of Layard, cited by Loftus, appears to me +to furnish a possible explanation of this irruption. He "passed two or +three places where the sand, issuing from the earth like water, is +called 'Aioun-er-rummal,' sand springs." These "springs" are very +probably merely the drifting of sand from the ancient subsoil, where the +protecting crust of aquatic deposit and vegetable earth has been broken +through, as in the case of the drift which arose from the upturning of +an oak mentioned on a former page. When the valley of the Euphrates was +regularly irrigated and cultivated, the underlying sands were bound by +moisture, alluvial slime, and vegetation; but now, that all improvement +is neglected, and the surface, no longer watered, has become parched, +powdery, and naked, a mere accidental fissure in the superficial stratum +may soon be enlarged to a wide opening, that will let loose sand enongh +to overwhelm a province. The Landes of Gascony. The most remarkable sand +plain of France lies at the south-western extremity of the empire, and +is generally known as the Landes, or heaths, of Gascony. Clave thus +describes it: "Composed of pure sand, resting on an impermeable stratum +called alios, the soil of the Landes was, for centuries, considered +incapable of cultivation. [Footnote: The alios, which from its color and +consistence was supposed to be a ferruginous formation, appears from +recent observations to contain little iron and to owe most of its +peculiar properties to vegetable elements carried down into the soil by +the percolation of rain-water. See Revue des Eaux et Forets for 1870, p. +801.] Parched in summer, drowned in winter, it produced only ferns, +rushes, and heath, and scarcely furnished pasturage for a few +half-starved flocks. To crown its miseries, this plain was continually +threatened by the encroachments of the dunes. Vast ridges of sand, +thrown up by the waves, for a distance of more than fifty leagues along +the coast, and continually renewed, were driven inland by the west wind, +and, as they rolled over the plain, they buried the soil and the +hamlets, overcame all resistance, and advanced with fearful regularity. +The whole province seemed devoted to certain destruction, when +Bremontier invented his method of fixing the dunes by plantations of the +maritime pine." [Footnote: Etudes Forestieres, p. 250. See, also, Reclus, +La Terre, i., 105, 106.] Although the Landes had been almost abandoned +for ages, they show numerous traces of ancient cultivation and +prosperity, and it is principally by means of the encroachments of the +sands that they have become reduced to their present desolate condition. +The destruction of the coast towns and harbors, which furnished markets +for the products of the plains, the damming up of the rivers, and the +obstruction of the smaller channels of natural drainage by the advance +of the dunes, were no doubt very influential causes; and if we add the +drifting of the sea-sand over the soil, we have at least a partial +explanation of the decayed agriculture and diminished population of this +great waste. When the dunes were once arrested, and the soil to the east +of them was felt to be secure against invasion by them, experiments, in +the way of agricultural improvement, by drainage and plantation, were +commenced, and they have been attended with such signal success, that +the complete recovery of one of the dreariest and most extensive wastes +in Europe may be considered as both a probable and a near +event. [Footnote: Lavergne, Economie Rurale de la France, p. 300, +estimates the area of the Landes of Gascony at 700,000 hectares, or +about 1,700,000 acres. The same author states (p. 301), that when the +Moors were driven from Spain by the blind cupidity and brutal +intolerance of the age, they demanded permission to establish themselves +in this desert; but political and religious prejudices prevented the +granting of this liberty. At this period the Moors were a far more +cultivated people than their Christian persecutors, and they had carried +many arts, that of agriculttire especially, to a higher pitch than any +other European nation. But France was not wise enough to accept what +Spain had cast out, and the Landes remained a waste for three centuries +longer. + +For a brilliant account of the improvement of the Landes, see Edmond +About, Le Progres, chap. vii. + +The forest of Fontainebleau, which contains above 40,000 acres, is not a +plain, but its soil is composed almost wholly of sand, interspersed with +ledges of rock. The sand forms not less than ninety-eight per cent of +the earth, and, as it is almost without water, it would be a drifting +desert but for the artificial propagation of forest trees upon it. The +Landes of Sologne and of Brenne are less known than those of Gascony, +because they are not upon the old great lines of communication. They +once compoaed a forest of 1,200,000 acres, but by clearing the woods +have relapsed into their primitive condition of a barren sand waste. +Active efforts are now in progress to reclaim them.] + +In the northern part of Belgium, and extending across the confines of +Holland, is another very similar heath plain, called the Campine. This +is a vast sand flat, interspersed with marshes and inland dunes, and, +until recently, considered almost wholly incapable of cultivation. +Enormous sums had been expended in reclaiming it by draining and other +familiar agricultural processes, but without results at all proportional +to the capital invested. In 1849, the unimproved portion of the Campine +was estimated at little less than three hundred and fifty thousand +acres. The example of France prompted experiments in the planting of +trees, especially the maritime pine, upon this barren waste, and the +results have now been such as to show that its sands may both be fixed +and made productive, not only without loss, but with positive pecuniary +advantage. [Footnote: Economie Rurale de la Belgique, par Emile De +Laveleye, Revue des Deux Mondes, Juin, 1861, pp. 6l7-644. The quantity +of land annually reclaimed on the Campine is stated at about 4,000 +acres. Canals for navigation and irrigation have been constructed +through the Campine, and it is said that its barren sands, improved at +an expense of one hundred dollars per acre, yield, from the second year, +a return of twenty-five dollars to the acre.] + +There are still unsubdued sand wastes in many parts of interior Europe +not familiarly known to tourists or even geographers. "Olkuez and +Schiewier in Poland," says Naumann, "lie in true sand deserts, and a +boundless plain of sand stretches around Ozenstockau, on which there +grows neither tree nor shrub. In heavy winds, this plain resembles a +rolling sea, and the sand-hills rise and disappear like the waves of the +ocean. The heaps of waste from the Olkuez mines are covered with sand to +the depth of four fathoms." [Footnote: Geognosie, ii., p. 1173.] No +attempts have yet been made to subdue the sands of Poland, but when +peace and prosperity shall be restored to that unhappy country, there is +no reasonable doubt that the measures, which have proved so successful +on similar formations in Germany and near Odessa, may be employed with +advantage in the Polish deserts. [Footnote: "Sixteen years ago," says an +Odessa landholder, "I attempted to fix the sand of the steppes, which +covers the rocky ground to the depth of a foot, and forms moving +hillocks with every change of wind. I tried acacias and pines in vain; +nothing would grow in such a soil. At length I planted the varnish tree, +or ailanthus, which succeeded completely in binding the sand." This +result encouraged the proprietor to extend his plantations over both +dunes and sand steppes, and in the course ot sixteen years this rapidly +growing tree had formed real forests. Other landholders have imitated +his example with great advantage.--Rentsch, Der Wald, pp. 44, 45.] + + + +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. + + + +In a former chapter I spoke of the influence of human action on the +surface of the globe as immensely superior in degree to that exerted by +brute animals, if not essentially different from it in kind. The eminent +Italian geologist, Stoppani, goes further than I had ventured to do, and +treats the action of man as a new physical clement altogether sui +generis. According to him, the existence of man constitutes a geological +period which he designates as the ANTHROPOZOIC ERA. "The creation of +man," says he, "was the introduction of a new element into nature, of a +force wholly unknown to earlier periods." "It is a new telluric force +which in power and universality may be compared to the greater forces of +the earth." [Foonote: Corso Di Geologia, Milano, 1873, vol ii., cap. +xxxi., section 1327.] It has already been abundantly shown that, though +the undesigned and unforeseen results of man's action on the +geographical conditions of the earth have perhaps been hitherto greater +and more revolutionary than the effects specially aimed at by him, yet +there is scarcely any assignable limit to his present and prospective +voluntary controlling power over terrestrial nature. + + +Cutting of Marine Isthmuses. + +Besides the great enterprises of physical transformation of which I have +already spoken, other works of internal improvement or change have been +projected in ancient and modern times, the execution of which would +produce considerable, and, in some cases, extremely important, +revolutions in the face of the earth. Some of the schemes to which I +refer are evidently chimerical; others are difficult, indeed, but cannot +be said to be impracticable, though discouraged by the apprehension of +disastrous consequences from the disturbance of existing natural or +artificial arrangements; and there are still others, the accomplishment +of which is ultimately certain, though for the present forbidden by +economical considerations. + +Nature sometimes mocks the cunning and the power of man by spontaneously +performing, for his benefit, works which he shrinks from undertaking, +and the execution of which by him she would resist with unconquerable +obstinacy. A dangerous sand bank, that all the enginery of the world +could not dredge out in a generation, may be carried off in a night by a +strong river-flood, or by a current impelled by a violent wind from an +unusual quarter, and a passage scarcely navigable by fishing-boats may +be thus converted into a commodious channel for the largest ship that +floats upon the ocean. In the remarkable gulf of Liimfjord in Jutland, +referred to in the preceding chapter, nature has given a singular +example of a canal which she alternately opens as a marine strait, and, +by abutting again, converts into a fresh-water lagoon. The Liimfjord was +doubtless originally an open channel from the Atlantic to the Baltic +between two islands, but the sand washed up by the sea blocked up the +western entrance, and built a wall of dunes to close it more firmly. +This natural dike, as we have seen, has been more than once broken +through, and it is perhaps in the power of man, either permanently to +maintain the barrier, or to remove it and keep a navigable channel +constantly open. If the Liimfjord becomes an open strait, the washing of +sea-sand through it would perhaps block some of the belts and small +channels now important for the navigation of the Baltic, and the direct +introduction of a tidal current might produce very perceptible effects +on the hydrography of the Cattegat. + +When we consider the number of narrow necks or isthmuses which separate +gulfs and bays of the sea from each other, or from the main ocean, and +take into account the time and cost, and risks of navigation which would +be saved by executing channels to connect such waters, and thus avoiding +the necessity of doubling long capes and promontories, or even +continents, it seems strange that more of the enterprise and money which +have been so lavishly expended in forming artificial rivers for internal +navigation should not have been bestowed upon the construction of +maritime canals. Many such have been projected in early and in recent +ages, and some trifling cuts between marine waters had been actually +made; but before the construction of the Suez Canal, no work of this +sort, possessing real geographical or even commercial importance, had +been effected. + +These enterprises are attended with difficulties and open to objections +which are not, at first sight, obvious. Nature guards well the chains by +which she connects promontories with mainlands, and binds continents +together. Isthmuses are usually composed of adamantine rock or of +shifting sands--the latter being much the more refractory material to +deal with. In all such works there is a necessity for deep excavation +below low-water mark--always a matter of great difficulty; the +dimensions of channels for sea-going ships must be much greater than +those of canals of inland navigation; the height of the masts or +smokepipes of that class of vessels would often render bridging +impossible, and thus a ship-canal might obstruct a communication more +important than that which it was intended to promote; the securing of +the entrances of marine canals and the construction of ports at their +termini would in general be difficult and expensive, and the harbors and +the channel which connected them would be extremely liable to fill up by +deposits washed in from sea and shore. Besides all this there is, in +many cases, an alarming uncertainty as to the effects of joining +together waters which nature has put asunder. A new channel may deflect +strong currents from safe courses, and thus occasion destructive erosion +of shores otherwise secure, or promote the transportation of sand or +slime to block up important harbors, or it may furnish a powerful enemy +with dangerous facilities for hostile operations along the coast. The +most colossal project of canalization ever suggested, whether we +consider the physical difficulties of its execution, the magnitude and +importance of the waters proposed to be united, or the distance which +would be saved in navigation, is that of a channel between the Gulf of +Mexico and the Pacific, across the Isthmus of Darien. I do not now speak +of a lock-canal, by way of the Lake of Nicaragua or any other route--for +such a work would not differ essentially from other canals, and would +scarcely possess a geographical character--but of an open cut between +the two seas. The late survey by Captain Selfridge, showing that the +lowest point on the dividing ridge is 763 feet above the sea-level, must +be considered as determining in the negative the question of the +possibility of such a cut, by any means now at the control of man; and +both the sanguine expectations of benefits, and the dreary suggestions +of danger, from the realization of this great dream, may now be +dismissed as equally chimerical. + + + +Suez Canal. + +The cutting of the Isthmus of Suez--the grandest and most truly +cosmopolite physical improvement ever undertaken by man--threatens none +of these dangers, and its only immediate geographical effect will +probably be that interchange between the aquatic animal and vegetable +life of two seas and two zones to which I alluded in a former chapter. +[Footnote: According to an article by Ascherson, in Petermann's +Mitthielungen, vol. xvii., p. 247, the sea-grass floras of the opposite +sides of the Isthmus of Suez are as different as possible. It does not +appear whether they have yet intermixed.] A collateral feature of this +great enterprise deserves notice as possessing no inconsiderable +geographical importance. I refer to the conduit or conduits constructed +from the Nile to the isthmus, primarily to supply fresh water to the +laborers on the great canal, and ultimately to serve as aqueducts for +the city of Suez and other towns on the line of the canal, and for the +irrigation and reclamation of a large extent of desert soil. In the +flourishing days of the Egyptian empire, the waters of the Nile were +carried over important districts cast of the river. In later ages, most +of this territory relapsed into a desert, from the decay of the canals +which once fertilized it. There is no difficulty in restoring the +ancient channels, or in constructing new, and thus watering not only all +the soil that the wisdom of the Pharaohs had improved, but much +additional land. Hundreds of square miles of arid sand waste would thus +be converted into fields of perennial verdure, and the geography of +Lower Egypt would be thereby sensibly changed. Considerable towns are +growing up at both ends of the channel, and at intermediate points, all +depending on the maintenance of aqueducts from the Nile, both for water +and for the irrigation of the neighboring fields which are to supply +them with bread. Important interests will thus be created, which will +secure the permanence of the hydraulic works and of the geographical +changes produced by them, and Suez, or Port Said, or Ismailieh, may +become the capital of the government which has been so long established +at Cairo. Maritime Canals in Greece. A maritime canal executed and +another projected in ancient times, the latter of which is again +beginning to excite attention, deserve some notice, though their +importance is of a commercial rather than a geographical character. The +first of those is the cut made by Xerxes through the rock which connects +the promontory of Mount Athos with the mainland; the other, a navigable +canal through the Isthmus of Corinth. In spite of the testimony of +Herodotus and Thucydides, the Romans classed the canal of Xerxes among +the fables of "mendacious Greece," and yet traces of it are perfectly +distinct at the present day through its whole extent, except at a single +point where, after it had become so choked as to be no longer navigable, +it was probably filled up to facilitate communication by land between +the promontory and the country in the rear of it. The emperor Nero +commenced the construction of a canal across the Isthmus of Corinth, +solely to facilitate the importation of grain from the East for +distribution among the citizens of Rome--for the encouragement of +general commerce was no part of the policy either of the republic or the +empire, and though the avidity of traders, chiefly foreigners, secured +to the luxury of the imperial city an abundant supply of far-fetched +wares, yet Rome had nothing to export in return. The line of Nero's +excavations is still traceable for three-quarters of a mile, or more +than a fifth of the total distance between gulf and gulf. + +If the fancy kingdom of Greece shall ever become a sober reality, escape +from its tutelage and acquire such a moral as well as political status +that its own capitalists--who now prefer to establish themselves and +employ their funds anywhere else rather than in their native land--have +any confidence in the permanency of its institutions, a navigable +channel may be opened between the gulfs of Lepanto and AEgina. The +annexation of the Ionian Islands to Greece will make such a work almost +a political necessity, and it would not only furnish valuable facilities +for domestic intercourse, but become an important channel of +communication between the Levant and the countries bordering on the +Adriatic, or conducting their trade through that sea. SHort as is the +distance, the work would be a somewhat formidable undertaking, for the +lowest point of the summit ridge of the isthmus is stated to be 246 feet +above the water, and consequently the depth of excavation must be not +less than 275 feet. As I have said, the importance of this latter canal +and of a navigable channel between Mount Athos and the continent would +be chiefly commercial, but both of them would be conspicuous instances +of the control of man over nature in a field where he has thus far done +little to interfere with her spontaneous arrangements. If they were +constructed upon such a scale as to admit of the free passage of the +water through them, in either direction, as the prevailing winds should +impel it, they would exercise a certain influence on the coast currents, +which are important as hydrographical elements, and also as producing +abrasion of the coast and a drift at the bottom of seas, and hence they +would be entitled to rank higher than simply as artificial means of +transit. It has been thought practicable to cut a canal across the +peninsula of Gallipoli from the outlet of the Sea of Marmora into the +Gulf of Saros. It may be doubted whether the mechanical difficulties of +such a work would not be found insuperable; but when Constantinople +shall recover the important political and commercial rank which +naturally belongs to her, the execution of such a canal will be +recommended by strong reasons of military expediency, as well as by the +interests of trade. An open channel across the peninsula would divert a +portion of the water which now flows through the Dardanelles, +diminishing the rapidity of that powerful current, and thus in part +remove the difficulties which obstruct the navigation of the strait. It +would considerably abridge the distance by water between Constantinople +and the northern coast of the AEgean, and it would have the important +advantage of obliging an enemy to maintain two blockading fleets instead +of one. + + +Canals Communicating with Dead Sea. + +The project of Captain Allen for opening a new route to India by cuts +between the Mediterranean and the Dead Sea, and between the Dead Sea and +the Red Sea, presents many interesting considerations. [Footnote: The +Dead Sea a new Route to India. 2 vols. 12mo, London, 1855.] The +hypsometrical observations of Bertou, Roth, and others, render it highly +probable, if not certain, that the watershed in the Wadi-el-Araba +between the Dead Sea and the Red Sea is not less than three hundred feet +above the main level of the latter, and if this is so, the execution of +a canal from the one sea to the other is quite out of the question. But +the summit level between the Mediterranean and the Jordan, near Jezreel, +is believed to be little, if at all, more than one hundred feet above +the sea, and the distance is so short that the cutting of a channel +through the dividing ridge would probably be found by no means an +impracticable undertaking. Although, therefore, we have no reason to +believe it possible to open a navigable channel to India by way of the +Dead Sea, there is not much doubt that the basin of the latter might be +made accessible from the Mediterranean. + +The level of the Dead Sea lies 1,316.7 feet below that of the ocean. It +is bounded east and west by mountain ridges, rising to the height of +from 2,000 to 4,000 feet above the ocean. From its southern end, a +depression called the Wadi-el-Araba extends to the Gulf of Akaba, the +eastern arm of the Red Sea. The Jordan empties into the northern +extremity of the Dead Sea, after having passed through the Lake of +Tiberias at an elevation of 663.4 feet above the Dead Sea, or 653.3 +below the Mediterranean, and drains a considerable valley north of the +lake, as well as the plain of Jericho, which lies between the lake and +the sea. If the waters of the Mediterranean were admitted freely into +the basin of the Dead Sea, they would raise its surface to the general +level of the ocean, and consequently flood all the dry land below that +level within the basin. I do not know that accurate levels have been +taken in the valley of the Jordan above the Lake of Tiberias, and our +information is very vague as to the hypsometry of the northern part of +the Wadi-el-Araba. As little do we know where a contour line, carried +around the basin at the level of the Mediterranean, would strike its +eastern and western borders. We cannot, therefore, accurately compute +the extent of now dry land which would be covered by the admission of +the waters of the Mediterranean, or the area of the inland sea which +would be thus created. Its length, however, would certainly exceed one +hundred and fifty miles, and its mean breadth, including its gulfs and +bays, could scarcely be less than fifteen, perhaps even twenty. It would +cover very little ground now occupied by civilized or even uncivilized +man, though some of the soil which would be submerged--for instance, +that watered by the Fountain of Elisha and other neighboring sources--is +of great fertility, and, under a wiser government and better civil +institutions, might rise to importance, because, from its depression, it +possesses a very warm climate, and might supply South-eastern Europe +with tropical products more readily than they can be obtained from any +other source. Such a canal and sea would be of no present commercial +importance, because they would give access to no new markets or sources +of supply; but when the fertile valleys and the deserted plains cast of +the Jordan shall be reclaimed to agriculture and civilization, these +waters would furnish a channel of communication which might become the +medium of a very extensive trade. Whatever might be the economical +results of the opening and filling of the Dead Sea basin, the creation +of a new evaporable area, adding not less than 2,000 or perhaps 3,000 +square miles to the present fluid surface of Syria, could not fail to +produce important meteorological effects. The climate of Syria would +probably be tempered, its precipitation and its fertility increased, the +courses of its winds and the electrical condition of its atmosphere +modified. The present organic life of the valley would be extinguished, +and many tribes of plants and animals would emigrate from the +Mediterranean to the new home which human art had prepared for them. It +is possible, too, that the addition of 1,300 feet, or forty atmospheres, +of hydrostatic pressure upon the bottom of the basin might disturb the +equilibrium between the internal and the external forces of the crust of +the earth at this point of abnormal configuration, and thus produce +geological convulsions the intensity of which cannot be even +conjectured. + +It is now established by the observations of Rohlf and others that +Strabo was right in asserting that a considerable part of the Libyan +desert, or Sahara, lay below the level of the Mediterranean. At some +points the depression exceeds 325 feet, and at Siwah, in the oasis of +Jupiter Ammon, it is not less than 130 feet. It has been proposed to cut +a canal through the coast dunes, on the shore south of the Syrtis Major, +or Dschnn el Kebrit of the Arabs, and another project is to reopen the +communication which appears to have once existed between the Palus +Tritonis, or Sebcha el Nandid, and the Syrtis Parva. As we do not know +the southern or eastern limits of this depression, we cannot determine +the area which would thus be covered with water, but it would certainly +be many thousands of square miles in extent, and the climatic effects +would doubtless be sensible through a considerable part of Northern +Africa, and possibly even in Europe. The rapid evaporation would require +a constant influx of water from the Mediterranean, which might perhaps +perceptibly influence the current through the Straits of Gibraltar. + + + +Maritime Canals in Europe. + +A great navigable cut across the peninsula of Jutland, forming a new and +short route between the North Sea and the Baltic, if not actually +commenced, is determined upon. The motives for opening such a +communication are perhaps rather to be found in political than in +geographical or even commercial considerations, but it will not be +without an important bearing on the material interests of all the +countries to whose peoples it will furnish new facilities for +communication and traffic. + +The North Holland canal between the Helder and the port of Amsterdam, a +distance of fifty miles, executed a few years since at a cost of +$5,000,000, and with dimensions admitting the passage of a frigate, was +a magnificent enterprise, but it is thrown quite into the shade by the +shorter channel now in process of construction for bringing that +important city into almost direct communication with the North Sea, and +thus restoring to it something at least of its ancient commercial +importance. The work involves some of the heaviest hydraulic operations +yet undertaken, including the construction of great dams, locks, dikes, +embankments, and the execution of draining works and deep cutting under +circumstances of extreme difficulty. In the course of these labors many +novel problems have presented themselves for practical solution by the +ingenuity of modern engineers, and the now inventions and processes thus +necessitated are valuable contributions to our means of physical +improvement. + + +Cape Cod Canal. + +The opening of a navigable cut through the narrow neck which separates +the southern part of Cape Cod Bay in Massachusetts from the Atlantic, +was long ago suggested, and there are few coast improvements on the +Atlantic shores of the United States which are recommended by higher +considerations of utility. It would save the most important coasting +trade of the United States the long and dangerous navigation around Cape +Cod, afford a new and safer entrance to Boston harbor for vessels from +Southern ports, secure a choice of passages, thus permitting arrivals +upon the coast and departures from it at periods when wind and weather +might otherwise prevent them, and furnish a most valuable internal +communication in case of coast blockade by a foreign power. The +difficulties of the undertaking are no doubt formidable, but the expense +of maintenance and the uncertainty of the effects of currents getting +through the new strait are still more serious objections. [Footnote: The +opening of a channel across Cape Cod would have, though perhaps to a +smaller extent, the same effects in interchanging the animal life of the +southern and northern shores of the isthmus, as in the case of the Suez +Canal; for although the breadth of Cape Cod does not anywhere exceed +twenty miles, and is in some places reduced to one, it appears from the +official reports on the Natural History of Massachusetts, that the +population of the opposite waters differs widely in species. + +Not having the original documents at hand, I quote an extract from the +Report on the Invertebrate Animals of Mass., given by Thoreau, +Excursions, p. 69: "The distribution of the marine shells is well worthy +of notice as a geological fact. Cape Cod, the right arm of the +Commonwealth, reaches out into the ocean some fifty or sixty miles. It +is nowhere many miles wide; but this narrow point of land has hitherto +proved a barrier to the migration of many species of mollusca. Several +genera and numerous species, which are separated by the intervention of +only a few miles of land, are effectually prevented from mingling by the +Cape, and do not pass from one side to the other. ... Of the one hundred +and ninety-seven marine species, eighty-three do not pass to the south +shore, and fifty are not found on the north shore of the Cape." + +Probably the distribution of the species of mollusks is affected by +unknown local conditions, and therefore an open canal across the Cape +might not make every species that inhabits the waters on one side common +to those of the other; but there can be no doubt that there would be a +considerable migration in both directions. + +The fact stated in the report may suggest an important caution in +drawing conclusions upon the relative age of formations from the +character of their fossils. Had a geological movement or movements +upheaved to different levels the bottoms of waters thus separated by a +narrow isthmus, and dislocated the connection between those bottoms, +naturalists, in after ages, reasoning from the character of the fossil +faunas, might have assigned them to different, and perhaps very widely +distant, periods.] + + +Changes in the Caspian. + +The Russian Government has contemplated the establishment of a nearly +direct water communication between the Caspian Sea and the Sea of Azoff, +partly by natural and partly by artificial channels, and there are now +navigable canals between the Don and the Volga; but these works, though +not wanting in commercial and political interest, do not possess any +geographical importance. It is, however, very possible to produce +appreciable geographical changes in the basin of the Caspian by the +diversion of the great rivers which flow from Central Russia. The +surface of the Caspian is eighty-three feet below the level of the Sea +of Azoff, and its depression has been explained upon the hypothesis that +the evaporation exceeds the supply derived, directly and indirectly, +from precipitation, though able physicists now maintain that the sinking +of this sea is due to a subsidence of its bottom from geological causes. +At Tsaritsin, the Don, which empties into the Sea of Azoff, and the +Volga, which pours into the Caspian, approach each other within ten +miles. Near this point, by means of open or subterranean canals, the Don +might be turned into the Volga, or the Volga into the Don. If we suppose +the whole or a large proportion of the waters of the Don to be thus +diverted from their natural outlet and sent down to the Caspian, the +equilibrium between the evaporation from that sea and its supply of +water might be restored, or its level even raised above its ancient +limits. If the Volga were turned into the Sea of Azoff, the Caspian +would be reduced in dimensions until the balance between loss and gain +should be re-established, and it would occupy a much smaller area than +at present. Such changes in the proportion of solid and fluid surface +would have some climatic effects in the territory which drains into the +Caspian, and on the other hand, the introduction of a greater quantity +of fresh water into the Sea of Azoff would render that gulf less saline, +affect the character and numbers of its fish, and perhaps be not wholly +without sensible influence on the water of the Black Sea. + + +Diversion of the Nile. + +Perhaps the most remarkable project of great physical change, proposed +or threatened in earlier ages, is that of the diversion of the Nile from +its natural channel, and the turning of its current into either the +Libyan Desert or the Red Sea. The Ethiopian or Abyssinian princes more +than once menaced the Memlouk sultans with the execution of this +alarming project, and the fear of so serious an evil is said to have +induced the Moslems to conciliate the Abyssinian kings by large +presents, and by some concessions to the oppressed Christians of Egypt. +Indeed, Arabian historians affirm that in the tenth century the +Ethiopians dammed the river, and, for a whole year, cut off its waters +from Egypt. [Footnote: "Some haue writte, that by certain kings +inhabiting aboue, the Nilus should there be stopped; & at a time +prefixt, let loose vpon a certaine tribute payd them by the Aegyptians. +The error springing perhaps fro a truth (as all wandring reports for the +most part doe) in that the Sultan doth pay a certaine annuall summe to +the Abissin Emperour for not diuerting the course of the Riuer, which +(they say) he may, or impouerish it at the least."--George Sandys, A +Relation of a Journey, etc., p. 98. See, also, Vansles, Voyage en +Egypte, p. 61.] The probable explanation of this story is to be found in +a season of extreme drought, such as have sometimes occurred in the +valley of the Nile. + +The Libyan Desert, above the junction of the two principal branches of +the Nile at Khartum, is so much higher than the level of the river below +that point, that there is no reason to believe a new channel for the +united waters of the two streams could be found in that direction; but +the Bahr-el-Abiad flows through, if it does not rise in, a great +table-land, and some of its tributaries are supposed to communicate in +the rainy season with branches of great rivers flowing in quite another +direction. Hence it is probable that a portion at least of the waters of +this great arm of the Nile--and perhaps a quantity the abstraction of +which would be sensibly felt in Egypt--might be sent to the Atlantic by +the Congo or Niger, lost in inland lakes and marshes in Central Africa, +or employed to fertilize the Libyan sand wastes. + +About the beginning of the sixteenth century, Albuquerque the "Terrible" +revived the scheme of turning the Nile into the Red Sea, with the hope +of destroying the transit trade through Egypt by way of Kosseir. In 1525 +the King of Portugal was requested by the Emperor of Abyssinia to send +him engineers for that purpose; a successor of that prince threatened to +attempt the project about the year 1700, and even as late as the French +occupation of Egypt, the possibility of driving out the intruder by this +means was suggested in England. + +It cannot be positively affirmed that the diversion of the waters of the +Nile to the Red Sea is impossible. In the chain of mountains which +separates the two valleys, Brown found a deep depression or wadi, +extending from the one to the other, apparently at no great elevation +above the bed of the river, but the height of the summit level was not +measured. Admitting the possibility of turning the whole river into the +Red Sea, let us consider the probable effect of the change. + +First and most obvious is the total destruction of the fertility of +Middle and Lower Egypt, the conversion of that part of the valley into a +desert, and the extinction of its imperfect civilization, if not the +absolute extirpation of its inhabitants. This is the calamity threatened +by the Abyssinian princes and the ferocious Portuguese warrior, and +feared by the Sultans of Egypt. Beyond these immediate and palpable +consequences neither party then looked; but a far wider geographical +area, and far more extensive and various human interests, would be +affected by the measure. The spread of the Nile during the annual +inundation covers, for many weeks, several thousand square miles with +water, and at other seasons of the year pervades the same and even a +larger area with moisture by infiltration. The abstraction of so large +an evaporating surface from the southern shores of the Mediterranean +could not but produce important effects on many meteorological +phenomena, and the humidity, the temperature, the electrical condition +and the atmospheric currents of North-eastern Africa might be modified +to a degree that would sensibly affect the climate of Europe. + +The Mediterranean, deprived of the contributions of the Nile, would +require a larger supply, and of course a stronger current, of water from +the Atlantic through the Straits of Gibraltar; the proportion of salt it +contains would be increased, and the animal life of at least its +southern borders would be consequently modified; the current which winds +along its southern, eastern, and north-eastern shores would be +diminished in force and volume, if not destroyed altogether, and its +basin and its harbors would be shoaled by no new deposits from the +highlands of inner Africa. + +In the much smaller Red Sea, more immediately perceptible, if not +greater, effects, would be produced. The deposits of slime would reduce +its depth, and perhaps, in the course of ages, divide it into an inland +and an open sea, the former of which, receiving no supply from rivers, +would, as in the case of the northern part of the Gulf of California, +soon be dried up by evaporation, and its whole area added to the +Africo-Arabian desert; the waters of the latter would be more or less +freshened, and their immensely rich marine fauna and flora changed in +character and proportion, and, near the mouth of the river, perhaps even +destroyed altogether; its navigable channels would be altered in +position and often quite obstructed; the flow of its tides would be +modified by the new geographical conditions; the sediment of the river +would form new coast-lines and lowlands, which would be covered with +vegetation, and probably thereby produce sensible climatic changes. + + +Diversion of the Rhine. + +The interference of physical improvements with vested rights and ancient +arrangements, is a more formidable obstacle in old countries than in +new, to enterprises involving anything approaching to a geographical +revolution. Hence such projects meet with stronger opposition in Europe +than in America, and the number of probable changes in the face of +nature in the former continent is proportionally less. I have noticed +some important hydraulic improvements as already executed or in progress +in Europe, and I may refer to some others as contemplated or suggested. +One of these is the diversion of the Rhine from its present channel +below Ragatz, by a cut through the narrow ridge near Sargans, and the +consequent turning of its current into the Lake of Wallenstadt. This +would be an extremely easy undertaking, for the ridge is but twenty feet +above the level of the Rhine, and hardly two hundred yards wide. There +is no present adequate motive for this diversion, but it is easy to +suppose that it may become advisable within no long period. The +navigation of the Lake of Constance is rapidly increasing in importance, +and the shoaling of the eastern end of that lake by the deposits of the +Rhine may require a remedy which can be found by no other so ready means +as the discharge of that river into the Lake of Wallenstadt. The +navigation of this latter lake is not important, nor is it ever likely +to become so, because the rocky and precipitous character of its shores +renders their cultivation impossible. It is of great depth, and its +basin is capacious enough to receive and retain all the sediment which +the Rhine would carry into it for thousands of years. [Footnote: Many +geographers suppose that the dividing ridge between the Lake of +Wallenstadt and the bed of the Rhine at Sargans is a fluviatile deposit, +which has closed a channel through which the Rhine anciently discharged +a part or the whole of its waters into the lake. In the flood of 1868, +the water of the Rhine rose to the level of the railway station at +Sargans, and for some days there was fear of the giving way of the +barrier and the diversion of the current of the river into the lake.] + + + +Improvements in North American Hydrography. + +We are not yet well enough acquainted with the geography of Central +Africa, or of the interior of South America, to conjecture what +hydrographical revolutions might there be wrought; but from the fact +that many important rivers in both continents drain extensive +table-lands, of moderate elevation and inclination, there is reason to +suppose that important changes in the course of those rivers might be +accomplished. Our knowledge of the drainage of North America is much +more complete, and it is certain that there are numerous points within +our territory where the courses of great rivers, or the discharge of +considerable lakes, might be completely diverted, or at least partially +directed into different channels. + +The surface of Lake Erie is 565 feet above that of the Hudson at Albany, +and it is so near the level of the great plain lying east of it, that it +was found practicable to supply the western section of the canal, which +unites it with the Hudson, with water from the lake, or rather from the +Niagara which flows out of it. The greatest depth of water yet sounded +in Lake Erie is but two hundred and seventy feet, the mean depth one +hundred and twenty. Open canals parallel with the Niagara, or directly +towards the Genesee, might be executed upon a scale which would exercise +an important influence on the drainage of the lake, if there were any +adequate motive for such an undertaking. Still easier would it be to +enlarge the outlet for the waters of Lake Superior at the Saut St. +Mary--where the river which drains the lake descends twenty-two feet in +a single mile--and thus to produce incalculable effects, both upon that +lake and upon the great chain of inland waters which communicate with +it. + +The summit level between the surface of Lake Michigan at its mean height +and that of the River Des Plaines, a tributary of the Illinois, at a +point some ten miles west of Chicago, is but ten and a half feet above +the lake. The lake once discharged a part or the whole of its waters +into the valley of the Des Plaines. A slight upheaval, at an unknown +period, elevated the bed of the Des Plaines, and the prairie between it +and the lake, to their present level, and the outflow of the lake was +turned into a new direction. The bed of the Des Plaines is higher than +the surface of the lake, and in recent times the Des Plaines, when at +flood, has sent more or less of its waters across the ridge into the bed +of the South Branch of Chicago River, and so into Lake Michigan. + +A navigable channel has now been cut, admitting a constant flow of water +from the lake, by the valley of the Des Plaines, into the Illinois. The +mean discharge by this channel does not much exceed 23,000 cubic feet +per minute, but it would be quite practicable to enlarge its +cross-section indefinitely, and the flow through it might be so +regulated as to keep the Illinois and the Mississippi at flood at all +seasons of the year. The increase in the volume of these rivers would +augment their velocity and their transporting power, and, consequently, +the erosion of their banks and the deposit of slime in the Gulf of +Mexico, while the opening of a communication between the lake and the +affluents of the Mississippi, unobstructed except by locks, and the +introduction of a large body of colder water into the latter, would very +probably produce a considerable effect on the animal life that peoples +them. The diversion of water from the common basin of the great lakes +through a new channel, in a direction opposite to their present +discharge, would not be absolutely without influence on the St. +Lawrence, though probably this effect might be too small to be readily +perceptible. [Footnote: From Reports of the Canal Commissioners of the +State of Illinois, and especially from a very interesting private letter +from William Gooding, Esq., an eminent engineer, which I regret I have +not space to print in full, I learn that the length of the present +canal, from the lake to the River Illinois, is 101 miles, with a total +descent of a trifle more than 145 feet, and that it is proposed to +enlarge this channel to the width of one hundred and sixty feet, with a +minimum depth of seven, and to create a slack-water navigation in the +Illinois by the construction of five dams, one of which is already +completed. The descent for the outlet of the canal at La Salle on the +Illinois to the Mississippi is twenty-eight feet, the distance being 230 +miles. The canal thus enlarged would cost about $16,000,000, and it +would establish a navigation for vessels of 1,200 to 1,500 tons burden +between Lake Michigan and the Mississippi, and consequently, by means of +the great lakes and the Welland canal, between the St. Lawrence and the +Gulf of Mexico.] + +In an able and interesting article in a California magazine, Dr. Widney +has suggested a probable cause and a possible remedy for the desiccation +of south-eastern California referred to in a former chapter. The +Colorado Desert which lies considerably below the level of the waters of +the Gulf of California, and has an area of about 4,000 square miles, +evidently once formed a part of that gulf. This northern extension of +the gulf appears to have been cut off from the main body by deposits +brought down by the great river Colorado, at no very distant period. +These deposits at the same time turned the course of the river to the +south, and it now enters the gulf at a point twenty miles distant from +its original outlet. + +When this northern arm of the gulf was cut off from the sea, and the +river which once discharged itself into it was diverted, it was speedily +laid dry by evaporation, and now yields no vapor to be condensed into +fog, rain, and snow on the neighboring mountains, which are now parched +and almost bare of vegetation. + +The ancient bed of the river may still be traced, and in floods the +Colorado still sends a part of its overflowing supply into its old +channel, and for a time waters a portion of the desert. It is believed +that the river might easily be turned back into its original course, and +indeed nature herself seems to be now tending, by various spontaneous +processes, to accomplish that object. The waters of the Colorado, though +perhaps not sufficient to fill the basin and keep it at the sea-level in +spite of the rapid evaporation in that climate, [Footnote: The +thermometer sometimes rises to 120 degrees F. at Fort Yuma, at the S. E. +angle of California in N. L. 33 degrees.] would at least create a +permanent lake in the lower part of the depression, the evaporation from +which, Dr. Widney suggests, might sensibly increase the humidity and +lower the temperature of an extensive region which is now an arid and +desolate wilderness. + + + +Soil below Rock. + +One of the most singular changes of natural surface effected by man is +that observed by Beechey and by Barth at Lin Tefla, and near Gebel +Genunes, in the district of Ben Gasi, in Northern Africa. In this region +the superficial stratum originally consisted of a thin sheet of rock +covering a layer of fertile earth. This rock has been broken up, and, +when not practicable to find use for it in fences, fortresses, or +dwellings, heaped together in high piles, and the soil, thus bared of +its stony shell, has been employed for agricultural purposes. [Footnote: +Barth, Wanderungen durch die Kusten des Mittelmeeres, i., p. 853. In a +note on page 380, of the same volume, Barth cites Strabo as asserting +that a similar practice prevailed in Iapygia; but the epithet [word in +Greek: traxeia], applied by Strabo to the original surface, does not +neceasarily imply that it was covered with a continuous stratum of +rock.] If we remember that gunpowder was unknown at the period when +these remarkable improvements were executed, and of course that the rock +could have been broken only with the chisel and wedge, we must infer +that land had at that time a very great pecuniary value, and, of course, +that the province, though now exhausted, and almost entirely deserted by +man, had once a dense population. + + +Covering Rock with Earth. + +If man has, in some cases, broken up rock to reach productive ground +beneath, he has, in many other instances, covered bare ledges, and +sometimes extensive surfaces of solid stone, with fruitful earth, +brought from no inconsiderable distance. Not to speak of the Campo Santo +at Pisa, filled, or at least coated, with earth from the Holy Land, for +quite a different purpose, it is affirmed that the garden of the +monastery of St. Catherine at Mount Sinai is composed of Nile mud, +transported on the backs of camels from the banks of that river. Parthey +and older authors state that all the productive soil of the Island of +Malta was brought over from Sicily. [Footnote: Parthey, Wanderungen durch +Sicilen und die Levante, i., p. 404.] The accuracy of the information +may be questioned in both cases, but similar practices, on a smaller +scale, are matter of daily observation in many parts of Southern Europe. +Much of the wine of the Moselle is derived from grapes grown on earth +carried high up the cliffs on the shoulders of men, and the steep +terraced slopes of the Island of Teneriffe are covered with soil +painfully scooped out from fissures in and between the rocks which have +been laid bare by the destruction of the native forests. [Footnote: +Mantegazza, Rio de la Plata e Teneriffa, p. 567.] In China, too, rock +has been artificially covered with earth to an extent which gives such +operations a real geographical importance, and the accounts of the +importation of earth at Malta, and the fertilization of the rocks on +Mount Sinai with slime from the Nile, may be not wholly without +foundation. + + +Valleys in Deserts. + +In the latter case, indeed, river sediment might be very useful as a +manure, but it could hardly be needed as a soil; for the growth of +vegetation in the wadies of the Sinaitic Peninsula shows that the +disintegrated rock of its mountains requires only water to stimulate it +to considerable productiveness. The wadies present, not unfrequently, +narrow gorges, which might easily be closed, and thus accumulations of +earth, and reservoirs of water to irrigate it, might be formed which +would convert many a square mile of desert into flourishing date gardens +and cornfields. For example, not far from Wadi Feiran, on the most +direct route to Wadi Esh-Sheikh, is a very narrow pass called by the +Arabs El Bueb (El Bab) or, The Gate, which might be securely closed to a +very considerable height, with little labor or expense. Above this pass +is a wide and nearly level expanse, filled up to a certain regular level +with deposits brought down by torrents before the Gate, or Bueb, was +broken through, and they have now worn down a channel in the deposits to +the bed of the wadi. If a dam were constructed at the pass, and +reservoirs built to retain the winter rains, a great extent of valley +might be rendered cultivable. + + +Effects of Mining. + +The excavations made by man, for mining and other purposes, may occasion +disturbance of the surface by the subsidence of the strata above them, +as in the case of the mine of Fahlun, in Sweden, but such accidents have +generally been too inconsiderable in extent to deserve notice in a +geographical point of view. [Footnote: In March, 1873, the imprudent +extension of the excavations in a slate mine near Morzine, in Savoy, +occasioned the fall of a mass of rock measuring more than 700,000 yards +in cubical contents. A forest of firs was destroyed, and a hamlet of +twelve houses crushed and buried by the slide.] It is said, however, +that in many places in the mining regions of England alarming +indications of a tendency to a wide dislocation of the superficial +strata have manifested themselves. Indeed, when we consider the measure +of the underground cavities which miners have excavated, we cannot but +be surprised that grave catastrophes have not often resulted from the +removal of the foundations on which the crust of our earth is laid. The +100,000,000 tons of coal yearly extracted from British mines require the +withdrawal of subterranean strata equal to an area of 20,000 acres one +yard deep, or 2,000 acres ten yards deep. These excavations have gone on +for several years at this rate, and in smaller proportions for +centuries. Hence, it cannot be doubted that by these and other like +operations the earth has been undermined and honey-combed in many +countries to an extent that may well excite serious apprehensions as to +the stability of the surface. In any event such excavations may +interfere materially with the course of subterranean waters, and it has +even been conjectured that the removal of large bodies of metallic ore +from their original deposits might, at least locally, affect in a +sensible degree the magnetic and electrical condition of the earth's +crust. [Footnote: The exhaustion of the more accessible deposits of coal +and other minerals has compelled the miners in Belgium, England, and +other countries, to carry their operations to great depths below the +surface. At the colliery Des Viviers, at Cilly near Charleroi, in +Belgium, coal is worked at the depth of 2,820 feet, and one pit has been +sunk to the depth of 3,411 feet. It is supposed that the internal heat +of the earth will render mining impossible below 4,000 feet. At Clifford +Amalgamated Mines, in Cornwall, the temperature at 1,590 feet stood at +100 degrees, but after the shaft had remained a year open it fell to 83 +degrees. In another Cornish mine men work at from 110 degrees to 120 +degrees, but only twenty minutes at a time, and with cold water thrown +frequently over them.--The last Thirty Years in Mining Districts, p. 95. + +Stopponi mentions an abandoned mine at Huttenberg, in Bohemia, of the +depth of 3,775 feet.--Corso di Geologia, i., p. 258.] + + +Hydraulic Mining. + +What is called hydraulic mining--a system substantially identical with +that described in an interesting way by Pliny the elder, in Book XXXV. +of his Natural History, as practised in his time in the gold mines of +Spain [Footnote: I have little doubt that the hydraulic mining in Gaul, +alluded to by Diodorus Siculus, Bibliotheca Historica, v. 27, as merely +a mode of utilizing the effects of water flowing in its natural +channels, was really the artificial method described by Pliny.]--is +producing important geographical effects in California. Artificially +directed currents of water have been long employed for washing down and +removing masses of earth, but in the Californian mining the process is +resorted to on a vastly greater scale than in any other modern +engineering operations, and with results proportioned to the means. +Brooks of considerable volume are diverted from their natural channels +and conducted to great distances in canals or wooden aqueducts, +[Footnote: In 1867 there were 6,000 miles (including branches) of +artificial water-courses employed for mining purposes in California. +The flumes of these canals are often of sheet-iron, and in some places +are carried considerable distances at a height of 250 feet above the +ground.--Raymond, Mineral Statistics west of the Rocky Mountains, 1870, +p. 476.] and then directed against hills and large level surfaces of +ground which it is necessary to remove to reach the gold-bearing strata, +or which themselves contain deposits of the precious mineral. [Footnote: +The water is sometimes driven through iron tubes under a hydrostatic +pressure of several hundred feet, with a force which cuts away rock of +considerable solidity almost as easily as hard earth. In this way of +using water, the cutting force might, doubtless, be greatly augmented by +introducing sand or gravel into the current.] Naked hills and fertile +soils are alike washed away by the artificial torrent, and the material +removed--vegetable mould, sand, gravel, pebbles--is carried down by the +current and often spread over ground lying quite out of the reach of +natural inundations, and burying it to the depth sometimes of +twenty-five feet. An orchard valued at $60,000, and another estimated at +not less than $200,000, are stated to have been thus sacrificed, and a +report from the Agricultural Bureau at Washington computes the annual +damage done by this mode of mining at the incredible sum of $12,000,000. + +Accidental fires in mines of coal or lignite sometimes lead to +consequences not only destructive to large quantities of valuable +material, but which may, directly or indirectly, produce results +important in geography. The coal is occasionally ignited by the miners' +lights or other fires used by them, and certain kinds of this mineral, +if long exposed to air in deserted galleries, may be spontaneously +kindled. Under favorable circumstances, a stratum of coal will burn +until it is exhausted, and a cavity may be burnt out in a few months +which human labor could not excavate in many years. Wittwer informs us +that a coal mine at St. Etienne in Dauphiny has been burning ever since +the fourteenth century, and that a mine near Duttweiler, another near +Epterode, and a third at Zwickau, have been on fire for two hundred +years. Such conflagrations not only produce cavities in the earth, but +communicate a perceptible degree of heat to the surface, and the author +just quoted cites cases where this heat has ben advantageously employed +in forcing vegetation. + + +Projects of Agricultural Improvements by Duponchel. + +Duponchel's schemes of agricultural improvement are so grandiose in +their nature, so vast in their sphere of operation, and so important in +their possible effects upon immense tracts of the earth's surface, that +they must be considered as projects of geographical revolution, and they +therefore merit more than a passing notice. In a memoir already quoted, +and in a later work, [Footnote: Traite d'Hydraulique et de Geologie +Agricole, 1868.] this engineer proposes to construct artificial torrents +for the purpose of grinding up calcareous rock, by rolling and attrition +along their beds, and thus reducing it into a fine slime; and at the +same time these torrents are to transport an argillaceous deposit which +is to be mingled with the calcareous slime, and distributed over the +Landes by watercourses constructed for the purpose. By this means, he +supposes that a very fertile soil may be formed, and so graded in +depositing as to secure for it a good drainage. + +In order that nothing may be wanting to recommend the project, Duponchel +suggests that, as some rivers of Western France are gold-bearing, it is +probable that gold enough may be collected by washing the sands to +reduce materially the expense of such operations. + +In the Landes of Gascony alone, he believes that 3,000,000 acres, now +barren, might be made productive at a moderate expense, and that similar +methods might be advantageously employed in France over an extent of not +less than 30,000,000 acres now almost wholly valueless. + +The successful execution of the plan would increase the fertile +territory of France by an area of four or five times the extent of +Sicily or of Sardinia. + +There seems to be no reason why the same method, applied for such +different purposes, should necessarily be destructive in the one case +while it is so advantageous in the other. A wiser economy might bring +about a harmony of action between the miners and the agriculturists of +California, and the soil which is removed by the former as an +incumbrance, judiciously deposited, might become for the latter a source +of wealth more solid and enduring than the gold now obtained by such a +sacrifice of agricultural interests. + + +Action of Man on the Weather. + +Espy's well-known suggestion of the possibility of causing rain +artificially, by kindling great fires, is not likely to be turned to +practical account, but the speculations of this able meteorologist are +not, for that reason, to be rejected as worthless. His labors exhibit +great industry in the collection of facts, much ingenuity in dealing +with them, remarkable insight into the laws of nature, and a ready +perception of analogies and relations not obvious to minds less +philosophically constituted. They have unquestionably contributed +essentially to the advancement of meteorological science. + +The possibility that the distribution and action of electricity may be +considerably modified by long lines of iron railways and telegraph +wires, is a kindred thought, and in fact rests much on the same +foundation as the belief in the utility of lightning-rods, but such +influence is too obscure and too uncertain to have been yet +demonstrated, though many intelligent observers believe that sensible +meteorological effects have been produced by it. + +It is affirmed that battles and heavy cannonades are generally followed +by rain and thunder-storms, and Powers has collected much evidence on +this subject, [Footnote: War and the Weather, or the Artificial +Production of Rain, Chicago, 1871. Paifer proposed, as early as 1814, +arrangements for producing rain by firing cannon and exploding shells in +the air. Ein wunderbarer Traum die Frucht, barkeit durch willkurlichen +Regen zu befordern, Metz, 1814. See, on the question of the possibility +of influencing the weather by artificial means, London Quarterly Journal +of Science, xxix., p. 126, and Nature, Feb. 16, 1871, p. 306.] but the +proposition does not seem to be by any means established. + + +Resistance to Great Natural Forces. + +I have often spoken of the greater and more subtile natural forces, and +especially of geological agencies, as powers beyond human guidance or +resistance. This is no doubt at present true in the main, but man has +shown that he is not altogether impotent to struggle with even these +mighty servants of nature, and his unconscious as well as his deliberate +action may in some cases have increased or diminished the intensity of +their energies. It is a very ancient belief that earthquakes are more +destructive in districts where the crust of the earth is solid and +homogeneous, than where it is of a looser and more interrupted +structure. Aristotle, Pliny the elder, and Seneca believed that not only +natural ravines and caves, but quarries, wells, and other human +excavations, which break the continuity of the terrestrial strata and +facilitate the escape of elastic vapors, have a sensible influence in +diminishing the violence and preventing the propagation of the +earth-waves. In all countries subject to earthquakes this opinion is +still maintained, and it is asserted that, both in ancient and in modern +times, buildings protected by deep wells under or near them have +suffered less from earthquakes than those the architects of which have +neglected this precaution. [Footnote: Landgrebe, Geschichte der Vulkane, +ii., pp. 19, 20.] + +If the commonly received theory of the cause of earthquakes is +true--that, namely, which ascribes them to the elastic force of gases +accumulated or generated in subterranean reservoirs--it is evident that +open channels of communication between such reservoirs and the +atmosphere might serve as a harmless discharge of gases that would +otherwise acquire destructive energy. The doubt is whether artificial +excavations can be carried deep enough to reach the laboratory where the +elastic fluids are distilled. There are, in many places, small natural +crevices through which such fluids escape, and the source of them +sometimes lies at so moderate a depth that they pervade the superficial +soil and, as it were, transpire from it, over a considerable area. When +the borer of an ordinary artesian well strikes into a cavity in the +earth, imprisoned air often rushes out with great violence, and this has +been still more frequently observed, in sinking mineral-oil wells. In +this latter case, the discharge of a vehement current of inflammable +fluid sometimes continues for hours and even longer periods. These facts +seem to render it not wholly improbable that the popular belief of the +efficacy of deep wells in mitigating the violence of earthquakes is well +founded. + +In general, light, wooden buildings are less injured by earthquakes than +more solid structures of stone or brick, and it is commonly supposed +that the power put forth by the earth-wave is too great to be resisted +by any amount of weight or solidity of mass that man can pile up upon +the surface. But the fact that in countries subject to earthquakes many +very large and strongly constructed palaces, temples, and other +monuments have stood for centuries, comparatively uninjured, suggests a +doubt whether this opinion is sound. The earthquake of the first of +November, 1755, which is asserted, though upon doubtful evidence, to +have been felt over a twelfth part of the earth's surface, was among the +most violent of which we have any clear and distinct account, and it +seems to have exerted its most destructive force at Lisbon. It has often +been noticed as a remarkable fact, that the mint, a building of great +solidity, was almost wholly unaffected by the shock which shattered +every house and church in the city, and its escape from the common ruin +can hardly be accounted for except upon the supposition that its weight, +compactness, and strength of material enabled it to resist an agitation +of the earth which overthrew all weaker structures. On the other hand, a +stone pier in the harbor of Lisbon, on which thousands of people had +taken refuge, sank with its foundations to a great depth during the same +earthquake; and it is plain that where subterranean cavities exist, at +moderate depths, the erection of heavy masses upon them would tend to +promote the breaking down of the strata which roof them over. + +No physicist, I believe, has supposed that man can avert the eruption of +a volcano or diminish the quantity of melted rock which it pours out of +the bowels of the earth; but it is not always impossible to divert the +course of even a large current of lava. "The smaller streams of lava +near Catania," says Ferrara, in describing the great eruption of 1669, +"were turned from their course by building dry walls of stone as a +barrier against them. ... It was proposed to divert the main current +from Catania, and fifty men, protected by hides, were sent with hooks +and iron bars to break the flank of the stream near Belpasso. [Footnote: +Soon after the current issues from the volcano, it is covered above and +at its sides, and finally in front, with scoriae, formed by the cooling +of the exposed surface, which bury and conceal the fluid mass. The +stream rolls on under the coating, and between the walls of scoriae, and +it was the lateral crust which was broken through by the workmen +mentioned in the text. + +The distance to which lava flows, before its surface begns to solidify, +depends on its volume, its composition, its temperature and that of the +air, the force with which it is ejected, and the inclination of the +declivity over which it runs. In most cases it is difficult to approach +the current at points where it is still entirely fluid, and hence +opportunities of observing it in that condition are not very frequent. +In the eruption of February, 1850, on the east side of Vesuvius, I went +quite up to one of the outlets. The lava shot out of the orifice upwards +with great velocity, like the water from a fountain, in a stream eight +or ten feet in diameter, throwing up occasionally volcanic bombs three +or four feet in diameter, which exploded at the height of eight or ten +yards, but it immediately spread out on the declivity down which it +flowed, to the width of several yards. It continued red-hot in broad +daylight, and without a particle of scoriae on its surface, for a course +of at least one hundred yards. At this distance, the suffocating, +sulphurous vapors became so dense that I could follow the current no +farther. The undulations of the surface were like those of a brook +swollen by rain. I estimated the height of the waves at five or six +inches by a breadth of eighteen or twenty. To the eye, the fluidity of +the lava seemed as perfect as that of water, but masses of cold lava +weighing ten or fifteen pounds floated upon it like cork. + +The heat emitted by lava currents seems extremely small when we consider +the temperature required to fuse such materials and the great length of +time they take in cooling. I saw at Nicolosi ancient oil-jars, holding a +hundred gallons or more, which had been dug out from under a stream of +old lava above that town. They had been very slightly covered with +volcanic ashes before the lava flowed over them, but the lead with which +holes in them had been plugged was not melted. The current that buried +Mompiliere in 1669 was thirty-five feet thick, but marble statues, in a +church over which the lava formed an arch, were found uncalcined and +uninjured in 1704, See Scrope, Volcanoes, chap. vi. Section 6.] + +When the opening was made, fluid lava poured forth and flowed rapidly +towards Paterno; but the inhabitants of that place, not caring to +sacrifice their own town to save Catania, rushed out in arms and put a +stop to the operation." [Footnote: Ferrara, Descrizione dell' Etna, p. +108.] In the eruption of Vesuvius in 1794, the viceroy saved from +impending destruction the town of Portici, and the valuable collection +of antiquities then deposited there but since removed to Naples, by +employing several thousand men to dig a ditch above the town, by which +the lava current was carried off in another direction. [Footnote: +Landgrebe, Naturgeschichte der Vulkane, ii., p. 82.] + + +Incidental Effects of Human Action. + +I have more than once alluded to the collateral and unsought +consequences of human action as being often more momentous than the +direct and desired results. There are cases where such incidental, or, +in popular speech, accidental, consequences, though of minor importance +in themselves, serve to illustrate natural processes; others, where, by +the magnitude and character of the material traces they leave behind +them, they prove that man, in primary or in more advanced stages of +social life, must have occupied particular districts for a longer period +than has been supposed by popular chronology. "On the coast of Jutland," +says Forchhammer, "wherever a bolt from a wreck or any other fragment of +iron is deposited in the beach sand, the particles are cemented +together, and form a very solid mass around the iron. A remarkable +formation of this sort was observed a few years ago in constructing the +sea-wall of the harbor of Elsineur. This stratum, which seldom exceeded +a foot in thickness, rested upon common beach sand, and was found at +various depths, less near the shore, greater at some distance from it. +It was composed of pebbles and sand, and contained a great quantity of +pins, and some coins of the reign of Christian IV., between the +beginning and the middle of the seventeenth century. Here and there, a +coating of metallic copper had been deposited by galvanic action, and +the presence of completely oxydized metallic iron was often detected. +Investigation made it in the highest degree probable that this formation +owed its origin to the street sweepings of the town, which had been +thrown upon the beach, and carried off and distributed by the waves over +the bottom of the harbor." [Footnote: Geognostische Studien am Meeres +Ufer, Leonhard und Bronn, 1841, pp. 25, 26.] These and other familiar +observations of the like sort show that a sandstone reef, of no +inconsiderable magnitude, might originate from the stranding of a ship +with a cargo of iron, [Footnote: Kohl, Schleswig-Holstein, ii., p. 45.] +or from throwing the waste of an establishment for working metals into +running water which might carry it to the sea. + +Parthey records a singular instance of unforeseen mischief from an +interference with the arrangements of nature. A landowner at Malta +possessed a rocky plateau sloping gradually towards the sea, and +terminating in a precipice forty or fifty feet high, through natural +openings in which the sea-water flowed into a large cave under the rock. +The proprietor attempted to establish salt-works on the surface, and cut +shallow pools in the rock for the evaporation of the water. In order to +fill the salt-pans more readily, he sank a well down to the cave +beneath, through which he drew up water by a windlass and buckets. The +speculation proved a failure, because the water filtered through the +porous bottom of the pans, leaving little salt behind. But this was a +small evil, compared with other destructive consequences that followed. +When the sea was driven into the cave by violent west or north-west +winds, it shot a jet d'eau through the well to the height of sixty feet, +the spray of which was scattered far and wide over the neighboring +gardens and blasted the crops. The well was now closed with stones, but +the next winter's storms hurled them out again, and spread the salt +spray over the grounds in the vicinity as before. Repeated attempts were +made to stop the orifice, but at the time of Parthey's visit the sea had +thrice burst through, and it was feared that the evil was without +remedy. [Footnote: Wanderungen durch Sicilien und die Levante, i., p. +406.] + +I have mentioned the great extent of the heaps of oyster and other +shells left by the American Indians on the Atlantic coast of the United +States. Some of the Danish kitchen-middens, which closely resemble them, +are a thousand feet long, from one hundred and fifty to two hundred +wide, and from six to ten high. These piles have an importance as +geological witnesses, independent of their bearing upon human history. +Wherever the coast line appears, from other evidence, to have remained +unchanged in outline and elevation since they were accumulated, they are +found near the sea, and not more than about ten feet above its level. In +some cases they are at a considerable distance from the beach, and in +these instances, so far as yet examined, there are proofs that the coast +has advanced in consequence of upheaval or of fluviatile or marine +deposit. Where they are altogether wanting, the coast seems to have sunk +or been washed away by the sea. The constancy of these observations +justifies geologists in arguing, where other evidence is wanting, the +advance of land or sea respectively, or the elevation or depression of +the former, from the position or the absence of these heaps alone. + +Every traveller in Italy is familiar with Monte Testaccio, the mountain +of potsherds, at Rome; [Footnote: Untill recently this hillock was +supposed to consist of shards of household pottery broken in using, but +it now appears to be ascertained that it is composed of fragments of +earthenware broken in transportation from the place of manufacture to +the emporium on the Tiber where such articles were landed.] but this +deposit, large as it is, shrinks into insignificance when compared with +masses of similar origin in the neighborhood of older cities. The +castaway pottery of ancient towns in Magna Grecia composes strata of +such extent and thickness that they have been dignified with the +appellation of the ceramic formation. The Nile, as it slowly changes its +bed, exposes in its banks masses of the same material, so vast that the +population of the world during the whole historical period would seem to +have chosen this valley as a general deposit for its broken vessels. + +The fertility imparted to the banks of the Nile by the water and the +slime of the inundations, is such that manures are little employed. +Hence much domestic waste, which would elsewhere be employed to enrich +the soil, is thrown out into vacant places near the town. Hills of +rubbish are thus piled up which astonish the traveller almost as much as +the solid pyramids themselves. The heaps of ashes and other household +refuse collected on the borders and within the limits of Cairo were so +large, that the removal of them by Ibrahim Pacha has been looked upon as +one of the great works of the age. + +These heaps formed almost a complete rampart around the city, and +impeded both the circulation of the air and the communication between +Cairo and its suburbs. At two points these accumulations are said to +have risen to the incredible height of between six and seven hundred +feet; and these two heaps covered two hundred and fifty acres. +[Footnote: Clot Bey, Egypte, i., p. 277.] During the occupation of Cairo +by the French, the invaders constructed redoubts on these hillocks which +commanded the city. They were removed by Mehemet Ali, and the material +was employed in raising the level of low grounds in the environs. +[Footnote: Egypt manufactures annually about 1,200,000 pounds of nitre, +by lixiviating the ancient and modern rubbish-heaps around the towns.] + +In European and American cities, street sweepings and other town refuse +are used as manure and spread over the neighboring fields, the surface +of which is perceptibly raised by them, by vegetable deposit, and by +other effects of human industry, and in spite of all efforts to remove +the waste, the level of the ground on which large towns stand is +constantly elevated. The present streets of Rome are twenty feet, and in +many places much more, above those of the ancient city. The Appian Way +between Rome and Albano, when cleared out a few years ago, was found +buried four or five feet deep, and the fields along the road were +elevated nearly or quite as much. The floors of many churches in Italy, +not more than six or seven centuries old, are now three or four feet +below the adjacent streets, though it is proved by excavations that they +were built as many feet above them. [Footnote: Rafinesque maintained +many years ago that there was a continual deposition of dust on the +surface of the earth from the atmosphere, or from cosmical space, +sufficient in quantity to explain no small part of the elevation +referred to in the text. Observations during the eclipse of Dec. 22, +1870, led some astronomers to believe that the appearance of the corona +was dependent upon or modified by cosmical dust or matter in a very +attenuated form diffused through space. + +Tyndall has shown by optical tests that the proportion of solid matter +suspended or floating in common air is very considerable, and there is +abundant other evidence to the name purpose. Ehrenberg has found African +and even American infusoria in dust transplanted by winds and let fall +in Europe, and Schliemann offers that the quantity of dust brought by +the scirocco from Africa is so great, that by cutting holes in the naked +rocks of Malta enough of Libyan transported earth can be caught and +retained, in the course of fourteen years, to form a soil fit for +cultivation.--Beilage zur Allgemeinen Zeitung, Mar. 24, 1870.] + + +Nothing Small in Nature. + +It is a legal maxim that "the law concerneth not itself with trifles," +de minimis non curat lex; but in the vocabulary of nature, little and +great are terms of comparison only; she knows no trifles, and her laws +are as inflexible in dealing with an atom as with a continent or a +planet. [Footnote: One of the sublimest, and at the same time most +fearful suggestions that have been prompted by the researches of modern +science, was made by Babbage in the ninth chapter of his Ninth +Bridgewater Treatise. I have not the volume at hand, but the following +explanation will recall to the reader, if it does not otherwise make +intelligible, the suggestion I refer to: + +No atom can be disturbed in place, or undergo any change of temperature, +of electrical state, or other material condition, without affecting, by +attraction or repulsion or other communication, the surrounding atoms. +These, again, by the same law, transmit the influence to other atoms, +and the impulse thus given extends through the whole material universe. +Every human movement, every organic act, every volition, passion, or +emotion, every intellectual process, is accompanied with atomic +disturbance, and hence every such movement, every such act or process, +affects all the atoms of universal matter. Though action and reaction +are equal, yet reaction does not restore disturbed atoms to their former +place and condition, and consequently the effects of the least material +change are never cancelled, but in some way perpetuated, so that no +action can take place in physical, moral, or intellectual nature, +without leaving all matter in a different state from what it would have +been if such action had not occurred. Hence, to use language which I +have employed on another occasion: there exists, not alone in the human +conscience or in the omniscience of the Creator, but in external nature, +an ineffaceable, imperishable record, possibly legible even to created +intelligence, of every act done, every word uttered, nay, of every wish +and purpose and thought conceived, by mortal man, from the birth of our +first parent to the final extinction of our race; so that the physical +traces of our most secret sins shall last until time shall be merged in +that eternity of which not science, but religion alone assumes to take +cognisance.] + +The human operations mentioned in the last few paragraphs, therefore, do +act in the ways ascribed to them, though our limited faculties are at +present, perhaps forever, incapable of weighing their immediate, still +more their ultimate consequences. But our inability to assign definite +values to these causes of the disturbance of natural arrangements is not +a reason for ignoring the existence of such causes in any general view +of the relations between man and nature, and we are never justified in +assuming a force to be insignificant because its measure is unknown, or +even because no physical effect can now be traced to it as its origin. +The collection of phenomena must precede the analysis of them, and every +new fact, illustrative of the action and reaction between humanity and +the material world around it, is another step towards the determination +of the great question, whether man is of material nature or above her. + +THE END + + + + + + + +End of the Project Gutenberg EBook of The Earth as Modified by Human Action +by George P. 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