Man and Nature Part 23

_Wadies of Arabia, Petraea._

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 acc.u.mulations 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. Not far from Wadi Feiran, on the most direct route to Wadi Esh-Sheikh, is a very narrow pa.s.s 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 pa.s.s is a wide and nearly level expanse, containing a hundred acres, perhaps much more.

This is 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 pa.s.s, and reservoirs built to retain the winter rains, a great extent of valley might be rendered cultivable.

_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 ill.u.s.trate 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 ma.s.s 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 sh.o.r.e, greater at some distance from it.

It was composed of pebbles and sand, and contained a great quant.i.ty 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. An investigation undertaken by Councillor Reinhard and myself, at the instance of the Society of Science, 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."[488] 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,[489] 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 toward 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 windla.s.s 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 northwest 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.[490]

I have mentioned the great extent of the heaps of oyster and other sh.e.l.ls 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 acc.u.mulated, 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; but this deposit, large as it is, shrinks into insignificance when compared with ma.s.ses of similar origin in the neighborhood of older cities. The castaway pottery of ancient towns in Magna Graecia 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 ma.s.ses 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.

The soil near cities, the street sweepings of which are spread upon the ground as manure, is perceptibly raised by them 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 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.

_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 h.o.m.ogeneous, 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 a.s.serted 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.[491]

If the commonly received theory of the cause of earthquakes is true--that, namely, which ascribes them to the elastic force of gases acc.u.mulated 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 ma.s.s 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 was felt over a twelfth part of the earth's surface, was probably 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 ma.s.ses 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 quant.i.ty 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 Belpa.s.so.[492] When the opening was made, fluid lava poured forth and flowed rapidly toward 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."[493] 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.[494]

_Effects of Mining._

The excavations made by man, for mining and other purposes, may sometimes occasion disturbance of the surface by the subsidence of the strata above them, as in the case of the mine of Fahlun, but such accidents must always be too inconsiderable in extent to deserve notice in a geographical point of view. Such excavations, however, 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 the magnetic and electrical condition of the earth's crust to a sensible degree.

Accidental fires in mines of coal or lignite sometimes lead to consequences not only destructive to large quant.i.ties of valuable material, but may, directly or indirectly, produce results important in geography. The coal occasionally takes fire from the miners' lights or other fires used by them, and, if long exposed to air in deserted galleries, may be spontaneously kindled. Under favorable circ.u.mstances, a stratum of coal will burn till 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 been advantageously employed in forcing vegetation.[495]

_Espy's Theories._

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 a.n.a.logies and relations not obvious to minds less philosophically const.i.tuted. They have unquestionably contributed very 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 small to have been yet detected.

_River Sediment._

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 quant.i.ties 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 ma.s.s the transfer of which from the surface of a large basin, and its acc.u.mulation 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 by man must have much augmented the quant.i.ty 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.

_Nothing Small in Nature._

It is a legal maxim that "the law concerneth not itself with trifles,"

_de minimus 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.[496] 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 a.s.sign 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 a.s.suming 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 a.n.a.lysis of them, and every new fact, ill.u.s.trative of the action and reaction between humanity and the material world around it, is another step toward the determination of the great question, whether man is of nature or above her.

FOOTNOTES:

[1] In the Middle Ages, feudalism, and a nominal Christianity whose corruptions had converted the most beneficent of religions into the most baneful of superst.i.tions, 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 these 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 cause of the rapid depopulation observed in the Middle Ages, and of the prodigious mult.i.tude 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.

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. The abbey 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, sowing, and harvesting, and therefore deserve some small share of the bread they have grown." "These are his own words," adds Courier; "he is speaking of the fortunate peasants, of those who had work and bread, and they were then the few."--_Pet.i.tion a la Chambre des Deputis pour les Villageois que l'on empeche de 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 mult.i.tude of heavy fines imposed for trifling offences, he enumerates about thirty seignorial rights, the very origin and nature of some of which are now unknown, while those of some others, claimed and enforced by ecclesiastical as well as by temporal lords, are as repulsive to humanity and morality, as the worst abuses ever practised by heathen despotism. 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 n.o.bility, were exempt from taxation. Who can wonder at the hostility of the French plebeian cla.s.ses toward the aristocracy in the days of the Revolution?

[2] 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 circ.u.mstances, 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.

[3] 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, 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 Pflanzenwelt in der Zeit_.

[4]

G.o.ds Almagt wenkte van den troon, En schiep elk volk een land ter woon: Hier vestte Zij een grondgebied, Dat Zij ons zelven scheppen liet.

[5] The udometric measurements of Belgrand, reported in the _Annales Forestieres_ for 1854, and discussed by Valles in chap. vi of his _etudes sur les Inondations_, const.i.tute the earliest, and, in some respects, the most remarkable series known to me, of persevering and systematic observations bearing directly and exclusively upon the influence of human action on climate, or, to speak more accurately, on precipitation and natural drainage. The conclusions of Belgrand, however, and of Valles, who adopts them, have not been generally accepted by the scientific world, and they seem to have been, in part at least, refuted by the arguments of Hericourt and the observations of Cantegril, Jeandel, and Belland. See chapter iii: _The Woods_.

[6] Verses addressed by G. C. to Sir Walter Raleigh.--HAKLUYT, i, p.

668.

[7]

----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.

[8] 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 serves as a guide to the eye, but there are sportsmen who fire with the but of the gun at the hip. In this case, as in the use of the sling, the la.s.so, 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 blow pipe 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.

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 flat and wet sh.e.l.l, 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 sh.e.l.l of the tortoise, and sticks in it." a.n.a.logous calculations--if such physico-mental operations can properly 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 all of them, and marksmanship depends almost wholly upon the power of that organ, whose directions the blind muscles implicitly follow. 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_.