Man and Nature Part 36

[332] "Forests," "woods," and "groves," are very frequently mentioned in the Old Testament as existing at particular places, and they are often referred to by way of ill.u.s.tration, 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.

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. See _Appendix_, No. 44.

Solomon antic.i.p.ated Chevandier in the irrigation of forest trees: "I made me pools of water, to water therewith the wood that bringeth forth trees."--_Ecclesiastes_ ii, 6.

[333] One of these, upon Mount Hor, two stories in height, is still in such preservation that I found not less than ten feet of water in it in the month of June, 1851.

The brook Ain Musa, which runs through the city of Petra and finally disappears in the sands of Wadi el Araba, is a considerable river 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 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 unequivocal remains of a sluice by which the water was diverted to the tunnel near the arch that crosses the Sik. 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 toward Wadi el Araba.

[334] The authorities differ as to the extent of the cultivable and the cultivated soil of Egypt. Lippincott's, or rather Thomas and Baldwin's, _Gazetteer_--a work of careful research--estimates "the whole area comprised in the valley [below the first cataract] and delta," at 11,000 square miles. Smith's _Dictionary of the Bible_, article "Egypt," says: "Egypt has a superficies of about 9,582 square geographical miles of soil, which the Nile either does or can water and fertilize. This computation includes the river and lakes as well as sundry tracts which can be inundated, and the whole s.p.a.ce either cultivated or fit for cultivation is no more than about 5,626 square miles." By geographical mile is here meant, I suppose, the nautical mile of sixty to an equatorial degree, or about 2,025 yards. The whole area, then, by this estimate, is 12,682 square statute or English miles, that of the s.p.a.ce "cultivated or fit for cultivation," 7,447. Smith's _Dictionary of Greek and Roman Geography_, article "aegyptus," gives 2,255 square miles as the area of the valley between Syene and the bifurcation of the Nile, exclusive of the Fayoom, which is estimated at 340. The area of the Delta is stated at 1,976 square miles between the main branches of the river, and, including the irrigated lands east and west of those branches, at 4,500 square miles. This latter work does not inform us whether these are statute or nautical miles, but nautical miles must be intended.

Other writers give estimates differing considerably from those just cited. The latest computations I have seen are those in the first volume of Kremer's _aegypten_, 1863. This author (pp. 6, 7) a.s.signs to the Delta an area of 200 square German geographical miles (fifteen to the degree); to all Lower Egypt, including, of course, the Delta, 400 such miles.

These numbers are equal, respectively, to 4,239 and 8,478 square statute miles, and the great lagoons are embraced in the areas computed. Upper Egypt (above Cairo) is said (p. 11) to contain 4,000,000 feddan of _culturflache_, or cultivable land. The feddan is stated (p. 37) to contain 7,333 square piks, the pik being 75 centimetres, and it therefore corresponds almost exactly to the English acre. Hence, according to Kremer, the cultivable soil of Upper Egypt is 6,250 square statute miles, or twice as much as the whole area of the valley between Syene and the bifurcation of the Nile, according to Smith's _Dictionary of Greek and Roman Geography_. I suspect that 4,000,000 feddan is erroneously given as the cultivable area of Upper Egypt alone, when in fact it should be taken for the arable surface of both Lower and Upper Egypt; for from the statistical tables in the same volume, it appears that 3,317,125 feddan, or 5,253 square statute miles, were cultivated, in both geographical divisions, in the year referred to in the tables, the date of which is not stated.

The area which the Nile would now cover at high water, if left to itself, is greater than 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 Ptolomies carried the Nile-water to large provinces which have now been long abandoned and have relapsed into the condition of a 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."

[335] A ca.n.a.l has been constructed, and new ones are in progress, to convey water from the Nile to the city of Suez, and to various points on the line of the s.h.i.+p ca.n.a.l, with the double purpose of supplying fresh water to the inhabitants and laborers, and of irrigating the adjacent soil. The area of land which may be thus reclaimed and fertilized is very large, but the actual quant.i.ty which it will be found economically expedient to bring under cultivation cannot now be determined.

[336] The so-called spring at Heliopolis is only a thread of water infiltrated from the Nile or the ca.n.a.ls.

[337] The date and the doum palm, the _sont_ and many other acacias, the caroub, the sycamore, and other trees, grow well in Egypt without irrigation, and would doubtless spread through the entire valley in a few years.

[338] Wilkinson has shown that the cultivable soil of Egypt has not been diminished by encroachment of the desert sands, or otherwise, but that, on the contrary, it must have been increased since the age of the Pharaohs. The Gotha _Almanac_ for 1862 states the population of Egypt in 1859 at 5,125,000 souls; but this must be a great exaggeration, even supposing the estimate to include the inhabitants of Nubia, and of much other territory not geographically belonging to Egypt. In general, the population of that country has been estimated at something more than three millions, or about six hundred to the square mile; but with a better government and better social inst.i.tutions, the soil would sustain a much greater number, and in fact it is believed that in ancient times its inhabitants were twice, perhaps even thrice, as numerous as at present.

Wilkinson (_Handbook for Travellers in Egypt_, p. 10) observes that the total population, which two hundred years ago was estimated at 4,000,000, amounted till lately only to about 1,800,000 souls, having been reduced since 1800 from 2,500,000 to that number.

[339] 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 ca.n.a.ls, 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 though, by ca.n.a.ls and embankments, man has done much to modify the natural distribution of the waters of the Nile, and possibly has even transferred its channel from one side of the valley to the other, 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 sh.o.r.es are much more likely to have been mora.s.ses than sands.

[340] _Memorie sui progetti per l'estensione dell' Irrigazione, etc., il Politecnico_, for January, 1863, p. 6.

[341] NIEL, _L'Agriculture des etats Sardes_, p. 232.

[342] NIEL, _Agriculture des etats Sardes_, p. 237. Lombardini's computation just given allows eighty-one cubic metres per day to the hectare, which, supposing the season of irrigation to be one hundred days, is equal to a precipitation of thirty-two inches. But in Lombardy, water is 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. 246) gra.s.s grounds ought to receive, in Germany, twenty-one centimetres of water per week, and with less than half that quant.i.ty it is not advisable to incur the expense of supplying it. The ground is irrigated twenty-five or thirty times, and if the full quant.i.ty of twenty-one centimetres is applied, it receives about 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 quant.i.ty is twenty centimetres 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.

Boussingault observes that rain water is vastly more fertilizing than the water of irrigating ca.n.a.ls, 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 gra.s.s 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 Ca.n.a.l Cavour, just now commenced--which is to take its supply from the Po at Chiva.s.so, fourteen or fifteen miles below Turin--will furnish 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 icefields 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.

[343] 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.

Professor 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 const.i.tuents of its 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."

The first of the paragraphs just quoted is not in accordance with the alleged experience of agriculturists in those parts of Italy where irrigation is most successfully applied. They believe that the const.i.tuents 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 far more valuable for irrigation than water from the same source, which has not been impregnated with fertilizing substances by pa.s.sing 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.

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 ca.n.a.ls 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 ca.n.a.ls must be calculated with reference to the area intended to be irrigated, and when they and their branches are once constructed, it is 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 ca.n.a.ls, 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 quant.i.ty of supply must be regulated by a general system applicable, as far as may be, to the whole area irrigated by the same ca.n.a.l, 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 clas.h.i.+ng 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 ca.n.a.ls, lead not unfrequently to ruinous injustice toward individual landholders. These circ.u.mstances discourage the division of the soil into small properties, and there is a constant tendency to the acc.u.mulation of large estates of irrigated land in the hands of great capitalists, and consequently to the dispossession of the small cultivators, who pa.s.s from the condition of owners of the land to that of hireling tillers. The farmers are no longer yeomen, but peasants. Having no interest in the soil which composes their country, they are virtually expatriated, and the middle cla.s.s, which ought to const.i.tute 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.

[344] BOUSSINGAULT, _economie Rurale_, ii, pp. 248, 249.

[345] The cultivation of rice is so prejudicial to health everywhere that nothing but the necessities of a dense population can justify the sacrifice of life it costs in countries where it is pursued.

It has been demonstrated by actual experiment, that even in Mississippi, cotton can be advantageously raised by the white man without danger to health; and in fact, a great deal of the cotton brought to the Vicksburg market for some years past has been grown exclusively by white labor.

There is no reason why the cultivation of cotton should be a more unhealthy occupation in America than it is in other countries where it was never dreamed of as dangerous, and no well-informed American, in the Slave States or out of them, believes that the abolition of slavery in the South would permanently diminish the cotton crop of those States.

[346] _L'Italie a propos de l'Exposition de Paris_, p. 92.

[347] The very valuable memoirs of Lombardini, _Cenni idrografi sulla Lombardia, Intorno al sistema idraulico del Po_, and other papers on similar subjects, were published in periodicals little known out of Italy; and the _Idraulica Pratica_ of Mari has not, I believe, been translated into French or English. These works, and other sources of information equally inaccessible out of Italy, have been freely used by Baumgarten, in a memoir ent.i.tled _Notice sur les Rivieres de la Lombardie_, in the _Annales des Ponts et Chaussees_, 1847, 1er semestre, pp. 129 _et seqq._, and by Dumont, _Des Travaux Publics dans leurs Rapports avec l'Agriculture_, note, viii, pp. 269 _et seqq._ For the convenience of my readers, I shall use these two articles instead of the original authorities on which they are founded.

[348] Sir John F. W. 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 metres; 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 many times more than any physical geographer has ever estimated the quant.i.ty supplied by all the rivers on the face of the globe.

[349] The Drac, a torrent emptying into the Isere a little below Gren.o.ble, has discharged 5,200, the Isere, which receives it, 7,800 cubic yards, and the Durance an equal quant.i.ty, per second.--MONTLUISANT, _Note sur les Dessechements, etc., Annales des Ponts et Chaussees_, 1833, 2me semestre, p. 288.

The floods of some other French rivers 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.--BELGRAND, _De l'Influence des Forets, etc., Annales des Ponts et Chaussees_, 1854, 1er semestre, p. 15, note.

[350] 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.

[351] "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.

I take this occasion to acknowledge myself indebted to the interesting memoir just quoted for all the statements I make respecting the floods of the Ardeche, except the comparison of the volume of its waters with that of the Nile, and the computation with respect to the capacity required for reservoirs to be constructed in its basin.

[352] 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 the 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 a much later period. See _App._, No. 45.

[353] _Memoire sur les Inondations des Rivieres de l'Ardeche_, p. 16.

"The terrific roar, the thunder of the raging torrents proceeds princ.i.p.ally 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 Oesterreichischien Alpenlander_, i, p. 113. See _Appendix_, No. 48.

[354] FRISI, _Del modo di regolare i Fiumi e i Torrenti_, pp. 4-19.

[355] SURELL, _etude sur les Torrents_, pp. 31-36.

[356] CHAMPION, _Les Inondations en France_, iii, p. 156, note.

[357] Notwithstanding this favorable circ.u.mstance, 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.

[358] TROY, _etude sur le Rebois.e.m.e.nt des Montagnes_, ---- 6, 7, 21.

[359] For accounts of damage from the bursting of reservoirs, see VALLeE, _Memoire sur les Reservoirs d'Alimentation des Canaux, Annales des Ponts et Chaussees_, 1833, 1er semestre, p. 261.