CHAPTER IV.

THE WATERS.

LAND ARTIFICIALLY WON FROM THE WATERS: _a_, EXCLUSION OF THE SEA BY

DIKING; _b_, DRAINING OF LAKES AND MARSHES; _c_, GEOGRAPHICAL INFLUENCE

OF SUCH OPERATIONS--LOWERING OF LAKES--MOUNTAIN LAKES--CLIMATIC EFFECTS

OF DRAINING LAKES AND MARSHES--GEOGRAPHICAL AND CLIMATIC EFFECTS OF

AQUEDUCTS, RESERVOIRS, AND CANALS--SURFACE AND UNDERDRAINING, AND THEIR

CLIMATIC AND GEOGRAPHICAL EFFECTS--IRRIGATION AND ITS CLIMATIC AND

GEOGRAPHICAL EFFECTS.

INUNDATIONS AND TORRENTS: _a_, RIVER EMBANKMENTS; _b_, FLOODS OF THE

ARDECHE; _c_, CRUSHING FORCE OF TORRENTS; _d_, INUNDATIONS OF 1856 IN

FRANCE; _e_, REMEDIES AGAINST INUNDATIONS--CONSEQUENCES IF THE NILE HAD

BEEN CONFINED BY LATERAL DIKES.

IMPROVEMENTS IN THE VAL DI CHIANA--IMPROVEMENTS IN THE TUSCAN

MAREMME--OBSTRUCTION OF RIVER MOUTHS--SUBTERRANEAN WATERS--ARTESIAN

WELLS--ARTIFICIAL SPRINGS--ECONOMIZING PRECIPITATION.

_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, he has promoted the deposit of solid matter

in the sea, thus reducing its depth, 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, lighthouses, 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. 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 sea beach. 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 results are all in a considerable degree

subject to control, or rather to direction and resistance, by human

power, and it is in guiding and combating them that man has achieved

some of his most remarkable and 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 an

ingenuity which has contrived means of executing them, and which gives

promise of yet greater performance in time to come.

Men have ceased to admire the 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 surpass the vastest remains of

ancient architectural art in mass and weight of matter, 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 railroad has been

constructed at twice the cost which would now build that stupendous

monument. 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!"

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.

a. _Exclusion of the Sea by Diking._

The draining of the Lincolnshire fens in England, which converted about

400,000 acres of marsh, pool, and tide-washed flat into plough land 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, Frisic, 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 are much 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 these terrible inundations are recorded, and in very

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 much 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.

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.[306] 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.[307] 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 accumulation 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.[308]

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.[309] 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."[310] 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.[311]

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.[312] 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 sandbanks, 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.

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 greater 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 sandbanks 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."[313]

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.[314]

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 Frisic, 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.[315]

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 sea water also, when heavy or long-continued

west winds drove it landward. 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 to 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

(_sommer-deich_, pl. _sommer-deiche_, German; _zomerkaai_, _zomerkade_,

pl. _zomerkaaie_, _zomerkaden_, Dutch). 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 sandbanks, 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.[316] 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_.[317] 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; 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.[318] 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 subsoil 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.[319]

b. _Draining of Lakes and Marshes._

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 and 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 were reclaimed from the waters, and

added to the agricultural domain of the Netherlands, between 1815 and

1858. The most important of these undertakings was the draining of the

Lake of Haarlem, and for this purpose some of the most powerful

hydraulic engines ever constructed were designed and executed.[320] 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 afterward covered by the

Lake of Haarlem, and they have more 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 northwest winds, those of the

Lake of Haarlem were raised proportionally and driven southward, while

winds from the south tended to create a flow in the opposite direction.

The shores of the lake were everywhere low, and though in the course of

the eighty years between 1767 and 1848 more than L350,000 or $1,700,000

had been expended in checking its encroachments, it often burst its

barriers, and produced destructive inundations. On the 29th of November,

1836, a south wind brought its waters to the very gates of Amsterdam,

and on the 26th of December of the same year, in a northwest 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

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,[321] 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.

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 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.

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 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

watercourses on one side, and exposing the coast to erosion by the sea

upon the other.

c. _Geographical Influence of such Operations._

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 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.

_Lowering of Lakes._

The hydraulic works of the Netherlands and of the neighboring states are

of such magnitude, that 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.

One of the best known of these 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, but 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 Dionysins 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 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 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

drain the lake, 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 seems to have answered its design for some centuries. 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.

Works have now been some years in progress 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 this tunnel is 18,634 feet, or rather more than three miles

and a half. Of course, it is one of the longest subterranean galleries

yet executed in Europe, and it offers many curious particulars in its

original design which cannot here be described. The difference between

the highest and the lowest known levels of the surface of the lake

amounts to at least forty feet, and the difference of area covered at

these respective stages is not much less than eight thousand acres. The

tunnel will reduce the water to a much lower point, and it is computed

that, including the lands occasionally overflowed, not less than forty

thousand acres of as fertile soil as any in Italy will be recovered from

the lake and permanently secured from inundation by its waters.

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.[322] They are sometimes attended with wholly

unexpected evils, as, for example, in the case of Barton Pond, in

Vermont, and in that of the Lake Storsjoe, 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 toward 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.

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.

_Mountain 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

negligence of man has permitted to disappear. Auguste de Gasparin,

brother of the illustrious agriculturist, demonstrated more than thirty

years ago, in an original paper, that many natural dikes formerly

existed in the mountain valleys, which have been swept away by the

waters. He proposed to rebuild and to multiply them. This interesting

suggestion has reappeared several times since, but has met with strong

opposition from skilful engineers. It would, nevertheless, be well to

try the experiment of creating artificial lakes which should fill

themselves with the water of melting snows and deluging rains, to be

drawn out in times of drought. If this plan has able opposers, it has

also warm advocates. Experience alone can decide the question."[323]

_Climatic Effects of Draining Lakes and Marshes._

The draining of lakes, marshes, and other superficial accumulations of

moisture, reduces the water surface of a country, and, of course, the

evaporation from it. Lakes, too, in elevated positions, lose a part of

their water by infiltration, and thereby supply other lakes, springs,

and rivulets at lower levels. Hence, it is evident that the draining of

such waters, if carried on upon a large scale, must affect both the

humidity and the temperature of the atmosphere, and the permanent supply

of water for extensive districts.[324]

_Geographical and Climatic Effects of Aqueducts, Reservoirs, and

Canals._

Many 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.

Similar effects must have followed from the construction of the numerous

aqueducts which supplied ancient Rome with such a profuse abundance of

water. 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, 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 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;[325] 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.

_Climatic and Geographical Effects of Surface and Underground Draining._

I have commenced this chapter with a description of the dikes and other

hydraulic works of the Netherland engineers, because the geographical

results of such operations are more obvious and more easily measured,

though certainly not more important, than those of the 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.

_Surface and Under-draining and their Effects._

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, many small ridges and 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.

The beneficial effects of surface drainage, the necessity of extending

the fields as population increased, and the inconveniences resulting

from the presence of marshes in otherwise improved regions, must have

suggested at a very early period of human industry the expediency of

converting bogs and swamps into dry land by drawing off their waters;

and it would not be long after the introduction of this practice before

further acquisition of agricultural territory would be made by lowering

the outlet of small ponds and lakes, and adding the ground they covered

to the domain of the husbandman.

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 apparently

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, 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.[326] 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, in behalf of the municipal authorities, 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 this latter, 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 upon 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 Seine, that

it cannot possibly affect it to a sensible degree. I would, however,

advise determined water drinkers living at Paris to adopt his

conclusions, without studying his facts and his arguments; for it is

quite possible that he may convert his readers to a faith opposite to

his own, and that they will finally agree with the poet who held water

an "ignoble beverage."

_Climatic and Geographical Effects of Surface Draining._

When we remove water from the surface, we diminish the evaporation from

it, and, of course, the refrigeration which accompanies all evaporation

is diminished in proportion. Hence superficial draining ought to be

attended with an elevation of atmospheric temperature, and, in cold

countries, it might be expected to lessen the frequency 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 very

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.[327]

In England, under-drains are not generally laid below the reach of daily

variations of temperature, or below a point from which moisture 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.

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.

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.[328]

_Irrigation and its Climatic and Geographical Effects._

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 barbarism, and created for itself the

arts of social life.[329] 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, plough land 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.

There are few things in Continental 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. The summers in

Northern Italy, though longer, are very often not warmer than in New

England; and in ordinary years, the summer rains are as frequent and as

abundant in the former country as in the latter. Yet in Piedmont and

Lombardy, irrigation is bestowed upon almost every crop, while in New

England 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.[330]

The summers in Egypt, in Syria, and in Asia Minor and even Rumelia, are

almost rainless. In such climates, the necessity of irrigation is

obvious, and the loss of the ancient means of furnishing it readily

explains the diminished fertility of most of the countries in

question.[331] 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.[332]

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.[333] 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 Southern Europe, in the Turkish Empire, and in many other countries,

a very large proportion of the surface is, if not absolutely flooded, at

least thoroughly moistened by irrigation, a great number of times in the

course of every season, and this, especially, at periods when it would

otherwise be quite dry, and when, too, the power of the sun and the

capacity of the air for absorbing moisture are greatest. Hence it is

obvious that the amount of evaporation from the earth in these

countries, and, of course, the humidity and the temperature of both the

soil and the atmosphere in contact with it, must be much affected by the

practice of irrigation. The cultivable area of Egypt, or the space

accessible to cultivation, between desert and desert, is more than seven

thousand square statute miles. 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 confined to an area of five or

six 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 five or six thousand

square miles, or more than a square equatorial degree, to the evaporable

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.[334] The

fresh-water canals now constructing, in connection with the works for

the Suez canal, will not only restore the long abandoned fields east of

the Nile, but add to the arable soil of Egypt hundreds of square miles

of newly reclaimed desert, and thus still further increase the climatic

effects of irrigation.[335]

The Nile receives not a single tributary in its course through Egypt;

there is not so much as one living spring in the whole land,[336] 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.[337] 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.[338] 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.[339]

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.

In general, it may be said 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 withdrawn from the canals at any one 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.

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 of land 45,000,000 cubic metres 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."[340] Niel states the quantity of land irrigated in the former

kingdom of Sardinia, including Savoy, in 1856, at 240,000 hectares, or

not much less 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 France 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.[341] 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, 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. 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.[342] The rice grounds and the _marcite_ of Lombardy are

not included in these estimates of the amount of water applied.

Arrangements are concluded, and new plans proposed, for an immense

increase of the lands fertilized by irrigation in France 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 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.[343] 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 completely

absorbed, so that it does not reach the river which it naturally feeds,

except in such proportion as it is conveyed to it by infiltration.

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 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 commenced 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 twenty-nine cubic metres per day sufficed to irrigate

a hectare in the Delta.[344] This is equivalent to a fall of rain of two

millimetres and nine tenths per day, or, if we suppose water to be

applied for one hundred and fifty days during the dry season, to a total

precipitation of 435 millimetres, about seventeen inches and one third.

Taking the area of actually cultivated soil in Egypt at the low estimate

of 3,600,000 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 61,000,000 cubic yards, which--the mean daily

delivery of the Nile being in round numbers 320,000,000 cubic yards--is

nearly one fifth of the average quantity of water contributed to the

Mediterranean by that river.

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 Slave States of the

American Union and in Italy. The climate of the Southern States is 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.[345] The neighborhood of the rice fields is 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 Escourrou

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."[346]

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. Recent observations in India, a notice of

which I find in an account of a meeting of the Asiatic Society in the

Athenaeum of December 20, 1862, No. 1834, suggest a possible explanation

of this fact. At this meeting, Professor Medlicott read an essay on "the

saline efflorescence called 'Reh' and 'Kuller,'" which 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. Mr. Medlicott pronounces "these salts (which, in small

quantities are favorable to fertility of soil) 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 at the seasons when their

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. 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.

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 the only

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 causes, the

restoration of the woods is not, under present circumstances, to be

hoped for. Even where that measure is feasible and in actual process of

execution, a great number of years must elapse before the action of the

destructive causes in question can be arrested or perhaps even sensibly

mitigated by it. Besides this, leaving out of view the objections urged

by Belgrand and his followers to the generally received opinions

concerning the beneficial influence of the forest as respects river

inundations--for no one disputes its importance in preventing the

formation and limiting the ravages of mountain torrents--floods will

always occur in years of excessive precipitation, whether the surface of

the soil be generally cleared or generally wooded.

Physical improvement in this respect, then, cannot he confined to

preventive measures, but, in countries subject to damage by inundation,

means must he 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.

a. _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. 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 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 afterward 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. 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.

Few rivers, like the Nile, more than compensate by the fertilizing

properties of their water and their slime for the damage they may do in

inundations, and, consequently, there are few whose floods are not an

object of dread, few whose encroachments upon their banks are not a

source of constant anxiety and expense to the proprietors of the lands

through which they flow. River dikes, for confining the spread of

currents at high water, are of great antiquity in the East, and those of

the Po and its tributaries were begun before we have any trustworthy

physical or political annals of the provinces upon their borders. From

the earliest ages, the Italian hydraulic engineers have stood in the

front rank of their profession, and the Italian literature of this

branch of material improvement is exceedingly voluminous. But the

countries for which I write have no rivers like the Po, no plains like

those of Lombardy, and the dangers to which the inhabitants of English

and American river banks are exposed are more nearly analogous to those

that threaten the soil and population in the valleys and plains of

France, than to the perils and losses of the Lombard. The writings of

the Italian hydrographers, too, though rich in professional instruction,

are less accessible to foreigners and less adapted to popular use than

those of French engineers.[347] For these reasons I shall take my

citations principally from French authorities, though I shall

occasionally allude to Italian writers on the floods of the Tiber, of

the Arno, and some other Italian streams which much resemble those of

the rivers of England and the United States.

b. _Floods of the Ardeche._

The floods of 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, which has given its

name to a department in France, 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 1827, 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 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.[348] 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 contains 500,000 square miles of surface, or more than five

hundred times as much as that of the former.

The average annual precipitation in the basin of the Ardeche is not

greater than 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.[349] The

inundation of the 10th September, 1857, was accompanied with a terrific

hurricane, which passed along the eastern slope of the high grounds

where the Ardeche and several other western affluents of the Rhone take

their rise. The wind tore up all the trees in its path, and the rushing

torrents bore their trunks down to the larger streams, which again

transported them to the Rhone in such rafts that one might almost have

crossed that river by stepping from trunk to trunk.[350] 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 height and violence of the inundations of most great rivers are

determined by the degree in which the floods of the different

tributaries are coincident in time. Were all the affluents of the Rhone

to pour their highest annual floods into its channel at once, 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.[351]