The drifting of the dunes on the coast of Prussia commenced not much

more than a hundred years ago. The Frische Nehrung is separated from the

mainland by the Frische Haff, and there is but a narrow strip of arable

land along its eastern borders. Hence its rolling sands have covered a

comparatively small extent of dry land, but fields and villages have

been buried and valuable forests laid waste by them. The loose coast-row

has drifted over the inland ranges, which, as was noticed in the

description of these dunes on a former page, were protected by a surface

of different composition, and the sand has thus been raised to a height

which it could not have reached upon level ground. This elevation has

enabled it to advance upon and overwhelm woods, which, upon a plain,

would have checked its progress, and, in one instance, a forest of many

hundred acres of tall pines was destroyed by the drifts between 1804 and

1827.

Control of Dunes by Man.

There are three principal modes in which the industry of man is brought

to bear upon the dunes. First, the creation of them, at points where,

from changes in the currents or other causes, new encroachments of the

sea are threatened; second, the maintenance and protection of them where

they have been naturally formed; and third, the removal of the inner

rows where the belt is so broad that no danger is to be apprehended from

the loss of them.

In describing the natural formation of dunes, it was said that they

began with an accumulation of sand around some vegetable or other

accidental obstruction to the drifting of the particles. A high,

perpendicular cliff, which deadens the wind altogether, prevents all

accumulation of sand; but, up to a certain point, the higher and broader

the obstruction, the more sand will heap up in front of it, and the more

will that which falls behind it be protected from drifting further. This

familiar observation has taught the inhabitants of the coast that an

artificial wall or dike will, in many situations, give rise to a broad

belt of dunes. Thus a sand dike or wall, of three or four miles in

length, thrown in 1610 across the Koegras, a tide-washed flat between

the Zuiderzee and the North Sea, has occasioned the formation of rows of

dunes a mile in breadth, and thus excluded the sea altogether from the

Koegras. A similar dike, called the Zijperzeedijk, has produced another

scarcely less extensive belt in the course of two centuries. A few years

since, the sea was threatening to cut through the island of Ameland,

and, by encroachment on the southern side and the blowing off of the

sand from a low flat which connected the two higher parts of the island,

it had made such progress, that in heavy storms the waves sometimes

rolled quite across the isthmus. The construction of a breakwater and a

sand dike have already checked the advance of the sea, and a large

number of sand-hills has been formed, the rapid growth of which promises

complete future security against both wind and wave. Similar effects

have been produced by the erection of plank fences, and even of simple

screens of wattling and reeds. [Footnote: Staring, De Bodem van

Nederland, i., pp. 329-331. Id., Voormaals en Thans, p. 163. Andresen,

Om Klitformationen, pp. 280, 295.

The creation of new dunes, by the processes mentioned in the text, seems

to be much older in Europe than the adoption of measures for securing

them by planting. Dr. Dwight mentions a case in Massachusetts, where a

beach was restored, and new dunes formed, by planting beach grass.

"Within the memory of my informant, the sea broke over the beach which

connects Truro with Province Town, and swept the body of it away for

some distance. The beach grass was immediately planted on the spot; in

consequence of which the beach was again raised to a sufficient height,

and in various places into hills."--Travels, iii., p. 93.]

The dunes of Holland are sometimes protected from the dashing of the

waves by a revetement of stone, or by piles; and the lateral high-water

currents, which wash away their base, are occasionally checked by

transverse walls running from the foot of the dunes to low-water mark;

but the great expense of such constructions has prevented their adoption

on a large scale. [Footnote: Staring, i., pp. 310, 332.] The principal

means relied on for the protection of the sand-hills are the planting of

their surfaces and the exclusion of burrowing and grazing animals. There

are grasses, creeping plants, and shrubs of spontaneous growth, which

flourish in loose sand, and, if protected, spread over considerable

tracts, and finally convert their face into a soil capable of

cultivation, or, at least, of producing forest trees. Krause enumerates

one hundred and seventy-one plants as native to the coast sands of

Prussia, and the observations of Andresen in Jutland carry the number of

these vegetables up to two hundred and thirty-four.

Some of these plants, especially the Arundo arenaria or arenosa, or

Psamma or Psammophila arenaria--Klittetag, or Hjelme in Danish, helm in

Dutch, Dunenhalm, Sandschilf, or Hugelrohr in German, gourbet in French,

and marram in English--are exclusively confined to sandy soils, and

thrive well only in a saline atmosphere. [Footnote: There is some

confusion in the popular use of these names, and in the scientific

designations of sand-plants, and they are possibly applied to different

plants in different places. Some writers style the gourbet Calamagrostis

arenaria, and distinguish it from the Danish Klittetag or Hjelme.] The

arundo grows to the height of about twenty-four inches, but sends its

strong roots with their many rootlets to a distance of forty or fifty

feet. It has the peculiar property of flourishing best in the loosest

soil, and a sand-shower seems to refresh it as the rain revives the

thirsty plants of the common earth. Its roots bind together the dunes,

and its leaves protect their surface. When the sand ceases to drift, the

arundo dies, its decaying roots fertilizing the sand, and the

decomposition of its leaves forming a layer of vegetable earth over it.

Then follows a succession of other plants which gradually fit the

sand-hills by growth and decay, for forest planting, for pasturage, and

sometimes for ordinary agricultural use.

But the protection and gradual transformation of the dunes is not the

only service rendered by this valuable plant. Its leaves are nutritious

food for sheep and cattle, its seeds for poultry; [Footnote: Bread, not

indeed very palatable, has been made of the seeds of the arundo, but the

quantity which can be gathered is not sufficient to form an important

economical resource.--Andresen, Om Klitformationen, p. 160.] cordage and

netting twine are manufactured from its fibres, it makes a good material

for thatching, and its dried roots furnish excellent fuel. These useful

qualities, unfortunately, are too often prejudicial to its growth. The

peasants feed it down with their cattle, cut it for rope-making, or dig

if up for fuel, and it has been found necessary to resort to severe

legislation to prevent them from bringing ruin upon themselves by thus

improvidently sacrificing their most effectual safeguard against the

drifting of the sands. [Footnote: Bergsoe, Reventlovs Virksomhed, ii.,

p. 4.]

In 1539 a decree of Christian III., king of Denmark, imposed a fine upon

persons convicted of destroying certain species of sand-plants upon the

west coast of Jutland. This ordinance was renewed and made more

comprehensive in 1558, and in 1569 the inhabitants of several districts

were required, by royal rescript, to do their best to check the

sand-drifts, though the specific measures to be adopted for that purpose

are not indicated. Various laws against stripping the dunes of their

vegetation were enacted in the following century, but no active measures

were taken for the subjugation of the sand-drifts until 1779, when a

preliminary system of operation for that purpose was adopted. This

consisted in little more than the planting of the Arundo arenaria, and

other sand-plants, and the exclusion of animals destructive to those

vegetables. [Footnote: Measures were taken for the protection of the

dunes of Cape Cod, in Massachusetts, during the colonial period, though

I believe they are now substantially abandoned. A hundred years ago,

before the valley of the Mississippi, or even the rich plains of Central

and Western New York, were opened to the white settler, the value of

land was relatively much greater in New England than it is at present,

and consequently some rural improvements were then worth making, which

would not now yield sufficient returns to tempt the investment of

capital. The money and the time required to subdue and render productive

twenty acres of sea-sand on Cape Cod, would buy a "section" and rear a

family in Illinois. The son of the Pilgrim, therefore, abandons the

sea-hills, and seeks a better fortune on the fertile prairies of the

West. See Dwight, Travels, i., pp. 92, 93.] Ten years later, plantations

of forest trees, which have since proved so valuable a means of fixing

the dunes and rendering them productive, were commenced, and have been

continued ever since. [Footnote: Andresen, Om Klitformationen, pp. 237,

240.] During this latter period, Bremontier, without any knowledge of

what was doing in Denmark, experimented upon the cultivation of forest

trees on the dunes of Gascony, and perfected a system, which, with some

improvements in matters of detail, is still largely pursued on those

shores.

The example of Denmark was soon followed in the neighboring kingdom of

Prussia, and in the Netherlands; and, as we shall see hereafter, these

improvements have been everywhere crowned with most flattering success.

Under the administration of Reventlov, a little before the close of the

last century, the Danish Government organized a regular system of

improvement in the economy of the dunes. They were planted with the

arundo and other vegetables of similar habits, protected against

trespassers, and at last partly covered with forest trees. By these

means much waste soil has been converted into arable ground, a large

growth of valuable timber obtained, and the further spread of the

drifts, which threatened to lay waste the whole peninsula of Jutland, to

a considerable extent arrested.

In France, the operations for fixing and reclaiming the dunes--which

began under the direction of Bremontier about the same time as in

Denmark, and which are, in principle and in many of their details,

similar to those employed in the latter kingdom--have been conducted on

a far larger scale, and with greater success, than in any other country.

This is partly owing to a climate more favorable to the growth of

suitable forest trees than that of Northern Europe, and partly to the

liberality of the Government, which, having more important landed

interests to protect, has put larger means at the disposal of the

engineers than Denmark and Prussia have found it convenient to

appropriate to that purpose. The area of the dunes already secured from

drifting, and planted by the processes invented by Bremontier and

perfected by his successors, is about 100,000 acres. [Footnote: "These

plantations, perseveringly continued from the time of Bremontier, now

cover more than 40,000 hectares, and compose forests which are not only

the salvation of the department, but constitute its wealth." --Clave,

Etudes Forestieres, p. 254. Other authors have stated the plantations of

the French dunes to be much more extensive.] This amount of productive

soil, then, has been added to the resources of France, and a still

greater quantity of valuable land has been thereby rescued from the

otherwise certain destruction with which it was threatened by the

advance of the rolling sand-hills.

The improvements of the dunes on the coast of West Prussia began in

1795, under Soren Bjorn, a native of Denmark, and, with the exception of

the ten years between 1807 and 1817, they have been prosecuted ever

since. The methods do not differ essentially from those employed in

Denmark and France, though they are modified by local circumstances,

and, with respect to the trees selected for planting, by climate. In

1850, between the mouth of the Vistula and Kahlberg, 6,300 acres,

including about 1,900 acres planted with pines and birches, had been

secured from drifting; between Kahlberg and the eastern boundary of West

Prussia, 8,000 acres; and important preliminary operations had been

carried on for subduing the dunes on the west coast. [Footnote: Kruse,

Dunenbau, pp. 34, 38, 40.]

The tree which has been fonnd to thrive best upon the sand-hills of the

French coast, and at the same time to confine the sand most firmly and

yield the largest pecuniary returns, is the maritime pine, Pinus

maritima, a species valuable both for its timber and for its resinous

products. It is always grown from seed, and the young shoots require to

be protected for several seasons, by the branches of other trees,

planted in rows, or spread over the surface and staked down, by the

growth of the Arundo arenaria and other small sand-plants, or by wattled

hedges. The beach, from which the sand is derived, has been generally

planted with the arundo, because the pine does not thrive well so near

the sea; but it is thought that a species of tamarisk is likely to

succeed in that latitude even better than the arundo. The shade and the

protection offered by the branching top of this pine are favorable to

the growth of deciduous trees, and, while still young, of shrubs and

smaller plants, which contribute more rapidly to the formation of

vegetable mould, and thus, when the pine has once taken root, the

redemption of the waste is considered as effectually secured.

In France, the maritime pine is planted on the sands of the interior as

well as on the dunes of the seacoast, and with equal advantage. This

tree resembles the pitch pine of the Southern American States in its

habits, and is applied to the same uses. The extraction of turpentine

from it begins at the age of about twenty years, or when it has attained

a diameter of from nine to twelve inches. Incisions are made up and down

the trunk, to the depth of about half an inch in the wood, and it is

insisted that if not more than two such slits are cut, the tree is not

sensibly injured by the process. The growth, indeed, is somewhat

checked, but the wood becomes superior to that of trees from which the

turpentine is not extracted. Thus treated, the pine continues to

flourish to the age of one hundred or one hundred and twenty years, and

up to this age the trees on an acre yield annually 300 pounds of essence

of turpentine, and 250 pounds of resin, worth together not far from ten

dollars. The expense of extraction and distillation is calculated at

about four dollars, and a clear profit of more than five dollars per

acre is left. [Footnote: These processes are substantially similar to

those employed in the pineries of the Carolinas, but they are better

systematized and more economically conducted in France. In the latter

country, all the products of the pine, even to the cones, find a

remunerating market, while, in America, the price of resin is so low,

that in the fierce steamboat races on the great rivers, large quantities

of it are thrown into the furnaces to increase the intensity of the

fires. In a carefully prepared article on the Southern pineries

published in an American magazine--I think Harper's--a few years ago, it

was stated that the resin from the turpentine distilleries was sometimes

allowed to run to waste; and the writer, in one instance, observed a

mass, thus rejected as rubbish, which was estimated to amount to two

thousand barrels. Olmsted saw, near a distillery which had been in

operation but a single year, a pool of resin estimated to contain three

thousand barrels, which had been allowed to run off as waste.--A Journey

in the seaboard Slave States, 1863, p. 345.] This is exclusive of the

value of the timber, when finally cut, which, of course, amounts to a

very considerable sum. In Denmark, where the climate is much colder,

hardier conifers, as well as the birch and other northern trees, are

found to answer a better purpose than the maritime pine, and it is

doubtful whether this tree would be able to resist the winter on the

dunes of Massachusetts. Probably the pitch-pine of the Northern States,

in conjunction with some of the American oaks, birches, and poplars, and

especially the robinia or locust, would prove very suitable to be

employed on the sand-hills of Cape Cod and Long Island. The ailanthus,

now coming into notice as a sand-loving tree, some species of tamarisk,

and perhaps the Aspressus macrocarpa, already found useful on the dunes

in California, may prove valuable auxiliaries in resisting the

encroachment of drifting sands, whether in America or in Europe, and the

intermixing of different species would doubtless be attended with as

valuable results in this as in other branches of forest economy. It

cannot, indeed, be affirmed that human power is able to arrest

altogether the incursions of the waves on sandy coasts, by planting the

beach, and clothing the dunes with wood. On the contrary, both in

Holland and on the French coast, it has been found necessary to protect

the dunes themselves by piling and by piers and sea-walls of heavy

masonry. But experience has amply shown that the processes referred to

are entirely successful in preventing the movement of the dunes, and the

drifting of their sands over cultivated lands behind them; and that, at

the same time, the plantations very much retard the landward progress of

the waters. [Footnote: See a very interesting article entitled "Le

Littoral de la France," by Elisee Reclus, in the Revue des Deux Mondes

for December, 1862, pp. 901, 936.]

Besides the special office of dune plantations already noticed, these

forests have the same general uses as other woods, and they have

sometimes formed by their droppings so thick a layer of vegetable mould

that the sand beneath has become sufficiently secured to allow the wood

to be felled, and the surface to be ploughed and cultivated with

ordinary field crops.

In some cases it has been found possible to confine and cultivate coast

sand-hills, even without preliminary forestal plantation. Thus, in the

vicinity of Cap Breton in France, a peculiar process is successfully

employed, both for preventing the drifting of dunes, and for rendering

the sands themselves immediately productive; but this method is

applicable only in exceptional cases of favorable climate and exposure.

It consists in planting vineyards upon the dunes, and protecting them by

hedges of broom, Erica scoparia, so disposed as to form rectangles about

thirty feet by forty. The vines planted in these enclosures thrive

admirably, and the grapes produced by them are among the best grown in

France. The dunes are so far from being an unfavorable soil for the

vine, that fresh sea-sand is regularly employed as a fertilizer for it,

alternating every other season with ordinary manure. The quantity of

sand thus applied every second year, raises the surface of the vineyard

about four or five inches. The vines are cut down every year to three or

four shoots, and the raising of the soil rapidly covers the old stocks.

As fast as buried, they send out new roots near the surface, and thus

the vineyard is constantly renewed, and has always a youthful

appearance, though it may have been already planted a couple of

generations. This practice is ascertained to have been followed for two

centuries, and is among the oldest well-authenticated attempts of man to

resist and vanquish the dunes. [Footnote: Boitel, Mise en valeur des

Terres pauvres, pp. 212, 218.]

The artificial removal of dunes, no longer necessary as a protection,

does not appear to have been practiced upon a large scale except in the

Netherlands, where the numerous canals furnish an easy and economical

means of transporting the sand, and where the construction and

maintenance of sea and river dikes, and of causeways and other

embankments and fillings, create a great demand for that material. Sand

is also employed in Holland, in large quantities, for improving the

consistence of the tough clay bordering upon or underlying diluvial

deposits, and for forming an artificial soil for the growth of certain

garden and ornamental vegetables. When the dunes are removed, the ground

they covered is restored to the domain of industry; and the quantity of

land recovered in the Netherlands by the removal of the barren sands

which encumbered it, amounts to hundreds and perhaps thousands of acres.

Inland Dunes.

Vast deposits of sand, both in the form of dunes and of plains, are

found far in the interior of continents, in the Old World and in the

New. The deserts of Gobi, of Arabia, and of Africa have been rendered

familiar by the narratives of travellers, but the sandy wilderness of

America, and even of Europe, have not yet been generally recognized as

important elements in the geography of the regions where they occur.

There are immense wastes of drifting sands in Poland and other interior

parts of Europe, in Peru, and in the less known regions of our own

Western territory, where their extent is greater than that of all the

coast dunes together which have hitherto been described by European and

American geographers. [Footnote: On the Niobrara river alone, the dunes

cover a surface of twenty thousand square miles.--Hayden, Report on

Geological Survey of Wyoming, 1870, p. 108.] The inland sand-hills of

both hemispheres are composed of substantially the same material and

aggregated by the action of the same natural forces as the dunes of the

coast. There is, therefore, a general resemblance between them, but they

appear, nevertheless, to be distinguished by certain differences which a

more attentive study may perhaps enable geologists to recognize in the

sandstone formed by them. The sand of which they are composed comes in

both principally from the bed of the sea being brought to the surface in

one case by the action of the wind and the waves, in the other by

geological upheaval. [Footnote: American observers do not agree in their

descriptions of the form and character of the sand-grains which compose

the interior dunes of the North American desert. C. C. Parry, geologist

to the Mexican Boundary Commission, in describing the dunes near the

station at a spring thirty-two miles west from the Rio Grande at El

Paso, says: "The separate grains of the sand composing the sand-hills

are seen under a lens to be angular, and not rounded, as would be the

case in regular beach deposits."--U. S. Mexican Boundary Survey, Report

of, vol i., Geological Report of C. C. Parry, p. 10.

In the general description of the country traversed, same volume, p. 47,

Colonel Emory says that on an "examination of the sand with a microscope

of sufficient power," the grains are seen to be angular, not rounded by

rolling in water.

On the other hand, Blake, in Geological Report, Pacific Railroad Rep.,

vol. v., p. 119, observes that the grains of the dune sand, consisting

of quartz, chalcedony, carnelian, agate, rose quartz, and probably

chrysolite, were much rounded; and on page 241, he says that many of the

sand grains of the Colorado desert are perfect spheres. On page 20 of a

report in vol. ii. of the Pacific Railroad Report, by the same observer,

it is said that an examination of dunes brought from the Llano Estacado

by Captain Pope, showed the grains to be "much rounded by attrition."

The sands described by Mr. Parry and Colonel Emory are not from the same

localities as those examined by Mr. Blake, and the difference in their

character may be due to a difference of origin or of age. In New Mexico,

sixty miles south of Fort Stanton, there are island dunes composed of

finely granulated gypsum.--American Naturalist, Jan. 1871, p. 695.] The

sand of the coast dunes is rendered, to a certain extent, cohesive by

moisture and by the saline and other binding ingredients of sea-water,

while long exposure to meteoric influences has in a great measure

deprived the inland sands of these constituents, though there are not

wanting examples of large accumulations of sand far from the sea, and

yet agglutinated by saline material. Hence, as might be expected, inland

dunes, when not confined by a fixed nucleus, are generally more movable

than those of the coast, and the form of such dunes is more or less

modified by their want of consistence. Thus, the crescent or falciform

shape is described by all observers as more constant and conspicuous in

these sandhills than in those of littoral origin; they tend less to

unite in continuous ridges, and they rarely attain the height or other

dimensions of the dunes of the seashore. Meyer describes the sand-hills

of the Peruvian desert as perfectly falciform in shape and from seven to

fifteen feet high, the chord of their arc measuring from twenty to

seventy paces. The slope of the convex face is described as very small,

that of the concave as high as 70 degrees or 80 degrees, and their

surfaces were rippled. No smaller dunes were observed, nor any in the

process of formation. The concave side uniformly faced the north-west,

except towards the centre of the desert, where, for a distance of one or

two hundred paces, they gradually opened to the west, and then again

gradually resumed the former position. Tschudi observed, in the same

desert, two species of dunes, fixed and movable, and he ascribes a

falciform shape to the movable, a conical to the fixed dunes, or

medanos. "The medanos," he observes, "are hillock-like elevations of

sand, some having a firm, others a loose base. The former [latter],

which are always crescent-shaped, are from ten to twenty feet high, and

have an acute crest. The inner side is perpendicular, and the outer or

bow side forms an angle with a steep inclination downwards. [Footnote:

The dunes of the plains between Bokhara and the Oxus are all horse-shoe

shaped, convex towards the north, from which the prevailing wind blows.

On this side they are sloping, inside precipitous, and from fifteen to

twenty feet high.--Burnes, Journal in Bokhara, ii., pp. 1, 2.] When

driven by violent winds, the medanos pass rapidly over the plains. The

smaller and lighter ones move quickly forward, before the larger; but

the latter soon overtake and crush them, whilst they are themselves

shivered by the collision. These medanos assume all sorts of

extraordinary figures, and sometimes move along the plain in rows

forming most intricate labyrinths.... A plain often appears to be

covered with a row of medanos, and some days afterwards it is again

restored to its level and uniform aspect.... "The medanos with immovable

bases are formed on the blocks of rocks which are scattered about the

plain. The sand is driven against them by the wind, and as soon as it

reaches the top point, it descends on the other side until that is

likewise covered; thus gradually arises a conical-formed hill. [Footnote:

The sand-hills observed by Desor in the Algerian desert were fixed,

changing their form only on the surface as sand was blown to and from

them.--Sahara und Atlas, 1865, p. 21.] Entire hillock chains with acute

crests are formed in a similar manner.... On their southern declivities

are found vast masses of sand, drifted thither by the mid-day gales. The

northern declivity, though not steeper than the southern, is only

sparingly covered with sand. If a hillock chain somewhat distant from

the sea extends in a line parallel with the Andes, namely, from S. S. E.

to N. N. W., the western declivity is almost entirely free of sand, as

it is driven to the plain below by the south-east wind, which constantly

alternates with the wind from the south." [Footnote: Travels in Peru,

New York, 1848, chap. ix.] It is difficult to reconcile this description

with that of Meyen, but if confidence is to be reposed in the accuracy

of either observer, the formation of the sand-hills in question must be

governed by very different laws from those which determine the structure

of coast dunes. Captain Gilliss, of the American navy, found the

sand-hills of the Peruvian desert to be in general crescent-shaped, as

described by Meyen, and a similar structure is said to characterize the

inland dunes of the Llano Estacado and other plateaus of the North

American desert, though those latter are of greater height and other

dimensions than those described by Meyen. There is no very obvious

explanation of this difference in form between maritime and inland

sand-hills, and the subject merits investigation. It is, however,

probable that the great mobility of the flying dunes of the Peruvian

desert is an effect of their dryness, no rain falling in that desert,

and of the want of salt or other binding material to hold their

particles together.

Inland Sand Plains.

The inland sand plains of Europe are either derived from the drifting of

dunes or other beach sands, or consist of diluvial deposits, or are

ancient sea-beds uplifted by geological upheaval. As we have seen, when

once the interior of a dune is laid open to the wind, its contents ars

soon scattered far and wide over the adjacent country, and the beach

sands, no longer checked by the rampart which nature had constrained

them to build against their own encroachments, are also carried to

considerable distances from the coast. Few regions have suffered so much

from this cause, in proportion to their extent, as the peninsula of

Jutland. So long as the woods, with which nature had planted the Danish

dunes, were spared, they seem to have been stationary, and we have no

historical evidence, of an earlier date than the sixteenth century, that

they had become in any way injurious. From that period there are

frequent notices of the invasions of cultivated grounds by the sands;

and excavations are constantly bringing to light proof of human

habitation and of agricultural industry, in former ages, on soils now

buried beneath deep drifts from the dunes and beaches of the seacoast.

[Footnote: For details, consult Andresen, Om Klitformationen, pp. 223,

236.]

Extensive tracts of valuable plain land in the Netherlands and in France

have been covered in the same way with a layer of sand deep enough to

render them infertile, and they can be restored to cultivation only by

processes analogous to those employed for fixing and improving the

dunes. [Footnote: When the deposit is not very deep, and the adjacent

land lying to the leeward of the prevailing winds is covered with water,

or otherwise worthless, the surface is sometimes freed from the drifts

by repeated harrowings, which loosen the sand, so that the wind takes it

up and transports it to grounds where accumulations of it are less

injurious.] Diluvial sand plains, also, have been reclaimed by these

methods in the Duchy of Austria, between Vienna and the Semmering ridge,

in Jutland, and in the great champaign country of Northern Germany,

especially the Mark Brandenburg, where artificial forests can be

propagated with great ease, and where, consequently, this branch of

industry has been pursued on a great scale, and with highly beneficial

results, both as respects the supply of forest products and the

preparation of the soil for agricultural use.

As has been already observed, inland sands are generally looser, dryer,

and more inclined to drift, than those of the seacoast, where the moist

and saline atmosphere of the ocean keeps them always more or less humid

and cohesive. The sands of the valley of the Lower Euphrates--themselves

probably of submarine origin, and not derived from dunes are advancing

to the north-west with a rapidity which seems fabulous when compared

with the slow movement of the sand-hills of Gascony and the Low German

coasts. Loftus, speaking of Niliyya, an old Arab town a few miles east

of the ruins of Babylon, says that, "in 1848, the sand began to

accumulate around it, and in six years, the desert, within a radius of

six miles, was covered with little, undulating domes, while the ruins of

the city were so buried that it is now impossible to trace their

original form or extent." [Footnote: Travels and Researchs in Chaldaea,

chap. ix.

Dwight mentions (Travels, vol. iii, p. 101) an instance of great

mischief from the depasturing of the beach grass which had been planted

on a sand plain in Cape Cod: "Here, about one thousand acres were

entirely blown away to the depth, in many places, of ten feet.... Not a

green thing was visible except the whortleberries, which tufted a few

lonely hillocks rising to the height of the original surface and

prevented by this defence from being blown away also. These, although

they varied the prospect, added to the gloom by their strongly

picturesque appearance, by marking exactly the original level of the

plain, and by showing us in this manner the immensity of the mass which

had been thus carried away by the wind. The beach grass had been planted

here, and the ground had been formerly enclosed; but the gates had been

left open, and the cattle had destroyed this invaluable plant."] Loftus

considers this sand-flood as the "vanguard of those vast drifts which

advancing from the south-east, threaten eventually to overwhelm Babylon

and Baghdad." An observation of Layard, cited by Loftus, appears to me

to furnish a possible explanation of this irruption. He "passed two or

three places where the sand, issuing from the earth like water, is

called 'Aioun-er-rummal,' sand springs." These "springs" are very

probably merely the drifting of sand from the ancient subsoil, where the

protecting crust of aquatic deposit and vegetable earth has been broken

through, as in the case of the drift which arose from the upturning of

an oak mentioned on a former page. When the valley of the Euphrates was

regularly irrigated and cultivated, the underlying sands were bound by

moisture, alluvial slime, and vegetation; but now, that all improvement

is neglected, and the surface, no longer watered, has become parched,

powdery, and naked, a mere accidental fissure in the superficial stratum

may soon be enlarged to a wide opening, that will let loose sand enongh

to overwhelm a province. The Landes of Gascony. The most remarkable sand

plain of France lies at the south-western extremity of the empire, and

is generally known as the Landes, or heaths, of Gascony. Clave thus

describes it: "Composed of pure sand, resting on an impermeable stratum

called alios, the soil of the Landes was, for centuries, considered

incapable of cultivation. [Footnote: The alios, which from its color and

consistence was supposed to be a ferruginous formation, appears from

recent observations to contain little iron and to owe most of its

peculiar properties to vegetable elements carried down into the soil by

the percolation of rain-water. See Revue des Eaux et Forets for 1870, p.

801.] Parched in summer, drowned in winter, it produced only ferns,

rushes, and heath, and scarcely furnished pasturage for a few

half-starved flocks. To crown its miseries, this plain was continually

threatened by the encroachments of the dunes. Vast ridges of sand,

thrown up by the waves, for a distance of more than fifty leagues along

the coast, and continually renewed, were driven inland by the west wind,

and, as they rolled over the plain, they buried the soil and the

hamlets, overcame all resistance, and advanced with fearful regularity.

The whole province seemed devoted to certain destruction, when

Bremontier invented his method of fixing the dunes by plantations of the

maritime pine." [Footnote: Etudes Forestieres, p. 250. See, also, Reclus,

La Terre, i., 105, 106.] Although the Landes had been almost abandoned

for ages, they show numerous traces of ancient cultivation and

prosperity, and it is principally by means of the encroachments of the

sands that they have become reduced to their present desolate condition.

The destruction of the coast towns and harbors, which furnished markets

for the products of the plains, the damming up of the rivers, and the

obstruction of the smaller channels of natural drainage by the advance

of the dunes, were no doubt very influential causes; and if we add the

drifting of the sea-sand over the soil, we have at least a partial

explanation of the decayed agriculture and diminished population of this

great waste. When the dunes were once arrested, and the soil to the east

of them was felt to be secure against invasion by them, experiments, in

the way of agricultural improvement, by drainage and plantation, were

commenced, and they have been attended with such signal success, that

the complete recovery of one of the dreariest and most extensive wastes

in Europe may be considered as both a probable and a near

event. [Footnote: Lavergne, Economie Rurale de la France, p. 300,

estimates the area of the Landes of Gascony at 700,000 hectares, or

about 1,700,000 acres. The same author states (p. 301), that when the

Moors were driven from Spain by the blind cupidity and brutal

intolerance of the age, they demanded permission to establish themselves

in this desert; but political and religious prejudices prevented the

granting of this liberty. At this period the Moors were a far more

cultivated people than their Christian persecutors, and they had carried

many arts, that of agriculttire especially, to a higher pitch than any

other European nation. But France was not wise enough to accept what

Spain had cast out, and the Landes remained a waste for three centuries

longer.

For a brilliant account of the improvement of the Landes, see Edmond

About, Le Progres, chap. vii.

The forest of Fontainebleau, which contains above 40,000 acres, is not a

plain, but its soil is composed almost wholly of sand, interspersed with

ledges of rock. The sand forms not less than ninety-eight per cent of

the earth, and, as it is almost without water, it would be a drifting

desert but for the artificial propagation of forest trees upon it. The

Landes of Sologne and of Brenne are less known than those of Gascony,

because they are not upon the old great lines of communication. They

once compoaed a forest of 1,200,000 acres, but by clearing the woods

have relapsed into their primitive condition of a barren sand waste.

Active efforts are now in progress to reclaim them.]

In the northern part of Belgium, and extending across the confines of

Holland, is another very similar heath plain, called the Campine. This

is a vast sand flat, interspersed with marshes and inland dunes, and,

until recently, considered almost wholly incapable of cultivation.

Enormous sums had been expended in reclaiming it by draining and other

familiar agricultural processes, but without results at all proportional

to the capital invested. In 1849, the unimproved portion of the Campine

was estimated at little less than three hundred and fifty thousand

acres. The example of France prompted experiments in the planting of

trees, especially the maritime pine, upon this barren waste, and the

results have now been such as to show that its sands may both be fixed

and made productive, not only without loss, but with positive pecuniary

advantage. [Footnote: Economie Rurale de la Belgique, par Emile De

Laveleye, Revue des Deux Mondes, Juin, 1861, pp. 6l7-644. The quantity

of land annually reclaimed on the Campine is stated at about 4,000

acres. Canals for navigation and irrigation have been constructed

through the Campine, and it is said that its barren sands, improved at

an expense of one hundred dollars per acre, yield, from the second year,

a return of twenty-five dollars to the acre.]

There are still unsubdued sand wastes in many parts of interior Europe

not familiarly known to tourists or even geographers. "Olkuez and

Schiewier in Poland," says Naumann, "lie in true sand deserts, and a

boundless plain of sand stretches around Ozenstockau, on which there

grows neither tree nor shrub. In heavy winds, this plain resembles a

rolling sea, and the sand-hills rise and disappear like the waves of the

ocean. The heaps of waste from the Olkuez mines are covered with sand to

the depth of four fathoms." [Footnote: Geognosie, ii., p. 1173.] No

attempts have yet been made to subdue the sands of Poland, but when

peace and prosperity shall be restored to that unhappy country, there is

no reasonable doubt that the measures, which have proved so successful

on similar formations in Germany and near Odessa, may be employed with

advantage in the Polish deserts. [Footnote: "Sixteen years ago," says an

Odessa landholder, "I attempted to fix the sand of the steppes, which

covers the rocky ground to the depth of a foot, and forms moving

hillocks with every change of wind. I tried acacias and pines in vain;

nothing would grow in such a soil. At length I planted the varnish tree,

or ailanthus, which succeeded completely in binding the sand." This

result encouraged the proprietor to extend his plantations over both

dunes and sand steppes, and in the course ot sixteen years this rapidly

growing tree had formed real forests. Other landholders have imitated

his example with great advantage.--Rentsch, Der Wald, pp. 44, 45.]

CHAPTER VI.

GREAT PROJECTS OF PHYSICAL CHANGE ACCOMPLISHED OR PROPOSED BY MAN.

Cutting of Isthmuses--Canal of Suez--Maritime Canals in Greece--Canals

to Dead Sea--Canals to Libyan Desert--Maritime Canals in Europe--Cape

Cod Canal--Changes in Caspian--Diversion of the Nile--Diversion of the

Rhine--Improvements in North American Hydrography--Soil below

Rock--Covering Rock with Earth--Desert Valleys--Effects of

Mining--Duponchel's Plans of Improvement--Action of Man on the

Weather--Resistance to Great Natural Forces--Incidental Effects of Human

Action--Nothing small in Nature.

In a former chapter I spoke of the influence of human action on the

surface of the globe as immensely superior in degree to that exerted by

brute animals, if not essentially different from it in kind. The eminent

Italian geologist, Stoppani, goes further than I had ventured to do, and

treats the action of man as a new physical clement altogether sui

generis. According to him, the existence of man constitutes a geological

period which he designates as the ANTHROPOZOIC ERA. "The creation of

man," says he, "was the introduction of a new element into nature, of a

force wholly unknown to earlier periods." "It is a new telluric force

which in power and universality may be compared to the greater forces of

the earth." [Foonote: Corso Di Geologia, Milano, 1873, vol ii., cap.

xxxi., section 1327.] It has already been abundantly shown that, though

the undesigned and unforeseen results of man's action on the

geographical conditions of the earth have perhaps been hitherto greater

and more revolutionary than the effects specially aimed at by him, yet

there is scarcely any assignable limit to his present and prospective

voluntary controlling power over terrestrial nature.

Cutting of Marine Isthmuses.

Besides the great enterprises of physical transformation of which I have

already spoken, other works of internal improvement or change have been

projected in ancient and modern times, the execution of which would

produce considerable, and, in some cases, extremely important,

revolutions in the face of the earth. Some of the schemes to which I

refer are evidently chimerical; others are difficult, indeed, but cannot

be said to be impracticable, though discouraged by the apprehension of

disastrous consequences from the disturbance of existing natural or

artificial arrangements; and there are still others, the accomplishment

of which is ultimately certain, though for the present forbidden by

economical considerations.

Nature sometimes mocks the cunning and the power of man by spontaneously

performing, for his benefit, works which he shrinks from undertaking,

and the execution of which by him she would resist with unconquerable

obstinacy. A dangerous sand bank, that all the enginery of the world

could not dredge out in a generation, may be carried off in a night by a

strong river-flood, or by a current impelled by a violent wind from an

unusual quarter, and a passage scarcely navigable by fishing-boats may

be thus converted into a commodious channel for the largest ship that

floats upon the ocean. In the remarkable gulf of Liimfjord in Jutland,

referred to in the preceding chapter, nature has given a singular

example of a canal which she alternately opens as a marine strait, and,

by abutting again, converts into a fresh-water lagoon. The Liimfjord was

doubtless originally an open channel from the Atlantic to the Baltic

between two islands, but the sand washed up by the sea blocked up the

western entrance, and built a wall of dunes to close it more firmly.

This natural dike, as we have seen, has been more than once broken

through, and it is perhaps in the power of man, either permanently to

maintain the barrier, or to remove it and keep a navigable channel

constantly open. If the Liimfjord becomes an open strait, the washing of

sea-sand through it would perhaps block some of the belts and small

channels now important for the navigation of the Baltic, and the direct

introduction of a tidal current might produce very perceptible effects

on the hydrography of the Cattegat.

When we consider the number of narrow necks or isthmuses which separate

gulfs and bays of the sea from each other, or from the main ocean, and

take into account the time and cost, and risks of navigation which would

be saved by executing channels to connect such waters, and thus avoiding

the necessity of doubling long capes and promontories, or even

continents, it seems strange that more of the enterprise and money which

have been so lavishly expended in forming artificial rivers for internal

navigation should not have been bestowed upon the construction of

maritime canals. Many such have been projected in early and in recent

ages, and some trifling cuts between marine waters had been actually

made; but before the construction of the Suez Canal, no work of this

sort, possessing real geographical or even commercial importance, had

been effected.

These enterprises are attended with difficulties and open to objections

which are not, at first sight, obvious. Nature guards well the chains by

which she connects promontories with mainlands, and binds continents

together. Isthmuses are usually composed of adamantine rock or of

shifting sands--the latter being much the more refractory material to

deal with. In all such works there is a necessity for deep excavation

below low-water mark--always a matter of great difficulty; the

dimensions of channels for sea-going ships must be much greater than

those of canals of inland navigation; the height of the masts or

smokepipes of that class of vessels would often render bridging

impossible, and thus a ship-canal might obstruct a communication more

important than that which it was intended to promote; the securing of

the entrances of marine canals and the construction of ports at their

termini would in general be difficult and expensive, and the harbors and

the channel which connected them would be extremely liable to fill up by

deposits washed in from sea and shore. Besides all this there is, in

many cases, an alarming uncertainty as to the effects of joining

together waters which nature has put asunder. A new channel may deflect

strong currents from safe courses, and thus occasion destructive erosion

of shores otherwise secure, or promote the transportation of sand or

slime to block up important harbors, or it may furnish a powerful enemy

with dangerous facilities for hostile operations along the coast. The

most colossal project of canalization ever suggested, whether we

consider the physical difficulties of its execution, the magnitude and

importance of the waters proposed to be united, or the distance which

would be saved in navigation, is that of a channel between the Gulf of

Mexico and the Pacific, across the Isthmus of Darien. I do not now speak

of a lock-canal, by way of the Lake of Nicaragua or any other route--for

such a work would not differ essentially from other canals, and would

scarcely possess a geographical character--but of an open cut between

the two seas. The late survey by Captain Selfridge, showing that the

lowest point on the dividing ridge is 763 feet above the sea-level, must

be considered as determining in the negative the question of the

possibility of such a cut, by any means now at the control of man; and

both the sanguine expectations of benefits, and the dreary suggestions

of danger, from the realization of this great dream, may now be

dismissed as equally chimerical.

Suez Canal.

The cutting of the Isthmus of Suez--the grandest and most truly

cosmopolite physical improvement ever undertaken by man--threatens none

of these dangers, and its only immediate geographical effect will

probably be that interchange between the aquatic animal and vegetable

life of two seas and two zones to which I alluded in a former chapter.

[Footnote: According to an article by Ascherson, in Petermann's

Mitthielungen, vol. xvii., p. 247, the sea-grass floras of the opposite

sides of the Isthmus of Suez are as different as possible. It does not

appear whether they have yet intermixed.] A collateral feature of this

great enterprise deserves notice as possessing no inconsiderable

geographical importance. I refer to the conduit or conduits constructed

from the Nile to the isthmus, primarily to supply fresh water to the

laborers on the great canal, and ultimately to serve as aqueducts for

the city of Suez and other towns on the line of the canal, and for the

irrigation and reclamation of a large extent of desert soil. In the

flourishing days of the Egyptian empire, the waters of the Nile were

carried over important districts cast of the river. In later ages, most

of this territory relapsed into a desert, from the decay of the canals

which once fertilized it. There is no difficulty in restoring the

ancient channels, or in constructing new, and thus watering not only all

the soil that the wisdom of the Pharaohs had improved, but much

additional land. Hundreds of square miles of arid sand waste would thus

be converted into fields of perennial verdure, and the geography of

Lower Egypt would be thereby sensibly changed. Considerable towns are

growing up at both ends of the channel, and at intermediate points, all

depending on the maintenance of aqueducts from the Nile, both for water

and for the irrigation of the neighboring fields which are to supply

them with bread. Important interests will thus be created, which will

secure the permanence of the hydraulic works and of the geographical

changes produced by them, and Suez, or Port Said, or Ismailieh, may

become the capital of the government which has been so long established

at Cairo. Maritime Canals in Greece. A maritime canal executed and

another projected in ancient times, the latter of which is again

beginning to excite attention, deserve some notice, though their

importance is of a commercial rather than a geographical character. The

first of those is the cut made by Xerxes through the rock which connects

the promontory of Mount Athos with the mainland; the other, a navigable

canal through the Isthmus of Corinth. In spite of the testimony of

Herodotus and Thucydides, the Romans classed the canal of Xerxes among

the fables of "mendacious Greece," and yet traces of it are perfectly

distinct at the present day through its whole extent, except at a single

point where, after it had become so choked as to be no longer navigable,

it was probably filled up to facilitate communication by land between

the promontory and the country in the rear of it. The emperor Nero

commenced the construction of a canal across the Isthmus of Corinth,

solely to facilitate the importation of grain from the East for

distribution among the citizens of Rome--for the encouragement of

general commerce was no part of the policy either of the republic or the

empire, and though the avidity of traders, chiefly foreigners, secured

to the luxury of the imperial city an abundant supply of far-fetched

wares, yet Rome had nothing to export in return. The line of Nero's

excavations is still traceable for three-quarters of a mile, or more

than a fifth of the total distance between gulf and gulf.

If the fancy kingdom of Greece shall ever become a sober reality, escape

from its tutelage and acquire such a moral as well as political status

that its own capitalists--who now prefer to establish themselves and

employ their funds anywhere else rather than in their native land--have

any confidence in the permanency of its institutions, a navigable

channel may be opened between the gulfs of Lepanto and AEgina. The

annexation of the Ionian Islands to Greece will make such a work almost

a political necessity, and it would not only furnish valuable facilities

for domestic intercourse, but become an important channel of

communication between the Levant and the countries bordering on the

Adriatic, or conducting their trade through that sea. SHort as is the

distance, the work would be a somewhat formidable undertaking, for the

lowest point of the summit ridge of the isthmus is stated to be 246 feet

above the water, and consequently the depth of excavation must be not

less than 275 feet. As I have said, the importance of this latter canal

and of a navigable channel between Mount Athos and the continent would

be chiefly commercial, but both of them would be conspicuous instances

of the control of man over nature in a field where he has thus far done

little to interfere with her spontaneous arrangements. If they were

constructed upon such a scale as to admit of the free passage of the

water through them, in either direction, as the prevailing winds should

impel it, they would exercise a certain influence on the coast currents,

which are important as hydrographical elements, and also as producing

abrasion of the coast and a drift at the bottom of seas, and hence they

would be entitled to rank higher than simply as artificial means of

transit. It has been thought practicable to cut a canal across the

peninsula of Gallipoli from the outlet of the Sea of Marmora into the

Gulf of Saros. It may be doubted whether the mechanical difficulties of

such a work would not be found insuperable; but when Constantinople

shall recover the important political and commercial rank which

naturally belongs to her, the execution of such a canal will be

recommended by strong reasons of military expediency, as well as by the

interests of trade. An open channel across the peninsula would divert a

portion of the water which now flows through the Dardanelles,

diminishing the rapidity of that powerful current, and thus in part

remove the difficulties which obstruct the navigation of the strait. It

would considerably abridge the distance by water between Constantinople

and the northern coast of the AEgean, and it would have the important

advantage of obliging an enemy to maintain two blockading fleets instead

of one.

Canals Communicating with Dead Sea.

The project of Captain Allen for opening a new route to India by cuts

between the Mediterranean and the Dead Sea, and between the Dead Sea and

the Red Sea, presents many interesting considerations. [Footnote: The

Dead Sea a new Route to India. 2 vols. 12mo, London, 1855.] The

hypsometrical observations of Bertou, Roth, and others, render it highly

probable, if not certain, that the watershed in the Wadi-el-Araba

between the Dead Sea and the Red Sea is not less than three hundred feet

above the main level of the latter, and if this is so, the execution of

a canal from the one sea to the other is quite out of the question. But

the summit level between the Mediterranean and the Jordan, near Jezreel,

is believed to be little, if at all, more than one hundred feet above

the sea, and the distance is so short that the cutting of a channel

through the dividing ridge would probably be found by no means an

impracticable undertaking. Although, therefore, we have no reason to

believe it possible to open a navigable channel to India by way of the

Dead Sea, there is not much doubt that the basin of the latter might be

made accessible from the Mediterranean.

The level of the Dead Sea lies 1,316.7 feet below that of the ocean. It

is bounded east and west by mountain ridges, rising to the height of

from 2,000 to 4,000 feet above the ocean. From its southern end, a

depression called the Wadi-el-Araba extends to the Gulf of Akaba, the

eastern arm of the Red Sea. The Jordan empties into the northern

extremity of the Dead Sea, after having passed through the Lake of

Tiberias at an elevation of 663.4 feet above the Dead Sea, or 653.3

below the Mediterranean, and drains a considerable valley north of the

lake, as well as the plain of Jericho, which lies between the lake and

the sea. If the waters of the Mediterranean were admitted freely into

the basin of the Dead Sea, they would raise its surface to the general

level of the ocean, and consequently flood all the dry land below that

level within the basin. I do not know that accurate levels have been

taken in the valley of the Jordan above the Lake of Tiberias, and our

information is very vague as to the hypsometry of the northern part of

the Wadi-el-Araba. As little do we know where a contour line, carried

around the basin at the level of the Mediterranean, would strike its

eastern and western borders. We cannot, therefore, accurately compute

the extent of now dry land which would be covered by the admission of

the waters of the Mediterranean, or the area of the inland sea which

would be thus created. Its length, however, would certainly exceed one

hundred and fifty miles, and its mean breadth, including its gulfs and

bays, could scarcely be less than fifteen, perhaps even twenty. It would

cover very little ground now occupied by civilized or even uncivilized

man, though some of the soil which would be submerged--for instance,

that watered by the Fountain of Elisha and other neighboring sources--is

of great fertility, and, under a wiser government and better civil

institutions, might rise to importance, because, from its depression, it

possesses a very warm climate, and might supply South-eastern Europe

with tropical products more readily than they can be obtained from any

other source. Such a canal and sea would be of no present commercial

importance, because they would give access to no new markets or sources

of supply; but when the fertile valleys and the deserted plains cast of

the Jordan shall be reclaimed to agriculture and civilization, these

waters would furnish a channel of communication which might become the

medium of a very extensive trade. Whatever might be the economical

results of the opening and filling of the Dead Sea basin, the creation

of a new evaporable area, adding not less than 2,000 or perhaps 3,000

square miles to the present fluid surface of Syria, could not fail to

produce important meteorological effects. The climate of Syria would

probably be tempered, its precipitation and its fertility increased, the

courses of its winds and the electrical condition of its atmosphere

modified. The present organic life of the valley would be extinguished,

and many tribes of plants and animals would emigrate from the

Mediterranean to the new home which human art had prepared for them. It

is possible, too, that the addition of 1,300 feet, or forty atmospheres,

of hydrostatic pressure upon the bottom of the basin might disturb the

equilibrium between the internal and the external forces of the crust of

the earth at this point of abnormal configuration, and thus produce

geological convulsions the intensity of which cannot be even

conjectured.

It is now established by the observations of Rohlf and others that

Strabo was right in asserting that a considerable part of the Libyan

desert, or Sahara, lay below the level of the Mediterranean. At some

points the depression exceeds 325 feet, and at Siwah, in the oasis of

Jupiter Ammon, it is not less than 130 feet. It has been proposed to cut

a canal through the coast dunes, on the shore south of the Syrtis Major,

or Dschnn el Kebrit of the Arabs, and another project is to reopen the

communication which appears to have once existed between the Palus

Tritonis, or Sebcha el Nandid, and the Syrtis Parva. As we do not know

the southern or eastern limits of this depression, we cannot determine

the area which would thus be covered with water, but it would certainly

be many thousands of square miles in extent, and the climatic effects

would doubtless be sensible through a considerable part of Northern

Africa, and possibly even in Europe. The rapid evaporation would require

a constant influx of water from the Mediterranean, which might perhaps

perceptibly influence the current through the Straits of Gibraltar.

Maritime Canals in Europe.

A great navigable cut across the peninsula of Jutland, forming a new and

short route between the North Sea and the Baltic, if not actually

commenced, is determined upon. The motives for opening such a

communication are perhaps rather to be found in political than in

geographical or even commercial considerations, but it will not be

without an important bearing on the material interests of all the

countries to whose peoples it will furnish new facilities for

communication and traffic.

The North Holland canal between the Helder and the port of Amsterdam, a

distance of fifty miles, executed a few years since at a cost of

$5,000,000, and with dimensions admitting the passage of a frigate, was

a magnificent enterprise, but it is thrown quite into the shade by the

shorter channel now in process of construction for bringing that

important city into almost direct communication with the North Sea, and

thus restoring to it something at least of its ancient commercial

importance. The work involves some of the heaviest hydraulic operations

yet undertaken, including the construction of great dams, locks, dikes,

embankments, and the execution of draining works and deep cutting under

circumstances of extreme difficulty. In the course of these labors many

novel problems have presented themselves for practical solution by the

ingenuity of modern engineers, and the now inventions and processes thus

necessitated are valuable contributions to our means of physical

improvement.

Cape Cod Canal.

The opening of a navigable cut through the narrow neck which separates

the southern part of Cape Cod Bay in Massachusetts from the Atlantic,

was long ago suggested, and there are few coast improvements on the

Atlantic shores of the United States which are recommended by higher

considerations of utility. It would save the most important coasting

trade of the United States the long and dangerous navigation around Cape

Cod, afford a new and safer entrance to Boston harbor for vessels from

Southern ports, secure a choice of passages, thus permitting arrivals

upon the coast and departures from it at periods when wind and weather

might otherwise prevent them, and furnish a most valuable internal

communication in case of coast blockade by a foreign power. The

difficulties of the undertaking are no doubt formidable, but the expense

of maintenance and the uncertainty of the effects of currents getting

through the new strait are still more serious objections. [Footnote: The

opening of a channel across Cape Cod would have, though perhaps to a

smaller extent, the same effects in interchanging the animal life of the

southern and northern shores of the isthmus, as in the case of the Suez

Canal; for although the breadth of Cape Cod does not anywhere exceed

twenty miles, and is in some places reduced to one, it appears from the

official reports on the Natural History of Massachusetts, that the

population of the opposite waters differs widely in species.

Not having the original documents at hand, I quote an extract from the

Report on the Invertebrate Animals of Mass., given by Thoreau,

Excursions, p. 69: "The distribution of the marine shells is well worthy

of notice as a geological fact. Cape Cod, the right arm of the

Commonwealth, reaches out into the ocean some fifty or sixty miles. It

is nowhere many miles wide; but this narrow point of land has hitherto

proved a barrier to the migration of many species of mollusca. Several

genera and numerous species, which are separated by the intervention of

only a few miles of land, are effectually prevented from mingling by the

Cape, and do not pass from one side to the other. ... Of the one hundred

and ninety-seven marine species, eighty-three do not pass to the south

shore, and fifty are not found on the north shore of the Cape."

Probably the distribution of the species of mollusks is affected by

unknown local conditions, and therefore an open canal across the Cape

might not make every species that inhabits the waters on one side common

to those of the other; but there can be no doubt that there would be a

considerable migration in both directions.

The fact stated in the report may suggest an important caution in

drawing conclusions upon the relative age of formations from the

character of their fossils. Had a geological movement or movements

upheaved to different levels the bottoms of waters thus separated by a

narrow isthmus, and dislocated the connection between those bottoms,

naturalists, in after ages, reasoning from the character of the fossil

faunas, might have assigned them to different, and perhaps very widely

distant, periods.]

Changes in the Caspian.

The Russian Government has contemplated the establishment of a nearly

direct water communication between the Caspian Sea and the Sea of Azoff,

partly by natural and partly by artificial channels, and there are now

navigable canals between the Don and the Volga; but these works, though

not wanting in commercial and political interest, do not possess any

geographical importance. It is, however, very possible to produce

appreciable geographical changes in the basin of the Caspian by the

diversion of the great rivers which flow from Central Russia. The

surface of the Caspian is eighty-three feet below the level of the Sea

of Azoff, and its depression has been explained upon the hypothesis that

the evaporation exceeds the supply derived, directly and indirectly,

from precipitation, though able physicists now maintain that the sinking

of this sea is due to a subsidence of its bottom from geological causes.

At Tsaritsin, the Don, which empties into the Sea of Azoff, and the

Volga, which pours into the Caspian, approach each other within ten

miles. Near this point, by means of open or subterranean canals, the Don

might be turned into the Volga, or the Volga into the Don. If we suppose

the whole or a large proportion of the waters of the Don to be thus

diverted from their natural outlet and sent down to the Caspian, the

equilibrium between the evaporation from that sea and its supply of

water might be restored, or its level even raised above its ancient

limits. If the Volga were turned into the Sea of Azoff, the Caspian

would be reduced in dimensions until the balance between loss and gain

should be re-established, and it would occupy a much smaller area than

at present. Such changes in the proportion of solid and fluid surface

would have some climatic effects in the territory which drains into the

Caspian, and on the other hand, the introduction of a greater quantity

of fresh water into the Sea of Azoff would render that gulf less saline,

affect the character and numbers of its fish, and perhaps be not wholly

without sensible influence on the water of the Black Sea.

Diversion of the Nile.

Perhaps the most remarkable project of great physical change, proposed

or threatened in earlier ages, is that of the diversion of the Nile from

its natural channel, and the turning of its current into either the

Libyan Desert or the Red Sea. The Ethiopian or Abyssinian princes more

than once menaced the Memlouk sultans with the execution of this

alarming project, and the fear of so serious an evil is said to have

induced the Moslems to conciliate the Abyssinian kings by large

presents, and by some concessions to the oppressed Christians of Egypt.

Indeed, Arabian historians affirm that in the tenth century the

Ethiopians dammed the river, and, for a whole year, cut off its waters

from Egypt. [Footnote: "Some haue writte, that by certain kings

inhabiting aboue, the Nilus should there be stopped; & at a time

prefixt, let loose vpon a certaine tribute payd them by the Aegyptians.

The error springing perhaps fro a truth (as all wandring reports for the

most part doe) in that the Sultan doth pay a certaine annuall summe to

the Abissin Emperour for not diuerting the course of the Riuer, which

(they say) he may, or impouerish it at the least."--George Sandys, A

Relation of a Journey, etc., p. 98. See, also, Vansles, Voyage en

Egypte, p. 61.] The probable explanation of this story is to be found in

a season of extreme drought, such as have sometimes occurred in the

valley of the Nile.

The Libyan Desert, above the junction of the two principal branches of

the Nile at Khartum, is so much higher than the level of the river below

that point, that there is no reason to believe a new channel for the

united waters of the two streams could be found in that direction; but

the Bahr-el-Abiad flows through, if it does not rise in, a great

table-land, and some of its tributaries are supposed to communicate in

the rainy season with branches of great rivers flowing in quite another

direction. Hence it is probable that a portion at least of the waters of

this great arm of the Nile--and perhaps a quantity the abstraction of

which would be sensibly felt in Egypt--might be sent to the Atlantic by

the Congo or Niger, lost in inland lakes and marshes in Central Africa,

or employed to fertilize the Libyan sand wastes.

About the beginning of the sixteenth century, Albuquerque the "Terrible"

revived the scheme of turning the Nile into the Red Sea, with the hope

of destroying the transit trade through Egypt by way of Kosseir. In 1525

the King of Portugal was requested by the Emperor of Abyssinia to send

him engineers for that purpose; a successor of that prince threatened to

attempt the project about the year 1700, and even as late as the French

occupation of Egypt, the possibility of driving out the intruder by this

means was suggested in England.

It cannot be positively affirmed that the diversion of the waters of the

Nile to the Red Sea is impossible. In the chain of mountains which

separates the two valleys, Brown found a deep depression or wadi,

extending from the one to the other, apparently at no great elevation

above the bed of the river, but the height of the summit level was not

measured. Admitting the possibility of turning the whole river into the

Red Sea, let us consider the probable effect of the change.

First and most obvious is the total destruction of the fertility of

Middle and Lower Egypt, the conversion of that part of the valley into a

desert, and the extinction of its imperfect civilization, if not the

absolute extirpation of its inhabitants. This is the calamity threatened

by the Abyssinian princes and the ferocious Portuguese warrior, and

feared by the Sultans of Egypt. Beyond these immediate and palpable

consequences neither party then looked; but a far wider geographical

area, and far more extensive and various human interests, would be

affected by the measure. The spread of the Nile during the annual

inundation covers, for many weeks, several thousand square miles with

water, and at other seasons of the year pervades the same and even a

larger area with moisture by infiltration. The abstraction of so large

an evaporating surface from the southern shores of the Mediterranean

could not but produce important effects on many meteorological

phenomena, and the humidity, the temperature, the electrical condition

and the atmospheric currents of North-eastern Africa might be modified

to a degree that would sensibly affect the climate of Europe.

The Mediterranean, deprived of the contributions of the Nile, would

require a larger supply, and of course a stronger current, of water from

the Atlantic through the Straits of Gibraltar; the proportion of salt it

contains would be increased, and the animal life of at least its

southern borders would be consequently modified; the current which winds

along its southern, eastern, and north-eastern shores would be

diminished in force and volume, if not destroyed altogether, and its

basin and its harbors would be shoaled by no new deposits from the

highlands of inner Africa.

In the much smaller Red Sea, more immediately perceptible, if not

greater, effects, would be produced. The deposits of slime would reduce

its depth, and perhaps, in the course of ages, divide it into an inland

and an open sea, the former of which, receiving no supply from rivers,

would, as in the case of the northern part of the Gulf of California,

soon be dried up by evaporation, and its whole area added to the

Africo-Arabian desert; the waters of the latter would be more or less

freshened, and their immensely rich marine fauna and flora changed in

character and proportion, and, near the mouth of the river, perhaps even

destroyed altogether; its navigable channels would be altered in

position and often quite obstructed; the flow of its tides would be

modified by the new geographical conditions; the sediment of the river

would form new coast-lines and lowlands, which would be covered with

vegetation, and probably thereby produce sensible climatic changes.

Diversion of the Rhine.

The interference of physical improvements with vested rights and ancient

arrangements, is a more formidable obstacle in old countries than in

new, to enterprises involving anything approaching to a geographical

revolution. Hence such projects meet with stronger opposition in Europe

than in America, and the number of probable changes in the face of

nature in the former continent is proportionally less. I have noticed

some important hydraulic improvements as already executed or in progress

in Europe, and I may refer to some others as contemplated or suggested.

One of these is the diversion of the Rhine from its present channel

below Ragatz, by a cut through the narrow ridge near Sargans, and the

consequent turning of its current into the Lake of Wallenstadt. This

would be an extremely easy undertaking, for the ridge is but twenty feet

above the level of the Rhine, and hardly two hundred yards wide. There

is no present adequate motive for this diversion, but it is easy to

suppose that it may become advisable within no long period. The

navigation of the Lake of Constance is rapidly increasing in importance,

and the shoaling of the eastern end of that lake by the deposits of the

Rhine may require a remedy which can be found by no other so ready means

as the discharge of that river into the Lake of Wallenstadt. The

navigation of this latter lake is not important, nor is it ever likely

to become so, because the rocky and precipitous character of its shores

renders their cultivation impossible. It is of great depth, and its

basin is capacious enough to receive and retain all the sediment which

the Rhine would carry into it for thousands of years. [Footnote: Many

geographers suppose that the dividing ridge between the Lake of

Wallenstadt and the bed of the Rhine at Sargans is a fluviatile deposit,

which has closed a channel through which the Rhine anciently discharged

a part or the whole of its waters into the lake. In the flood of 1868,

the water of the Rhine rose to the level of the railway station at

Sargans, and for some days there was fear of the giving way of the

barrier and the diversion of the current of the river into the lake.]

Improvements in North American Hydrography.

We are not yet well enough acquainted with the geography of Central

Africa, or of the interior of South America, to conjecture what

hydrographical revolutions might there be wrought; but from the fact

that many important rivers in both continents drain extensive

table-lands, of moderate elevation and inclination, there is reason to

suppose that important changes in the course of those rivers might be

accomplished. Our knowledge of the drainage of North America is much

more complete, and it is certain that there are numerous points within

our territory where the courses of great rivers, or the discharge of

considerable lakes, might be completely diverted, or at least partially

directed into different channels.

The surface of Lake Erie is 565 feet above that of the Hudson at Albany,

and it is so near the level of the great plain lying east of it, that it

was found practicable to supply the western section of the canal, which

unites it with the Hudson, with water from the lake, or rather from the

Niagara which flows out of it. The greatest depth of water yet sounded

in Lake Erie is but two hundred and seventy feet, the mean depth one

hundred and twenty. Open canals parallel with the Niagara, or directly

towards the Genesee, might be executed upon a scale which would exercise

an important influence on the drainage of the lake, if there were any

adequate motive for such an undertaking. Still easier would it be to

enlarge the outlet for the waters of Lake Superior at the Saut St.

Mary--where the river which drains the lake descends twenty-two feet in

a single mile--and thus to produce incalculable effects, both upon that

lake and upon the great chain of inland waters which communicate with

it.

The summit level between the surface of Lake Michigan at its mean height

and that of the River Des Plaines, a tributary of the Illinois, at a

point some ten miles west of Chicago, is but ten and a half feet above

the lake. The lake once discharged a part or the whole of its waters

into the valley of the Des Plaines. A slight upheaval, at an unknown

period, elevated the bed of the Des Plaines, and the prairie between it

and the lake, to their present level, and the outflow of the lake was

turned into a new direction. The bed of the Des Plaines is higher than

the surface of the lake, and in recent times the Des Plaines, when at

flood, has sent more or less of its waters across the ridge into the bed

of the South Branch of Chicago River, and so into Lake Michigan.

A navigable channel has now been cut, admitting a constant flow of water

from the lake, by the valley of the Des Plaines, into the Illinois. The

mean discharge by this channel does not much exceed 23,000 cubic feet

per minute, but it would be quite practicable to enlarge its

cross-section indefinitely, and the flow through it might be so

regulated as to keep the Illinois and the Mississippi at flood at all

seasons of the year. The increase in the volume of these rivers would

augment their velocity and their transporting power, and, consequently,

the erosion of their banks and the deposit of slime in the Gulf of

Mexico, while the opening of a communication between the lake and the

affluents of the Mississippi, unobstructed except by locks, and the

introduction of a large body of colder water into the latter, would very

probably produce a considerable effect on the animal life that peoples

them. The diversion of water from the common basin of the great lakes

through a new channel, in a direction opposite to their present

discharge, would not be absolutely without influence on the St.

Lawrence, though probably this effect might be too small to be readily

perceptible. [Footnote: From Reports of the Canal Commissioners of the

State of Illinois, and especially from a very interesting private letter

from William Gooding, Esq., an eminent engineer, which I regret I have

not space to print in full, I learn that the length of the present

canal, from the lake to the River Illinois, is 101 miles, with a total

descent of a trifle more than 145 feet, and that it is proposed to

enlarge this channel to the width of one hundred and sixty feet, with a

minimum depth of seven, and to create a slack-water navigation in the

Illinois by the construction of five dams, one of which is already

completed. The descent for the outlet of the canal at La Salle on the

Illinois to the Mississippi is twenty-eight feet, the distance being 230

miles. The canal thus enlarged would cost about $16,000,000, and it

would establish a navigation for vessels of 1,200 to 1,500 tons burden

between Lake Michigan and the Mississippi, and consequently, by means of

the great lakes and the Welland canal, between the St. Lawrence and the

Gulf of Mexico.]

In an able and interesting article in a California magazine, Dr. Widney

has suggested a probable cause and a possible remedy for the desiccation

of south-eastern California referred to in a former chapter. The

Colorado Desert which lies considerably below the level of the waters of

the Gulf of California, and has an area of about 4,000 square miles,

evidently once formed a part of that gulf. This northern extension of

the gulf appears to have been cut off from the main body by deposits

brought down by the great river Colorado, at no very distant period.

These deposits at the same time turned the course of the river to the

south, and it now enters the gulf at a point twenty miles distant from

its original outlet.

When this northern arm of the gulf was cut off from the sea, and the

river which once discharged itself into it was diverted, it was speedily

laid dry by evaporation, and now yields no vapor to be condensed into

fog, rain, and snow on the neighboring mountains, which are now parched

and almost bare of vegetation.

The ancient bed of the river may still be traced, and in floods the

Colorado still sends a part of its overflowing supply into its old

channel, and for a time waters a portion of the desert. It is believed

that the river might easily be turned back into its original course, and

indeed nature herself seems to be now tending, by various spontaneous

processes, to accomplish that object. The waters of the Colorado, though

perhaps not sufficient to fill the basin and keep it at the sea-level in

spite of the rapid evaporation in that climate, [Footnote: The

thermometer sometimes rises to 120 degrees F. at Fort Yuma, at the S. E.

angle of California in N. L. 33 degrees.] would at least create a

permanent lake in the lower part of the depression, the evaporation from

which, Dr. Widney suggests, might sensibly increase the humidity and

lower the temperature of an extensive region which is now an arid and

desolate wilderness.

Soil below Rock.

One of the most singular changes of natural surface effected by man is

that observed by Beechey and by Barth at Lin Tefla, and near Gebel

Genunes, in the district of Ben Gasi, in Northern Africa. In this region

the superficial stratum originally consisted of a thin sheet of rock

covering a layer of fertile earth. This rock has been broken up, and,

when not practicable to find use for it in fences, fortresses, or

dwellings, heaped together in high piles, and the soil, thus bared of

its stony shell, has been employed for agricultural purposes. [Footnote:

Barth, Wanderungen durch die Kusten des Mittelmeeres, i., p. 853. In a

note on page 380, of the same volume, Barth cites Strabo as asserting

that a similar practice prevailed in Iapygia; but the epithet [word in

Greek: traxeia], applied by Strabo to the original surface, does not

neceasarily imply that it was covered with a continuous stratum of

rock.] If we remember that gunpowder was unknown at the period when

these remarkable improvements were executed, and of course that the rock

could have been broken only with the chisel and wedge, we must infer

that land had at that time a very great pecuniary value, and, of course,

that the province, though now exhausted, and almost entirely deserted by

man, had once a dense population.

Covering Rock with Earth.

If man has, in some cases, broken up rock to reach productive ground

beneath, he has, in many other instances, covered bare ledges, and

sometimes extensive surfaces of solid stone, with fruitful earth,

brought from no inconsiderable distance. Not to speak of the Campo Santo

at Pisa, filled, or at least coated, with earth from the Holy Land, for

quite a different purpose, it is affirmed that the garden of the

monastery of St. Catherine at Mount Sinai is composed of Nile mud,

transported on the backs of camels from the banks of that river. Parthey

and older authors state that all the productive soil of the Island of

Malta was brought over from Sicily. [Footnote: Parthey, Wanderungen durch

Sicilen und die Levante, i., p. 404.] The accuracy of the information

may be questioned in both cases, but similar practices, on a smaller

scale, are matter of daily observation in many parts of Southern Europe.

Much of the wine of the Moselle is derived from grapes grown on earth

carried high up the cliffs on the shoulders of men, and the steep

terraced slopes of the Island of Teneriffe are covered with soil

painfully scooped out from fissures in and between the rocks which have

been laid bare by the destruction of the native forests. [Footnote:

Mantegazza, Rio de la Plata e Teneriffa, p. 567.] In China, too, rock

has been artificially covered with earth to an extent which gives such

operations a real geographical importance, and the accounts of the

importation of earth at Malta, and the fertilization of the rocks on

Mount Sinai with slime from the Nile, may be not wholly without

foundation.

Valleys in Deserts.

In the latter case, indeed, river sediment might be very useful as a

manure, but it could hardly be needed as a soil; for the growth of

vegetation in the wadies of the Sinaitic Peninsula shows that the

disintegrated rock of its mountains requires only water to stimulate it

to considerable productiveness. The wadies present, not unfrequently,

narrow gorges, which might easily be closed, and thus accumulations of

earth, and reservoirs of water to irrigate it, might be formed which

would convert many a square mile of desert into flourishing date gardens

and cornfields. For example, not far from Wadi Feiran, on the most

direct route to Wadi Esh-Sheikh, is a very narrow pass called by the

Arabs El Bueb (El Bab) or, The Gate, which might be securely closed to a

very considerable height, with little labor or expense. Above this pass

is a wide and nearly level expanse, filled up to a certain regular level

with deposits brought down by torrents before the Gate, or Bueb, was

broken through, and they have now worn down a channel in the deposits to

the bed of the wadi. If a dam were constructed at the pass, and

reservoirs built to retain the winter rains, a great extent of valley

might be rendered cultivable.

Effects of Mining.

The excavations made by man, for mining and other purposes, may occasion

disturbance of the surface by the subsidence of the strata above them,

as in the case of the mine of Fahlun, in Sweden, but such accidents have

generally been too inconsiderable in extent to deserve notice in a

geographical point of view. [Footnote: In March, 1873, the imprudent

extension of the excavations in a slate mine near Morzine, in Savoy,

occasioned the fall of a mass of rock measuring more than 700,000 yards

in cubical contents. A forest of firs was destroyed, and a hamlet of

twelve houses crushed and buried by the slide.] It is said, however,

that in many places in the mining regions of England alarming

indications of a tendency to a wide dislocation of the superficial

strata have manifested themselves. Indeed, when we consider the measure

of the underground cavities which miners have excavated, we cannot but

be surprised that grave catastrophes have not often resulted from the

removal of the foundations on which the crust of our earth is laid. The

100,000,000 tons of coal yearly extracted from British mines require the

withdrawal of subterranean strata equal to an area of 20,000 acres one

yard deep, or 2,000 acres ten yards deep. These excavations have gone on

for several years at this rate, and in smaller proportions for

centuries. Hence, it cannot be doubted that by these and other like

operations the earth has been undermined and honey-combed in many

countries to an extent that may well excite serious apprehensions as to

the stability of the surface. In any event such excavations may

interfere materially with the course of subterranean waters, and it has

even been conjectured that the removal of large bodies of metallic ore

from their original deposits might, at least locally, affect in a

sensible degree the magnetic and electrical condition of the earth's

crust. [Footnote: The exhaustion of the more accessible deposits of coal

and other minerals has compelled the miners in Belgium, England, and

other countries, to carry their operations to great depths below the

surface. At the colliery Des Viviers, at Cilly near Charleroi, in

Belgium, coal is worked at the depth of 2,820 feet, and one pit has been

sunk to the depth of 3,411 feet. It is supposed that the internal heat

of the earth will render mining impossible below 4,000 feet. At Clifford

Amalgamated Mines, in Cornwall, the temperature at 1,590 feet stood at

100 degrees, but after the shaft had remained a year open it fell to 83

degrees. In another Cornish mine men work at from 110 degrees to 120

degrees, but only twenty minutes at a time, and with cold water thrown

frequently over them.--The last Thirty Years in Mining Districts, p. 95.

Stopponi mentions an abandoned mine at Huttenberg, in Bohemia, of the

depth of 3,775 feet.--Corso di Geologia, i., p. 258.]

Hydraulic Mining.

What is called hydraulic mining--a system substantially identical with

that described in an interesting way by Pliny the elder, in Book XXXV.

of his Natural History, as practised in his time in the gold mines of

Spain [Footnote: I have little doubt that the hydraulic mining in Gaul,

alluded to by Diodorus Siculus, Bibliotheca Historica, v. 27, as merely

a mode of utilizing the effects of water flowing in its natural

channels, was really the artificial method described by Pliny.]--is

producing important geographical effects in California. Artificially

directed currents of water have been long employed for washing down and

removing masses of earth, but in the Californian mining the process is

resorted to on a vastly greater scale than in any other modern

engineering operations, and with results proportioned to the means.

Brooks of considerable volume are diverted from their natural channels

and conducted to great distances in canals or wooden aqueducts,

[Footnote: In 1867 there were 6,000 miles (including branches) of

artificial water-courses employed for mining purposes in California.

The flumes of these canals are often of sheet-iron, and in some places

are carried considerable distances at a height of 250 feet above the

ground.--Raymond, Mineral Statistics west of the Rocky Mountains, 1870,

p. 476.] and then directed against hills and large level surfaces of

ground which it is necessary to remove to reach the gold-bearing strata,

or which themselves contain deposits of the precious mineral. [Footnote:

The water is sometimes driven through iron tubes under a hydrostatic

pressure of several hundred feet, with a force which cuts away rock of

considerable solidity almost as easily as hard earth. In this way of

using water, the cutting force might, doubtless, be greatly augmented by

introducing sand or gravel into the current.] Naked hills and fertile

soils are alike washed away by the artificial torrent, and the material

removed--vegetable mould, sand, gravel, pebbles--is carried down by the

current and often spread over ground lying quite out of the reach of

natural inundations, and burying it to the depth sometimes of

twenty-five feet. An orchard valued at $60,000, and another estimated at

not less than $200,000, are stated to have been thus sacrificed, and a

report from the Agricultural Bureau at Washington computes the annual

damage done by this mode of mining at the incredible sum of $12,000,000.

Accidental fires in mines of coal or lignite sometimes lead to

consequences not only destructive to large quantities of valuable

material, but which may, directly or indirectly, produce results

important in geography. The coal is occasionally ignited by the miners'

lights or other fires used by them, and certain kinds of this mineral,

if long exposed to air in deserted galleries, may be spontaneously

kindled. Under favorable circumstances, a stratum of coal will burn

until it is exhausted, and a cavity may be burnt out in a few months

which human labor could not excavate in many years. Wittwer informs us

that a coal mine at St. Etienne in Dauphiny has been burning ever since

the fourteenth century, and that a mine near Duttweiler, another near

Epterode, and a third at Zwickau, have been on fire for two hundred

years. Such conflagrations not only produce cavities in the earth, but

communicate a perceptible degree of heat to the surface, and the author

just quoted cites cases where this heat has ben advantageously employed

in forcing vegetation.

Projects of Agricultural Improvements by Duponchel.

Duponchel's schemes of agricultural improvement are so grandiose in

their nature, so vast in their sphere of operation, and so important in

their possible effects upon immense tracts of the earth's surface, that

they must be considered as projects of geographical revolution, and they

therefore merit more than a passing notice. In a memoir already quoted,

and in a later work, [Footnote: Traite d'Hydraulique et de Geologie

Agricole, 1868.] this engineer proposes to construct artificial torrents

for the purpose of grinding up calcareous rock, by rolling and attrition

along their beds, and thus reducing it into a fine slime; and at the

same time these torrents are to transport an argillaceous deposit which

is to be mingled with the calcareous slime, and distributed over the

Landes by watercourses constructed for the purpose. By this means, he

supposes that a very fertile soil may be formed, and so graded in

depositing as to secure for it a good drainage.

In order that nothing may be wanting to recommend the project, Duponchel

suggests that, as some rivers of Western France are gold-bearing, it is

probable that gold enough may be collected by washing the sands to

reduce materially the expense of such operations.

In the Landes of Gascony alone, he believes that 3,000,000 acres, now

barren, might be made productive at a moderate expense, and that similar

methods might be advantageously employed in France over an extent of not

less than 30,000,000 acres now almost wholly valueless.

The successful execution of the plan would increase the fertile

territory of France by an area of four or five times the extent of

Sicily or of Sardinia.

There seems to be no reason why the same method, applied for such

different purposes, should necessarily be destructive in the one case

while it is so advantageous in the other. A wiser economy might bring

about a harmony of action between the miners and the agriculturists of

California, and the soil which is removed by the former as an

incumbrance, judiciously deposited, might become for the latter a source

of wealth more solid and enduring than the gold now obtained by such a

sacrifice of agricultural interests.

Action of Man on the Weather.

Espy's well-known suggestion of the possibility of causing rain

artificially, by kindling great fires, is not likely to be turned to

practical account, but the speculations of this able meteorologist are

not, for that reason, to be rejected as worthless. His labors exhibit

great industry in the collection of facts, much ingenuity in dealing

with them, remarkable insight into the laws of nature, and a ready

perception of analogies and relations not obvious to minds less

philosophically constituted. They have unquestionably contributed

essentially to the advancement of meteorological science.

The possibility that the distribution and action of electricity may be

considerably modified by long lines of iron railways and telegraph

wires, is a kindred thought, and in fact rests much on the same

foundation as the belief in the utility of lightning-rods, but such

influence is too obscure and too uncertain to have been yet

demonstrated, though many intelligent observers believe that sensible

meteorological effects have been produced by it.

It is affirmed that battles and heavy cannonades are generally followed

by rain and thunder-storms, and Powers has collected much evidence on

this subject, [Footnote: War and the Weather, or the Artificial

Production of Rain, Chicago, 1871. Paifer proposed, as early as 1814,

arrangements for producing rain by firing cannon and exploding shells in

the air. Ein wunderbarer Traum die Frucht, barkeit durch willkurlichen

Regen zu befordern, Metz, 1814. See, on the question of the possibility

of influencing the weather by artificial means, London Quarterly Journal

of Science, xxix., p. 126, and Nature, Feb. 16, 1871, p. 306.] but the

proposition does not seem to be by any means established.

Resistance to Great Natural Forces.

I have often spoken of the greater and more subtile natural forces, and

especially of geological agencies, as powers beyond human guidance or

resistance. This is no doubt at present true in the main, but man has

shown that he is not altogether impotent to struggle with even these

mighty servants of nature, and his unconscious as well as his deliberate

action may in some cases have increased or diminished the intensity of

their energies. It is a very ancient belief that earthquakes are more

destructive in districts where the crust of the earth is solid and

homogeneous, than where it is of a looser and more interrupted

structure. Aristotle, Pliny the elder, and Seneca believed that not only

natural ravines and caves, but quarries, wells, and other human

excavations, which break the continuity of the terrestrial strata and

facilitate the escape of elastic vapors, have a sensible influence in

diminishing the violence and preventing the propagation of the

earth-waves. In all countries subject to earthquakes this opinion is

still maintained, and it is asserted that, both in ancient and in modern

times, buildings protected by deep wells under or near them have

suffered less from earthquakes than those the architects of which have

neglected this precaution. [Footnote: Landgrebe, Geschichte der Vulkane,

ii., pp. 19, 20.]

If the commonly received theory of the cause of earthquakes is

true--that, namely, which ascribes them to the elastic force of gases

accumulated or generated in subterranean reservoirs--it is evident that

open channels of communication between such reservoirs and the

atmosphere might serve as a harmless discharge of gases that would

otherwise acquire destructive energy. The doubt is whether artificial

excavations can be carried deep enough to reach the laboratory where the

elastic fluids are distilled. There are, in many places, small natural

crevices through which such fluids escape, and the source of them

sometimes lies at so moderate a depth that they pervade the superficial

soil and, as it were, transpire from it, over a considerable area. When

the borer of an ordinary artesian well strikes into a cavity in the

earth, imprisoned air often rushes out with great violence, and this has

been still more frequently observed, in sinking mineral-oil wells. In

this latter case, the discharge of a vehement current of inflammable

fluid sometimes continues for hours and even longer periods. These facts

seem to render it not wholly improbable that the popular belief of the

efficacy of deep wells in mitigating the violence of earthquakes is well

founded.

In general, light, wooden buildings are less injured by earthquakes than

more solid structures of stone or brick, and it is commonly supposed

that the power put forth by the earth-wave is too great to be resisted

by any amount of weight or solidity of mass that man can pile up upon

the surface. But the fact that in countries subject to earthquakes many

very large and strongly constructed palaces, temples, and other

monuments have stood for centuries, comparatively uninjured, suggests a

doubt whether this opinion is sound. The earthquake of the first of

November, 1755, which is asserted, though upon doubtful evidence, to

have been felt over a twelfth part of the earth's surface, was among the

most violent of which we have any clear and distinct account, and it

seems to have exerted its most destructive force at Lisbon. It has often

been noticed as a remarkable fact, that the mint, a building of great

solidity, was almost wholly unaffected by the shock which shattered

every house and church in the city, and its escape from the common ruin

can hardly be accounted for except upon the supposition that its weight,

compactness, and strength of material enabled it to resist an agitation

of the earth which overthrew all weaker structures. On the other hand, a

stone pier in the harbor of Lisbon, on which thousands of people had

taken refuge, sank with its foundations to a great depth during the same

earthquake; and it is plain that where subterranean cavities exist, at

moderate depths, the erection of heavy masses upon them would tend to

promote the breaking down of the strata which roof them over.

No physicist, I believe, has supposed that man can avert the eruption of

a volcano or diminish the quantity of melted rock which it pours out of

the bowels of the earth; but it is not always impossible to divert the

course of even a large current of lava. "The smaller streams of lava

near Catania," says Ferrara, in describing the great eruption of 1669,

"were turned from their course by building dry walls of stone as a

barrier against them. ... It was proposed to divert the main current

from Catania, and fifty men, protected by hides, were sent with hooks

and iron bars to break the flank of the stream near Belpasso. [Footnote:

Soon after the current issues from the volcano, it is covered above and

at its sides, and finally in front, with scoriae, formed by the cooling

of the exposed surface, which bury and conceal the fluid mass. The

stream rolls on under the coating, and between the walls of scoriae, and

it was the lateral crust which was broken through by the workmen

mentioned in the text.

The distance to which lava flows, before its surface begns to solidify,

depends on its volume, its composition, its temperature and that of the

air, the force with which it is ejected, and the inclination of the

declivity over which it runs. In most cases it is difficult to approach

the current at points where it is still entirely fluid, and hence

opportunities of observing it in that condition are not very frequent.

In the eruption of February, 1850, on the east side of Vesuvius, I went

quite up to one of the outlets. The lava shot out of the orifice upwards

with great velocity, like the water from a fountain, in a stream eight

or ten feet in diameter, throwing up occasionally volcanic bombs three

or four feet in diameter, which exploded at the height of eight or ten

yards, but it immediately spread out on the declivity down which it

flowed, to the width of several yards. It continued red-hot in broad

daylight, and without a particle of scoriae on its surface, for a course

of at least one hundred yards. At this distance, the suffocating,

sulphurous vapors became so dense that I could follow the current no

farther. The undulations of the surface were like those of a brook

swollen by rain. I estimated the height of the waves at five or six

inches by a breadth of eighteen or twenty. To the eye, the fluidity of

the lava seemed as perfect as that of water, but masses of cold lava

weighing ten or fifteen pounds floated upon it like cork.

The heat emitted by lava currents seems extremely small when we consider

the temperature required to fuse such materials and the great length of

time they take in cooling. I saw at Nicolosi ancient oil-jars, holding a

hundred gallons or more, which had been dug out from under a stream of

old lava above that town. They had been very slightly covered with

volcanic ashes before the lava flowed over them, but the lead with which

holes in them had been plugged was not melted. The current that buried

Mompiliere in 1669 was thirty-five feet thick, but marble statues, in a

church over which the lava formed an arch, were found uncalcined and

uninjured in 1704, See Scrope, Volcanoes, chap. vi. Section 6.]

When the opening was made, fluid lava poured forth and flowed rapidly

towards Paterno; but the inhabitants of that place, not caring to

sacrifice their own town to save Catania, rushed out in arms and put a

stop to the operation." [Footnote: Ferrara, Descrizione dell' Etna, p.

108.] In the eruption of Vesuvius in 1794, the viceroy saved from

impending destruction the town of Portici, and the valuable collection

of antiquities then deposited there but since removed to Naples, by

employing several thousand men to dig a ditch above the town, by which

the lava current was carried off in another direction. [Footnote:

Landgrebe, Naturgeschichte der Vulkane, ii., p. 82.]

Incidental Effects of Human Action.

I have more than once alluded to the collateral and unsought

consequences of human action as being often more momentous than the

direct and desired results. There are cases where such incidental, or,

in popular speech, accidental, consequences, though of minor importance

in themselves, serve to illustrate natural processes; others, where, by

the magnitude and character of the material traces they leave behind

them, they prove that man, in primary or in more advanced stages of

social life, must have occupied particular districts for a longer period

than has been supposed by popular chronology. "On the coast of Jutland,"

says Forchhammer, "wherever a bolt from a wreck or any other fragment of

iron is deposited in the beach sand, the particles are cemented

together, and form a very solid mass around the iron. A remarkable

formation of this sort was observed a few years ago in constructing the

sea-wall of the harbor of Elsineur. This stratum, which seldom exceeded

a foot in thickness, rested upon common beach sand, and was found at

various depths, less near the shore, greater at some distance from it.

It was composed of pebbles and sand, and contained a great quantity of

pins, and some coins of the reign of Christian IV., between the

beginning and the middle of the seventeenth century. Here and there, a

coating of metallic copper had been deposited by galvanic action, and

the presence of completely oxydized metallic iron was often detected.

Investigation made it in the highest degree probable that this formation

owed its origin to the street sweepings of the town, which had been

thrown upon the beach, and carried off and distributed by the waves over

the bottom of the harbor." [Footnote: Geognostische Studien am Meeres

Ufer, Leonhard und Bronn, 1841, pp. 25, 26.] These and other familiar

observations of the like sort show that a sandstone reef, of no

inconsiderable magnitude, might originate from the stranding of a ship

with a cargo of iron, [Footnote: Kohl, Schleswig-Holstein, ii., p. 45.]

or from throwing the waste of an establishment for working metals into

running water which might carry it to the sea.

Parthey records a singular instance of unforeseen mischief from an

interference with the arrangements of nature. A landowner at Malta

possessed a rocky plateau sloping gradually towards the sea, and

terminating in a precipice forty or fifty feet high, through natural

openings in which the sea-water flowed into a large cave under the rock.

The proprietor attempted to establish salt-works on the surface, and cut

shallow pools in the rock for the evaporation of the water. In order to

fill the salt-pans more readily, he sank a well down to the cave

beneath, through which he drew up water by a windlass and buckets. The

speculation proved a failure, because the water filtered through the

porous bottom of the pans, leaving little salt behind. But this was a

small evil, compared with other destructive consequences that followed.

When the sea was driven into the cave by violent west or north-west

winds, it shot a jet d'eau through the well to the height of sixty feet,

the spray of which was scattered far and wide over the neighboring

gardens and blasted the crops. The well was now closed with stones, but

the next winter's storms hurled them out again, and spread the salt

spray over the grounds in the vicinity as before. Repeated attempts were

made to stop the orifice, but at the time of Parthey's visit the sea had

thrice burst through, and it was feared that the evil was without

remedy. [Footnote: Wanderungen durch Sicilien und die Levante, i., p.

406.]

I have mentioned the great extent of the heaps of oyster and other

shells left by the American Indians on the Atlantic coast of the United

States. Some of the Danish kitchen-middens, which closely resemble them,

are a thousand feet long, from one hundred and fifty to two hundred

wide, and from six to ten high. These piles have an importance as

geological witnesses, independent of their bearing upon human history.

Wherever the coast line appears, from other evidence, to have remained

unchanged in outline and elevation since they were accumulated, they are

found near the sea, and not more than about ten feet above its level. In

some cases they are at a considerable distance from the beach, and in

these instances, so far as yet examined, there are proofs that the coast

has advanced in consequence of upheaval or of fluviatile or marine

deposit. Where they are altogether wanting, the coast seems to have sunk

or been washed away by the sea. The constancy of these observations

justifies geologists in arguing, where other evidence is wanting, the

advance of land or sea respectively, or the elevation or depression of

the former, from the position or the absence of these heaps alone.

Every traveller in Italy is familiar with Monte Testaccio, the mountain

of potsherds, at Rome; [Footnote: Untill recently this hillock was

supposed to consist of shards of household pottery broken in using, but

it now appears to be ascertained that it is composed of fragments of

earthenware broken in transportation from the place of manufacture to

the emporium on the Tiber where such articles were landed.] but this

deposit, large as it is, shrinks into insignificance when compared with

masses of similar origin in the neighborhood of older cities. The

castaway pottery of ancient towns in Magna Grecia composes strata of

such extent and thickness that they have been dignified with the

appellation of the ceramic formation. The Nile, as it slowly changes its

bed, exposes in its banks masses of the same material, so vast that the

population of the world during the whole historical period would seem to

have chosen this valley as a general deposit for its broken vessels.

The fertility imparted to the banks of the Nile by the water and the

slime of the inundations, is such that manures are little employed.

Hence much domestic waste, which would elsewhere be employed to enrich

the soil, is thrown out into vacant places near the town. Hills of

rubbish are thus piled up which astonish the traveller almost as much as

the solid pyramids themselves. The heaps of ashes and other household

refuse collected on the borders and within the limits of Cairo were so

large, that the removal of them by Ibrahim Pacha has been looked upon as

one of the great works of the age.

These heaps formed almost a complete rampart around the city, and

impeded both the circulation of the air and the communication between

Cairo and its suburbs. At two points these accumulations are said to

have risen to the incredible height of between six and seven hundred

feet; and these two heaps covered two hundred and fifty acres.

[Footnote: Clot Bey, Egypte, i., p. 277.] During the occupation of Cairo

by the French, the invaders constructed redoubts on these hillocks which

commanded the city. They were removed by Mehemet Ali, and the material

was employed in raising the level of low grounds in the environs.

[Footnote: Egypt manufactures annually about 1,200,000 pounds of nitre,

by lixiviating the ancient and modern rubbish-heaps around the towns.]

In European and American cities, street sweepings and other town refuse

are used as manure and spread over the neighboring fields, the surface

of which is perceptibly raised by them, by vegetable deposit, and by

other effects of human industry, and in spite of all efforts to remove

the waste, the level of the ground on which large towns stand is

constantly elevated. The present streets of Rome are twenty feet, and in

many places much more, above those of the ancient city. The Appian Way

between Rome and Albano, when cleared out a few years ago, was found

buried four or five feet deep, and the fields along the road were

elevated nearly or quite as much. The floors of many churches in Italy,

not more than six or seven centuries old, are now three or four feet

below the adjacent streets, though it is proved by excavations that they

were built as many feet above them. [Footnote: Rafinesque maintained

many years ago that there was a continual deposition of dust on the

surface of the earth from the atmosphere, or from cosmical space,

sufficient in quantity to explain no small part of the elevation

referred to in the text. Observations during the eclipse of Dec. 22,

1870, led some astronomers to believe that the appearance of the corona

was dependent upon or modified by cosmical dust or matter in a very

attenuated form diffused through space.

Tyndall has shown by optical tests that the proportion of solid matter

suspended or floating in common air is very considerable, and there is

abundant other evidence to the name purpose. Ehrenberg has found African

and even American infusoria in dust transplanted by winds and let fall

in Europe, and Schliemann offers that the quantity of dust brought by

the scirocco from Africa is so great, that by cutting holes in the naked

rocks of Malta enough of Libyan transported earth can be caught and

retained, in the course of fourteen years, to form a soil fit for

cultivation.--Beilage zur Allgemeinen Zeitung, Mar. 24, 1870.]

Nothing Small in Nature.

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

de minimis non curat lex; but in the vocabulary of nature, little and

great are terms of comparison only; she knows no trifles, and her laws

are as inflexible in dealing with an atom as with a continent or a

planet. [Footnote: One of the sublimest, and at the same time most

fearful suggestions that have been prompted by the researches of modern

science, was made by Babbage in the ninth chapter of his Ninth

Bridgewater Treatise. I have not the volume at hand, but the following

explanation will recall to the reader, if it does not otherwise make

intelligible, the suggestion I refer to:

No atom can be disturbed in place, or undergo any change of temperature,

of electrical state, or other material condition, without affecting, by

attraction or repulsion or other communication, the surrounding atoms.

These, again, by the same law, transmit the influence to other atoms,

and the impulse thus given extends through the whole material universe.

Every human movement, every organic act, every volition, passion, or

emotion, every intellectual process, is accompanied with atomic

disturbance, and hence every such movement, every such act or process,

affects all the atoms of universal matter. Though action and reaction

are equal, yet reaction does not restore disturbed atoms to their former

place and condition, and consequently the effects of the least material

change are never cancelled, but in some way perpetuated, so that no

action can take place in physical, moral, or intellectual nature,

without leaving all matter in a different state from what it would have

been if such action had not occurred. Hence, to use language which I

have employed on another occasion: there exists, not alone in the human

conscience or in the omniscience of the Creator, but in external nature,

an ineffaceable, imperishable record, possibly legible even to created

intelligence, of every act done, every word uttered, nay, of every wish

and purpose and thought conceived, by mortal man, from the birth of our

first parent to the final extinction of our race; so that the physical

traces of our most secret sins shall last until time shall be merged in

that eternity of which not science, but religion alone assumes to take

cognisance.]

The human operations mentioned in the last few paragraphs, therefore, do

act in the ways ascribed to them, though our limited faculties are at

present, perhaps forever, incapable of weighing their immediate, still

more their ultimate consequences. But our inability to assign definite

values to these causes of the disturbance of natural arrangements is not

a reason for ignoring the existence of such causes in any general view

of the relations between man and nature, and we are never justified in

assuming a force to be insignificant because its measure is unknown, or

even because no physical effect can now be traced to it as its origin.

The collection of phenomena must precede the analysis of them, and every

new fact, illustrative of the action and reaction between humanity and

the material world around it, is another step towards the determination

of the great question, whether man is of material nature or above her.

THE END