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The northern and southern hemispheres appear to present nearly the same curvature under equal degrees of latitude, but pendulum experiments and measurements of degrees yield such different results for individual portions of the Earth's surface, that no regular figure can be given which would reconcile all the results hitherto obtained by this method. The true figure of the Earth is to a regular figure as the uneven surfaces of water in motion are to the even surface of water at rest.1_HUMBOLDT.
ECONOMICAL RESULTS OF EXTERNAL FORMS” OF TRACTS
In considering the “external forms” of tracts of land simply in a geological point of view, it may appear quite accidental that such a plain should or should not have risen from the bosom of the waters; that such a mountain rises at this place or that; that such a continent should be cut up into peninsulas, or piled into a compact mass, accompanied by or deprived of islands. When, finally, we reflect that a depression of a few hundred feet, which would make no change in the essential forms of the solid mass of the globe, would cause a great part of Asia and of Europe to disappear beneath the water of the oceans, and would reduce America to a few large islands, we might draw from it the conclusion that the external shape of the continents has but an inconsiderable importance.
But in physics neither of these circumstances is unimportant. Simple examples, without further demonstration, will be sufficient to set this in a clear light.
Is the question of the forms of contour ? Nothing characterizes Europe better than the variety of its indentations, of its peninsulas, of its islands. Suppose, for a moment, that beautiful Italy, Greece with its entire Archipelago, were added to the central mass of the continent, and augmented Germany or Russia by the number of square miles they contain; this change of form would not give us another Germany, but we should have an Italy and a Greece the less. Unite with the body of Europe all its islands and peninsulas into one compact mass, and instead of this continent, so rich in various elements, you will have a New Holland with all its uniformity.
1 The exterior figure of the earth is supposed to be that formed by a crust around an interior, a large portion of which must be supposed to be hollow. The mean density of the earth is between five and six times that of water; the mean density of the liquids and solids with which we are acquainted is nearly twice that of water; from these two quantities, compared with its magnitude, a hollow interior surrounded with a crust of increasing density downwards has been deduced. The interior of the earth is supposed to be of matter in a high state of temperature : its internal heat is intimately connected with its magnetic phenomena.
Do we look to the forms of relief, of height? Is it a matter of indifference whether an entire country is elevated into the dry and cold regions of the atmosphere, like the central table land of Asia, or is placed on the level of the ocean? See, under the same sky, the warm and fertile plains of Hindoostan, adorned with the brilliant vegetation of the tropics, and the cold and desert plateaus of Upper Tibet; compare the burning region of Vera Cruz and its fevers with the lofty plains of Mexico and its perpetual spring; the immense forests of the Amazon, where vegetation puts forth all its splendours, and the desolate paramos of the summits of the Andes, and you have the answer.
And the relative position? Is it not to their position that the three peninsulas of the south of Europe owe their mild and soft climate, their lovely landscape, their numerous relations, and their common life? Is it not to their situation that the two great peninsulas of India owe their rich nature, and the conspicuous part which one of them at least has played in all ages ? Place them on the north of their continents, Italy and Greece become a Scandinavia, and India a Kamtschatka.
All Europe owes its temperate atmosphere to its position relatively to the great marine and atmospheric currents, and to the vicinity of the burning regions of Africa. Place it at the east of Asia, it will be only a frozen peninsula.
Suppose that the Andes, transferred to the eastern coast of South America, hindered the trade wind from bearing the vapours of the ocean into the interior of the continent, and the plains of the Amazon and of Paraguay would be nothing but a desert.
In the same manner, if the Rocky Mountains bordered the eastern coast of North America, and closed against the nations of the east of Europe the entrance to the rich valley of the Mississippi; or if this immense chain extended from east to west across the northern part of this continent, and barred the passage of the polar winds which now rush unobstructed over these vast plains ; let us even say less--if, preserving all
the great present features of this continent, we suppose only that the interior plains were slightly inclined towards the north, and that the Mississippi emptied into the Frozen Ocean, who does not see that, in these various cases, the relations of warmth and moisture, the climate, in a word, and with it the vegetation and the animal world, would undergo most important modifications, and that these changes of form and of relative position would have an influence greater still upon the destinies of human societies, both in the present and in the future ?
1. The forms, the arrangement, and the distribution of the terrestrial masses on the surface of the globe, though accidental in appearance, yet reveal a plan which we are enabled to understand by the evolutions of history.
2. The continents are made for human societies, as the body is made for the soul.
3. Each of the northern, or historical continents, is peculiarly adapted by its nature to perform a special part which corresponds to the wants of humanity in one of the great phases of its history.
Thus nature and history, the earth and man, stand in the closest relations to each other, and form only one grand harmony.
FORMS OF THE CONTINENTS.
Africa is by far the most simple in its form. Its mass, nearly round or ellipsoidal, is concentrated upon itself. It projects into the ocean no important peninsula, nor anywhere lets into its bosom the waters of the ocean. It seems to close itself against every influence from without. Thus the extension of the line of its coasts is only 14,000 geographical miles, of 60 to the degree, for a surface of 8,720,000 square miles ; so that Africa has only one mile of coast for 623 miles of surface.
Asia, although bathed on three sides only by the ocean, is rich, especially on its eastern and southern coasts, in large peninsulas, as Arabia and the two Indies, Corea, Kamtschatka, Whole countries push out into the ocean, as Mandchouria and China ; nevertheless the extent of this continent is such, that, in spite of the depth of the indentations, there yet remains at its centre a greatly preponderating mass of undivided land, which commands the maritime regions as the body commands the limbs. Asia is indebted to this configuration for a line of coast of 30,800 miles; it is double that of Africa, which is, nevertheless, only one-third smaller. Asia, therefore, possesses a mile of coast to 459 square miles of surface.
Of all the continents, Europe is the one whose forms of contour are most varied. Its principal mass is deeply cut in all parts, by the ocean and by inland seas, and seems almost on the point of resolving itself into peninsulas. These peninsulas themselves, as Greece, Scandinavia, repeat to infinity the phenomena of articulation and indentation of coasts, which are characteristic of the entire continent. The inland seas, and the portions of the ocean which its outer limits enclose, form nearly half of its surface. The line of its shores is thus carried to the extent of 17,200 miles, an enormous proportion compared with its small size; for it is 3200 miles more than Africa, which is nevertheless three times greater. Europe enjoys one mile of coast for every 156 square miles of surface. It is thus the continent most open to the sea for foreign connexions, at the same time that it is the most individualized, and the richest in local and independent districts.
In this regard there is, as we see, a sensible gradation between the three principal continents of the Old World. Africa is the most simple ; it is a body without members, a tree without branches. Asia is a mighty trunk, the numerous members of which, however, make only a fifth of its
In Europe the members overrule the principal body, the branches cover the trunk; the peninsulas form almost a third of its entire surface. Africa is closed to the ocean ; Asia opens only its margins; Europe surrenders entirely to it, and is the most accessible of all the continents.
America repeats the same contrasts, although in a less decided manner. North America, like Europe, is more indented than South America, the configuration of which, in the exterior at least, reminds us of the forms of Africa, and the uniformity of its contours. The two continents of the New World are more alike; nevertheless, the line of the shores is much more extended in North than in South America. It is 24,000 miles in the former, or one mile of coast to 228 square miles of surface; in the latter it is 13,600 miles, or a mile of coast for 376 miles of surface.
CONTOURS OF ELEVATION, OR GENERAL RELIEFS.
The examination of the general reliefs, of the great masses of dry land on the surface of the globe, leads us to the recognition of certain great analogies, certain great laws of relief, which apply, whether to certain groups of continents, or to all the continents taken together, or to the whole earth. We shall point out, one after another, these general facts ; and we hope to make clear the general law which appears to follow from them.
1. All the continents rise gradually from the shores of the seas towards the interior, to a line of highest elevation of the masses, ånd of the peaks which surmount them, to a maximum of swell.
This fact appears trivial in the stating, because it seems so much according to the nature of things; but it is not so for him who knows the geological history of our continents and the revolutions which their surface has undergone. The question is asked, why we should not have, in the interior of vast continents like Asia or America, some great depression, the bed of which should be sunk below the surface of the oceans? and, in fact, this circumstance is not absolutely wanting to our continents : we may cite, as a case of the kind, the great hollow of which the Caspian Sea occupies the bottom. It is known that the surface of this sea, and even of a great part of the surrounding countries, is below the common level of the oceans; further, its basis presents in its southern parts considerable depths. The valley of the Jordan and Dead Sea, together with its lakes and the river, is almost entirely below the level of the Mediterranean. The recent measurements of Bertou, Russiger, and of Major Symonds, and others, among whom we may mention, as the most recent of these bold explorers, an American, Lieutenant Lynch, have proved that the level of the Dead Sea is about 1380 feet below the level of the ocean, and that its depth descends at least as much more. What masks these depressions, moreover, is the water which fills them, the surface of which must be considered as forming a part of that of the continents. Besides the three largest of the lakes of Canada, several of the lakes of the Italian Alps, the bed of which sinks below the level of the sea, would appear to us as similar excavations. We may say the same of the midland seas