Slike stranica
[ocr errors]

The Superficial Dimensions of the Land and Water on the Globe.

The equatorial diameter of the earth, 7925.6 miles, multiplied into the circumference, 24898 8, equals 197,339,590, the number of square miles on the earth's surface, reckoning as if of a true sphere. The deduction to be made, in consequence of its spheroidal shape, has not yet been estimated with any approach to nicety. The sum indicated above is exact enough to satisfy geographical purposes; enough to lead to the laws of relative rather than to a minute individualization. The proportion even of land to water has not been determined, except with approximate accuracy. It has been commonly stated that two-thirds are water and one-third land; others have computed three-fifths to be water and two-fifths land. The most accurate measurements, those instituted by Humboldt, have left it in this statement, that if the whole be taken as one, the sea occupies 734, the land 265, or, reduced and simplified in almost unchanged form, a little more than three-quarters water, a little less than onequarter land. Of course it is impossible, as yet, to attain to accuracy in these estimates, as our knowledge is imperfect regarding the polar regions; there are about 17,000,000 square miles unexplored.

The ascertaining of superficial areas with exactness is one of the most costly operations undertaken in the interest of science. The first mathematical survey of France, one hundred and fifty years ago, undertaken by Cassini, cost four millions; the second sixteen millions; a third, still more costly, has been made within the present century. Still, it must be said that few countries have expended money in this direction with as much prodigality as

France. In Turkey, for instance, so little accuracy has been attained, that the survey of that country, undertaken by Beauchamp early in this century, resulted in es,tablishing the Sultan in possession of 17,000 square miles which he had supposed were covered by the Black Sea. The recent surveys of Prussia have rectified similar mistakes, and, in the constantly increasing accuracy, have given hundreds of square miles to the Crown. Many countries, and in truth the most, have never been subjected to a strict mensuration. The jagged coast lines. of islands and continents have been so great a barrier, that we have to speak with great uncertainty of the superficial contents which they inclose. The statements of these make no pretense, therefore, to accuracy. We must be content, at present, with the rudest approximation. This accounts for the discrepancy in our geographical compendia; no two of them agree, unless one servilely copies the other. The statistics relating to the superficial contents of continents, and of separate countries, must be taken with a great deal of allowance. The evil cannot be remedied at present; it will be, doubtless, at some future day. The discrepancies which it occasions will be seen, from the fact that the area of Europe has been computed to be between 3,254,800 and 3,870,500 square miles; that of Asia between 16,180,000 and 16,831,600; that of Africa between 11,257,200 and 11,513,600; that of America between 12,140,400 and 15,963,600; that of Australia between 2,756,000 and 3,201,200 square miles.

According to this, Asia is five times as large as Europe, and almost six times as large as the continent of Australia Africa is three times as large as Europe. America is four times as large as Europe, and is as large as Africa and Australia combined. Europe would make about one-third

of Africa, one-quarter of America, one-fifth of Asia. Our present knowledge does not allow us to speak more definitely nor exactly.

Contrast of the Land and Water Hemispheres.

Whether we divide the globe into northern and southern or eastern and western hemispheres, their relative amounts of land and water will be different. The northern hemisphere contains (speaking approximatively as above) 38,541,600 square miles of land, and 59,619,700 of water; the southern, 12,847,200 of land, and 85,526,100 of water. The eastern hemisphere contains 36,760,800 square miles of land, and 61,401,000 of water; the western, 14,628,000 of land, and 83,533,300 of water.

Besides the division quantitatively, the division in respect to symmetry of shape is entirely irregular. Symmetry, as we usually use the word, consists in the arrangement of parts at equal distances, or two sides at least, from some central point or line. Mineral crystals are regarded in relation to the point where crystallization began; plants are viewed in relation to the stem-axis; animals in relation to the symmetry of the entire structure. A similar law of symmetry is entirely wanting to the globe; its arrangement is altogether unlike this; it is not nearly so perceptible at first glance, yet it is far more profound in design and comprehensive in its relations.

The land is broken up into masses, varying in size, and called, arbitrarily, continents and islands. Strictly speaking, there are but two continents, the old world forming one, the new world the other. Australia may be called the smallest continent or the largest island; it is the connecting link between the forms, and shows at a glance the arbitrary distinction. We might easily go further and call

New Guinea, Borneo, Sumatra, Great Britain, and Java, continents, and, on the other hand, we might designate the old and the new world as islands. There is nothing absolute here but the usage of speech.

The continents and islands lie mainly in the northern hemisphere, (38,341,600 square miles,) scarcely a third part of their superficies (12,847,200 square miles) being in the southern.

The continents are so situated also that the eastern contains by far the largest body of land, (36,760,800 square miles,) the western being only about one-third as large, (13,628,000 square miles.) America, the western, it will be seen, has no first-class island lying near it; it stands isolated.

It is seen by this that the greatest mass of land lies in the northern hemisphere, dividing the earth in one way, and in the eastern dividing it in another; the smallest mass in the southern and the western. In the northeast the watery realm is the most contracted, in the southwest the least. We are thus enabled to speak of the land side of the globe, the land hemisphere, and a water side, the water hemisphere.

The central point of the water hemisphere is at the island of New Zealand. Toward this the points of all the continents are directed. The center of the land hemisphere is in the northwest of Europe, at a point near southeast of England, the northeast of France, and the coast of Holland. The dwellers around the North Sea are the antipodes of the New Zealanders. Great Britain is the country which, as a whole, is the middle point of the continental world. In the oceanic world, the islands lie like scattered dots, insignificant in respect to area, in comparison with the waste of waters which surrounds them, while,

on the other hand, the land hemisphere is so solidly com pacted, that even the Arctic Ocean becomes merely a broad channel.

Thus arises the first great contrast which we have to study: the first, and next to the great primary distinction between the North and South, the most important. The division into land and water, aside from commerce, must exercise the strongest influence on the distribution of heat and cold, affecting the temperature of all the zones. This influence has been fully noticed and brought before the world by Alexander von Humboldt. It is sufficient to refer to it now as a well-determined fact in physical geography.

The heat equator is a little farther north than the mathematical equator, because the land hemisphere has a greater heat capacity (if we may use an awkward but apt word) than the water hemisphere. All other isothermal lines are modified in their greater or less coincidence with the parellels of latitude as they advance from the heat equator toward the maximum of the land hemisphere, or, in general terms, as they go northward. In the western hemisphere the isothermal lines follow much more exactly the parallels of latitude than in the eastern, which is preeminently the land hemisphere. In America the proximity of immense masses of water causes a perceptible reduction of the heat from that of the eastern where the land form prevails. And the heat diminishes more as we advance toward the South Pole, than toward the North, in consequence of the greater deficiency of land in the southern hemisphere; while in Lapland, Greenland, and in Siberia, even within the polar circle itself, men find sustenance. and trees live, in the same latitude, at the South Pole, no vegetable life, worth mentioning, is found. The frigid

« PrethodnaNastavi »