Page:Popular Science Monthly Volume 41.djvu/419

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THE WASTE AND GAIN OF THE DRY LAND.

of the emerged soil, for the space they occupy is taken from the sea. The sea, moreover, does not eat away all the shores. There are coasts where the waves, instead of carrying away parcels of the dry land, operate to fill up the bays and to add to the littoral and prolong it in the direction of the sea. Thus the ocean every year deposits several million cubic metres of sand along the shores of the Gulf of Gascony.

Another accrement which has a right to be regarded as considerable is contributed by the legions of polyps constructing reefs and atolls of coral, to which is due the building up of whole archipelagoes in Oceania and the Indian seas. The islands formed by these minute zoophytes are growing continually in extent and number, and are probably destined ultimately, by joining, to give rise to vast lands, real continents, which will gradually occupy the immense voids of the Pacific.

The shells of numerous species of animals and other remains of dead organisms, meteorites and cosmic dusts falling from celestial space, certainly produce further sensible augmentations of the continental mass.

Another essential cause of increase of dry land that might be added is the decrease of the ocean itself in consequence of infiltrations of water through the crust of the earth, which is a kind of porous mass, into which the liquid element percolates by innumerable fissures, taking possession of the depths and directing itself slowly toward the center, as the internal fire diminishes and the crusts crack open in consequence. It is understood that the activity of volcanoes and many earthquakes is largely due to this inevitable penetration of the water, which internal heat transforms into vapor under pressure. Some geologists think that the primitive ocean has already diminished in this way one fiftieth of its volume.

The water is all destined to disappear from the surface of the globe by being absorbed by the subterranean rocks, with which it will form chemical combinations. The heavenly spheres exhibit sufficiently striking examples of such an evolution. The planet Mars shows what will become of the earth in some thousands of centuries. Its seas are only shallow Mediterraneans of less surface than the continents, and these do not appear to be very high; and in the appearance of the moon, all cracked and dried up, we have a view of the final state of the earth for the absorption of the water by the solid nucleus will be followed by that of the atmosphere.

We see, therefore, M. Léotard continues, that not only is there no equilibrium in the struggle between the oceans and the continents, but that, inversely to the conclusions of M. de L'Apparent, the event that may be considered very probable in a future repre-