During the long periods of its vital splendor, when, leading the chorus of the worlds, it bore on its surface an intelligent race, victors over the blind forces of nature, a protecting atmosphere, beneath which went on all the play of life and happiness, guarded its flourishing empires. An essential element of nature, water, regulated terrestrial life; from the very beginning this element had entered into the composition of every substance, vegetable, animal and human. It formed the active principle of atmospheric circulation; it was the chief agent in the changes of climate and seasons; it was the sovereign of the terrestrial state. From century to century the quantity of water in the sea, the rivers and the atmosphere diminished. A portion of the rain water was absorbed by the earth, and did not return to the sea; for, instead of flowing into the sea over impermeable strata, and so forming either springs or subterranean and submarine watercourses, it had filtered deeper within the surface, insensibly filling every void, every fissure, and saturating the rocks to a great depth. So long as the internal heat of the globe was sufficient to prevent the indefinite descent of this water, and to convert it into vapor, a considerable quantity remained upon the surface; but the time came when the internal heat of the globe was entirely dispersed in space and offered no obstacle to infiltration. Then the surface water gradually diminished; it united with the rocks, in the form of hydrates, and thus disappeared from circulation. Indeed, were the loss of the surface water of the globe to amount only to a few tenths of a millimeter yearly, in ten million years none would remain. This vapor of water in the atmosphere had made warmth and life possible; with its disappearance came cold and death. If at present the aqueous vapor of the atmosphere should disappear, the heat of the sun would be incapable of maintaining animal and vegetable life; life which, moreover, could not exist, inasmuch as vegetables and animals are chiefly composed of water.[4] Footnote 4: