If we advance into the future a period of one or two million years, we witness a vast flux and reflux of life and things. How many times in this period of ten or twenty thousand centuries, how many times have the waves of the sea covered the former dwelling-places of man! How many times the earth has emerged anew, fresh and regenerated, from the abysses of the ocean! In primitive times, when the still warm and liquid planet was covered only by a thin shell, cooling on the surface of the burning ocean within, these changes took place brusquely, by sudden breaking down of natural barriers, earthquakes, volcanic eruptions, and the uprising of mountain ranges. Later, as this superficial crust grew thicker and became consolidated, these transformations were more gradual; the slow contraction of the earth had led to the formation of hollow spaces within the solid envelope, to the falling in of portions of this envelope upon the liquid nucleus, and finally to oscillating movements which had changed the profile of the continents. Later still, insensible modifications had been produced by external agents; on the one hand the rivers, constantly carrying to their mouths the débris of the mountains, had filled up the depths of the sea and slowly increased the area of the dry land, making in time inland cities of ancient seaports; and on the other hand, the action of the waves and of storms, constantly eating away the shores, had increased the area of the ocean at the expense of the dry land. Ceaselessly the geographical configuration of the shore had changed. For the historian our planet had become another world. Everything had changed: continents, seas, shores, races, languages, customs, body and mind, sentiments, ideas—everything. France beneath the waves, the bottom of the Atlantic in the light of the sun, a portion of the United States gone, a continent in the place of Oceanica, China submerged; death where was life, and life where was death; and everywhere sunk into eternal oblivion all which had once constituted the glory and greatness of nations. If today one of us should emigrate to Mars, he would find himself more at home than if, after the lapse of these future ages, he should return to the earth. [Illustration] CHAPTER III. While these great changes in the planets were taking place, humanity had continued to advance; for progress is the supreme law. Terrestrial life, which began with the rudimentary protozoans, without mouths, blind, deaf, mute and almost wholly destitute of sensation, had acquired successively the marvellous organs of sense, and had finally reached its climax in man, who, having also grown more perfect with the lapse of centuries, had risen from his primitive savage condition as the slave of nature to the position of a sovereign who ruled the world by mind, and who had made it a paradise of happiness, of pure contemplation, of knowledge and of pleasure.