Like changes had taken place in the animal kingdom. Animal forms had been greatly modified. The wild species had either disappeared or been domesticated. The scarcity of water had modified the food of herbivora as well as carnivora. The most recent species, evolved from those which preceded them, were smaller, with less fat and a larger skeleton. The number of plants had sensibly decreased. Less of the carbonic acid of the air was absorbed, and a proportionally greater quantity existed in the atmosphere. As for the human race, its metamorphosis was so absolute that it was with an astonishment bordering on incredulity that one saw in geological museums fossil specimens of men of the twentieth or one hundredth century, with great brutal teeth and coarse intestines; it was difficult to admit that organisms so gross could really be the ancestors of intellectual man.
Though millions of years had passed, the Sun still poured upon the Earth almost the same quantity of heat and light. At most, the loss had not exceeded one-tenth. The only difference was that the Sun appeared a little yellower and a little smaller.
The Moon still revolved about the Earth, but more slowly. Its distance from the Earth had increased and its apparent diameter had diminished. At the same time the period of the Earth’s rotation had lengthened. This slower rotatory motion of the Earth, increase in the distance of the Moon, and lengthening of the lunar month, were the results of the friction of the tides, whose action resembled that of a brake. If the Earth and the Moon last long enough, and there are still oceans and tides, calculation would enable us to predict that the time would come when the periodic time of the Earth’s rotation would finally equal the lunar month, so that there would be but five and one-quarter days in the year: the Earth would then always present the same side to the Moon. But this would require more than 150 million years. The period of which we are speaking, ten million years, is but a fifteenth of the above; and the time of the Earth’s rotation, instead of being seventy times, was only four and one-half times greater than it now is, or about 110 hours.
These long days exposed the Earth to the prolonged action of the Sun, but except in those regions where its rays were normal to the surface, that is to say in the equatorial zone between the two tropical circles, this exposure availed nothing; the obliquity of the ecliptic had not changed; the inclination of the axis of the Earth being the same, about two degrees, and the changes in the eccentricity of the Earth’s orbit had produced no sensible effect upon the seasons or the climate.
The human form, food, respiration, organic functions, physical and intellectual life, ideas, opinions, religion, science, language—all had changed. Of present man almost nothing survived.
IV
The last habitable regions of the globe were two wide valleys near the equator, the basins of dried up seas; valleys of slight depth, for the general level was almost absolutely uniform. No mountain peaks, ravines or wild gorges, not a single wooded valley or precipice was to be seen; the world was one vast plain, from which rivers and seas had gradually disappeared. But as the action of meteorological agents, rainfall and streams, had diminished in intensity with the loss of water, the last hollows of the sea bottom had not been entirely filled up, and shallow valleys remained, vestiges of the former structure of the globe. In these a little ice and moisture were left, but the circulation of water in the atmosphere had ceased, and the rivers flowed in subterranean channels as in invisible veins.
As the atmosphere contained no aqueous vapor, the sky was always cloudless, and there was neither rain nor snow. The sun, less dazzling and less hot than formerly, shone with the yellowish splendor of a topaz. The color of the sky was sea-green rather than blue. The volume of the atmosphere had diminished considerably. Its oxygen and nitrogen had become in part fixed in metallic combinations, as oxides and nitrides, and its carbonic acid had slowly increased, as vegetation, deprived of water, became more and more rare and absorbed an ever decreasing amount of this gas. But the mass of the Earth, owing to the constant fall of meteorites, bolides and uranolites, had increased with time; so that the atmosphere, though considerably less in volume, had retained its density and exerted nearly the same pressure.
Strangely enough, the snow and ice had diminished as the Earth grew cold; the cause of this low temperature was the absence of water vapor from the atmosphere, which had decreased with the superficial area of the sea. As the water penetrated the interior of the Earth and the general level became more uniform, first the depth and then the area of seas had been reduced, the invisible envelope of aqueous vapor had lost its protecting power, and the day came when the return of the heat received from the sun was no longer prevented, it was radiated into space as rapidly as it was received, as if it fell upon a mirror incapable of absorbing its rays.
Such was the condition of the Earth. The last representatives of the human race had survived all these physical transformations solely by virtue of its genius of invention and power of adaptation. Its last efforts had been directed toward extracting nutritious substances from the air, from subterranean water, and from plants, and replacing the vanished
