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below incandescence, and would be alternately obstructing and reflecting the sunlight in a series of eclipses and full moons.
    And so with a tremendous slowness through the vastness of time, the Earth would grow more and more like the Earth on which we live, until at last an age would come when, in the cooling air, steam would begin to condense into clouds, and the first rain would fall hissing upon the first rocks below. For endless millennia the greater part of the Earth's water would still be vaporized in the atmosphere, but there would now be hot streams running over the crystallizing rocks below and pools and lakes into which these streams would be carrying detritus and depositing sediment.
    At last a condition of things must have been attained in which a man might have stood upon Earth and looked about him and lived. If we could have visited the Earth at that time we should have stood on great lava-like masses of rock without a trace of soil or touch of living vegetation, under a storm-rent sky. Hotand violent winds, exceeding the fiercest tornado that ever blows, and downpours of rain such as our milder, slower Earth today knows nothing of, might have assailed us. The water of the downpour would have rushed by us, muddy with the spoils of the rocks, coming together into torrents, cutting deep gorges and canyons as they hurried past to deposit their sediment in the earliest seas. Through the clouds we should have glimpsed a great sun moving visibly across the sky, and in its wake and in the wake of the moon would have come a diurnal tide of earthquake and upheaval. And the moon, which nowadays keeps one constant face to Earth, would then have been rotating visibly and showing the side it now hides so inexorably.
    The Earth aged. One million years followed another, and the day lengthened, the sun grew more distant and milder, the moon's pace in the sky slackened; the intensity of rain and storm diminished and the water in the first seas increased and ran together into the ocean garment our planet henceforth wore.
    But there was no life as yet upon the Earth; the seas were lifeless, and the rocks were barren.

4
The Age of Fishes
    In the days when the world was supposed to have endured for only a few thousand years, it was supposed that the different species of plants and animals were fixed and final; they had all been created exactly as they are today, each species by itself. But as men began to discover and study the Record of the Rocks this belief gave place to the suspicion that many species had changed and developed slowly through the course of ages, and this again expanded into a belief in what is called Organic Evolution, a belief that all species of life upon Earth, animal and vegetable alike, are descended by slow continuous processes of change from some very simple ancestral form of life, some almost structureless living substance, far back in the so-called Azoic seas.
    This question of organic evolution, like the question of the age of the Earth, has in the past been the subject of much bitter controversy. There was a time when a belief in organic evolution was for rather obscure reasons supposed to be incompatible with sound Christian, Jewish and Moslem doctrine. That time has passed, and men of the most orthodox Catholic, Protestant, Jewish and Muhammedan belief are now free to accept this newer and broader view of a common origin of all living things. No life seems to have happened suddenly upon Earth. Life grew and grows. Age by age through gulfs of time at which imagination reels, life has been growing from a mere stirring in the intertidal slime towards freedom, power and consciousness.
    Life consists of individuals. These individuals are definite things; they are not like the lumps and masses, nor even thelimitless and motionless crystals, of non-living matter, and they have two characteristics no dead matter possesses. They can assimilate other matter into themselves and make it part of themselves, and