“Oh, tell us about that!”
“Some time!—The interior of the earth is still hot, but the rock crust allows very little of it to rise to the surface. After the Formative Era came the Archeozoic Era, when life began in the form of amœbas or some simple form of protoplasm. For with the formation of the gases of the earth mass into an envelope of air, to moderate the sun’s warmth by day and retain some of it by night,—life became possible.”
“But where did those first creatures come from?” Ted could not restrain himself from asking.
“According to one theory, the first germs of life flew here from some other planet, and not necessarily one of those revolving around our own sun, for space is full of suns and planetary systems. But that theory can neither be proved nor disproved. When I was a student, Osborn’s theory was the latest. That was in 1916. Without going into it too deeply, it had to do with the electric energy of the chemical elements that compose protoplasm, and these always had been latent in the earth mass.”
“Then they must have been latent in the sun, too,” marveled Ted. “And in other suns and their planets too.”
“Very likely,” assented the Geological Survey man. “Now of course the ocean waters collected in the depressed areas over the heavier rock bottoms, the basalt. You remember just after we lost the burro we were on a basalt formation––”
“Then that was formerly a part of the ocean floor?” asked Ted.
“Either that or volcanic lava.”
“But how did it––”
“Just a minute. Of course land masses have gone down as well as up, but the general trend has been decidedly upward, while the trend of the ocean floor has been downward. At that, the shell of the earth—so to speak—is only about 150 miles thick or a fiftieth of the earth’s present diameter.”