“Because of the wing-flapping?”
“Yes, for one reason. But the pterodactyls might have developed that. Indeed, some of the little ones may have been able to flap. It was the cold that first gave the birds their real start.”
“The Ice Age?”
“Not the one you mean, Perry, but the second Ice Age, at the end of the Age of Chalk. It makes the geological history of the world a great deal easier to remember, if you divide it into the three great Ages of Ice. The first came at the end of the Coal-Forest time or the Carboniferous Period and closed the Empire of Fishes and Amphibians; the Second Age of Ice came at the end of the Age of Chalk, or the Cretaceous Period, and it closed the Empire of Reptiles; the Third Ice Age came at the end of the Pliocene Period and it closed the Empire of the Beasts. As the Ice-sheet of the Glacial Epoch slowly drew back toward the North Pole, Man took his place as the leader of Life.”
The boy looked up quickly.
“That’s a dandy division, Antoine,” he said; “it’s heaps easier to remember that way. And you say it was the Second Ice Age that shoved the birds ahead?”
“Yes, yes. During the Age of Chalk, nearly all Europe was under a warm sea. There were millions of little sea-creatures with shells, in those tepid waters. Sea-shells, you know, are made out of the lime that is dissolved in the sea, but after that lime has been made into a sea-shell it does not dissolve. These billions of microscopic shellfish lived, made their homes and died, so that their shells rained continually through the water to the ocean floor, and, inch by inch, the accumulated shells made deep beds of lime or chalk. Some beds are hundreds of feet thick.
“Slowly, slowly, the bed of the ocean rose, until it came near the surface of the sea. Still it rose, throwing off the water that had covered it. The oceans rushed into a new bed, and Western America, Southern Europe and Southern Asia rose above the water for the last time, much in their present outlines.
“The changes of the earth’s crust made numberless volcanoes, especially in those parts of the earth that had just appeared above the surface. In the glare of eruptions that never stopped, amid the thunder of vast explosions, the hissing of great geysers and the unceasing growl of earthquakes, the land grew higher and higher above the sea, and the world grew colder and colder. It was the end of the Empire of Reptiles.”
“Ah!” exclaimed Perry, remembering his dream.