Millions of years pass,—and when we look through our telescope again the country has so changed that we cannot recognize it. Instead of being hotter than now, it is colder. Most of it, in fact, has disappeared, under an immensely thick sheet of ice. This icy mantle covers nearly all Canada, and a great part of the United States. Its edge advances, century after century, farther and farther south, slowly but surely, wiping out forests, grinding and grooving the rocks underneath, as glaciers always do. Then it slowly retires,—through more centuries,—advances again, and again withdraws to the north. A third time the land is covered before the final retreat of the Arctic ice.
How did this happen? Most likely by the surfaces of the earth and sea-bottom in these northern parts rising many hundred feet and then sinking, to rise and sink again and again. In some parts of the world even now the level of the land is rising, in others falling; and wherever the land is high enough to-day, with a considerable snowfall, we know it is always covered with snow and ice, summer and winter.
Let us take a look at our country as it was when the second ice-cap had melted and the last had not yet formed.
The monsters have gone, for ever vanished from the earth. Gone are the tree-ferns and towering palms. New birds have come, like those we know, and sing among trees and shrubs of the kind still growing around us. The hairy rhinoceros, the mammoth and the mastodon, thunder over the grassy plain. We see our northern musk ox grazing as far south as Kentucky and Tennessee.
We look for men and find none at all. Not one man, woman or child, in all these two vast continents. Fifteen million square miles, empty and waiting, all ready for man, but waiting for him in vain; perhaps till even the last and smallest of the ice-caps has disappeared.
Far away in the north-west the land comes to an end; but looking over the water we see the coast of Asia only sixty miles off, with a convenient little group of islands half-way over. There is nothing to prevent man from coming over in a canoe in summer, or on the ice in winter.
LOOK far enough, and we see him, a wanderer with his little family, starting from the heart of Asia, hunting and fishing as they go, camping for a few years or a century in one place, moving on when their number increases and food is not enough for all, or when some other tribe comes up behind and drives them on,—moving on, and on, and on,—a few families at a time or hundreds together. They belong, as all the American “Indians” do, to one great human stock that spread out east and west along the northern lands of Asia and Europe, where their closest kin to-day are found among the tribes of North Siberia and the Lapps of Russia and Norway. Another branch of the same ancestral stock settled in China, where it made many new inventions and slowly built up a civilization of its own, with high achievements in literature and art. But our “Indians” must have broken away long before that, for they had none of these inventions to bring with them,—not even that of the wheel, either for vehicles, for spinning, or for pottery; though the wheel was in common use among the Chinese and other old-world races thousands of years ago.