The coral reefs of Florida, built up at the rate of one foot in a century, each reef adding ten miles to the coast, have required, according to Agassiz, at least one hundred and thirty-five thousand years for building. Human remains in a bluff on the shores of Lake Monroe, in Florida, he shows to be at least ten thousand years old.
Under the streets of Glasgow, Scotland, seventeen canoes have been dug up, one in a vertical position, as if it had sunk in a storm, with the prow uppermost. Twelve canoes one hundred yards back from the river were found nineteen feet beneath the surface. Almost all were single oak trees, hollowed out by blunt tools, probably stone axes, aided by fire, relics of the stone age.
In caverns near Liège, France, human bones have been found, with the cave-bear, elephant, rhinoceros, and other species now extinct. Skulls found in these primeval caves, especially one near Düsseldorf, called the "Neanderthal," "is the most brutal of all known human skulls, resembling those of the apes." These rude men probably were living at the same time, or even later, than the makers of the "refuse heaps" of Denmark.
Wales has been under the sea to the depth of fourteen hundred feet, as proved by glacial shells; its submergence and reëlevation would require, by careful computation, about two hundred and twenty-four thousand years.
Lyell showed that the Alps, Andes, and Himalaya Mountains were all elaborated under water. "The Alps have acquired four thousand, and even, in some places, more than ten thousand feet of their present altitude since the commencement of the Eocene (dawn of recent) period.... It is not too much to say that every spot which is now dry land has been sea at some former period, and every part of the space now covered by the deepest ocean has been land. The present distribution of land and water encourages us to believe that almost every conceivable transformation in the external form of the earth's crust may have been gone through. In one epoch the land may have been chiefly equatorial; in another, for the most part polar and circumpolar."
Lyell showed also the great age of the world by the changes which have taken place in climate. In Greenland are a multitude of fossil plants, which show that it formerly enjoyed a mild and genial climate. Fossil tulip and walnut trees have been found within the Arctic circle.
"On the North American continent, between the Arctic circle and the forty-second parallel of latitude," said Lyell, "we meet with signs of ice-action on a scale as grand, if not grander than in Europe." The drift covered from the Atlantic border of New England and Labrador westward to Dakota and Lake Winnipeg, and farther north, across the continent. Some stones in this bed of ice were thirty feet square, weighing over four million pounds. Some boulders from the Alps, weighing three thousand tons each, are now found on the Juras. "It must, I think," said Lyell, "be conceded that the period required for the coming-on of the greatest cold, and for its duration when most intense, and the oscillations to which it was subject, as well as the retreat of the glaciers and the 'great thaw,' or disappearance of snow, from many mountain-chains where the snow was once perpetual, required not tens, but hundreds, of thousands of years."
In Arctic Siberia herds of elephants must have roamed, as their bodies, covered with hair and flesh, have been dug up in recent years. Great Britain and Europe have been much warmer than now. Our own immense coal fields show a former tropical climate, with their great tree-ferns and tree-rushes, while the remains of reindeers have been found in Connecticut.
No wonder Lyell became fascinated with the history of the changes of this planet, and the life of man before historic times. A great book seemed open to him, and he studied it by night and by day: the Archæan Time—no life; Paleozoic Time, including the Silurian Age, with its shells and trilobites; the Devonian, with its fishes; Carboniferous, with its coal plants; Mesozoic Time, including the Reptilian Age with its reptiles; Cenozoic Time, including the Mammalian or Tertiary, with its mammals, and Quaternary, or age of man. Paleozoic means "ancient life;" Mesozoic, "middle life;" Cenozoic, "recent life."
Lyell divided the Tertiary strata into three groups: Eocene, recent dawn; Miocene, less recent; Pliocene, more recent. In the Eocene Age Great Britain was sub-tropical, and, in North America, Vermont was like North Carolina in temperature. Then came the Glacial Period, with ice probably five thousand feet thick over New England. Then the Champlain Period, with its floods, continents depressed, and climate warm, followed in Europe by a second Glacial Period.