rence on the north, and a similar estuary of the embryo Connecticut on the west (Fig. 67). Toward the close of this reign the continent had assumed the similitude of its present form and extent (Fig. 77). The Atlantic coast stretched from the neighborhood of New York City to the Delaware River, and thence southwestward to South Carolina, along a line now sixty or seventy miles inland. Delaware and Chesapeake Bays were consequently out at sea, and the Delaware River emptied into the Atlantic at Trenton. From South Carolina the shore-line turned gradually westward, and crossed the States of Georgia, Alabama, and Mississippi at the distance of one or two hundred miles from the present gulf coast. A deep bay set northward along the future valley of the Mississippi River as far as the mouth of the Ohio, or beyond, so that at this time the confluence of those two rivers was at their mouth. West of the Missouri was a vast inland sea or elongated gulf, which stretched along the eastern flanks of the Rocky Mountains to the Arctic Ocean. This gulf was perhaps interrupted at one or two places by spurs of the mountains. Into this gulf emptied the Athabasca, Slave, and Great Bear Lakes. The upper watershed of the present Missouri was beneath the sea; and the basin of the Mississippi was more limited in extent than that of the Ohio, which probably was the larger stream. West of this Mediterranean Gulf was a broad belt of land stretching from the isthmus far to the northwest, and probably to Behring's Straits, if not across them. The Pacific coast was a hundred and fifty miles farther inland than at present. Lake Superior was the only one of the great lakes then in existence. The stream which drained it wound past the future sites of Detroit, Cleveland, and Buffalo, and, plunging over the escarpment near Lewiston, became the ancestor of the present St. Lawrence. The basins of the other lakes are the result of

later geological agencies. Probaly large portions of Greenland and other arctic lands had emerged, besides the principal portion of the West India Islands.

The climate of the period was much warmer than that of the same localities in the present age. Coral-builders, and other marine animals now restricted to tropical regions, then flourished throughout the whole length of the continent, from latitude 60° north to the Straits of Magellan on the south. The superior warmth of former ages of the world is probably due, in some measure, to the more highly heated condition of the globe-a source which, through all ages, has been undergoing a gradual diminution. It has also been suggested that the connection which existed between the Gulf of Mexico and the Arctic Ocean permitted the Gulf Stream to flow through the centre of the continent, and thus, while it carried a tropical temperature far toward the north, ameliorated the climate of the regions to the east of it, as the same ocean stream now moderates the cold of high latitudes upon European shores. Thus, while the Northern States were terra firma, the rich cotton-fields of Alabama and Texas were gathering their calcareous sediments beneath the Gulf of Mexico. Fleets might have sailed over the rolling prairies of Kansas and Dacotah, and the anchor of the mariner might have fastened in the summit of Pike's Peak. But fleets of Nautili, and their cousins the Ammonites, were the only keels that plowed that Mediterranean sea, and the polyp and the oyster were the only mariners that cast their anchor on the sunken ridges. Eastward, the broad rolling plains of Illinois and Ohio were adorned with a growth of sub-tropical vegetation, and the west wind of even a winter sky breathed softly over its never-fading foliage. But the shining cities of the West were not there. The kingly alligator alone disturbed the waters of the Ohio. The railroad car, the church spire, the

golden wheat, the thronging population-these all were scenes and objects still shut up in the silence and night of the far-distant future. An intelligent being may have stood on the bank of the river, and pictured to himself the shifting scenes of the next half million of years, as we now portray to imagination the expansion of American civilization, and its destined continental grasp of empire a hundred years hence; but no intelligent hand impressed its influence upon the features fashioned by Nature. An occasional voice of monstrous Deinosaur broke the dreadful

silence of the broad continent. No song of bird was heard in the grove, and rarely the hum of insect in the air. Bland as the breezes were, and seductive the dimate, it was not a fit place for man to be in. Frogs and salamanders must be his pets-lizards and crocodiles his domestic animals. Providence reserved him for a more finished condition of the world.

1

CHAPTER XVIII.

THE REIGN OF MAMMALS.

ANOTHER cycle of eternity was past.

The progress

of geological agencies had brought the crust of the earth to a tension which was to be relieved by another collapse. As the Paleozoic Time was closed by the sudden sinking of the beds of the Atlantic and Pacific Oceans, and the corresponding protrusion of the ridges of the Appalachians, so the Mesozoic Time was closed by a farther progress in the same direction. The ever-shrinking nucleus necessitated the ever-enlarging wrinkles of the enveloping crust. The furrows must deepen and the folds must rise. The uplift which marked the close of Mesozoic Time affected the whole continental body. It was not a sudden uprising accomplished in a day. It may have extended through a century; but it was an interval of movements so much accelerated as to mark a pretty definite boundary between two stages of continental development and two great periods in the history of the world. During the Cretaceous Age which had now just closed, the great Mediterranean Gulf represented in Fig. 77 had been broader along its eastern borders, and continuous to the Gulf of Mexico. Through this, perhaps, the Gulf Stream had coursed to the Frozen Ocean. Now, by an upheaval of the central region, this gulf was severed in twain. On the south it retreated to nearly the modern limits of the Mexican Gulf, while northward remained an elongated body of water, swelling out in the central portion of the continent, in two places, to dimensions exceeding the Caspian and

Black Seas of the Old World. Indeed, the area covered by this shallow expanse of deserted and isolated sea-water was the Lectonia of the New World, which, like the level region in the south of Russia, once overflowed by the higher waters of the great seas which stretch along the confines

Fig. 77. Outlines of the North American Continent at the end of Mesozoic Time. The existing boundaries are indicated by dotted lines.

a, a, a. The great Tertiary Sea, stretching from the Arctic Ocean, along the eastern flanks of the Rocky Mountains, to Texas. b, b. The great "Central Plateau," in modern times a worn-out continental area.

of the two continents, was destined to be gradually drained. The drainage in both cases was effected partly by the upraising of the continent, and partly by the bursting of barriers and deepening of channels at the point where the imprisoned waters were escaping. But, while the drainage