Page:Popular Science Monthly Volume 15.djvu/328

 its sediments the Humboldt Group. In the middle province was a smaller body of water called the North Park Lake, of which the area is underlain by beds to which the same name has been given by Hague and Hayden, while in the region of the Great Plains the Niobrara Group of Marsh was laid down in what King terms the Cheyenne Lake.

The details of the description of these Tertiary lakes, and of the history of their formation and disappearance, are among the many things which Mr. King's volume contains, that for want of space must be passed without notice.

—One of the most interesting chapters in Mr. King's volume is that which describes the records of the Quaternary age in the region which he surveyed. The salient points in this history are briefly as follows: Along the fortieth parallel in the far West during the glacial period there was no general glaciation, no continental ice-sheet, but glaciers formed on all the more important mountain-ranges, extending down from their summits to the level of from 6,000 to 9,000 feet above the sea. Traces of these ancient glaciers are seen in excavated lake-basins, glaciated valleys, and terminal and lateral moraines. The glaciers of the Uintah Mountains were by far the most important in all this region. Snow and ice crowned the Park and Medicine Bow Ranges, and extended down all the valleys which radiated from them; but the ice-covered area was small as compared with the great breadth of the country. The Uintah Mountains, however, according to Mr. King, then formed a broad-topped table-land 17,000 or 18,000 feet above the sea, all of which was one great ice-field, with local glaciers descending the valleys both toward the north and south. The whole length of the range was thus covered, and the ice-field had a north and south width of some fifty miles. Thus it formed a glacial area considerably larger than that of the Alps at present. West of the Great Basin, as we know from the reports of King and Le Conte, the Sierra Nevada was the theatre of glacial action on a still grander scale.

The topographical changes in the far West during the Quaternary age seem to have been numerous, but not consequent upon great disturbances, although this unquiet region has shown more or less of its instability to the present day. The changes which would most strike an observer were variations in the water-surface; for Mr. King, joining his observations to those of G. K. Gilbert, has shown that even as late as the Quaternary the Great Basin was a well-watered country, and contained two lakes, which in magnitude were scarcely exceeded by any of those now existing on the continent. Of these, one called by Gilbert Lake Bonneville, occupied the Great Salt Lake Valley, with a vast extension toward the south and west. Great Salt Lake occupies the deepest portion of its basin, and, with Utah and Sevier Lakes, represents the residue of its water after a long period of dryness, during which the evaporation exceeded the precipitation. The other great Quaternary lake of this region has been named by Mr. King