284 The Realm of Nature CHAP. 



steep front to the west, cut into by rugged transverse 

 valleys, with scenery of the wildest grandeur. Its highest 

 peak is Mount Whitney (14,900 feet), and at Mount Shasta 

 it passes into the Cascade Range, which runs northward, 

 diminishing in height, to Alaska, its chief summit being 

 Mount St. Elias (13,900 feet). Between latitudes 35 

 and 40 N. a lower mountain ridge, the Coast Range, joined 

 to the Sierra Nevada on the north and the south, encloses 

 a remarkable low plain, the Californian Valley, the rivers of 

 which find access to the sea through an abrupt gap near 

 the middle of the range. The eastern part of the centre 

 of the plateau between the Rocky Mountains and the 

 parallel Wahsatch Range, in longitude 112 W., forms 

 the most elevated region, and is crossed by the Uintah 

 Mountains, running from west to east. Cutting right 

 through the Uintah range, and southward across the 

 plateau to the Gulf of California, the great Colorado River 

 and its tributaries lay bare the structure of the rocks, 

 showing the horizontal sedimentary strata, interspersed with 

 outflows of basalt, based on a bed of Archaean gneiss. The 

 other great river of the Pacific slope is the Columbia, the 

 tributaries of which converge from all parts of the Rocky 

 Mountains, from near Mount Brown in the north to the 

 Wahsatch Range. In the north-west, where the low border- 

 ing ranges* spread out, the great Yukon flows down the 

 northern slope of the diminished plateau into Bering Sea. 

 Gold, and the ores of silver, lead, mercury, and copper, 

 occur very abundantly in the valleys and mountains of the 

 plateau. 



365. The Great Basin. Between the Wahsatch Moun- 

 tains and the Sierra Nevada the plateau sinks slightly into 

 a vast triangular area of internal drainage, known as the 

 Great Basin. It is most depressed near the sides, and 

 rises in the middle in a series of mountain ridges. In the 

 Quaternary period a wide sheet of water called Lake 

 Bonneville occupied the eastern depression, and its 

 shrunken remnant now forms the Great Salt Lake, at the 

 base of the Wahsatch Mountains. A smaller expanse 

 Lake Lahontan filled the western depression, which is 



