314 OKNITHOLOGY. 



This re<;ion constitutes tlie uorthern portion of what was at first designated as 

 the "Great Easin," the high plateau, without outlet for its waters, separated on the 

 north by low divides from the valley of the Snake Kiver and continuing southward 

 until it merges into the desert of the Lower Colorado. Geologically considered, how- 

 ever, as well as botanically, the term is now properly made to include the whole similar 

 arid stretch of country northward to the plains of the Columbia, in latitude 48'=. 



The lofty and unbroken range of the Sierras bounds this section of the Basin 

 on the one side by its steep eastern slope, entering Nevada at only a single point, 

 where it throws over the border a high Qanking-spur, the Washoe Mountains. On the 

 opposite side lies the broad and nearly equally elevated system of the Wahsatch, 

 broken through by the Bear, Weber, and Provo Rivers, which head among the peaks 

 of the adjoining Uintahs. The intervening space, 4(>0 miles broad in latitude 42°, bufc 

 narrowed by the convergence of the opposing mountains to about 200 miles in latitude 

 31°, is for the most part occupied by numerous short and somewhat isolated minor 

 ranges, having a general north and south trend, and at average distances of about 

 twenty miles. The bases of these ranges are usually very narrow, even in the most 

 elevated, rarely exceeding eight or ten miles in breadth, the slopes abrupt and the lines 

 of foothills contracted, the mesas grading at a low and nearly uniform angle into the 

 broad uninterrupted valleys. Over the larger portion of the territory, and especially 

 in Nevada, the combined areas of the valleys and the area occupied by the mountains 

 and accompanying foothills are very nearly equal. The main depressions within this 

 region are two, one at the base of the Sierras at a level of about 3,850 feet above the 

 sea, into which flows all of drainage there is from the whole northern half of Nevada 

 and from the eastern slope of the Sierras, the other the "Great Salt Lake Basin," at an 

 altitude 400 feet greater, close upon the base of the Wahsatch and receiving the waters 

 from that range above latitude 40° and from the northeastern portion of the Uintahs. 

 Into the first How the Truckee, Carson, Quinn's, and Humboldt Rivers. The TrucUee 

 is a cleir, cold stream, which issues from Lake Tahoe in the Sierras, and after a rapid 

 descent breaks through the Virginia Mountains and turning north soon em[)ties into 

 Pyramid and Winuemucca Lakes. These are much the deepest of all the lakes of the 

 Basin, being hemmed in by mountains, and are moderately saline. The Carson River 

 also rises in the Sierras farther to the south, but after leaving the base of the moun- 

 tains is a less rapid stream and gradually becomes somewhat alkaline. Inclining more 

 to the eastward it forms a small shallow lake on the border of Carson Desert, and 

 thence issues in a number of devious channels, and is finally spent in an extensive 

 '•sink'' or alkaline mud-plain of some twenty or thirty miles in diameter. Of a like 

 character are the "Mud Lakes," lying north of Pyramid Lake and fed by Quinn's 

 Kiver, which has its source in southeastern Oregon. Beyond the limits of the survey 

 to the south are Walker's and some other smaller lakes, supplied by streams from the 

 Sierras, but all strongly saline. 



From this western depression the general level of the country rises gradually to 

 the eastward very nearly to the border of Nevada, where the valleys have an altitude 

 of about G,000 feet. Here in the northeastern part of the State the Humboldt River 

 takes its rise, by far the most important river of the Basin, not only as the longest but 

 as opening a ()assage for three hundred miles to the Central Pacific Railroad through 

 the mountain ranges, that would otherwise have jirovcd a serious obstruction. It is 

 nowhere a large stream, receives few afQuents, and in some parts of its course is very 



