744 DESCEIPTIVE GEOLOGY. 



Near Brown's Station, opposite Humboldt Lake, a quantity of the 

 saline incrustation found covering the ground was collected, mixed with 

 the fine impalpable soil of the valley. On analysis, it yielded Mr. R "W. 

 Woodward the following composition : 

 Soluble in water, 27.71 per cent. 



Chloride of sodium 49.67 



Sulphate of soda 20.88 



Sesquicarbonate of soda 18.15 



Borate of soda 1 1.30 



100.00 

 The Carson Desert. — In its general features, the Carson Desert resem- 

 bles the depressed meridional valleys which lie between the parallel basin 

 ranges, covering, however, a much larger area, and extending from the Pah- 

 Ute Range westward to the Kawsoh Mountains, a distance of 40 miles. To 

 the north and south, it is rimmed in by low volcanic hills connecting the 

 main uplifts. Its average elevation may be taken at 4,000 feet, the lowest 

 portion in the region of Carson Lake standing about 3,875 feet above sea- 

 level, which agrees very closely with the elevation of Pyramid Lake and 

 the series of Mud Lakes to the northwest. Both Humboldt and Carson 

 Rivers empty into the Carson Lake; the former, receiving the drainage of a 

 large portion of Northern Nevada, brings down the greater part of the alka- 

 line accumulations that are deposited in the lake, while the latter taking its 

 rise in the sno^vy regions of the Sierras, although a very considerable stream, 

 has a much less tortuous course across the arid regions of the basin. Car- 

 son Lake, which receives these streams, is about 20 miles long by 12 wide, 

 and, although occupying a large superficial area, is undoubtedly a shallow 

 sheet of water varying each year, in its outlines. Its waters have never 

 been analyzed, but are probably quite similar in composition to those of 

 Humboldt Lake, except that having no outlet they possess a much greater 

 density. Completely encircling the lakejs a narrow belt of Lower Quater- 

 nary silts and fine gravels, which on the western side extend nearly up to 

 the base of the West Humboldt Range, with scarcely any vegetation but 

 alkaline grasses. On the opposite side of the lake is a chain of sand-dunes, 

 formed of the sands which the prevalent westerly winds have blown from 



