48 GEOLl GICAL HISTORY OF LAKE LAHONTAN. 



water is subjected during its underground passage render it an active 

 solvent. Hot springs are therefore frequently charged with a great variety 

 of mineral substances in solution. 



The Lahontan basin, in common with the entire northern half of the 

 Great Basin (the southern portion not being so thoroughly explored), is 

 remarkable for the number of springs which rise from a great depth throiigh 

 fissures. These almost invariably occur along lines of displacement, and 

 range in temperature from 50° or 60° F. up to the temperature of boiling- 

 water for the elevation at which they occur. 



The springs of the Lahontan basin are indicated on the accompanying 

 map, Plate VlII; their maximum temperature when known being shown 

 by figures in red. 



As springs performed an important part in the history of Lake Lahon- 

 tan, we shall devote a few pages to the description of those now rising in 

 its basin. A knowledge of the phenomena they now present will assist in 

 interpreting the records of the similar springs that flowed long ago. 



Beginning at the south, the first group of springs requiring notice is 

 found in the northern part of Mason Valley, about one mile northward of 

 Wabusca station. These springs occur in circular basins, sometimes at the 

 tops of low mounds, and are of all degrees of temperature, from about the 

 mean of the region up to 16-° F. The water flowing from them is clear 

 and spArkling, but is somewhat alkaline to the taste, and contains a small 

 percentage of sulphate and carbonate of soda, common salt, etc. The water 

 collecting in small basins on the desert is evaporated, and has foi'med a 

 saline deposit of considerable extent, a section of which is given below: 



White, hard crust of sulphate of soda, with couuuou .salt, some calcium carbon- 

 ate, etc inches . . 1-2 



Soft, mealy or clayey deposit of sodium sulphate, calcium carbonate, calcium 



sidphate, etc . inches.. 2-7 



Clear transparent crystals of sodium sulphate, with some earthy imi)urities, rest- 

 ing on saline cluy feet . . 6-S 



The svtrface of the desert about the more abundant accumulation of 

 salts is covered over a large area with a white saline efflorescence. These 

 springs occur in an east and west line, that coincides with the course of a 



