KAWSOH MOUNTAINS. 773 



and finely-reticulated surfaces worn by the constant attrition of loose sands 

 driven by the prevailing westerly winds through the gap south of the 

 Truckee Range. 



Just east of Hot Spring Station, on the line of the railroad, and about 

 250 yards from a low basaltic ridge, occurs a group of six warm springs, 

 which reach the surface through the nearly horizontal Tertiary strata. The 

 waters are quite clear, palatable when cool, and free from any considerable 

 amount of saline ingredients. The main pool, 3 feet below the surface of 

 the ground, is nearly 3^ feet in diameter, and the only one having a tem- 

 perature up to the boiling-point. Thermometric observations gave, for the 

 remaining springs, temperatures varying from 189° to 158°. 



White alkaline efflorescences are found on the desert plains south of 

 the springs. One of these, analyzed by Prof. 0. D. Allen, yields : 



Chloride of sodium 95.67 



Sulphate of lime 1.63 



Water 0.73 



Insoluble residue 1.97 



100.00 



a quite pure salt, but the deposit is much too limited to be of any economic 

 value, where others of almost unlimited extent are so easily accessible. 



It seems evident that the sedimentary beds in the neighborhood of the 

 springs, although obscurely exposed, belong to the Miocene strata, present- 

 ing the same finely-comminuted material of volcanic tufas, and mor^ or less 

 compact sands, in which the microscope detects the same Infusorim as are 

 found in the beds at Fossil Hill. 



South of the Kawsoh Mountains, and separated from them by a narrow 

 pass connecting the Truckee Valley with the Carson Desert, lies an irreg- 

 ular group of hills, only the northern portion of which comes within the 

 limit of the map. They border on the Carson River, and, at their widest 

 part, measure about 9 miles. 



Geologically, they represent a continuation southward of the same 

 structure as the Kawsoh Mountains ; an underlying sedimentary series of 



