SPRINGS OF THE LAHONTAN BASIN. 



49 



post-Lahontan fault which is plainly shown by an irregular scarp, in some 

 places 20 feet high. 



Allen's Springs are situated on the southern border of South Carson 

 Lake at the base of a high basaltic butte which once formed an island in 

 Lake Lahontan. These springs at present are very small, the discharge at 

 the surface being less than half a gallon per minute. In this desert coun- 

 try even this meager supply is important, as it is the only drinkable water 

 within a radius of over twenty miles. These springs are of interest to the 

 geologist because of their antiquity. The amount of yellowish, porous, 

 tufa deposited about them indicates that the flow of water was formerly 

 more copious than at present, and at various times has issued from a num- 

 ber of orifices. Much of the tufa that is plainly a spring deposit is incrusted 

 with thinolite and dendritic tufa which we know was precipitated from the 

 waters of Lake Lahontan, and shows that the springs were in existence at 

 least as early as the middle Lahontan period. 



The Hot Spring, at Hot Spring station on the Central Pacific Railroad, 

 as shown by Dr. T. M. Chatard's analysis, has the following composition: 



Conetituents. 



Silica {Si02) 



AlnrainoiD ( Al) 



Calcium (Ca) 



Magnesium {Mg) — 



Potassinni (K) 



Lithum (Li) 



Sodium (Na) 



Chlorine (CD 



Sulphuiic acid (SO4) . 

 Oxygen* in SiOa 



Total 



One liter of 

 water con- 

 tains in 

 grammes — 



0. 2788 

 0. OOlO 

 0. 0305 

 0.0010 

 0. 0669 

 Trace. 

 0. 7743 

 0. 9679 

 0. 3555 

 0. 0194 



Per cent, in 

 total solids. 



11.14 



0.04 



1.23 



0.04 



2.69 



Trace. 



31.04 



38.79 



14.25 



0.78 



Constituents. 



2. 4953 



100. 00 



Silica (SiOj) 



Sodium .silicate (NaSiOs) 



Aluminum sulpliale (AI[S04]s) - 



Calcium sulpbato (CaSOa) 



Magnesium sulpliatc (MgS04) 



Sodium sulphate (NaSoj) 



Sodium chloiide ( XaCl) 



Potassium chloride (KCl) 



Probable com- 

 bination (in 

 grammes per 

 Eter). 



Total. 



0. 2060 

 0. 1480 

 0. 0063 

 0. 1037 

 0. 0050 

 0. 4039 

 1.4946 

 0. 1278 



2. 4953 



* Extra oxygen in silicate. 



^No carbonic acitl in residut^ left by evaporation. 



At a number of orifices the waters of this spring issue in a state of ac- 

 tive ebullition. When the openings become obstructed the steam escapes 

 with a hissing and roaring sound. The spring occurs in a line of recent 

 faulting, and has evidently been crowded southward as the deposits from 

 the waters closed the previous channels of discharge. On cooling, an 

 MoN. XI — 4 



