296 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



basin, Russell was unable to get any positive evidence of 

 two high-water periods, but as Gilbert remarks,' this may 

 easily be due to imperfection of exposure. 



The direct evidence of the coexistence of glaciers and 

 these Pleistocene lakes consists in the association of mo- 

 raines with the lake deposits. In the case of the Lahontan 

 basin no glaciers extended down to the lake level, but at 

 Lake Bonneville, Emmons and Gilbert describe moraines 

 which lie within the area of the lake beds. These moraines 

 were deposited by glaciers from the Wasatch Mountains. 

 From the field evidence Gilbert concludes that these mo- 

 raines were formed during the second high-water epoch, 

 but before the water was at its highest stage, since the 

 moraines do not show any trace of the Bonneville or 

 highest shore-line, as they probably would if they had been 

 formed previous to this highest stage of the water. 



At Mono Lake^ there are several moraines which extend 

 into the area formerly covered by the lake waters in 

 earlier Pleistocene time. On these moraines, both the 

 older and the newer according to Gilbert, the waves cut a 

 shore-line more or less distinct,^ showing that they had been 

 deposited before or during a high-water stage of the lake. 



Fossil shells from the Lake Bonneville beds of the 

 second high-water epoch were compared by Call* of the 

 Smithsonian Institution with recent shells of the same 

 species from Utah Lake, a fresh-water residual of Bonne- 

 ville, and were found to be smaller. Call also found that 

 the shells of fresh-water molluscs were of smaller size in 

 cold than in warm waters, hence the conclusion that the 

 water of Lake Bonneville at the second high-water stage 

 was colder than the water in the same region to-day. Sal- 

 inity also has a retarding influence on the growth of the 

 shells of fresh-water molluscs, but as Bonneville overflowed 

 in glacial times, it is fair to assume that the water was 

 fresh. 



1 Monograph I., U. S. Geol. Surv., 1890, p. 306. 



2 Russell, Eighth Annual Report, U. S. Geol. Surv., Part I, 1889, p. 369. 

 Gilbert, Monograph I, p. 311. 



s This was also noted by Clarence King. See Whitney, Climatic Changes, p. 51. 

 4 Bulletin U. S. Geol. Surv., No. ii, (884. 



