THE ]S"ON-GLACIAL ORIGIN" OF THE LAKES OF CALIFORNIA. 93 



them from the non-glaciated? In the use of the phrase "characteristic 

 features," it is not intended to inchide such phenomena as have been fully 

 indicated above as being the legitimate work of the glacier, but to suggest 

 the possibility of other more obscure and uncertain results of ice-work which 

 may not reveal themselves at once to the observer, but which, on the other 

 hand, may be deciphered by a careftd study of the topographical features of 

 the regions in which ice has been shown to have done geological work in 

 former times. Among such results might be the occurrence of lakes, to which 

 reference has already been made, or peculiar forms of the cross-sections of 

 the valleys, or the terraced arrangement of the detrital materials; and in 

 reference to each of these topics some remarks will here be made, which 

 may be taken as supplementary to anything which may have been said on 

 the same subjects in previous pages. 



In regard to the formation of certain lakes partly or wholly through the 

 agency of ice a few words may here be introduced. And first with reference 

 to what has more especially come under the writer's own observation, in 

 California and the Great Basin. All the important lakes of Cahfornia are 

 strictly of orographic origin ; that is to say, the water which fills them 

 occupies portions of depressions wdiich have been produced, not by eroding 

 agencies of any kind, but by the same crust movements which have given 

 rise to the mountains and valleys. We find lakes of this kind somewhat 

 abundant in California, and in all stages of progress toward entire desicca- 

 tion, as will be set forth in the next chapter. Most of these lakes belong to 

 the Great Basin system ; they are to the east of the main divide of the 

 Sierra Nevada, or entirely to the south of that chain. These will be noticed 

 more fully in connection with the phenomena of their gradual diminution, as 

 indicating one of the most general and important climatic changes of later 

 geological times. 



The Coast Ranges of California enclose within their limits but very few 

 lakes, either large or small. South of San Francisco Bay, indeed, there is 

 hardly a single body of water worthy of being called a lake. This is naturally 

 to be expected, since the rocks are, almost everywhere, very pei-meable, the 

 precipitation moderate, or even small in the southern portion of the State, 

 and the evaporation large. Clear Lake offers a striking exception, and is the 

 only body of water of any importance within the Coast Eange system. It 

 is clearly of orographic origin, and it marks the temnination of the volcanic 

 formations on the north. 



