AQUEOUS AGENCIES. 7? 



either, a, by indefinite concentration of river water in a 

 lake without outlet ; or, b, by isolation of a portion of 

 sea water by movement of the earth's crust (upheaval of 

 sea bed). The salt lakes scattered over the Nevada 

 Basin e. g., Pyramid, Winnemucca, Carson, Humboldt, 

 and Walker Lakes, etc. probably belong to the former 

 class, for some of them are but slightly salt even yet. 

 Great Salt Lake has been regarded as belonging to the 

 latter class, but if it once had an outlet, as now seems 

 certain, it must have been formed like all the other lakes 

 in this region. The Dead Sea, from the composition of its 

 water, is regarded as an example under the second class. 

 The Caspian is usually regarded as an example under the 

 first class, for, though it has apparently dried away from 

 much greater dimensions, yet its waters are much less 

 salt than those of the ocean. Nevertheless, there are 

 some reasons for thinking that the Caspian was once con- 

 nected with the Black Sea and with the Arctic Ocean. 



Alkaline Lakes. Saline lakes are of two principal 

 kinds, salt and alkaline. All those mentioned above are 

 salt. Alkaline lakes are rare ; they are found in Hungary, 

 Lower Egypt, and especially in Nevada and California. 

 The largest of these are Lakes Mono and Owen, both in 

 California. The waters of Lake Mono are a strong solu- 

 tion of sodic carbonate (sal-soda), with some carbonate of 

 lime, borax, and salt. Lake Owen contains about equal 

 parts of soda and salt. Salt lakes may be formed in either 

 of two ways, but alkaline lakes in only one viz., by in- 

 definite concentration of river or spring water in a lake 

 without an outlet. If in the river or spring water alkaline 

 chlorides predominate, the lake will be salt ; if alkaline 

 carbonates predominate, it will be alkaline. 



Borax Lakes. These are still rarer than alkaline 

 lakes. They ;ire found only in Thibet and in California 

 and Nevada. Borax lakes are of course formed only by 

 concentration of spring water. 



