RELATION OF LAKES TO CLL>LVTIC CONDITIONS. 89 



salts to the waters flowing over them or percolating through their inter- 

 stices ; while the rocks of the eastern area are largely sedimentary in 

 origin, and supply sodium chloride in excess of sodium carbonate. 



The chemical history of the lakes of the Arid region is not only an 

 interesting and attractive study, "but one of great economic importance, 

 as they hold an ahnost uidimited supply of common salt, and of sodium 

 carbonate and l)i( ;ul)()natc, sodium sulphate, and other salts in less al)un- 

 dance. This su[)[)ly is still farther augmented liy the deposits of former 

 lakes now evaporated to dryness. The salts precipitated from these ex- 

 tinct lakes, i]i some instances, whiten the surfaces of desert valleys, but 

 more frequently they are buried beneath or absorbed in the clays forming 

 the smooth plains left l)y the evaporation of playa lakes. 



The importance of the lakes of the Arid region to those interested in 

 salt and alkali industries is so great that the table on page 72 has been 

 inserted to show the com[)arative values of the brines thus far analyzed. 

 More detailed information in this connection may be found in the publi- 

 cations cited below. ^ 



1 G. K. Gilbert, "Lake Bonneville." IJ. S. Geol. Surv., Monograph No. L — L C. Russell, 

 "Lake Lahontan," U. S. Geol. Surv., Monograph No. IL — L C. Ku.ssell, "Lake Mono," 

 r. S. Geol. Surv., 8th Ann. Kep., 1886-87, pp. 287-290. — L C. Kussell, " Reconnoissance in 

 Washington," V. S. Geol. Surv., Bulletin No. 108. —T. M. Chatard, "Natural Soda," U. S. 

 (ieol. Surv., Bulletin No. 60. — T. M. Chatard, " Analyses of the Water of Some American 

 Alkaline Lakes," Am. Jour. Sci., 3d Ses., vol. 36, 1888, pp. 146-150. —T. M. Chatard, 

 "Urano," Am. Jour. Sci., 3d Ses., vol. .38, 1889, pp. 59-66. —J. E. Talmage, "The waters 

 of Great Salt Lake," Science, vol. 14, 1889, pp. 444-446. — E. Waller, "Analysis of the 

 Water of Great Salt Lake," School of Mines [Columbia College] Quarterly, vol. 14, 1892, 

 pp. 56-01. 



