DEPOSITS OF SODA, ETC. 361 



miles from the sea the incrustations on the plain consist chietly of 

 sulphate of soda, with only seven per cent, of common salt, while 

 nearer to the coast the common salt increased to T^y parts in a hun- 

 dred. 



Deposits of Sodium Sulphate and Carbonate. 



In the Great Basin region of North America soda lakes are not 

 uncommon. In Wyoming lakes of this type form deposits on their 

 floors which contain 40 to 45 per cent, sodium sulphate, alternating 

 with clay layers. The Donney lakes contain a bed of soda 2 to 3 

 meters thick. At Wilmington a bed of natural soda more than four 

 meters thick was found at the bottom of the lake. Similar sedi- 

 ments are found in Mono Lake, California ; Albert Lake, Oregon ; 

 and Owens Lake, California. Sevier Lake, Utah, was covered m 

 January, 1880, by a crust of salt 10 to 12 cm. thick, beneath which 

 the following sediments occurred in descending order : 



Sodium sulphate 5 cm. 



Sodium sulphate with NaCl 2 cm. 



Sodium sulphate 5 cm. 



Gray clay with wood fibers 5 cm. 



Fine sand with fresh water shells 15 cm. 



This lake is at times entirely dry. Other lakes depositing sodium 

 sulphate are Altai Beisk, Domoshakovo, Kisil-Kull, and Schunett 

 lakes in Siberia. Great Salt Lake likewise deposits sodium sulphate 

 during the winter, even casting it up in heaps upon the shore (Gil- 

 bert-i8). Lakes depositing alkaline carbonates are also common. 

 They occur in Hungary, Egypt, Armenia, Venezuela, and in Utah, 

 California, and Nevada, especially in the playas of the last named 

 state. Those of the Soda Lakes near Ragtown, Nevada, may be 

 taken as typical, they having been worked for commercial pur- 

 poses. The sodium carbonate of these lakes is but slightly con- 

 taminated by sodium sulphate and chloride. These soda lakes gave 

 the following analyses, the first from Big, the others from Little 

 Soda Lake, the last being market soda (Clarke-ioi/p/; 226) : 



(I) (2) (3) 



NasCOa 45.05 44.25 52.20 



NaHCOs 34-66 3490 25.05 



Na2S04 1 . 29 o . 99 510 



NaCl 1. 61 1 . 10 3.31 



Si02 0.27 



Insoluble : .80 2.81 



H2O 16.19 1595 14.16 



99.60 100.00 100.09 



