SALT LAKES AND SALINAS 357 



Of these, Elton Lake, a natural Ilittern with a salinity of 271 per- 

 mille, furnishes a good example. It lies in the flat clayey steppe, 

 has clay banks, a length of 18 km. and a width of 14 km. As 

 shown by the analyses in the table (p. 158, B2), it contains only o.i 

 per cent, of Ca, but 17.55 P^^ cent, of Mg. while the sodium is only 

 11.27 per cent. This is due to the fact that a part of the sodium 

 has crystallized out as NaCl, from a liquor formerly of much higher 

 salinity. Two layers of salt are found at the bottom of the lake, 

 the lower 2.5 cm., the upper 4 to 5 cm. thick. Analyses of these 

 salts gave the following: 



Upper Bed Lower Bed 



NaCl 87.08 90.50 



MgCh 3.25 2.17 



MgS04 0.53 0.47 



CaS04 1. 13 1-49 



H2O 6.85 3.51 



99.84 98.14 



Into this lake flows a small stream, the Chara Zacha, which an- 

 nually carries enough salt into the lake to make a crust 4 cm. in 

 thickness. 



Baskunchak Lake (Walther-6i '-jSj) , also in the Astrakhan dis- 

 trict of Russia, north of the present Caspian, is another example. 

 It lies on the eastern border of the Volga and has a length of 16 km. 

 and a breadth of 9 km. Analysis by Goebel ( i ) and Nikitinsky 

 (2) gave the following composition of the brine: 



(I) (2) 



NaCl.. 

 MgClj. 

 CaCh . 

 KCl . . , 

 MgS04 

 MgBr2 . 

 CaS04. 



97.803 98.68 



In the center of the lake was found a salt bed averaging 160 cm. in 

 thickness, the thickness at 500 meters from shore being considerably 

 over 2 meters. Eight distinct layers are recognizable, separated 

 by layers of clay. The upper layer contained 91 per cent. NaCl, 

 the second 95.4 per cent. NaCl, the fourth 97.2 per cent., the eighth 



