DEPOSITION OF SALT BEDS 1 3 



in addition, of chloride of sodium, chloride of lime, chlo- 

 ride of potassium and bromide of magnesium. Similar 

 conditions exist in lakes Elton and Bogdo which lie be- 

 tween the Volga and Ural rivers in a broad steppe in which 

 there is a rock-salt deposit. From this a number of streams 

 carrying salt flow into these lakes. As they have no outlet 

 and the water which comes in is removed by evaporation 

 the salt separates upon the bottom and borders of the lakes 

 in solid beds. The streams bring into the lakes chloride 

 of potassium, and sulphate of magnesium, beside chloride 

 of sodium, as well as mud in the spring time. The latter 

 forms thin layers between the strata of salt, while the more 

 easily soluble salts have enriched the lake water to a con- 

 centrated mother liquor, which in the Elton lake contains 



Sulphate of Magnesium 5 . 32 



Chloride of Sodium 3.83 



Chloride of Potassium .23 



Chloride of Magnesium 19-75 



Water 70.87 



100 . 00 



The Great Salt Lake in Utah is also a saturated brine de- 

 positing salt, as proved by the incrustations of salt about its 

 margin in dry seasons. 



As an example of the continuous deposit of salt in a basin 

 where evaporation and separation of salt is continually re- 

 placed by an influx of sea water over or through a sand bar ; 

 we may mention the Adschi-Darga bay of the Caspian Sea, 

 of which the bottom is covered with a continually thickening 

 deposit of salt and gypsum. 



The formation of salt beds in the geological past must 

 have occurred in a precisely similar manner and conse- 

 quently they represent former inland seas, or bays cut off 

 from the ocean by the upheaval of sand bars and of which the 

 fluviatile or marine influx contained salt in solution, but yet 

 was not greater in quantity than the amount of the evapo- 

 ration from the basin. From this it is evident that the con- 



