DEPOSITION OF SALT BEDS I I 



is sufficient to cause the sulphate of lime to crystallize as 

 anhydrite. This condition would exist at the bottom of a 

 lake 325 feet deep. 



Finally, if the waters of the inland sea, upon the bottom of 

 which the deposit of rock-salt is taking place, contain in solu- 

 tion beside chloride of sodium and sulphate of lime other more 

 soluble salts, such as the chlorides of magnesium, potassium 

 and lime, and the sulphates of potash, soda and magnesia, 

 these will be concentrated in the waters diminishing in bulk 

 by evaporation, and by constant separation of the chloride 

 of sodium a mother liquor is formed from which, when the 

 evaporation is complete, they separate as a solid mass and 

 sink to the bottom. 



By the drying up of an inland sea, originally containing 

 salts in solution, according to the principles above noted a 

 deposit of gypsum would first separate, then a complex 

 layer of rock-salt with thin layers of clay, marl or gypsum, 

 and finally on the top a layer of the more easily soluble 

 sulphates and haloid salts. These conditions would, how- 

 ever, produce salt deposits of comparatively small thickness 

 since they are limited to the separation of salt from the sea 

 water contained in a basin which is drying up. The exist- 

 ence of deposits of salt, such as those of Stassfurt and 

 Sperenburg in Germany which have a thickness of 1470 

 and 3600 feet could only be possible in connection with a 

 continual influx of salt water. This might be due to rivers, 

 as in the case of the Dead Sea, or to the cutting off of bays 

 and gulfs of considerable depth by sand bars, over which 

 only as much sea water can enter as is evaporated from 

 the surface. In this way beds of salt may be formed, of 

 which the thickness depends only upon the duration of 

 the conditions which cause the separation of the salt. Such 

 a continuous process of deposition aided by rivers carry- 

 ing salt in solution goes on in the Dead Sea. The waters 

 of the latter are in the condition of a mother liquor, result- 

 ing from a long continued evaporation of salt water. Of 



