DYNAMICAL GEOLOGY. 219 



in volume, and the salt deposits steadily accumulating in its 

 shallow offshoot called the Karaboghaz. 



Gilbert arrived at a similar conclusion with regard to the 

 Great Salt Lake of Utah. The surface of this lake is now at a 

 height of 4,250 feet above sea-level, but old lacustrine terraces 

 are present at higher levels round its margins, the highest being 

 940 feet above the present surface-level. Gilbert explains the 

 shrinkage in the size of the lake as a result of local meteoro- 

 logical changes. Owing to the diminution in the rainfall and 

 in the volume of inflowing rivers, the surface of the lake sank 

 below its former outlet, and the lake-water became more and 

 more saline until it arrived at its present degree of concentration. 



The most complete accounts of the Dead Sea and its salt 

 formations are those given by O. Fraas and L. Lartet. The 

 deposition of salt and gypsum takes place every summer, when 

 evaporation is rapid, and a layer of mud is deposited during 

 the intervening period of diminished evaporation. 



Geologists early recognised the agreement of the chief 

 products of super-saturation of existing sea-water and salt lakes 

 with the layers of rock-salt in ancient geological formations of 

 the crust. Fichtel (anfe, p. 88) had expressed the view that 

 the Transylvanian salt-deposits represented evaporation pro- 

 ducts formed from sea-water, which had found ingress into 

 underground cavities after the consolidation of the crust. The 

 upright position of salt-veins at Bex, in the Rhone Valley, led 

 the younger Charpentier to the conclusion that the salt must 

 have originated from sublimation in crust-fractures. 



Several geologists about the middle of the nineteenth century 

 suggested the probability of a plutonic origin of salt-layers after 

 the manner of the massive crystalline rocks. This view was 

 warmly repudiated by G. Bischof, who rightly argued from his 

 knowledge of the recent deposits in the Dead Sea and the 

 North Caspian depressions, that the salt-deposits within the 

 earth's crust had taken origin in the same way from ancient 

 basins of water as they became desiccated. The salt-layers of 

 Stassfurt and Kalusz remained for a long time an unsolved 

 problem, since no direct comparison could be found between 

 them and any natural deposit in present course of formation. 

 At Stassfurt, thin beds of highly deliquescent salts succeed the 

 main salt-layer; first, a thin band of anhydrite, then a bed of 

 deliquescent chlorides, including some sodium chloride, then a 

 bed of potassium and magnesium sulphate, and lastly an upper 



