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THE ULTIMATE SOURCE 



offer examples of the formation of rock salt by deposition 

 in the beds of inland lakes which are gradually evapor- 

 ating and filling up. Lake Kosiak, situated on the right 

 bank of the Irtysh in Asiatic Russia, is a similar example. 

 Some of the zoutpans, in South Africa, are likewise 

 solidifying. But the best illustration is found in Lake 

 Inder, which lies in the valley of the Ural River. The bottom 

 of this lake is an immense solid mass of salt, covered with a 

 shallow sheet of brine. At the end of summer, the lake 

 entirely dries up, and forms one solid block of salt. These 

 lakes teach us that large masses of solid salt may be formed 

 in comparatively small areas, by evaporation, under certain 

 climatic conditions, even at the present day. 



Let us consider the conditions which prevailed when the 

 old rock salt was formed, as far as they affect crystalline 

 structure. Some deposits, it will be remembered, are 

 1,200 in thickness. Considering that it takes about 6 cubic 

 feet of saturated brine to produce one cubic foot of salt, 

 and that when salt deposits, the brine has a specific gravity 

 of 1,208, and lies in the deepest hollow of its basin, we 

 can imagine what an enormous depth of dense brine must 

 have presided over such salt formations. The salt must 

 have been formed at profound, motionless depths, in which 

 the stillness was only broken by the growth of crystal 

 structure. It must have been formed under gigantic 

 pressure, from such depth and density of brine. We have 

 no parallel to these conditions of crystal growth, at the 

 present day ; we can only imagine, d jjriori, that the resulting 

 crystal must be very perfect, resembling a mass of glass. 



But the effect of crystalline contraction, the effect of lapse 

 of time, and the effect of superincumbent pressure have also 

 to be considered. The force of crystal growth is a very 

 powerful one. Where, as in the growth of ice, it takes the 

 form of expansion, it bursts iron pipes with ease. In salt 



