The Origin of Rock- Salt 35 



vol. ii. p. 98). In the present connection, however, we 

 are not specially concerned with the salt obtained by this 

 means; because the object in view here is to show that 

 there is abundant evidence, in the cases where the rivers 

 flow into areas of inland drainage, of the concentration of 

 their saline and other dissolved constituents in great 

 quantities. It must be perfectly obvious in such circum- 

 stances that the total quantity so deposited is limited only 

 by — (1) the percentage held in solution in the feeders of the 

 lake ; and (2) by the time during which these special 

 geographical conditions remain in operation. 



Facts similar to those just passed in review are presented 

 by many other areas of the Globe. The reader desirous 

 of obtaining further information regarding these will find 

 it given by Bischof in his "Chemical Geology" (English 

 translation), vol. i. chap, xviii., which, like the rest of that 

 work, is a great storehouse of facts, most of them of the 

 highest value, even at the present day. It may be added 

 here that a large proportion of the salt consumed in various 

 parts of the globe is of recent date, and is largely obtained 

 from atmospheric salt, concentrated from rain-water which 

 has flowed into areas where the rate of evaporation has long 

 been at least equal to that of supply. Much of the salt 

 gathered by Oriental people on the shores of the Aralo- 

 Caspian lakes, for example, may well have formed part 

 of the saline constituents of the ocean only a few years 

 before it has been gathered by human hands. 



When one is called upon for an explanation of other and 

 older deposits of salt whose mode of formation is not so 

 obvious, it is probable that no answer that can be given 

 would quite satisfy all the inquirers. As regards the 

 particular case of the salt deposits of Jebel Usdem, which 

 rise to a considerable elevation above the shores of the Dead 

 Sea, many persons have thought that they represent a deposit 

 left by dessicated sea- water — supposed to have been derived 

 from the Mediterranean or from an arm of the Eed Sea. On 

 the other hand, it can be shown that the continued dessica- 

 tion of sea-water would give rise to a deposit different from 

 that of Jebel Usdem in many essential respects. It seems a 



