OF COMMON SALT. 



143 



examine, in detail, its claims to be considered as an aqueous 

 rock. 



Many salt areas, or salt regions as they are called, are made 

 up of a number of salt deposits, linked together as it were 

 on one horizon. The explanation of this phenomenon 

 is so intimately associated with the theory of the gradual 

 upheaval of areas of dry land from the ocean's bed, that I 

 must notice both theories together here. One can easily 

 imagine that if large tracts of undulating country, forming 

 natural basins, were submerged in the sea and brought to 

 the surface again, the natural basins would be filled with 

 salt water, which would, on evaporation, yield linked salt 

 deposits of the kind referred to. Now this is almost pre- 

 cisely what is believed to have happened, for it matters 

 little whether the undulating surface was an original sea-bed, 

 or one formed by subsidence. Original sea beds are 

 unknown, at present. 



The theory of the gradual interchange of dry land and ocean, 

 which is as well established as any demonstrated geologi- 

 cal fact, is associated in many ways with the study of the 

 origin of salt deposits. It is of the greatest importance in 

 explaining the wide geographical distribution of rock salt. It 

 is the key to its position in so many pages of the palseonto- 

 logical record, from the Tertiary to the Silurian era. It 

 furnishes the reason for the otherwise inexplicable position 

 of rock salt deposits at various elevations above, as well as 

 below, the present sea level. 



It is believed by geologists, and for ample proof I must 

 refer the reader to works on geology, that slow upheavals 

 and subsidings of land have been going on since the begin- 

 ning of things, as far as we can trace them ; that the dry- 

 land has been washed, by gradual denudation, into the sea, 

 and that other dry land has risen from the sea to take its 

 place ; that there have been compensatory sinkings as well 



