152 Frank Carney 



go more than two thousand feet. The thickness of the individual 

 beds varies from five to sixty feet . Water is pumped into the wells 

 which forms a solute that is pumped out and evaporated. Some 

 of the wells not far distant from each other have been operated so 

 long that they now open into a single cavern which has been devel- 

 oped by the gradual solution of the salt, from the bottom of either 

 well. 



Origin of salt. Above the Silurian, the formations bear their 

 salt in the form of brines, that is, saline water exists in the rock. 

 It is possible that this brine represents small particles of salt 

 originally deposited with the sediments ; ground water, circulating 

 at a later date, may have dissolved these small bits of salt, thus 

 producing the brine. Again it has been suggested that the salt 

 water, with which the sediment was saturated as it was deposited, 

 may have been retained; this would be possible, provided the 

 saline sediment immediately overlies an impervious bed and is 

 also capped by an impervious bed ; thus the brine would be im- 

 prisoned. When we recall, however, that jointing exists in almost 

 all rocks, it hardly seems probable that imprisoned waters would 

 remain in these sediments through much geologic time. 



Much speculation has arisen from the great thickness of rock 

 salt frequently found in some localities. In this country a homo- 

 geneous bed 325 feet thick has been bored through, but at Speren- 

 berg, Germany, a bed 3600 feet thick has been reported. Geolo- 

 gists suggest that rock salt probably represents evaporation and 

 precipitation in basins containing sea water, isolated from the 

 ocean. As the water in these basins, shut off from tidal influence, 

 evaporates, their level is lowered, and by the seeping through the 

 isolating barrier, water from the sea is constantly added. This 

 supply of sea water and its continuous evaporation w^ould in time 

 form a bed of salt, the thickness of which would be conditioned 

 upon the continuance of the above factors. It is known that to- 

 day several depressed areas contain bodies of water to which 

 drainage is constantly being added, but from which there is 

 no flow ; the only escape is by evaporation ; such bodies of water 

 are saline, for example, the Great Salt Lake, Caspian Sea, Kara 

 Burgas, Aral Sea, and the Dead Sea. 



