56 TRANSACTIONS OF THE [mARC'H 23, 



hut from brine pumped from wells which penetrate a great mass 

 of sand, gravel, etc., that fills one of the old buried channels 

 formed when the continent stood higher above the ocean tlian 

 now — before the Ice Period, when they were to a large extent 

 filled and obliterated — and its surface was deeply scored along 

 the lines of drainage. The old channel at Salina, cutting across 

 the strata, receives the drainage from deeply buried beds of salt, 

 long ago suspected to exist, which have lately been discovered 

 by l)orin2;s into the country south. Salt being very soluble, 

 rain falling on the surface and penetrating the rocks to these 

 beds of salt has gradually dissolved them to form brine, which 

 flowing down to a lower level, has filled the reservoir formed by 

 the old channel referred to, and from this has been pumped up 

 and evaporated. 



The salt deposits of the Salina Group exhibit an interesting 

 diversity of composition. Some are almost chemically pure, 

 while others contain a large quantity of chloride of calcium, 

 cliloride of magnesium, sulphate of magnesia, etc., which consti- 

 tute the " bitterns " of the salt boilers. These differences are 

 apparently the result of different conditions under which the 

 precipitates were made. Salt water contains a great variety of 

 substances held in solution, among which gypsum, common salt, 

 sulphate of soda, sulphate of magnesia and the chlorides men- 

 tioned are most abundant. When it is evaporated these salts 

 are thrown down in the inverse order of their solubilities. For 

 example, the sulphate of lime (gypsum) being the least soluble, 

 is first deposited ; then when the solution is more concentrated, 

 chloride of sodium and the other salts in order, until finally 

 only the deliquescent salts mentionad are left. These have such 

 affinity for water that they do not exist in nature except in solu- 

 tion, and after being artificially prepared rapidly absorb mois- 

 ture from the atmosphere. These facts give us an explanation 

 of the varying purity of the salt, and the occm'rence in certain 

 places of great sheets of gypsum. Wliere a land-locked basin 

 receives the drainage from the surrounding country — M'hich, 

 though apparenth" pure water, always contains some salts — by 

 evaporation the water becomes " salt " ; a chai-acteristic of all 

 undrained lakes ; Great Salt Lake and the Dead Sea being good 

 examples. If such a solution should be further concentrated, 

 the least soluble iugredient, gypsum, would ])e first thrown 

 down; and a sheet of this might be precipitated while yet 



