IX.] CHEMISTRY OF NATURAL WATERS. 119 



evaporation separates it from the water in the solid form ; and 

 that the two processes, one of which replaces the chloride of 

 calcium by chloride of sodium, while the other eliminates the 

 latter salt from the solution, might have been going on simulta- 

 neously or alternately. As the nature of the waters now under 

 consideration shows that the process of evaporation had been 

 carried so far as to separate the sulphate in the form of gypsum, 

 and probably also a portion of the chloride of sodium in a 

 solid state, it is evident that we have not yet the data necessary 

 for determining the composition of the water of the ancient 

 Cambrian ocean, as regards the proportions of the sodium, cal- 

 cium, and magnesium which it held in solution ; and we can 

 only conclude from these mother-liquors, that the amount of 

 the earthy bases was relatively very large. 



39. As already remarked in 22, the mother-liquor from 

 modern sea-water contains no chloride of calcium, but, on the 

 contrary, large quantities of sulphate of magnesia ; the lime in 

 the modern ocean being less than one half that required to 

 combine with the sulphate present. If, however, we examine 

 the numerous analyses of rock-salt and of brines from various 

 saliferous formations, we shall find that chloride of calcium is 

 very frequently present in both of them ; thus supporting the 

 conclusions already announced in 24 with regard to the com- 

 position of the seas of former geological periods. The oldest 

 saliferous formation which has been hitherto investigated is the 

 Onondaga Salt-group of the New York geologists, which be- 

 longs to the upper part of the Silurian series, and supplies the 

 strong brines of Syracuse and Salina in New York. These, 

 notwithstanding their great purity, contain small proportions 

 of chlorides of calcium and magnesium, as shown by the 

 analyses of Beck, and the recent and careful examinations of 

 Goessmann. In the brines of this region the solid matters are 

 equal to from 14.3 to 16.7 per cent, and contain on an average, 

 according to the latter chemist, 1.54 of sulphate of lime, 0.93 

 of chloride of calcium, and 0.88 of chloride of magnesium in 

 100 ; the remainder being chloride of sodium.* 



* Goessmann, Reports on the Brines of Onondaga : Syracuse, 1862 and 1864; 

 also Report on the Onondaga Salt Co. : Syracuse, 1862. 



