166 £THE CANADIAN NATURALIST. [June 



separate the soluble lime-salt as carbonate, leaving to a subsequent 

 stage the magnesian chlorid (§ 18.) As this reaction replaces the 

 calcium-salt by chlorid of sodium, it might be expected that there 

 would be an increase in the amount of the latter salt in the 

 water wherever the magnesian chlorid predominates, did we not 

 remember that evaporation separates it from the water in a 

 solid form ; and that the two processes, one of which replaces the 

 chlorid of calcium by chlorid of sodium, while the other eliminates 

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

 taneously 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 pro- 

 bably also a portion of the chlorid 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 Lower Silurian ocean, as re- 

 gards the proportions of the sodium, calcium, 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 chlorid of calcium, but, on the con- 

 trary, 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 forma- 

 tions, we shall find that chlorid of calcium is very frequently 

 present in both of them ; thus supporting the conclusions already 

 announced in § 24 with regard to the composition 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 belongs to the upper part of the Silu- 

 rian series, and supplies the almost saturated brines of Syracuse 

 and Saliua in New York. These, notwithstanding their great 

 purity, contain small proportions of chlorids of calcium and magne- 

 sium, as shown by the analyses of Beck, and the recent and careful 

 examinations of Goessmann. In the brines of that 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 chlorid of calcium, and 0.88 of chlorid of magnesium in 

 100.00 ; the remainder being chlorid of sodium.* 



* Goessmann. Report on the Brines of Onondaga : Syracuse, 1862 and 

 1864. Also Report on the Onondaga Salt Co. : Syracuse, 1862. 



