1865.] CHEMISTRY OF NATURAL WATERS. 167 



The nearly saturated brines from the Saginaw valley in Michi- 

 gan, which have their source at the base of the Carboniferous series, 

 contain, according to my calculation from an analysis by Prof. 

 Dubois, in 100.00 parts of solid matters: chlorid of calcium 9.81, 

 chlorid of magnesium 7.61, sulphate of lime 2.20, the remain- 

 der being chiefly chlorid of sodium. Another brine in the same 

 vicinity gave to Chilton an amount of chlorid of calcium equal to 

 3.76 per cent.* In a specimen of salt manufactured in this 

 region, Goessmann found 1.09 of chlorid of calcium ; and in two 

 specimens of Ohio salt, 0.61 and 1.43 per cent of the same 

 chlorid. The rock-salt from the Lias of Cheshire, according to 

 Nicol, contains small cavities, partly filled with air, and partly 

 with a concentrated solution of chlorid of magnesium, with some 

 chlorid of calcium, f 



* Winchell ; Silliman's Journal [2] xxxiv, 311. 



f Cited by Bischof, Lehrbucb, ii, 1671. The results of the analyses by 

 Mr. Northcote of the brines of Droitwich and Stoke in the same region 

 (L. E. & D. Philos. Mag. [4] ix, 32), as calculated by him, show no 

 earthy chlorids whatever, and no carbonate of lime, but carbonates of 

 soda and magnesia, and sulphates of soda and lime. He regarded the 

 whole of the lime present in the water as being in the form of sulphate. 

 If however we replace in calculating these analyses, the carbonate of 

 soda and sulphate of lime by sulphate of soda and carbonate of lime, 

 we shall have for the contents of these brines, chlorid of sodium, with 

 notable quantities of sulphate of soda, some sulphate of lime, and car- 

 bonates both of lime and magnesia ; a composition which is more in 

 accordance with the admitted laws of chemical combinations. From 

 these results, it would appear that the earthy chlorids, which according 

 to Nichol are present in the rock-salt of this formation, are decomposed 

 by sulphates in the waters which, by dissolving it, give rise to the 

 brines. 



It is to be regretted that in many water-analyses by chemists of note, 

 the results are so calculated as to represent the co-existence of incompa- 

 tible salts. Of the association of carbonates of soda and magnesia with 

 sulphate of lime, as in the analysis just noted, it might be said that I 

 have shown that it may occur in the presence of an excess of carbonic 

 acid. (Silliman's Jour. [2] xxviii, 174). By evaporation, however, such 

 ■solutions regenerate carbonate of lime and sulphates of soda and mag- 

 nesia ; and by the consent of the best chemists these elements are to be 

 represented as thus combined. But what shall be said when chlorid of 

 magnesium, carbonate of soda, and silicate of soda are given as the con- 

 stitueuts of a water whose recent analysis may be found in a late 

 number of the Chemical News ; or when bi-carbonates of soda, magnesia, 

 and lime are represented as co-existing in a water with sulphates and 

 chlorids of magnesium and aluminum ? These errors probably arise from 



