378 On some Relations of the Salts of Lime and Magnesia, 
water of the Ottawa, according to my analysis, contain 6°11 parts 
of solid matters, consisting of carbonate of lime 2°48, carbonate 
of magnesia 0°69, silica 2°06, sulphates and chlorids of potassium 
and sodium 0°47, and carbonate of soda 0°41. (Report Geol. Sur- 
vey of Canada, 1853-56, 360, and Philos. Mag., [4], xiii, 239.) 
Silica, although more abundant in alkaline river waters, which 
are chiefly derived from crystalline rocks, is not wanting in wa- 
ters containing neutral earthy salts, like the Seine and the Rhone, 
of the solid matters of which, according to Deville, it forms re- 
spectively 10°0 and 13:0 p. c—(Ann. de Chem. et Phys., [8], 
Xxili, 32.) 
The waters which rise from the Lower Silurian shales of the 
St. Lawrence valley are, as I have elsewhere shown, remarkable 
for the predominance of alkaline salts, which sometimes amount 
to one-thousandth, or more than one-half the solid matters pres- 
ent; these waters are distinguished from the river waters just 
mentioned by their comparatively small amount of silica and 
earthy carbonates, and by the presence of a notable proportion 
of borates.—( Rep, Geol. Survey of Canada, 1852, p. 165,—1853- 
56, p. 469, and Proc. Royal Soc., Phil. Mag., [4], xvi, 376.) 
e may here refer to the strongly alkaline waters furnished 
by the artesian wells of Paris and London as evidences of the 
The car 
in the decomposition of feldspathic minerals, and shows the con- 
tinance in our time of a process whose great activity in former 
geologic ages is attested, as I have elsewhere maintained, by vast 
the intervention of carbonate of soda has been formed from the 
chlorid of calcium of the primeval ocean and deposited as lime- 
stone. 
65. An indispensable condition for the precipitation of car- 
bonate of magnesia is the absence of chlorid of calcium from 
the solutions, and this in the presence of excess of sulphates 18 
attained simply by evaporating to the point where gypsum be- 
comes insoluble. In nearly all river and spring waters bicar- 
bonate of lime is present in a large proportion, and is often the 
most abundant salt. We have shown that when mingled with 
a solution containing sulphate of magnesia, it gives rise by double 
devoregteition tp bicarbonate of magnesia. aid sulphate of lime. 
3 
‘ 
3 
