1865.] CHEMISTRY OF NATURAL WATERS. 11 



The capacity of the 800 feet of Chazy and Trenton limestones 

 which succeed these lower formations, may be fairly taken at 

 one half that of those just named. But it is unnecessary to 

 multiply such calculations: enough has been said to show that 

 these sedimentary strata include in their pores great quantities 

 of water, which was originally that of the ocean of the paleozoic 

 age. These strata throughout the great Silurian basin of the 

 St. Lawrence, are now for the greater part beneath the sea-level ; 

 nor is there any good reason for supposing them to have ever 

 been elevated much above their present horizon. Wells and 

 borings sunk in various places in these rocks show them to be still 

 filled with bitter saline waters ; but in regions where these rocks 

 are inclined and dislocated, surface-waters gradually replace these 

 saline waters, which in a mixed and diluted state appear as 

 mineral springs. These saline solutions, other things being equal, 

 will be better preserved in limestones or argillaceous rocks than in 

 the more porous and permeable sandstones. 



§ 17. But besides the saline matters thus disseminated in a dis- 

 solved state in ordinary sedimentary rocks, there are great volumes 

 of saliferous strata, properly so called, charged with the results of the 

 evaporation of ancient sea-basins. These strata enclose not only gyp- 

 sum and rock-salt, but in some regions large quantities of the double 

 chlorid of potassium and magnesium, carnallite; and in others 

 sulphate of soda, sulphate of magnesia, and complex sulphates 

 like blodite and polyhallite. Besides these crystalline salts, the 

 mother liquors containing the more soluble and uncrystallizable 

 compounds, may also be supposed to impregnate, in some cases, the 

 sediments of these saliferous formations. The conditions under 

 which these various salts are deposited from sea-water, and their 

 relations to the composition of the ocean in earlier geological 

 periods, are reserved for consideration in § 22. Infiltrating waters 

 remove from these saliferous strata their soluble ingredients; 

 which, together with the ancient sea-waters of other sedimentary 

 rocks, give rise to the various neutral saline waters ; while the 

 mingling of these in various proportions with the alkaline waters 

 whose origin has been described in § 13, produces intermediate 

 classes of waters of much interest. 



§ 18. I have elsewhere described the results of a series 

 of experiments on the mutual action of the waters of these two 

 classes.* When a dilute solution of bicarbonate of soda is gradu- 



Silliman's Journal [2] xxviii, 170. 



