1865.] CHEMISTRY OF NATURAL WATERS. 9" 



§ 14. This explanation of the decomposition of alkaliferous sili- 

 cates and of the origin of carbonate of soda is opposed to the view 

 of Bischof, who conceives that carbonic acid is the chief agent in 

 decomposing feldspathic minerals.* The solvent action of waters 

 charged with carbonic acid is undoubted, as shown by various 

 experimenters, especially by the Messrs. Rogers,f but this acid is 

 not always present in the quantities required. The proportion of 

 it in atmospheric waters is so inadequate that it becomes necessary 

 to suppose some subterranean source of the gas, which is by no 

 means a constant accompaniment of natron-springs. A copious 

 evolution of carbonic acid is observed in the vicinity of the lake 

 of Laach, where the alkaline waters studied by Bischof occur. J 

 The same thing is met with in many other localities of such springs, 

 among which may be mentioned the region around Saratoga, where 

 saline waters containing carbonate of soda, and highly charged 

 with carbonic acid, rise in abundance from the Lower Silurian 

 strata ; but further northward, along the valleys of Lake Cham- 

 plain and the St. Lawrence, similar alkaline-saline waters, which 

 abound in the continuation of the same geological formations, 

 are not at all acidulous. From this the conclusion seems justifiable 

 that the production of carbonate of soda is a process, in some cases 

 at least, independent of the presence of free carbonic acid. In this 

 connection, it is well to recall the solvent power of pure water on 

 alkaliferous silicates, as shown more especially by Bunsen, and also 

 by Damour, who found that distilled water at temperatures much 

 below 212° takes up from silicates like palagonite and calcined 

 mesotype, comparatively large amounts both of silica and alkalies. 

 (Damour, Ann. Chim. et Phys. [3] xix, 481.) 



§ 15. Another and an important source of mineral impregnation 

 to waters exists in the soluble salts enclosed in sedimentary strata, 

 both in the solid state and in aqueous solution, and for the most 

 part of marine origin. In order to form some conception of the 

 amount of saline matters which may be contained in a dissolved 

 state in the rocky strata of the earth, we have made numerous 

 experiments to determine the porosity of various rocks; some 

 few of the results of which may here be noticed. Fragments of 

 the rocks were dried at a heat of 150° to 200° F., in a current of 



* Bischof, Chem. Geol. ii, 181. t Silliman's Journal [2] v, 401. 



J Bischof, Lehrbuch, i, 357-363. 



