IX.] CHEMISTRY OF NATURAL WATERS. 103 



comparatively large amounts both of silica and alkalies. (Ann. 

 Chim. et Phys. (3), XIX. 481.) 



[The view advanced in 13 is to be understood of the 

 subterranean decomposition of alkaliferous silicated minerals, 

 the results of which appear in waters like some noted further 

 on in 67, where, from a deficiency of carbonic acid, parts of 

 the bases are present as silicates, as in the solutions prepared 

 by Damour. At the same time it is clear that carbonic acid 

 greatly favors the process, as seen in the experiments of Eogers, 

 and has played a most important part in the subaerial decom- 

 position of crystalline rocks, from which, as Ebelman showed, 

 have been removed not only the alkalies of the feldspar, but 

 the lime and magnesia of the hornblende. The absence of 

 any excess of carbonic acid in many alkaline-saline waters, as 

 noticed in 66, appears a conclusive argument for the view set 

 forth in 13, that the subterranean decomposition of alkalifer- 

 ous sediments takes place independent of the intervention of 

 carbonic acid.] 



15. Another and an important source of mineral impregna- 

 tion 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 con- 

 ception of the amount of saline matters which may be contained 

 in a dissolved state in the rocky strata of the earth, I have 

 made numerous experiments to determine the porosity of various 

 rocks ; a few of the results, so far as regards the lower palae- 

 ozoic formations of the New York system (in which occur the 

 mineral waters named in the last section), are here given. For 

 further details, and for a table of results, the reader is referred 

 to the Appendix to this paper in the present volume. The 

 volume of water enclosed in 100 volumes of the various rocks 

 having been determined, it was found for three specimens of the 

 Potsdam sandstone to equal 2.26-2.71, and for three others of 

 the same rock, much more porous, 6.94 - 9.35. For four speci- 

 mens of the crystalline dolomite which makes up the so-called 

 Calciferous sand-rock the volume was equal to 1.89-2.53, and 

 for two other varieties of the same rock, 5.90-7.22. 



