IX.] CHEMISTRY OF NATURAL WATERS. 149 



uncombined with sulphuric acid or chlorine. Thus, accord- 

 ing to Pagenstecher and Miiller, the spring and well waters of 

 Berne do not contain sufficient carbonic acid for the lime 

 present, a part of which they suppose to be held in solution as 

 a silicate. See Bischof, Chem. Geology, I. 5 ; who remarks 

 that Lbwig seems to have observed the same fact in the ther- 

 mal spring of Pfaffers. For further examples of this kind see 

 Lersch, Hydro-Chemie, page 333. The carbonic acid in the 

 water of Toplitz is, according to him, not sufficient to form 

 bicarbonates unless the silica present be supposed to be com- 

 bined with a portion of bases ; while in the alkaline thermal 

 spring of Bertrich, according to the analysis of Mohr, a similar 

 deficiency of carbonic acid exists; leading to the conclusion 

 that a part of the earthy bases present is in combination with 

 silica and organic matters. The existence of solutions holding 

 comparatively large amounts of neutral carbonates of lime and 

 magnesia, as described in 56, is not without interest in this 

 connection ; since it at once affords an explanation of the na- 

 ture and origin of all such alkaline waters, and waters deficient 

 in carbonic acid, as contain earthy sulphates and chlorides. 



68. It was found that the waters of Charnbly in 1864, 

 and of the Sulphur Spring of Caledonia in 1865, gave with 

 lime-water a precipitate which was soluble in an excess of these 

 mineral waters, but to a much less extent than in the acidu- 

 lous saline water from the High-Eock Spring of Saratoga. 

 The latter, which contains bicarbonate of soda, and is highly 

 charged with carbonic acid, turns to a wine-red the blue color 

 of litmus-tincture, which is not changed by" the Chambly or 

 the Caledonia water. The Saratoga water, after some time, 

 gives a feeble alkaline reaction with dahlia-paper ; this is more 

 distinctly but slowly changed by the Caledonia water, and 

 almost immediately turned to green by that of Chambly. 

 This latter water readily changes to brown yellow tumeric- 

 paper, which is scarcely affected by the water of Caledonia. 



69. SILICA. The silica which exists in solution in cold 

 saline springs is generally very small in amount, as might be 

 expected from the insolubility of earthy silicates, which is 



