THERMAL SPBINGS. 201 



Bilicious deposits as a constructive material of which nature, 

 as it were, artificially composes the apparatus of Geysirs, we 

 must remember that silicic acid is also diffused in many colci 

 springs which contain a very small portion of carbonic acid. 



Acid springs and jets of carbonic acid gas, which were 

 long ascribed to deposits of coal and lignite, appear rather to 

 belong entirely to the processes of deep volcanic activity : 

 an activity which is universally disseminated, and therefore 

 does not exert itself merely in those places where volcanic 

 rocks testify to the existence of ancient local fiery eruptions. 

 In extinguished volcanoes jets of carbonic acid certainly re- 

 main longest after the Plutonic catastrophes ; they follow 

 the stage of Solfatara activity ; but nevertheless waters im- 

 pregnated with carbonic acid, and of the most various tem- 

 peratures, burst forth from granite, gneiss, and old and new 

 fioetz mountains. Acid springs become impregnated with 

 alkaline carbonates, and especially with carbonate of soda, 

 wherever water impregnated with carbonic acid acts upon 

 rocks containing alkaline silicates. 55 In the north of Ger- 

 many many of the carbonic acid springs and gaseous jets are 

 particularly remarkable for the dislocation of the strata 

 about them and for their eruption in circular valleys (Pyr- 

 mont, Driburg) which are usually completely closed. Fried- 

 rich Hoffman and Buckland have almost at the same time 

 very characteristically denominated such depressions valleys 

 of elevation ( Erhebu-ngs-Thaler). 



In the springs to which the name of sulphurous waters is 

 given, the sulphur by no means constantly occurs combined 

 in the same way. In many, which contain no carbonate of 

 soda, sulphuretted hydrogen is probably dissolved ; in others, 

 for example in the sulphurous waters of Aix (the Kaiser, 

 Cornelius, Rose, and Quirinus springs), no sulphuretted 

 hydrogen is contained, according to the precise experiments 

 of Bunsen and Liebig, in the gases obtained by boiling the 



quantity of oxygen to be only 0.299. We had previously found 0.31 

 of oxygen in meteoric waters (rain). Upon the nitrogen gas con- 

 tained in the acid springs of Neris and Bourbon 1'Archambault, seethe 

 works of Anglade and Longchatnp(lS34), and on carbonic acid exhala- 

 tions in general, see Bischof's admirable investigations in his Ckemiscfte 

 Geologic, Bd. i, s. 243350. 



55 Bunsen, in PoggendorfFs Annalen, Bd. Ixxxiii, s. 257; Bischof, 

 Geologic, Bd. i, s. 271. 



