THERMAL SPRINGS. 193 



nature, as it were, artificially composes the apparatus of 

 Geysers, we must remember that silicic acid is also diffused 

 in many cold 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 

 floetz mountains. Acid springs become impregnated with 

 alkaline carbonates, and especially with caibonate of soda, 

 wherever water impregnated with carbonic acid acts upon 

 rocks containing alkaline silicates.* 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 (Erhebungs-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, sulphureted hydrogen is probably dissolved ; in others, 

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

 Cornelius, Eose, and Quirinus springs), no sulphureted hy- 

 drogen is contained, according to the precise experiments of 

 Bunsen and Liebig, in the gases obtained by boiling the 

 waters without access of air ; indeed the Kaiserquelle alone 

 contains O31 per cent, of sulphureted hydrogen in gas bub- 

 bles which rise spontaneously from the springs.! 



* Bunsen, in Poggendorfl's Annaten, bd. Ixxxiii., s. 257; Bischof, 

 Geologic, bd. i., s. 271. 



f Liebig and Bunsen, Untersuchung derAackener Scheivefelquetten, in 

 the Annalen der Chemie und Pharmacie, bd. Ixxix. (1851), s. 101. In 

 the chemical anah-ses of mineral waters, which contain sulphurct of 

 sodium, carbonate of soda and sulphureted hydrogen ara often stated 

 to occur, from an excess of carbonic acid being present in those waters 

 VOL. V. I 



