368 Prof. Bischof o/i the Natural History of 



strata effected by the granite, which circumstance causes the 

 heating of these waters. 



In this point, I think both theories agree ; viz. that which 

 attributes the heat of springs to chemical processes, and that 

 which refers its origin to central heat : for those who hold 

 the former opinion will doubtless not assign the stratified for- 

 mations as the seat of these chemical actions, but the granite, 

 or the parts beneath it. According to both theories, then, the 

 meteoric water will become warmer in proportion as it ap- 

 proaches nearer to the source of heat, which can only be sought 

 for at great depths. 



As the subterraneous course of springs is subjected to many 

 kinds of local impediments, so veins of springs of similar ori- 

 gin may flow out at points very remote one from another ; and, 

 vice versa, veins of very dissimilar local origin may issue very 

 near one another. Nothing is therefore easier to conceive, than 

 that any stratum in which the materials requisite for the for- 

 mation of sulphureous springs are present, may be traversed by 

 springs arising from very various depths, and therefore possess- 

 ing very unequal temperatures, which circumstance would give 

 rise to springs of similar chemical composition, but dissimilar 

 temperature. 



Forbes* remarks that the hot springs at Baden-Baden^ on 

 the border of the ScJiwartzwald^ have a position almost iden- 

 tical with that which we have so invariably remarked in the 

 Pyrenees. They occur just where the slate rocks have been 

 violen.^ly upraised by a curious granitoidal porphyry, which 

 forms the picturesque elevations near the Alte ScJdoss, and 

 which passes into a true granite. ' Upon the slate, red sand- 

 stone lies unconformably. The elevation is among the older 

 of M. Elie de Beaumont's systems : he expressly states that 

 the Grcs bigarre is undisturbed. 



Relative to the thermal springs in the Pe7inine Alps, 

 Bakewellf remarks, that, according to his observations, the 

 exits of all of them lie partly in the primitive mountains of the 

 central chain itself, partly, and indeed most frequently, at 

 their extremities, at the boundary between the primitive moun- 

 tains and the secondary formations. 



* L. c, p. 609. t Philos. Magazine, January 1828, p. 14. 



