Natural History of Volcaiios and Earthqual:es. 71 



be the Neptunian formations, is an argument in favor of these 

 springs deriving their ingredients principally from the basalt. 



The organic matter found in such abundance in the sulphure- 

 ous springs of the Pyrenees (baregine, glairine, animal matter) 

 proves, that their chemical constituents must be derived, at least 

 in part, from the Neptunian formations. Since no carbonic acid 

 escapes from the rocks there, the granite in the interior may, in- 

 deed, suffer but slight decompositions. The formation of the sul- 

 phureous springs there, probably by the decomposition of sul- 

 phates by organic matter, is certainly much favored by the high 

 tem]3orature of these springs; and this again is a consequence of 

 the great depth to which the clefts extend in the strata, which 

 are piled up one on another in considerable masses, and partly 

 raised up, with many strata-surfaces between them. The coin- 

 cidence of various circumstances may thus produce one class of 

 thermal springs in preference to another. 



In the Alps, where, on account of the absence of escapes of 

 carbonic acid gas, decomposition of the granite and other vol- 

 canic rocks does not take place, and where even the Neptunian 

 formations contain few soluble substances, we find thermal 



warm 



water. 



On the other hand, we see thermal springs issuing, to all ap- 

 pearance, from erupted masses, which springs contain ingredients 

 apparently peculiar to those which can be proved to issue from 

 Neptunian formations. This is, for instance the case with the 

 salt-spring, which rises at Kreitznach out of porphyry. This 

 rock is but httle fissured, and yet the high temjjerature of the 

 springs, 58^ to 83^, indicates a deep origin. Since the porphyry 

 has penetrated the variegated sandstone, the latter, and also the 

 shelly limestone, lie in close contact with the springs, so that this 

 volcanic rock has no other share in the formation of these springs, 

 than the production of deep clefts between itself and the Neptu- 

 nian formations, which have permitted meteoric water to penetrate 

 into the strata containing the salts. We must not pass over one 

 circumstance, which induces us to attribute to these saline springs 

 a totally distinct origin, viz., that sulphate of lime, which other- 

 wise so generally accompanies the common salt, is here entirely 

 absent, and that these springs are remarkable for their abundance 

 of bromine and iodine. 



