Volcanos and Earthquakes, 379 



nic acid escapes from the rocks there, the granite in] the interior 

 may, indeed, suffer but slight decompositions. The formation 

 of the sulphureous springs there, probably by the decomposition 

 of sulphates by organic matter, is certainly much favoured by 

 the high temperature of these springs ; and this again is a con- 

 sequence 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 he- 

 tween them. The coincidence 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 

 springs, which are scarcely any thing morejthan ordinary warm 

 water. 



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

 pearance, from erupted masses, which springs contain ingre- 

 dients 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 Kreuznach out of porphyry. This 

 rock is but little fissured, and yet the high temperature of the 

 springs, 58° to 83°, indicates a deep origin. Since the por- 

 phyry 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 Neptunian 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 at- 

 tribute to these saline springs a totally distinct origin, viz., that 

 sulphate of lime, which otherwise so generally accompanies the 

 common salt, is here entirely absent, and that these springs are 

 remarkable for their abundance of bromine and iodine. 



As escapes of steam (fumaroles) shew themselves in regions 

 (Tuscany for example) where hot masses have approached the 

 surface of the earth by volcanic activity, one might perhaps be 

 induced to expect evolutions of steam from clefts penetrating 



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