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THE ULTIMATE SOURCE 



account for the heat, as well as for the saline phenomena of such 

 springs. As to Vesuvius, the salt formed in its eruptions is 

 associated in such proportions with the minerals which 

 invariably accompany rock salt formations, that geologists 

 have little doubt that the volcano is situated over an ancient 

 salt bed. As a rule, with the exception of Vesuvius, and 

 Heckla in Iceland, whose craters are incrusted with salt, 

 sodic chloride is not a volcanic product ; and Heckla, like 

 Vesuvius, it should be noticed, is situated near the sea, and 

 submarine volcanic action takes place at times off the coast. 

 Primary and eruptive rocks contain but little trace of sodic 

 chloride. It never forms dykes, and there is no stratigraphical 

 or other evidence of its igneous origin. 



In fact, it may be said, that the igneous theory takes its 

 origin, not in any positive evidence of igneous action in rock 

 salt, but in the evidence afforded by the position of gypsum, 

 and other facts, apparently excluding the aqueous theory. 

 Hence the consequent necessity for starting some other theory 

 to explain the presence of rock salt. It is true that semi- 

 anhydrite, a sulphate of lime crystallising with 6*21 parts 

 per cent, of water, which forms only under pressure and 

 at high temperatures, is sometimes found in the Indian 

 salt ranges. But this need only confirm the evidence, 

 which is otherwise strong enough, that many rock salt 

 formations have been subjected to volcanic action. There 

 are fatal objections to the igneous theory which practically put 

 it out of consideration. The association of rock salt with 

 naphtha and petroleum is justly held to exclude igneous 

 action, since these would otherwise have been burnt off and 

 volatilised. The unburnt organic remains, the unburnt coal, 

 and the presence of unburnt gypsum in all salt formations are 

 convincing proofs that these formations had not a birth and 

 baptism of fire. In conclusion, it may be affirmed that the 

 weight of evidence is entirely with those who believe that rock 



