71 SIXTH REPORT— 1836. 



cause; and M. Brongniavt* attributes the sulphuretted hydro- 

 gen present in the mineral water of Enghien, to the action of 

 organic matter upon beds of gypsum belonging to the Paris 

 Basin. 



But no one would attempt to explain in this manner, the sul- 

 phuretted hydrogen contained in many thermal waters, still less 

 that evolved from volcanos ; a phsenomenon, which seems to me 

 to supply just the same evidence of the decomposition of water 

 within the earth, which the emission of nitrogen affords of the 

 abstraction of oxjgen from atmospheric air. And if it should 

 be established, as many observers of volcanic phsenomena have 

 thought probable, that the sulphur, which finds its way to the 

 surface by the agency of volcanos, is always held in solution 

 either by oxygen or hydrogen gases, the enormous quantity of 

 either principle which is sent back to the atmosphere in con- 

 junction with this Inflammable, maybe in some measure appre- 

 ciated from one circumstance alone, namely, from the vast beds 

 of volcanic sulphur accumulated in many parts of Italy, and still 

 more remarkably in Sicily. 



Professor Phillips is even of opinion, that the origin of the mi- 

 neral impregnation of the waters of Harrogate is to be ascribed, 

 to the chemical effects specially exerted along the line of a 

 subterranean disturbance, which he has traced in the vicinity 

 of these springs ; and Mr. Murchison has been led to similar 

 conclusions, with respect to the sulphureous spring of Llanwr- 

 tyd, by the geological structure of that locality. 



Origin The Only remaining class of springs, that requires further no- 



!i'*;!,",. tice, is that which contains common salt, and the other ingre- 

 dients of our present seas. 



The origin of these springs from masses of salt or muriatiferous 

 clays, produced by the evaporation of sea-water, or of lakes 

 of similar composition, wovild seem sufficiently obvious; and 

 Mr. Lyellf has even attempted to explain the manner, in which 

 a deposition of salt may be taking place at the present day from 

 the waters of the Mediterranean, so as eventually to build up a 

 bed of rock salt underneath it. 



But although the law of the increasing specific gravity^ of 

 water, in proportion to the degree of its saline impregnation, 

 would favour the process of deposition, when once it had com- 

 menced, by keeping up a constant supply of the strongest brine 

 near the bottom of the sea, we still seem to want some agent, for 



* Diet. d'Hist. Nat., art. Eaux. + Principles of Geology, vol. i. p. 297. 

 X See a curious paper on the increasing strength of a brine well in propor- 

 tion to its depth, in the PhU. Mnrjazinr, vol. iv. p. 91. 



springs. 



