UEPORT ON MINERAL AND THERMAL WATERS. 75 



bringing about a separation of its solid contents, from a fluid so 

 far i-emoved from saturation, as the water of our present seas is 

 found to be. 



Now a submarine volcano, or any other independent cause, 

 producing a high temperature in any part of the bed of the 

 ocean, might supply this desideratum; it would separate the 

 salt from that portion of the water which came most within its 

 immediate influence, converting the fluid into vapour, which, in 

 a highly compressed condition, we may imagine to be interposed 

 between the bed of salt in the act of forming, and the body of the 

 superincumbent ocean. 



That volcanic action may have had some share in the forma- 

 tion of beds of salt, is no new idea, and is immediately suggested 

 by the almost constant association, of sulphuric salts, and espe- 

 cially of gypsum, with the former. 



Thus Von Buch*, remarking on the connexion of rock-salt 

 and brine springs with anhydrous gypsum at Bex in Switzer- 

 land, attributes them both to direct sublimation from the inte- 

 rior of the earth, the common salt being accompanied by sul- 

 phuretted hydrogen, which, by its gradual conversion into sul- 

 phuric acid, had given rise to the formation of sulphate of lime. 

 That rock-salt is sometimes sublimed from the bowels of the 

 earth we know by an examination of volcanos ; and where 

 common salt is found abundantly in thermal springs which are 

 of volcanic origin, and issue from primary rocks, as is the case 

 with that of St. Nectaire in Auvergne, and possibly that of 

 Wiesbaden in Nassau, it seems but I'easonable to attribute its 

 occurrence to a similar cause. 



Proust t even has stated, that the salt mine of Burgos in Spain 

 lies in the crater of an extinct volcano ; and though he may pos- 

 sibly be mistaken as to this exact point, stiU such a notion would 

 hardly have arisen, had not the beds been in a manner surrounded 

 by volcanic products. 



Without, however, proposing so bold an hypothesis as that of 

 sublimation, to account for the production of salt beds in general, 

 we may perhaps see reason to suppose, that volcanic heat has in 

 many cases caused their deposition, and that the sulphates which 

 accompany them have arisen from the sulphuretted hydrogen, 

 which is at the present day an ordinary effect of volcanic pro- 

 cesses. 



In my memoir on the Lake Amsanctus|, I have attempted to 

 trace the connexion, between the operations of volcanos, the 



* Poga;enclorff's ^-/«?i«?en, 1835. t Journal de Physique. 



X Published by the Ashmolean Society, Oxford 1S36. 



