242 THEORY of the EARTH. 



formed, below the bottom of the ocean, in the clofe cavity of 

 a marble ftratum. 



THUS, the additional proof, from the facts relating to the bi- 

 tuminous fubflances, confpiring with that from the phaenome- 

 na of other bodies, affords the ftrongeft corroboration of this 

 opinion, that the various concretions found in the internal parts 

 of ftrata have not been occafioned by means of aqueous folu- 

 tion, but by the power of heat and operation of fimple fufion, 

 preparing thofe different fubflances to concrete and cryftallize in 

 cooling. 



THE arguments which have been now employed for proving 

 that ftrata have been confolidated by the power of heat, or by 

 the means of fufion, have been drawn chiefly from the infolu- 

 ble nature of thofe confolidating fubftances in relation to wa- 

 ter, which is the only general menflruum that can be allowed 

 for the mineral regions. But there are found in the mineral 

 kingdom, many folid mafTes of fal gem, which is a foluble fub- 

 ftance. It may be now enquired, How far thefe mafTes, which 

 are not unfrequent in the earth, tend either to confirm the pre- 

 fent theory, or, on the contrary, to give countenance to that 

 which fuppofes water the chief inftrument in confolidating 

 ftrata. 



THE formation of fait at the bottom of the fea, without the 

 affiftance of fubterranean fire, is not a thing unfuppofable, as 

 at firft fight it might appear. Let us but fuppofe a rock placed 

 acrofs the gut of Gibraltar, (a cafe nowife unnatural), and the 

 bottom of the Mediterranean would be certainly filled with 

 fait, becaufe the evaporation from the furface of that fea ex- 

 ceeds the meafure of its fupply. 



BUT ftrata of fait, formed in this manner at the bottom of 

 the fea, are as far from being confolidated by means of aqueous 

 folution, as a bed of fand in the fame fituation ; and we can- 

 not explain the confolidation of fuch a ftratum of fait by 

 means of water, without fuppofing fubterranean heat employed, 



to 



