THEORY of the EARTH. 243 



to evaporate the brine which would fucceflively occupy the in- 

 terftices of the faline cryftals. But this, it may be obferved, is 

 equally departing from the natural operation of water, as the 

 means for confolidating the fediment of the ocean, as if we 

 were to fuppofe the fame thing done by heat and fufion. For 

 the queftion is not, If fubterranean heat be of fufficient inten- 

 fity for the purpofe of confolidating ftrata by the fufion of 

 their fubftances ; the queftion is, Whether it be by means of 

 this agent, fubterranean heat, or by water alone, without the 

 operation of a melting heat, that thofe materials have been va- 

 rioufly confolidated. 



THE example now under confederation, confolidated mineral 

 fait, will ferve to throw fome light upon the fubject ; for as it 

 is to be fhewn, that this body of fait had been confolidated by 

 perfect fufion, and not by means of aqueous folution, the con- 

 folidation of ftrata of indiflbluble fubftances, by the operation 

 of a melting heat, will meet with all that confirmation which 

 the confiftency of natural appearances can give. 



THE fait rock in Chefliire lies in ftrata of red marl. Jt is ho- 

 rizontal in its direction. I do not know its thicknefs, but it is 

 dug thirty or forty feet deep. The body of this rock is perfectly 

 folid, and the fait, in many places, pure, colourlefs and tranfpa- 

 rent, breaking with a fparry cubical ftructure. But the great- 

 eft part is tinged by the admixture of the marl, and that in va- 

 rious degrees, from the flighted tinge of red, to the moft per- 

 fect opacity. Thus, the rock appears as if it had been a mafs 

 of fluid fait, in which had been floating a quantity of marly 

 fubftance, not uniformly mixed, but every where feparating 

 and fubfiding from the pure faline fubftance. 



THERE is alfo to ;be obferved a certain regularity in this fe- 

 paration of the tinging from the colourlefs fubftance, which, 

 at a proper diftance, gives to the perpendicular fection of the 

 rock a diftinguifliable figure in its ftructure. When looking at 

 this appearance near the bottom of the rock, it, at firft, pre- 

 11 h 2 fented 



