162 ‘WARD AGT S ofate AT 
peding, the defcent of water from the fea above; fo that the 
water which had been driven from the fhells at the bottoni, 
would not return to them, or would return but flowly ; and 
they would be expofed dry»to the:action of heat *, 
In this cafe, one of two things would inevitably happen. Ei- 
ther the carbonic acid of ‘the fhells) would »be driven off by the 
heat, producing an incondenfable elaftic fluid, which, heaving 
up or penetrating the fuperincumbent beds, would force its 
way to the furface of the fea, and, produce a fubmarine erup- 
tion, as has happened at Santorini and elfewhere ; or the vo- 
latility of the carbonic acid would be reprefled by the weight of 
the fuperincumbent water (4#), and the fthell-bed, being fof- 
tened or fufed by the action of heat, would be converted into 
a ftratum of limeftone. mer 
Tue foregoing experiments enable us to decide! in any parti- 
cular cafe, which of thefe two events muft take place, when 
the heat of the lava and: the depth of the fea are known. 
Tue table fhews, that under,a fea no, deeper than 1708 
feet, near one-third of a mile,,a limeftone would be formed 
by proper heat; and that, in, a depth, of little more than 
one mile, it would enter into,entire fufion... Now, the .com- 
mon foundings of mariners extend to 200 fathoms, or 1200 
feet. Lord. Muxrcrave + found bottom at 4680 feet, or 
nearly nine-tenths of a mile; and Captain Exxis let down 
a fea-gage to the depth of 5346 feet,{. It thus, appears, 
; that 
* Turis fituation of things, is fimilar to what happens when {mall-coal is moi- 
ftened, in order to make it cake. The duft, drenched with water, is laid upon the 
fire, and remains long wet, while the heat below fuffers little or no abatement, 
+ Voyage towards the North Pole, p. 142. 
} Philofophical TranfaGions, 1751, Pp. 212. 
