1 64 EFFECTS oj HEAT 



carbonic acid*, would be very much increafed by that union 

 and by the ftiffnefs or tenacity of the fubftance. We have 

 feen numberlefs examples of this power in the courfe of thefe 

 experiments, in which barrels, both of iron and porcelain, 

 whofe thicknefs did not exceed one-fourth of an inch, have 

 exerted a force fuperior to the mere weight of a mile of fea. 

 Without fuppofing that the fubftance of a rock could in any 

 cafe act with the fame advantage as that of a uniform and con- 

 nected barrel 5 it feems obvious that a fimilar power mull, in 

 many cafes, have been exerted to a certain degree. 



We know of many calcareous maffes which, at this mo- 

 ment, are expofed to a preflure more than fufricient to accom- 

 plifh their entire fufion. The mountain of Saleve, near Geneva, 

 is 500 French fathoms, or nearly 3250 Englifh feet, in height, 

 from its bafe to its fummit. Its mafs confifts of beds, lying 

 nearly horizontal, of limeftone filled with fhells. Independent- 

 ly, then, of the tenacity of the mafs, and taking into account 

 its mere weight, the loweft bed of this mountain, mult, at this 

 moment, fuftain a prefTure of 3250 feet of limeftone, the fpecific 

 gravity of which is about 2.65. This preflure, therefore, is equal 

 to that of 8612 feet of water, being nearly a mile and a half of 

 fea, which is much more than adequate, as we have fhewn, to 

 accomplifh the entire fufion of the carbonate, on the appli- 

 cation of proper heat. Now, were an emanation from a 

 volcano, to rife up under Saleve, and to penetrate upwards 

 to its bafe, and flop there ; the limeftone to which the lava 

 approached, would inevitably be foftened, without being cal- 

 cined, and, as the heat retired, would cryftallize into a faline 

 marble. 



Some other circumftances, relating to this fubjecT:, are very 

 deferving of notice, and enable us ftill further to compare the 

 ancient and modern operations of fire. 



It 



