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be incapable of forming a heat even equal to that of our common 

 furnaces, as Mr. Dolonaieu has clearly Ihewn to be the cafe 

 with refpcdl to volcanic heat ; and again, allowing our author 

 air of fufficient purity to efFedl his purpo/es, what fliall prevent 

 the water, fuperincumbent on his loofe, fpongy ftrata, and 

 preffing upon rhem with immeafurable weight, from pene- 

 trating through thefe flrata, and extinguilhing this flame, or 

 at leaft from prefhng down the incombuftible ftrata upon the 

 inflamed coal, and, by intercepting all communication with 

 the air, from immediately fupprefling the flame? What £hall 

 prevent the air itfelf, rarefied by heat, from efcaping through 

 the loofe, and as yet, unconfolidated ftrata ? But to favour 

 the author ftill further, let us fuppofe the fire to originate in 

 caverns formed within the coaly matter itfelf, and let us fuppofe 

 fuch vaults (contrary to all probability) capable of fupporting 

 the weight not only of a fuperincumbent ocean, but of all the 

 ftrata fubjed to that ocean, which by heat are to be converted 

 into fione, the air, thus confined in thefe caverns, either would 

 admit of no combuflion at all, if incapable of expanding, or 

 would foon be fo diroiniflied by the abforbtion of its vital parts,, 

 as to admit the efcape of fixed air from the fubftances adted upon 

 (which would then be calcined) or fo contaminated by mephitic 

 and fixed airs as to be incapable of producing the violent and 

 extreme efl?eds required by this hypothefis ; then where fhall we 

 place the ftrata to be aded on ? if over the coaly vaults, they 

 will not be in contad with the flame ; if under or on one fide, 

 only their furface can be aded on. Thu«, on whatever fide 



we; 



