232 THEORY of the 



THE water of Giezer in Iceland undoubtedly contains this 

 fubftance in folution ; but there is no reafon to believe, that it 

 is here diflblved by any other than the natural means j that is, 

 an alkaline fubftance, by which liliceous bodies may be rendered 

 foluble in water. 



IT may be, therefore, afTerted, that no filiceous body lia-ving 

 the hardnefs of flint, nor any cryftallization of that fubftance, 

 has ever "been formed, except by fufion. If, by any art, this 

 fubftance mall be diflblved in fimple water, or made to cryftal- 

 lize from any folution, in that cafe, the aflertion which has been 

 here made may be denied. But where there is not the veftige 

 of any proof, to authorife the fuppofition of flinty matter be- 

 ing diflblved by water, or cryflallized from that folution, fuch 

 an hypothefis cannot be admitted, in oppofition to general and 

 evident appearances. 



BESIDES this proof for the fufion of filiceous bodies, which 

 is indirect, arifing from the indifTolubility of that fubftance in 

 water, there is another, -which is more direct, being founded 

 upon appearances which are plainly inconfiftent with any 

 other .fuppofition, except that of fimple fluidity induced by 

 heat. The proof I mean ,is, the penetration of many bodies 

 with a flinty fubftance, which, according to every collateral 

 circumftance, muft have been performed by the flinty matter 

 in a fimply fluid ftate, and not in a ftate of diflolution by . 

 folvent. 



THESE are flinty bodies perfectly infulated in ftrata both of 

 chalk and fand. It requires but infpection to be convinced. 

 It is not poflible that flinty matter could be conveyed into the 

 middle of thofe ftrata, by a menftruum in which it was dif- 

 folved, and thus depofited in that- place, without the fmalleft 

 .trace of 'depofition in the furrounding parts. 



BUT, befides this argument taken from what does not appear, 

 the actual form in which thofe flinty mafles are found, ctemon- 



flrates, 



