92 



ILLUSTRATIONS OF THE 



ing feated deep under the fur face. That this 

 iptenfity is confide rable, is certain from the ex- 

 eriments made by Sir James Hall on the fufi- 



P 

 b 



f whin-ftone and 

 that the lowed 



from which 



pe 



m 



either of thefe Hon 



Wed 2:6 wood 



melt, is about 30 



hich 



of 







s pyrometer. Some niineralogifts 

 d affirmed, that lava is melted, not by 



fity of th 



h 



feq 



of 



a certain 



pplied to 

 combinati 



but in 

 formed 



between it and bituminous fubftances, in a man- 

 ner which they do not attempt to explain, and 

 which has indeed no analogy to any thing that is 

 known. That a hypothecs, formed in fuch di- 

 red oppofition to the mod obvious principles of 

 indudive reafoning, fhould have been imagined 

 hy a philofopher who had examined the pheno- 

 mena of ^tna and Vefuvius with much atten- 

 tion, and defcribed them with great accuracy 

 and truth, is more wonderful than that it iliould 

 have been adopted hy mineralogifls, whofe views 

 of nature may have been confined within a ca- 

 binet or a laboratory. It is, however, a hy- 

 potheiis, which, having never had any fupport 

 but from other hypothefes, hardly merited the 



dire6l refutation that it has received from the 

 experiments juil mentioned. 



88. But, if the intenfity of volcanic heat be 



fuch as is here Hated, it will be found very 



difficult 



A 



