Elements of Mineralogy. 



obferved, and elegantly defcribed by our mo- 

 dern Pliny Sir William Hamilton. 



The fubftances ejected by volcanos are, 

 phlogifticated, fixed, and inflammable air, 

 water, afhes, pumiceftones, ftones that have 

 undergone no fufion, and lava. 



The water proceeds partly from that con- 

 tained in the volcano, partly from the con- 

 denfed vapors, and partly perhaps from the 

 intimate union of the phlogifton and dephlo- 

 gifticated air ; an union which fome late ex- 

 periments fhew to be productive of water in 

 certain circumftances. Part of the afhes is 

 plentifully moiftened with this water, and 

 forms tufa traafs> &c. 



Stones of all forts and fizes, even of 10 

 feet in diameter, are projected by volcanos* 

 and fometimes to great diftances : hence 

 probably thofe folitary maflfes of granite, 

 which are fometimes met with in lime-ftone 

 countries. 



Lavas, in their paflfage through the vol- 

 cano and its caverns, and during their flow- 

 ing, ,neceirarily involve various forts of ftone, 

 which are not therefore products of fire, 

 though found in lava ; fuch as quartz, fpar, 

 Ihoerl, &c. and thus various porphyries and 



pudding- 



