( 2Sg ) 



tremely tranfparent quartz. I know not 

 whether this powder be a decompolition of 

 quartz, which, however, does not appear 

 very probable, as it is found deep in the in- 

 ternal part of the lava, where it is not in 

 the leaft altered ; or whether it be an ex- 

 traneous and adventitious fubftance. Be- 

 fides the quartzofe grains, the petrofiliceou? 

 bafe contains a few very fmall feltfpars, 

 which, from their changeable briiliancrj, 

 their rhomboidal form, and their being 

 compofed of minute laminse, cannot be 

 confounded with the quartzofe grains. 



It is neceflary to obferve that the bads 

 of this lava, in the furnace, ferves for a 

 flux to thefe quartzofe grains ; the relult 

 being a homogeneous and white enamel, 

 without the fmaileft appearance of any 

 remains of the quartzofe grains, or the 

 feltfpars. 



Another lava, found on each fide of the 



road, in a place called the Pigozzo, oppofite 



VOL, III. U Catajo, 



