( ^53 ) 



colour and luflre of pitch, and contains 

 numerous feltfpars. In its external appear- 

 ance it does not differ from that before 

 defcribed. It has, however, one peculiarity 

 which mufl; render it valuable in the eyes 

 of the volcanift. 



Pumices are a kind of produds which 

 bear in them, demonftratively, the evidences 

 of fire ; and the traveller who on any 

 mountains meets with a vein of uncertain, 

 origin which pafTes immediately into the 

 ftate of pumice, is fully warranted to de- 

 clare it volcanic. This is the cafe in the 

 prefent pitch-ftone. It contains groups, 

 more or lefs large, of fibrous, light, cellular 

 pumice, not merely contained within it, 

 but compofmg one fmgle body with it : 

 whence it appears that foaie parts of this 

 rock, either by a more violent adion of 

 the fire, or becaufe they were more eafily 

 vitrifiable, have pafTed into the flate of 

 pumice. 



In the fame Monte Sieva, befides a lava 



with 



