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With a petrofillceous bafc, which, from its 

 compadnels, extremely refembles the natu- 

 ral petrofilex, but which is fufible in the 

 furnace, we find another vein of pitch- 

 flone lava, but of much greater extent, and 

 ■which is difpofed ahnoll vertically. On 

 digging into this vein, we find very beau- 

 tiful and well preferved pieces of pitch- 

 ilone lava. For the mofi: part it has the 

 colour of refin, an elegant luftre, a fine 

 grain, and great compattnefs. It is fmooth 

 and clear in the fracture, with amorphous 

 fragments, femi-tranfparent In the points. 

 It is not, however, fufficiently hard to give 

 fparks with fteel. It is not without felt- 

 fpars, which have a vitreous afpedt:. 



This lava does not entirely compofe 

 this extenfive vein ; but is found there in 

 pieces, ufually fmall, which are clofely 

 bound together by a ftony fubftance which 

 aQs with refpe^t to them as a gluten or 

 cement. Thefe pieces have not been rolled 

 by a ftream or weaves, and thereby become 

 round, but are amorphous, and with acute 



angles. 



