ITALY. LETTER XI. 147 



5. .If thrown up from under ground, why are 

 not all forts of fherls found in the lava ? The 

 above deicribed blend- like fherl, inclofed in the 

 micaceous limeftone fpar, though with that fpar 

 thrown out by fire, are never feen in the lavas ; 

 and thefe are rather filled with white garnets never 

 obferved in that micaceous limeftone. 



6. There are white and black fherl points, not 

 above the bignefs of a pin's head, glued into the 

 fubftance of lava. How is it to be afierted, that 

 thefe fmall regular bodies have been cryftallized 

 before in the rocks under ground ? In what other 

 mountains are fuch fmall merl-cryftallizations to be 

 found ? Why have they been fo exactly feparated 

 from their former rock-matrix, and been fo equally 

 diftributed in the lava ? The fame queftions will 

 do for the greater cryftallizations. 



7. Obferving the compacted black lavas by a 

 microfcope, we find in its fubftance a great many 

 white cryftalline fherl flakes ; which prove, that 

 they are fubftantial particles, which, being of a 

 fimilar nature, during the fufion of the heteroge- 

 neous melted materials, have approximated and 

 cont railed themfelves into fuch flakes or greater 

 cryftallizations. Such I imagine to be their origin, 

 as feeing no impoflibility that certain bodies, in a 

 ftate of hot fluidity, may be endowed with a ten- 

 dency to determined regular forms, as well as 



L 2 many 



