in the Pv rites. in 



as little as it does the black caft of the fcori^of 

 iron-pyrites, though it bring them fomewhat nearer 

 to a brown. I (hall leave to further reflection the 

 vitrification I performed, without additions, in a 

 glais furnace •, where, both from copper- ore, the 

 common pyrites, pure fulphur -pyrites, and the ar> 

 ienical, as the mifpickel, and mock-lead, I ufually 

 procured'a black, dark glafs. 



CHAP, 



