68 . Mountain Cork, &c. [Book VI. 



called mountain leather ; when twifted, mountain 

 cork. 



The mountain cork or leather contains in the hun- 

 dred from 56 to 62 parts of filiceous earth, from 22 

 to 26 of mild magnefia, from 7 to 14 of mild calca- 

 reous earth, 1.7 of clay, and 10.6 of iron. Thefe 

 afford a white flag by fufion. The fpecimens which 

 arc of a yellowifh brown colour are impure, and melt 

 pretty eaiily into a black flag. There is alfo a fpe- 

 cies of a light green colour, fomewhat more brittle, 

 and contaminated with iron. This laft is foluble by 

 heat into a femitranfparent glafs. 



