-Elements of Mineralogy. 



White Volcanic Earth. 



That of Solfatera, examined by Mr. Berg- 

 man, was found to confift chiefly of filex, 

 mixed with about 4 per cent, of argill, and 

 8 per cent, of allum. 3 Bergm. \ 98. 



Tripoli. 



Its colour is either white, grey, yellow, 

 reddifh, or brown, either indurated and brit- 

 tle, or loofe, powdery, and rough : it does 

 not foften in water, nor effervefce with acids. 

 According to Mr. UArcet, it is verifiable />#" 

 fe in a porcelain heat long continued ; and ac- 

 cording to Mr. Bergman, it yields to borax 

 and microcofmic fait, but fcarcely to fixed al- 

 kali. 



Mr. Haafe, who has lately anal y fed it, 

 found ico parts of it to contain 90 of filiceous 

 Earth, 7 of argill, and 3 of iron ; but the 

 red fort probably contains more iron. Ac- 

 cording to Mr. Gerhard, magnefia has fome- 

 times been extracted from it. 



It is evidently a volcanic product ; for a 

 coal-mine nearS/. Eftienne having accidentally 

 taken fire, and the fire in its progrefs having 

 extended to fome ftrata of fhiflus and bitumen, 

 tripoli was found in thofe parts of the ftrata 



that 



