( l62 ) 



of two of thefe pieces was a light'ifli blue, 

 and that of the three others a grey. The 

 bafe of the feven other pieces was a dark- 

 gi'een horn-ftone moderately hard. None 

 of them differed in their bafe, and fhoerla- 

 ceous and feltfpathofe cryftallizations, from 

 feveral volcanic lavas of the Eolian ifles. 



Thefe eleven pieces, however, excited in 

 me a ftrong fufpicion that the rocks from 

 which they were detached had not been 

 expofed to the allien of fire. The parti- 

 cles of the petrofilex in them were more 

 clofely united, had greater hardnefs, and a 

 more filiceous appearance, than in the fame 

 ftone of thofe illands which has been fub- 

 jeded to fufion. In like manner, the lavas 

 of a horn-ftone bafe ufually have fomewhat 

 of a fibrous nature, and a thinnefs in their 

 texture which is not feen in the ftone of 

 the fame kind. Thefe two rocks, therefore, 

 appeared to me to be in their natural ftate. 



I .confider thefe experiments as very in- 

 ftrudive with regard to the origin and 



formation 



