( 34^ ) 



I, therefore, refolved to endeavour to af- 

 certain whether this fubUmation took place, 

 likewife^ in crucibles in the furnace when 

 covered with other crucibles. I had nine- 

 teen in the whole, within which I placed 

 thofe kinds of volcanic matters which are 

 moft liable to inflate in large bubbles. On 

 the fides, and at the top of three of the 

 inverted crucibles that ferved as covers to 

 the others, I perceived evident figns of fub- 

 limation ; in fome fine vitreous traces, and a 

 great number of extremely minute vitreous 

 globules, which, in fubftance and colour, 

 did not in the leaft differ from the refpedive 

 matters fufed in the three crucibles. But 

 nothing fmiilar was apparent in the other 

 three crucibles. The former of thefe fads, 

 which is pofitlve, is a new and luminous 

 proof of the gafification of volcanifed produc- 

 tions ; and the latter, which is negative, no 

 proof to the contrary ; fmce, though every 

 one of thefe fixteen produds were ebullient 

 within the crucibles, and therefore, from 

 what has been above faid, there is the ftrong- 

 eft reafon to believe they were rendered fo 



by 



