( 339 y 



a general revifion of the various crucibles I 

 had before made ufe of in the furnace, and 

 which had contained veficular volcanic pro- 

 duds 5 as 1 had not before examined them 

 with a view to this objedt, believing that 

 the veficles or bubbles were caufed by fome 

 permanent gas. There were not a fev^r, to 

 fay the truth, the internal fides of which 

 exhibited, above the fufed produd:, fmall 

 drops of the fame fubftance : but it was 

 eafy to perceive that thefe were not coUeded 

 there by fublimation ; but were thrown to 

 that height by the inreftine motion of the 

 produds in fufion. There was, however, no 

 crucible which prefented that thin coating, 

 or that aggregate of infinitefimal globules, 

 obfervable in the laft experiment, and 

 which manifefted an evident fublimation of 

 the fufed fubflances. This, indeed, did not 

 furprife me ; as the crucibles were of a 

 cylindrical, or inverted conical form, and 

 open at the top ; fo that the particles which 

 might fublime met with no oppofing body 

 to detain and colled them. 



Z 2 I, there- 



