54 *Df tt>e J&etfnnteal tiftftftte 



agreeably to what I lately began to 

 obferve^ that a body may pafs for 

 absolutely fixt among the generality 

 of Chymiftsj and yet be unable to 

 perfevere in the fires of Founders and 

 Qlafs-makers: Which brings into my 

 mind, that not having obferved, that 

 Chymifts have examined the Fixity 

 of other bodies than metalline ones 

 by the Cupel, I had the Curiofity to 

 put dry Salt of Tartar upon it 5 and 

 found, as I expe&ed^ that in no long 

 time it manifeftly wafted in fo vehe- 

 ment a heat, wherein alfo the Air 

 came freely at ^(though Quick-lime, 

 handled after the fame way, loft not 

 of its weight,) and having well mix- 

 ed one ounce of good Salt of Tar- 

 tar with treble its weight of Tobac- 

 co-pipe Clay, we kept them but for 

 two., or at moft three hours, in a 

 ftrong fire 3 yet the Crucible being 

 purpofely left uncovered, we found 

 the Salt of Tartar fo wafted, that the 

 remaining mixture (which was not 

 flux'd) afforded us not near a quarter 

 of an ouqceof Salt* And indeed I 



fcarce 



