PHYSICAL AND LITERARY. 377 



ly, unlefs the fire is confiderably increa-« 

 fed ; and, after feveral hours, the matter 

 has ftill the appearance of a very moiil 

 fait, which is very corrofive, and, in bulk 

 and weight, greatly exceeds the (ilver 

 that was diflblved. When the fandheat 

 can make no further change on the mafs, 

 put it into a crucible, and fet it in a 

 Jjretty hnik. and clear fire : This expells 

 the remaining moifture and fuperfluous 

 acid ; after this the matter melts like 

 wax, and, when cold, is turned to a hard 

 fubftance ; the cauftic quality of which, 

 the increafe of weight above that of the 

 filver, and its aptnefs to moiften^ fliew, 

 that, after all the heat which the mafs has 

 fuftained, there is ftill a good quantity of 

 the faline part of the fpirit of nitre inti- 

 mately incorporated with the filv.er. Now, 

 tA/hen a piece of this hard flony fubftance 

 is put upon a piece of well kindled char- 

 coal, and blown a little, it makes an ex- 

 plofion with a fparkling and flame, like a 

 piece of common fdt petre ; the faline 

 matter is coniumed or turned into a flame 

 or fmoke, and the pure filver is left on 

 VoL.L Bbb the 



