[ 3** ] 



not to make ufe of any other fluxes than fuch as 

 have no attraction to the charcoal : if they, at 

 the fame time, are clear and tranfparent, when 

 melted, as the borax and the fa I fujibile wicrocof- 

 wicnm, it is ftill better : however, thetranfparency 

 or opacity are of no great confequence, if a fub- 

 ftance is eflayed only in order to difcover its fufi- 

 bility, without any attention to its colour •, in which 

 cafe, fome metallic (lag, perhaps, might be ufeful. 



SECT. LIV. 



When fuch ores are to be reduced whofe metals 

 are very apt to calcine, fuch as tin, zinc, &c. it 

 might perhaps be of fervice to add fome phlo- 

 gifton, iince the charcoal cannot afford enough of 

 it in the open fire of thefe elfays : fuch a phlogifton 

 might be the hard refin, or fome fuch body. The 

 manner of melting the volatile metals out of their 

 ores per defcenfum might alfo, perhaps, be imitated : 

 for inflance, a hole might be made in the charcoal, 

 "wide above, and very narrow at the bottom -, a 

 little piece of the ore being then laid at the upper 

 end of the hole, and covered with fome very fmall 

 pieces of the charcoal, the flame muft be directed 

 on the top : the metal might, perhaps, by this me- 

 thod gather in the hole below, concealed from the 

 violence of the fire, particularly if the ore is very 

 fufible, &c. 



Several of my experiments have indeed induced 

 me to believe the poffibility of thefe improvements •, 

 but as I have not yet had an opportunity of bring- 

 ing them to perfection, 1 will not deliver them 

 as infallible : thefe hints are only communicatee^ 

 fs an inducement to farther experience. 



SECT- 



