[ 312 ] 
not to make ufe of any other fluxes than fuch m 
have no attradion to the charcoal : if they, at 
the fame time, are clear and tranfparent, when 
melted, as the borax and the fal fuJihUe microcof- 
mcnm^ it is fl:ill better : however, the tranfparency 
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 ^hich 
cafe, fome metallic flag, perhaps, might be ufeful. 
SECT. LIV. 
When fuch ores are to be reduced whofe metals 
;ire very apt to calcine, fuch as tin, zinc, &c. it 
might perhaps be of fervice to add fome phlo- 
gifton, fmce the charcoal cannot afford enough of 
it in the open fire of thefe effays : fuch a phlogiflop 
might be the hard refin, or fome fuch body. The 
manner of melting the volatile metals out of their 
ores defcenfiim might alfo, perhaps, be imitated : 
for inftancc, 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 fiiiall 
pieces of the charcoal, the flame mufl; be direcfted 
on the top : the metal m/ight, perhaps, by this me- 
thod gather in the hole below, cqncealed from the 
violence of the fire, particularly if the ore is very 
fufible, &c. 
Several of my experiments have indeed induced 
me to believe thepoffibility of thefe improvements ; 
but as I have not yet had an opportunity of bring- 
ing them to perfedion, 1 v/i\\ not deliver them 
n-s infallible : thefe hints are only communicated 
^ an inducernen^ to farther experience. 
S E C 
