Obfervatiom on Lead Ore. 86g 
particles of it were fublimed to at leaft fix inches above 
the furface of the liquid in the crucible. After letting 
the crucible continue two hours in this ftate, I poured 
out its contents, and found them conli fling partly of 
lead, partly of lead ore, and partly of a very minute por- 
tion of brownifh fcoria. 
Thefe experiments prove, that fome fubftance or 
other is contained in lead ore, which muft be difperfed 
before the ore can be formed into lead ; and they fhew 
too, that it requires a confiderable time to effect the dif- 
perfion of this fubftance, fince fix ounces of ore, though 
kept three hours or more in complete fulion, were not 
wholly brought into the form of lead ; and, laftly, they 
render it probable, that the fumes, arifing from melted 
ore, carry off with them no inconsiderable portion of the 
lead itfelf. At the great fmelting houfes in Derby fhire, 
they put a ton of ore at a time into the furnace, and work, 
it off in eight hours ; the ore might be wholly melted in 
one hour, but the lead perhaps is not formed in the 
greateft poflible quantity in eight hours. 
Some fine teffelated lead ore from Derbyfhire was 
pounded into fmall lumps, each about the fize of a pea,, 
and carefully picked from fpar and other impurities- 
Sixteen ounces of this ore, thus previoufly cleanfed, were 
diftilled in an earthen retort; as foon at the ore felt the 
3 fee. 
