178 Observations on Lead Ores. 
At Patterdale, the ore yields fifty or sixty ounces of sil- 
ver to a ton. Ss 
The poorest lead ores yield most silver. 
rom seven to ten thousand tons of lead are smelted an- 
nually in Derbyshire. ; 
he tests or cupels are made of four parts of calcined 
bones, and one part unwashed fern ashes ; wood ashes are 
sometimes used without washing. 
If galena be free from pyrites the lead may be melted 
t without roasting, otherwise not. (Bl. II. 620: 
One-eighth of an ounce, or less, of gold or silver may be 
separated from one hundred pounds of lead by scorification. 
The lead is recovered from the cupels by pounding them 
up, and mixing the powder with inflammable matters by 
the aid of beat. 
I = emenariig dissolves out the silver,* but cupellation 
is best. 
~ Iron precipitates both lead and silver. (Fourcroy:) 
The proportion of silver in lead, varies from one-three 
hundreth to one-twelth. able | 
The lustre of galena is impaired by silver; this metal is 
more commonly found in the octohedral than the cubical 
varieties, | Liaiis 
Blende and calamine often oceur with galena. 
Antimony is commonly in argentiferous lead ores, which 
hardens the lead; and the p cesses for getting rid of the 
Ket are 7 pee as for extracting the silver. = 
7 pes may be made of any infusible earth of little co- 
nosioe, (Aikin, I. 110,)—cores of ox horns are preferred at 
- This may however be dangerous, as fulminating silver may be formed. 
