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Lead* 
The following article on the smelting of lead from Dr. 
Rees’s Cyclopaedia contains also many remarks of practi- 
cal consequence. 
Reduction of the Ores , or smelting of Lead, 
Two processes are employed for the smelting of lead* 
the one by means of a blast furnace, called an ore-hearth, 
and the other by means of a reverberatory furnace. The 
latter is used throughout Derbyshire and North Wales, 
and is undoubtedly the best, where coal is not very scarce. 
In the former of these methods the ore and the fuel are 
mixed together, and exposed to the blast. The heat dis- 
sipates the sulphuret,* the ore being the common sulpha- 
ret of lead or galena. A portion of the lead is oxydated, 
which facilitates the vitrification of the earthy parts of the 
ore, and of the fuel. These together constitute the slag 
or scoriae. The metallic lead falls into the lower part 
of the hearth, and is defended from the oxygen of the 
blast by the scoriae, which is fluid upon its surface. The 
liquid lead is let off from time to time, always retaining a 
portion for the scoriae to float upon. When the whole of 
the lead is to be drawn off, the blast must be stopped, and 
some lime thrown upon the liquid scoriae, which renders 
it concrete, while the lead, being still liquid, can be run 
off. 
The reverberatory furnace employed for smelting lead 
is made on the same plan with those commonly used for 
puddling iron, differing in size, and a few other particu- 
lars. The fire is made at one end, and the flame plays 
over the hearth, entering an oblique chimney at the end, 
which terminates in a perpendicular one, of considerable 
height. The length of the hearth, from the place where 
the fire enters, to the chimney, is II feet ; two feet of 
this length next the fire constitutes the throat of the fur- 
nace ; the width of the same is four feet, and its depth 
* Rather the sulphur .■ — T. C. 
