Lead . . 
245 
the metal : besides, the operation would require a period 
ten times as long as that used in general for refining, and 
would occasion ten times the expence in fuel, and a much 
greater loss of the metals than by the usual process, where 
the greater part of the lead is obtained in litharge, while a 
portion penetrates into the cupel! for about two inches of 
its thickness, which must be fused to revive the lead* 
This reduction is also more expensive, and experiences 
a greater loss than the litharge, which is easily fused, and 
which, without passing through the furnace, may be em- 
ployed as an article in commerce. 
Lead ore and litharge may be fused as in England, and 
the department of the ci-devant Brittany, in a reverberating 
furnace the soles or basons of which are formed of pound- 
ed and moistened clay. These soles can stand the action 
of heat and of the oxyd of lead for six or eight months of 
uninterrupted labour. 
The durability of these earthen soles gave me the first 
idea of the method, which I shall hereafter propose, for 
refining- furnaces, where the only thing required is to 
oxydate the lead to obtain it in litharge, and not to cause 
the cupeils to imbibe the whole of it, as is done when the 
object is to assay the metal in order to know whether it 
contains silver. In operating on a large scale, the cupel!, 
though of ashes, absorbs only a part of the lead, as I have 
-already said, observing at the same time that it would be 
much more advantageous to obtain the whole transformed 
into litharge, the reduction of which into lead is much 
easier than that of the oxyd contained in the ashes, which 
oppose fusion, and the scoria of which always carry with 
them some of the metal. 
In a cupell of ashes beat into an oval circle of iron, the 
greater diameter of which is only five or six feet and the 
less one yard, the English refine from a ton to 23 cwt. of 
lead, which is converted into beautiful litharge, except the 
