252 
Lead . 
those of ashes ; but in this case, and before the lead is in- 
troduced, you must fill up the gutter which has been 
made for the litharge to run off, after having removed with 
a chisel the kind of varnish which the oxyd of lead has 
left on the sides of it, in order that the new sand, some- 
what moistened, may form an intimate connection with 
the old sand, which must also be watered in that part be- 
fore the new sand is deposited. 
The long duration of earthen soles in reverberating fur- 
naces, where lead ore and even litharge are fused, as I 
have already mentioned, leaves no room for apprehension 
in regard to the action of the oxyd of lead, which will act 
only at the surface of the cupell, and will penetrate only a 
very small part of its thickness. 
After one or more operations of refining, this crust must 
be removed, and fused in a furnace in contact with fuel, 
in order to obtain the lead. This process will be as easy 
as the reduction of that metal contained in the ashes of 
common cupells, and in a much smaller quantity. More 
litharge then will be obtained by the new method than the 
old ; which is an advantage, as I have already observed. 
I shall here add, that as the sole of sand does not absorb 
so much oxyd of lead as that of ashes, it will not carry 
with it so much silver ; for it is well known that lead re- 
vived from its ashes always contains more than that which 
arises from the reduction of litharge. 
Instead of sand, argillaceous earth might be employed 
for the "construction of cupells, as is the case in regard to 
the soles of the reverberating furnaces in the ci-devant 
Brittany ; but it would be necessary to ram this earth re- 
peatedly for several days ; otherwise it would split, and 
these cracks would increase by the shrinking which must 
result from the heat, and lead would insinuate itself into 
these fissures : an inconvenience which cannot take place 
with sand even a little earthy. I shall observe also, that a 
