Lead . 
253 
sole of earth would harden too much to allow a gutter to 
be dug for the passage of the litharge : in this case it 
would be necessary that the place destined for the oxyd 
to run off should be constructed with sand or lixiviated 
ashes. 
I shall add also, that it will be advantageous to employ 
two kinds of sand in the formation of the bason of the 
cupell ; one kind fine like that used by founders, and 
the other coarser and not earthy : the latter will form the 
first stratum, which, after being beat with rammers des- 
tined for that purpose, ought to be about three inches 
and a half in thickness. The fine sand, a little earthy, 
must then be applied over this first stratum to form a se- 
cond, which is to be rammed like the former. Both these 
kinds of sand must be somewhat moistened before they 
are introduced into the furnace, in order that they may 
be better heaped up, and be consolidated by the ram- 
mers . 
The sand of the lower stratum, being coarser than that 
of the upper, will absorb the moisture of the latter in pro- 
portion as it evaporates ; and it will pass without any ob- 
stacle through the canals disposed for that purpose. 
The lower stratum of .sand may remain in its place 
when a new cupell is to be constructed with fine sand, 
and the part of the latter, which has not been impregnated 
with oxyd, must be mixed with new sand to form a cu- 
pell. Care must be taken in raising this sand not to 
touch the lower stratum ; for the sand of the latter, which 
is coarse, must not be mixed with the other. This in - 1 
convenience may be avoided by beating over the bed of 
coarse sand a thin stratum of ashes, at which you must 
stop in removing the fine sand of the upper stratum. 
It has been said that the founders’ sand must be some- 
what earthy, and that, if it is not, a little argil must be 
added to give it cohesion : but, as it is necessary that this 
