Lead . 
249 
scoriae, over which a pavement is to be made of one layer 
of the most porous bricks. 
On this area, which must be concave like the sole on 
which the ashes of common cupells are beat, place foun- 
ders’ sand a little moistened ; to which may be added a 
fifteenth part of argil, if it is not sufficiently earthy, in or- 
der to give it the requisite solidity ; and the whole must 
be carefully mixed. This sand must be rammed in the 
same manner as for consolidating ashes ; and a refining 
bason is to be formed in like manner, uniformly beat in 
all its parts. The thickness of this cupell must be six or 
seven inches : it may be formed of two strata, as will be 
seen hereafter. 
After the bason has been uniformly beat in every part, 
about a gallon of lixiviated wood-ashes may be sifted 
over its whole surface, and rendered adherent with beat* 
ers. 
When the cupell is thus prepared, let down the head 
on the furnace and make a moderate fire in the fire-hole ; 
which must be maintained for several hours, in order to 
cause a part of the water, with which the sand has been 
moistened, to evaporate. The surplus will be dissipated 
during the operation, without any inconvenience, by ca- 
nals of evaporation. 
After a sufficient desiccation, raise the head and suffer 
the cupell to cool a little ; spread out straw or hay over it, 
and arrange the ingots of lead, placing them gently on it 
that their weight may not derange the sand : it is to pre- 
vent such derangement that straw is employed, as is done 
in regard to cupells of bone-ashes.* When the quantity 
of lead necessary for filling the cupell is arranged in the 
furnace, let down the head, and, having luted it round 
* Instead of prismatic ingots it will be better to cast the lead 
in hemispherical iron moulds. Pieces of that form are less liable 
to damage the cupell • 
Vol. IIL li 
