so as to loosen and smooth the face of the cupel. The cupel is got out
by pressing up the disc of metal forming the false bottom; the removal
is more easily effected if the mould is somewhat conical, instead of
cylindrical, in form. The cupels are put in a warm place to dry for two
or three days. A conveniently sized cupel is 1-1/4 inches in diameter
and about 3/4 inch high. The cavity of the cupel is about 1/4 inch deep,
and something of the shape shown in fig. 5.

[Illustration: FIG. 6.]

[Illustration: FIG. 7.]

[Illustration: FIG. 8.]

There are two kinds of furnaces required, the "wind" and "muffle"
furnaces. These are built of brick, fire-brick, of course, being used
for the lining. They are connected with a chimney that will provide a
good draught. Figure 6 shows a section of the wind furnace, fig. 7 a
section of the muffle furnace, and fig. 8 a general view of a group
comprising a muffle and two wind furnaces suitable for general work.
When in operation, the furnaces are covered with iron-bound tiles. The
opening under the door of the muffle is closed with a loosely fitting
brick. The floor of the muffle is protected with a layer of bone-ash,
which absorbs any oxide of lead that may be accidentally spilt. The fire
bars should be easily removable.

Few tools are wanted; the most important are some cast-iron moulds,
tongs (fig. 9), stirrers for calcining (fig. 10), and light tongs of a
special form for handling scorifiers and cupels (_see_ SILVER).