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"Βut it is better at first to add as much lead as is required to the ore which
needs melting, rather than afterward when the melting has been half finished,
that the whole quantity may not vanish in fumes, but part of it remain
fast. When the heat of the fire has nearly consumed the lead, then is the
time when the gold and silver gleam in their varied colours, and when all the
lead has been consumed the gold or silver settles in the cupel. Then as
soon as possible remove the cupel out of the furnace, and take the button out
of it while it is still warm, in order that it does not adhere to the ashes. This
generally happens if the button is already cold when it is taken out. If the
ashes do adhere to it, do not scrape it with a knife, lest some of it be lost and
the assay be erroneous, but squeeze it with the iron tongs, so that the ashes
drop off through the pressure. Finally, it is of advantage to make two or
three assays of the same ore at the same time, in order that if by chance
one is not successful, the second, or in any event the third, may be certain.
While the assayer is assaying the ore, in order to prevent the great heat
of the fire from injuring his eyes, it will be useful for him always to have
ready a thin wooden tablet, two palms wide, with a handle by which it may
be held, and with a slit down the middle in order that he may look through
it as through a crack, since it is necessary for him to look frequently within
and carefully to consider everything.
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Now the lead which has absorbed the silver from a metallic ore is consumed in the cupel by the heat in the space of three quarters of an hour. When
the assays are completed the muffle is taken out of the furnace, and the
ashes removed with an iron shovel, not only from the brick and iron furnaces,
but also from the earthen one, so that the furnace need not be removed from
its foundation.
From ore placed in the triangular crucible a button is melted out, from
which metal is afterward made. First of all, glowing charcoal is put into
the iron hoop, then is put in the triangular crucible, which contains the ore
together with those things which can liquefy it and purge it of its dross ;
then the fire is blown with the double bellows, and the ore is heated until
the button settles in the bottom of the crucible. We have explained that
there are two methods of assaying ore,—one, by which the lead is mixed
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