shall be made caldarium copper. But when the copper, yellow or red or caldarium is re-smelted in the refining furnace, forty centumpondia are placed in
it, and from it they make at least twenty, and at most thirty-five, centumpondia. About twenty-two centumpondia of exhausted liquation cakes and
ten of yellow copper and eight of red, are simultaneously placed in this latter
furnace and smelted, in order that they may be made into refined copper.
The copper " bottoms " are alloyed in three different ways with lead.17
First, five-eighths of a centumpondium of copper and two and threequarters centumpondia of lead are taken ; and since one liquation cake is made
from this, therefore two and a half centumpondia of copper and eleven centumpondia of lead make four liquation cakes. Inasmuch as in each centumpondium of copper there is a third of a libra of silver, there would be in the whole
of the copper ten-twelfths of a libra of silver ; to these are added four centumpondia of lead re-melted from " slags," each centumpondium of which contains
a sicilicus and a drachma of silver, which weights make up a total of an uncia
and a half of silver. There is also added seven centumpondia of de-silverized
lead, in each centumpondium of which there is a drachma of silver ; therefore
in the four cakes of copper-lead alloy there is a total of a libra, a sicilicus and
a drachma of silver. In each single centumpondium of lead, after it has been
liquated from the copper, there is an uncia and a drachma of silver, which alloy
we call " poor " argentiferous lead, because it contains but little silver. But
as five cakes of that kind are placed together in the furnace, they liquate
from them usually as much as nine and three-quarters centumpondia of poor
