1are so placed on
the sole-stones that they project a palm at the sides, and at the
front the sole-stones project to the same extent; if rectangular stones are
not available, bricks are laid in their place. The copper plates are four feet
two palms and as many digits long, a cubit wide, and a palm thick; each
edge has a protuberance, one at the front end, the other at the back; these
are a palm and three digits long, and a palm wide and thick. The plates are
so laid upon the rectangular stones that their rear ends are three digits from
the third long wall; the stones project beyond the plate the same number
of digits in front, and a palm and three digits at the sides. When the plates
have been joined, the groove which is between the protuberances is a palm
and three digits wide, and four feet long, and through it flows the silver-lead
which liquates from the cakes. When the plates are corroded either by the
fire or by the silver-lead, which often adheres to them in the form of stalacÂ
tites, and is chipped off, they are exchanged, the right one being placed to the
left, and the left one, on the contrary, to the right; but the left side of the
plates, which, when the fusion of the copper took place, came into contact
with the copper, must lie flat; so that when the exchange of the plates has
been carried out, the protuberances, which are thus on the underside, raise
the plate from the stones, and they have to be partially chipped off, lest they
should prove an impediment to the work; and in each of their places is
laid a piece of iron, three palms long, a digit thick at both ends, and a palm
thick in the centre for the length of a palm and three digits.
front the sole-stones project to the same extent; if rectangular stones are
not available, bricks are laid in their place. The copper plates are four feet
two palms and as many digits long, a cubit wide, and a palm thick; each
edge has a protuberance, one at the front end, the other at the back; these
are a palm and three digits long, and a palm wide and thick. The plates are
so laid upon the rectangular stones that their rear ends are three digits from
the third long wall; the stones project beyond the plate the same number
of digits in front, and a palm and three digits at the sides. When the plates
have been joined, the groove which is between the protuberances is a palm
and three digits wide, and four feet long, and through it flows the silver-lead
which liquates from the cakes. When the plates are corroded either by the
fire or by the silver-lead, which often adheres to them in the form of stalacÂ
tites, and is chipped off, they are exchanged, the right one being placed to the
left, and the left one, on the contrary, to the right; but the left side of the
plates, which, when the fusion of the copper took place, came into contact
with the copper, must lie flat; so that when the exchange of the plates has
been carried out, the protuberances, which are thus on the underside, raise
the plate from the stones, and they have to be partially chipped off, lest they
should prove an impediment to the work; and in each of their places is
laid a piece of iron, three palms long, a digit thick at both ends, and a palm
thick in the centre for the length of a palm and three digits.
The passage under the plates between the rectangular stones is a foot
wide at the back, and a foot and a palm wide at the front, for it gradually
widens out. The hearth, which is between the sole-stones, is covered with a
bed of hearth-lead, taken from the crucible in which lead is separated from
silver. The rear end is the highest, and should be so high that it reaches to
within six digits of the plates, from which point it slopes down evenly to the
front end, so that the argentiferous lead alloy which liquates from the cakes
can flow into the receiving-pit. The wall built against the third long wall
in order to protect it from injury by fire, is constructed of bricks joined
together with lute, and stands on the copper plates; this wall is two feet, a
palm and two digits high, two palms thick, and three feet, a palm and three
digits wide at the bottom, for it reaches across both of them; at the top it is
three feet wide, for it rises up obliquely on each side. At each side of this wall,
at a height of a palm and two digits above the top of it, there is inserted in a
hole in the third long wall a hooked iron rod, fastened in with molten lead;
the rod projects two palms from the wall, and is two digits wide and one
digit thick; it has two hooks, the one at the side, the other at the end.
Both of these hooks open toward the wall, and both are a digit thick, and
both are inserted in the last, or the adjacent, links of a short iron chain. This
chain consists of four links, each of which is a palm and a digit long and half
a digit thick; the first link is engaged in the first hole in a long iron rod, and
one or other of the remaining three links engages the hook of the hooked rod.
The two long rods are three feet and as many palms and digits long, two
digits wide, and one digit thick; both ends of both of these rods have holes,
wide at the back, and a foot and a palm wide at the front, for it gradually
widens out. The hearth, which is between the sole-stones, is covered with a
bed of hearth-lead, taken from the crucible in which lead is separated from
silver. The rear end is the highest, and should be so high that it reaches to
within six digits of the plates, from which point it slopes down evenly to the
front end, so that the argentiferous lead alloy which liquates from the cakes
can flow into the receiving-pit. The wall built against the third long wall
in order to protect it from injury by fire, is constructed of bricks joined
together with lute, and stands on the copper plates; this wall is two feet, a
palm and two digits high, two palms thick, and three feet, a palm and three
digits wide at the bottom, for it reaches across both of them; at the top it is
three feet wide, for it rises up obliquely on each side. At each side of this wall,
at a height of a palm and two digits above the top of it, there is inserted in a
hole in the third long wall a hooked iron rod, fastened in with molten lead;
the rod projects two palms from the wall, and is two digits wide and one
digit thick; it has two hooks, the one at the side, the other at the end.
Both of these hooks open toward the wall, and both are a digit thick, and
both are inserted in the last, or the adjacent, links of a short iron chain. This
chain consists of four links, each of which is a palm and a digit long and half
a digit thick; the first link is engaged in the first hole in a long iron rod, and
one or other of the remaining three links engages the hook of the hooked rod.
The two long rods are three feet and as many palms and digits long, two
digits wide, and one digit thick; both ends of both of these rods have holes,