Agricola, Georgius, De re metallica, 1912/1950
page |< < of 679 > >|
The hearth is made of lute, and is covered either with copper plates,
such
as those of the furnaces in which silver is liquated from copper, although
they
have no protuberances, or it may be covered with bricks, if the owners
are
unwilling to incur the expense of copper plates.
The wider part of the
hearth
is made sloping in such a manner that the rear end reaches as high as
the
five vent-holes, and the front end of the hearth is so low that the back
of
the front arch is four feet, three palms and as many digits above it,
and
the front five feet, three palms and as many digits.
The hearth beyond
the
furnaces is paved with bricks for a distance of six feet.
Near the
furnace
, against the fourth long wall, is a tank thirteen feet and a palm
long
, four feet wide, and a foot and three palms deep.
It is lined on all sides
with
planks, lest the earth should fall into it; on one side the water flows
in
through pipes, and on the other, if the plug be pulled out, it soaks into the
earth
; into this tank of water are thrown the cakes of copper from which
the
silver and lead have been separated.
The fore part of the front furnace
arch
should be partly closed with an iron door; the bottom of this door is
six
feet and two digits wide; the upper part is somewhat rounded, and at
the
highest point, which is in the middle, it is three feet and two palms high.
It is made of iron bars, with plates fastened to them with iron wire, there
being
seven barsā€”three transverse and four uprightā€”each of which is two
digits
wide and half a digit thick.
The lowest transverse bar is six feet and
two
palms long; the middle one has the same length; the upper one is
curved
and higher at the centre, and thus longer than the other two.
The
upright
bars are two feet distant from one another; both the outer ones are
two
feet and as many palms high; but the centre ones are three feet and two
palms
.
They project from the upper curved transverse bar and have holes,
in
which are inserted the hooks of small chains two feet long; the topmost
links
of these chains are engaged in the ring of a third chain, which, when
extended
, reaches to one end of a beam which is somewhat cut out.
The chain
then
turns around the beam, and again hanging down, the hook in the other end
is
fastened in one of the links.
This beam is eleven feet long, a palm and two
digits
wide, a palm thick, and turns on an iron axle fixed in a near-by timber;
the
rear end of the beam has an iron pin, which is three palms and a digit long,
and
which penetrates through it where it lies under a timber, and projects
from
it a palm and two digits on one side, and three digits on the other side.
At this point the pin is perforated, in order that a ring may be fixed in it

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