Book IX

BOOK IX. 1
Since I have written of the varied work of pre−
paring the ores, I will now write of the various
methods of smelting them. Although those who
burn, roast and calcine 2 the ore, take from it some−
thing which is mixed or combined with the metals;
and those who crush it with stamps take away much;
and those who wash, screen and sort it, take away
still more; yet they cannot remove all which con−
ceals the metal from the eye and renders it crude
and unformed. Wherefore smelting is necessary, for by this means earths,
solidified juices, and stones are separated from the metals so that they
obtain their proper colour and become pure, and may be of great use to
mankind in many ways. When the ore is smelted, those things which
were mixed with the metal before it was melted are driven forth, because
the metal is perfected by fire in this manner. Since metalliferous ores
differ greatly amongst themselves, first as to the metals which they con−
tain, then as to the quantity of the metal which is in them, and then by
the fact that some are rapidly melted by fire and others slowly, there are,
therefore, many methods of smelting. Constant practice has taught the
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smelters by which of these methods they can obtain the most metal from
any one ore. Moreover, while sometimes there are many methods of
smelting the same ore, by which an equal weight of metal is melted out, yet
one is done at a greater cost and labour than the others. Ore is either melted
with a furnace or without one; if smelted with a furnace the tap−hole is either
temporarily closed or always open, and if smelted without a furnace, it is done
either in pots or in trenches. But in order to make this matter clearer, I will
describe each in detail, beginning with the buildings and the furnaces.
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A wall which will be called the "second wall" is constructed of brick
or stone, two feet and as many palms thick, in order that it may be strong
enough to bear the weight. It is built fifteen feet high, and its length depends
on the number of furnaces which are put in the works; there are usually
six furnaces, rarely more, and often less. There are three furnace walls, a
back one which is against the "second" wall, and two side ones, of which I
will speak later. These should be made of natural stone, as this is more
serviceable than burnt bricks, because bricks soon become defective and
crumble away, when the smelter or his deputy chips off the accretions which
adhere to the walls when the ore is smelted. Natural stone resists injury
by the fire and lasts a long time, especially that which is soft and devoid
of cracks; but, on the contrary, that which is hard and has many cracks
is burst asunder by the fire and destroyed. For this reason, furnaces which
are made of the latter are easily weakened by the fire, and when the accretions
are chipped off they crumble to pieces. The front furnace wall should be
made of brick, and there should be in the lower part a mouth three palms
wide and one and a half feet high, when the hearth is completed. A hole
slanting upward, three palms long, is made through the back furnace wall, at
the height of a cubit, before the hearth has been prepared; through this
hole and a hole one foot long in the "second" wallas the back of this wall
has an archis inserted a pipe of iron or bronze, in which are fixed the nozzles
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of the bellows. The whole of the front furnace wall is not more than five feet
high, so that the ore may be conveniently put into the furnace, together with
those things which the master needs for his work of smelting. Both the side
walls of the furnace are six feet high, and the back one seven feet, and they
are three palms thick. The interior of the furnace is five palms wide, six
palms and a digit long, the width being measured by the space which lies
between the two side walls, and the length by the space between the front and
the back walls; however, the upper part of the furnace widens out somewhat.
There are two doors in the second wall if there are six furnaces, one
of the doors being between the second and third furnaces and the other
between the fourth and fifth furnaces. They are a cubit wide and six feet
high, in order that the smelters may not have mishaps in coming and going.
It is necessary to have a door to the right of the first furnace, and similarly
one to the left of the last, whether the wall is longer or not. The second
wall is carried further when the rooms for the cupellation furnaces, or any
other building, adjoin the rooms for the blast furnaces, these buildings being
only divided by a partition. The smelter, and the ones who attend to the
first and the last furnaces, if they wish to look at the bellows or to do anything
else, go out through the doors at the end of the wall, and the other people go
through the other doors, which are the common ones. The furnaces are placed
at a distance of six feet from one another, in order that the smelters and their
assistants may more easily sustain the fierceness of the heat. Inasmuch as
the interior of each furnace is five palms wide and each is six feet distant
from the other, and inasmuch as there is a space of four feet three palms at
the right side of the first furnace and as much at the left side of the last
furnace, and there are to be six furnaces in one building, then it is necessary
to make the second wall fifty−two feet long; because the total of the widths
of all of the furnaces is seven and a half feet, the total of the spaces between
the furnaces is thirty feet, the space on the outer sides of the first and last
furnaces is nine feet and two palms, and the thickness of the two transverse
walls is five feet, which make a total measurement of fifty−two feet. 3
Outside each furnace hearth there is a small pit full of powder which is
compressed by ramming, and in this manner is made the forehearth which
receives the metal flowing from the furnaces. Of this I will speak later.
Buried about a cubit under the forehearth and the hearth of the furnace
is a transverse water−tank, three feet long, three palms wide and a cubit deep.
It is made of stone or brick, with a stone cover, for if it were not covered, the
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heat would draw the moisture from below and the vapour might be blown
into the hearth of the furnace as well as into the forehearth, and would
dampen the blast. The moisture would vitiate the blast, and part of the
metal would be absorbed and part would be mixed with the slags, and in
this manner the melting would be greatly damaged. From each water−tank
is built a walled vent, to the same depth as the tank, but six digits wide;
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AFURNACES. BFOREHEARTHS.
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this vent slopes upward, and sooner or later penetrates through to the other
side of the wall, against which the furnace is built. At the end of this vent
there is an opening where the steam, into which the water has been converted,
is exhausted through a copper or iron tube or pipe. This method of making
the tank and the vent is much the best. Another kind has a similar vent
but a different tank, for it does not lie transversely under the forehearth,
but lengthwise; it is two feet and a palm long, and a foot and three palms
wide, and a foot and a palm deep. This method of making tanks is not
condemned by us, as is the construction of those tanks without a vent;
the latter, which have no opening into the air through which the vapour may
discharge freely, are indeed to be condemned.
AFURNACES. BFOREHEARTH. CDOOR. DWATER TANK. ESTONE WHICH
COVERS IT. FMATERIAL OF THE VENT WALLS. GSTONE WHICH COVERS IT. HPIPE
EXHALING THE VAPOUR.
Fifteen feet behind the second wall is constructed the first wall, thirteen
feet high. In both of these are fixed roof beams 4 , which are a foot wide and
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thick, and nineteen feet and a palm long; these are placed three feet distant
from one another. As the second wall is two feet higher than the first wall,
recesses are cut in the back of it two feet high, one foot wide, and a palm deep,
and in these recesses, as it were in mortises, are placed one end of each of
the beams. Into these ends are mortised the bottoms of just as many posts;
these posts are twenty−four feet high, three palms wide and thick, and from
the tops of the posts the same number of rafters stretch downward to the
ends of the beams superimposed on the first wall; the upper ends of the
rafters are mortised into the posts and the lower ends are mortised into the
ends of the beams laid on the first wall; the rafters support the roof,
which consists of burnt tiles. Each separate rafter is propped up by a
separate timber, which is a cross−beam, and is joined to its post. Planks
close together are affixed to the posts above the furnaces; these planks are
about two digits thick and a palm wide, and they, together with the wicker
work interposed between the timbers, are covered with lute so that there may
be no risk of fire to the timbers and wicker−work. In this practical manner
is constructed the back part of the works, which contains the bellows, their
frames, the mechanism for compressing the bellows, and the instrument for
distending them, of all of which I will speak hereafter.
In front of the furnaces is constructed the third long wall and likewise
the fourth. Both are nine feet high, but of the same length and thickness as
the other two, the fourth being nine feet distant from the third; the
third is twenty−one and a half feet from the second. At a distance of
twelve feet from the second wall, four posts seven and a half feet high, a cubit
wide and thick, are set upon rock laid underneath. Into the tops of the
posts the roof beam is mortised; this roof beam is two feet and as many
palms longer than the distance between the second and the fifth transverse
walls, in order that its ends may rest on the transverse walls. If there should
not be so long a beam at hand, two are substituted for it. As the length of
the long beam is as above, and as the posts are equidistant, it is necessary
that the posts should be a distance of nine feet, one palm, two and two−fifths
digits from each other, and the end ones this distance from the transverse
walls. On this longitudinal beam and to the third and fourth walls are fixed
twelve secondary beams twenty−four feet long, one foot wide, three palms
thick, and distant from each other three feet, one palm, and two digits. In
these secondary beams, where they rest on the longitudinal beams, are mortised
the ends of the same number of rafters as there are posts which stand on the
second wall. The ends of the rafters do not reach to the tops of the posts,
but are two feet away from them, that through this opening, which is like
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the open part of a forge, the furnaces can emit their fumes. In order that
the rafters should not fall down, they are supported partly by iron rods,
which extend from each rafter to the opposite post, and partly supported
by a few tie−beams, which in the same manner extend from some rafters to
the posts opposite, and give them stability. To these tie−beams, as well as
to the rafters which face the posts, a number of boards, about two digits thick
and a palm wide, are fixed at a distance of a palm from each other, and are
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covered with lute so that they do not catch fire. In the secondary beams,
where they are laid on the fourth wall, are mortised the lower ends of the
same number of rafters as those in a set of rafters 5 opposite them. From
the third long wall these rafters are joined and tied to the ends of the opposite
rafters, so that they may not slip, and besides they are strengthened with
substructures which are made of cross and oblique timbers. The rafters
support the roof.
THE FOUR LONG WALLS: AFIRST. BSECOND. CTHIRD. DFOURTH. THE
SEVEN TRANSVERSE WALLS: EFIRST. FSECOND. GTHIRD. HFOURTH.
IFIFTH. KSIXTH. LSEVENTH, OR MIDDLE.
In this manner the front part of the building is made, and is divided into
three parts; the first part is twelve feet wide and is under the hood, which
consists of two walls, one vertical and one inclined. The second part is the
same number of feet wide and is for the reception of the ore to be smelted,
the fluxes, the charcoal, and other things which are needed by the smelter.
The third part is nine feet wide and contains two separate rooms of equal
size, in one of which is the assay furnace, while the other contains the metal
to be melted in the cupellation furnaces. It is thus necessary that in the
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building there should be, besides the four long walls, seven transverse walls,
of which the first is constructed from the upper end of the first long wall to
the upper end of the second long wall; the second proceeds from the end
of this to the end of the third long wall; the third likewise from this end of
the last extends to the end of the fourth long wall; the fourth leads from
the lower end of the first long wall to the lower end of the second long wall;
the fifth extends from the end of this to the end of the third long wall; the
sixth extends from this last end to the end of the fourth long wall; the
seventh divides into two parts the space between the third and fourth long
walls.
To return to the back part of the building, in which, as I said, are the
bellows 6 , their frames, the machinery for compressing them, and the instru−
ment for distending them. Each bellows consists of a body and a head.
The body is composed of two "boards," two bows, and two hides. The
upper board is a palm thick, five feet and three palms long, and two and a half
feet wide at the back part, where each of the sides is a little curved, and it is
a cubit wide at the front part near the head. The whole of the body of the
bellows tapers toward the head. That which we now call the "board"
consists of two pieces of pine, joined and glued together, and of two strips of
linden wood which bind the edges of the board, these being seven digits
wide at the back, and in front near the head of the bellows one and a half
digits wide. These strips are glued to the boards, so that there shall be less
damage from the iron nails driven through the hide. There are some people
who do not surround the boards with strips, but use boards only, which
are very thick. The upper board has an aperture and a handle; the
aperture is in the middle of the board and is one foot three palms distant
from where the board joins the head of the bellows, and is six digits long and
four wide. The lid for this aperture is two palms and a digit long and wide,
and three digits thick; toward the back of the lid is a little notch cut
into the surface so that it may be caught by the hand; a groove is cut out
of the top of the front and sides, so that it may engage in mouldings a palm
wide and three digits thick, which are also cut out in a similar manner under
the edges. Now, when the lid is drawn forward the hole is closed, and
when drawn back it is opened; the smelter opens the aperture a little so that
the air may escape from the bellows through it, if he fears the hides might be
burst when the bellows are too vigorously and quickly inflated; he, however,
closes the aperture if the hides are ruptured and the air escapes. Others
perforate the upper board with two or three round holes in the same place as
the rectangular one, and they insert plugs in them which they draw out
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when it is necessary. The wooden handle is seven palms long, or even longer,
in order that it may extend outside; one−half of this handle, two palms
wide and one thick, is glued to the end of the board and fastened with pegs
covered with glue; the other half projects beyond the board, and is rounded
and seven digits thick. Besides this, to the handle and to the board is fixed
a cleat two feet long, as many palms wide and one palm thick, and to the under
side of the same board, at a distance of three palms from the end, is fixed
another cleat two feet long, in order that the board may sustain the force
of distension and compression; these two cleats are glued to the board, and
are fastened to it with pegs covered with glue.
The lower bellows−board, like the upper, is made of two pieces of pine
and of two strips of linden wood, all glued together; it is of the same width
and thickness as the upper board, but is a cubit longer, this extension being
part of the head of which I have more to say a little later. This lower bellows−
board has an air−hole and an iron ring. The air−hole is about a cubit distant
from the posterior end, and it is midway between the sides of the bellows−
board, and is a foot long and three palms wide; it is divided into equal
parts by a small rib which forms part of the board, and is not cut from it;
this rib is a palm long and one−third of a digit wide. The flap of the air−
hole is a foot and three digits long, three palms and as many digits wide;
it is a thin board covered with goat skin, the hairy part of which is turned
toward the ground. There is fixed to one end of the flap, with small iron
nails, one−half of a doubled piece of leather a palm wide and as long as the
flap is wide; the other half of the leather, which is behind the flap, is twice
perforated, as is also the bellows−board, and these perforations are seven
digits apart. Passing through these a string is tied on the under side of the
board; and thus the flap when tied to the board does not fall away. In this
manner are made the flap and the air−hole, so when the bellows are distended
the flap opens, when compressed it closes. At a distance of about a foot
beyond the air−hole a slightly elliptical iron ring, two palms long and one
wide, is fastened by means of an iron staple to the under part of the bellows−
board; it is at a distance of three palms from the back of the bellows. In
order that the lower bellows−board may remain stationary, a wooden bolt is
driven into the ring, after it penetrates through the hole in the transverse
supporting plank which forms part of the frame for the bellows. There are
some who dispense with the ring and fasten the bellows−board to the frame
with two iron screws something like nails.
The bows are placed between the two boards and are of the same length
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as the upper board. They are both made of four pieces of linden wood three
digits thick, of which the two long ones are seven digits wide at the back and
two and a half at the front; the third piece, which is at the back, is two
palms wide. The ends of the bows are a little more than a digit thick, and are
mortised to the long pieces, and both having been bored through, wooden
pegs covered with glue are fixed in the holes; they are thus joined and glued
to the long pieces. Each of the ends is bowed ( arcuatur ) to meet the end of
the long part of the bow, whence its name "bow" originated. The fourth
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piece keeps the ends of the bow distended, and is placed a cubit distant from
the head of the bellows; the ends of this piece are mortised into the ends
of the bow and are joined and glued to them; its length without the tenons
is a foot, and its width a palm and two digits. There are, besides, two other
very small pieces glued to the head of the bellows and to the lower board,
and fastened to them by wooden pegs covered with glue, and they are three
palms and two digits long, one palm high, and a digit thick, one half being
slightly cut away. These pieces keep the ends of the bow away from the
hole in the bellows−head, for if they were not there, the ends, forced inward
by the great and frequent movement, would be broken.
The leather is of ox−hide or horse−hide, but that of the ox is far preferable
to that of the horse. Each of these hides, for there are two, is three and a
half feet wide where they are joined at the back part of the bellows. A
long leathern thong is laid along each of the bellows−boards and each of the
bows, and fastened by T−shaped iron nails five digits long; each of the
horns of the nails is two and a half digits long and half a digit wide. The
hide is attached to the bellows−boards by means of these nails, so that a horn
of one nail almost touches the horn of the next; but it is different with the
bows, for the hide is fastened to the back piece of the bow by only two nails,
and to the two long pieces by four nails. In this practical manner they put
ten nails in one bow and the same number in the other. Sometimes when the
smelter is afraid that the vigorous motion of the bellows may pull or tear
the hide from the bows, he also fastens it with little strips of pine by means of
another kind of nail, but these strips cannot be fastened to the back pieces of
the bow, because these are somewhat bent. Some people do not fix the
hide to the bellows−boards and bows by iron nails, but by iron screws,
screwed at the same time through strips laid over the hide. This method
of fastening the hide is less used than the other, although there is no doubt
that it surpasses it in excellence.
Lastly, the head of the bellows, like the rest of the body, consists of two
boards, and of a nozzle besides. The upper board is one cubit long, one and a
half palms thick. The lower board is part of the whole of the lower bellows−
board; it is of the same length as the upper piece, but a palm and a digit
thick. From these two glued together is made the head, into which, when it
has been perforated, the nozzle is fixed. The back part of the head, where
it is attached to the rest of the bellows−body, is a cubit wide, but three palms
forward it becomes two digits narrower. Afterward it is somewhat cut
away so that the front end may be rounded, until it is two palms and as
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many digits in diameter, at which point it is bound with an iron ring three
digits wide.
The nozzle is a pipe made of a thin plate of iron; the diameter in front is
three digits, while at the back, where it is encased in the head of the bellows,
it is a palm high and two palms wide. It thus gradually widens out, especially
at the back, in order that a copious wind can penetrate into it; the whole
nozzle is three feet long.
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AUPPER BELLOWS−BOARD. BLOWER BELLOWS−BOARD. CTHE TWO PIECES OF WOOD
OF WHICH EACH CONSISTS. DPOSTERIOR ARCHED PART OF EACH. ETAPERED FRONT
PART OF EACH. FPIECES OF LINDEN WOOD. GAPERTURE IN THE UPPER BOARD.
HLID. ILITTLE MOULDINGS OF WOOD. KHANDLE. LCLEAT ON THE OUTSIDE.
THE CLEAT INSIDE I AM NOT ABLE TO DEPICT. MINTERIOR OF THE LOWER BELLOWS−
BOARD. NPART OF THE HEAD. OAIR−HOLE. PSUPPORTING BAR. QFLAP.
RHIDE. STHONG. TEXTERIOR OF THE LOWER BOARD. VSTAPLE. XRING.
YBOW. ZITS LONG PIECES. AABACK PIECE OF THE BOW. BBTHE BOWED
ENDS. CCCROSSBAR DISTENDING THE BOW. DDTHE TWO LITTLE PIECES.
EEHIDE. FFNAIL. GGHORN OF THE NAIL. HHA SCREW. IILONG THONG.
KKHEAD. LLITS LOWER BOARD. MMITS UPPER BOARD. NNNOZZLE.
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The upper bellows−board is joined to the head of the bellows in the
following way. An iron plate 7 , a palm wide and one and a half palms long,
is first fastened to the head at a distance of three digits from the end; from
this plate there projects a piece three digits long and two wide, curved
in a small circle. The other side has a similar plate. Then in the same
part of the upper board are fixed two other iron plates, distant two digits
from the edge, each of which are six digits wide and seven long; in each
of these plates the middle part is cut away for a little more than three
digits in length and for two in depth, so that the curved part of the plates
on the head corresponding to them may fit into this cut out part. From
both sides of each plate there project pieces, three digits long and two
digits wide, similarly curved into small circles. A little iron pin is passed
through these curved pieces of the plates, like a little axle, so that the upper
board of the bellows may turn upon it. The little axle is six digits long and a
little more than a digit thick, and a small groove is cut out of the upper
board, where the plates are fastened to it, in such a manner that the little axle
when fixed to the plates may not fall out. Both plates fastened to the
bellows−board are affixed by four iron nails, of which the heads are on the
inner part of the board, whereas the points, clinched at the top, are
transformed into heads, so to speak. Each of the other plates is fastened
to the head of the bellows by means of a nail with a wide head, and by two
other nails of which the heads are on the edge of the bellows−head. Midway
between the two plates on the bellows−board there remains a space two
palms wide, which is covered by an iron plate fastened to the board by
little nails; and another plate corresponding to this is fastened to the head
between the other two plates; they are two palms and the same number
of digits wide.
The hide is common to the head as to all the other parts of the body;
the plates are covered with it, as well as the front part of the upper bellows−
board, and both the bows and the back of the head of the bellows, so that the
wind may not escape from that part of the bellows. It is three palms and as
many digits wide, and long enough to extend from one of the sides of the
lower board over the back of the upper; it is fastened by many T−headed
nails on one side to the upper board, and on the other side to the head of
the bellows, and both ends are fastened to the lower bellows−board.
In the above manner the bellows is made. As two are required for each
furnace, it is necessary to have twelve bellows, if there are to be six furnaces
in one works.
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Now it is time to describe their framework. First, two sills a little
shorter than the furnace wall are placed on the ground. The front one of
these is three palms wide and thick, and the back one three palms and two
digits. The front one is two feet distant from the back wall of the furnace, and
the back one is six feet three palms distant from the front one. They are set into
the earth, that they may remain firm; there are some who accomplish this by
means of pegs which, through several holes, penetrate deeply into the ground.
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Then twelve short posts are erected, whose lower ends are mortised into
the sill that is near the back of the furnace wall; these posts are two feet
high, exclusive of the tenons, and are three palms and the same number of
digits wide, and two palms thick. A slot one and a half palms wide is cut
through them, beginning two palms from the bottom and extending for a
height of three palms. All the posts are not placed at the same intervals, the
first being at a distance of three feet five digits from the second, and likewise
the third from the fourth, but the second is two feet one palm and three
digits from the third; the intervals between the other posts are arranged in
the same manner, equal and unequal, of which each four pertain to two
furnaces. The upper ends of these posts are mortised into a transverse
beam which is twelve feet, two palms, and three digits long, and projects
five digits beyond the first post and to the same distance beyond the fourth;
it is two palms and the same number of digits wide, and two palms thick.
Since each separate transverse beam supports four bellows, it is necessary to
have three of them.
Behind the twelve short posts the same number of higher posts are
erected, of which each has the middle part of the lower end cut out, so that
its two resulting lower ends are mortised into the back sill; these posts,
exclusive of the tenons, are twelve feet and two palms high, and are five palms
wide and two palms thick. They are cut out from the bottom upward, the
slot being four feet and five digits high and six digits wide. The upper ends of
these posts are mortised into a long beam imposed upon them; this long
beam is placed close under the timbers which extend from the wall at the
back of the furnace to the first long wall; the beam is three palms wide
and two palms thick, and forty−three feet long. If such a long one is
not at hand, two or three may be substituted for it, which when joined together
make up that length. These higher posts are not placed at equal distances,
but the first is at a distance of two feet three palms one digit from the second,
and the third is at the same distance from the fourth; while the second is at a
distance of one foot three palms and the same number of digits from the
third, and in the same manner the rest of the posts are arranged at equal
and unequal intervals. Moreover, there is in every post, where it faces the
shorter post, a mortise at a foot and a digit above the slot; in these mortises
of the four posts is tenoned a timber which itself has four mortises. Tenons
are enclosed in mortises in order that they may be better joined, and they
are transfixed with wooden pins. This timber is thirteen feet three palms
one digit long, and it projects beyond the first post a distance of two palms
and two digits, and to the same number of palms and digits beyond the
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fourth post. It is two palms and as many digits wide, and also two palms
thick. As there are twelve posts it is necessary to have three timbers of this
kind.
On each of these timbers, and on each of the cross−beams which are laid
upon the shorter posts, are placed four planks, each nine feet long, two palms
three digits wide, and two palms one digit thick. The first plank is five feet
one palm one digit distant from the second, at the front as well as at the back.
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for each separate plank is placed outside of the posts. The third is at the
same distance from the fourth, but the second is one foot and three digits
distant from the third. In the same manner the rest of the eight planks are
arranged at intervals, the fifth from the sixth and the seventh from the eighth
are at the same distances as the first from the second and the third from the
fourth; the sixth is at the same distance from the seventh as the second
from the third.
Two planks support one transverse plank six feet long, one foot wide, one
palm thick, placed at a distance of three feet and two palms from the back
posts. When there are six of these supporting planks, on each separate one
are placed two bellows; the lower bellows−boards project a palm beyond
them. From each of the bellows−boards an iron ring descends through a hole
in its supporting plank, and a wooden peg is driven into the ring, so that the
bellows−board may remain stationary, as I stated above.
The two bellows communicate, each by its own plank, to the back of a
copper pipe in which are set both of the nozzles, and their ends are tightly
AFRONT SILL. BBACK SILL. CFRONT POSTS. DTHEIR SLOTS. EBEAM
IMPOSED UPON THEM. FHIGHER POSTS. GTHEIR SLOTS. HBEAM IMPOSED UPON
THEM. ITIMBER JOINED IN THE MORTISES OF THE POSTS. KPLANKS. LTRANSVERSE
SUPPORTING PLANKS. MTHE HOLES IN THEM. NPIPE. OITS FRONT END. PITS
REAR END.
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fastened in it. The pipe is made of a rolled copper or iron plate, a foot and
two palms and the same number of digits long; the plate is half a digit
thick, but a digit thick at the back. The interior of the pipe is three digits
wide, and two and a half digits high in the front, for it is not absolutely round;
and at the back it is a foot and two palms and three digits in diameter. The
plate from which the pipe is made is not entirely joined up, but at the front
there is left a crack half a digit wide, increasing at the back to three digits.
This pipe is placed in the hole in the furnace, which, as I said, was in the
middle of the wall and the arch. The nozzles of the bellows, placed in this
pipe, are a distance of five digits from its front end.
The levers are of the same number as the bellows, and when depressed
by the cams of the long axle they compress the bellows. These levers
are eight feet three palms long, one palm wide and thick, and the ends are
inserted in the slots of the posts; they project beyond the front posts to a
distance of two palms, and the same distance beyond the back posts in order
that each may have its end depressed by its two cams on the axle. The
cams not only penetrate into the slots of the back posts, but project three
digits beyond them. An iron pin is set in round holes made through both
sides of the slot of each front post, at three palms and as many digits from the
bottom; the pin penetrates the lever, which turns about it when depressed
or raised. The back of the lever for the length of a cubit is a palm and a
digit wider than the rest, and is perforated; in this hole is engaged a bar
six feet and two palms long, three digits wide, and about one and one−half
digits thick; it is somewhat hooked at the upper end, and approaches the
handle of the bellows. Under the lever there is a nail, which penetrates
through a hole in the bar, so that the lever and bar may move together. The
bar is perforated in the upper end at a distance of six digits from the top;
this hole is two palms long and a digit wide, and in it is engaged the hook of
an iron implement which is a digit thick. At the upper part this implement
has either a round or square opening, like a link, and at the lower end is
hooked; the link is two digits high and wide and the hook is three digits long;
the middle part between the link and the hook is three palms and two
digits long. The link of this implement engages either the handle of the
bellows, or else a large ring which does engage it. This iron ring is a digit thick,
two palms wide on the inside of the upper part, and two digits in the
lower part, and this iron ring, not unlike the first one, engages the
handle of the bellows. The iron ring either has its narrower part turned
upward, and in it is engaged the ring of another iron implement, similar
to the first, whose hook, extending upward, grips the rope fastened to the
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iron ring holding the end of the second lever, of which I will speak
presently; or else the iron ring grips this lever, and then in its hook is
engaged the ring of the other implement whose ring engages the handle of the
bellows, and in this case the rope is dispensed with.
Resting on beams fixed in the two walls is a longitudinal beam, at a
distance of four and a half feet from the back posts; it is two palms wide,
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ALEVER WHICH WHEN DEPRESSED BY MEANS OF A CAM COMPRESSES THE BELLOWS.
BSLOTS THROUGH THE POSTS. CBAR. DIRON IMPLEMENT WITH A RECTANGULAR
LINK. EIRON INSTRUMENT WITH ROUND RING. FHANDLE OF BELLOWS. GUPPER
POST. HUPPER LEVER. IBOX WITH EQUAL SIDES. KBOX NARROW AT THE
BOTTOM. LPEGS DRIVEN INTO THE UPPER LEVER.
one and a half palms thick. There are mortised into this longitudinal beam
the lower ends of upper posts three palms wide and two thick, which are six
feet two palms high, exclusive of their tenons. The upper ends of these
posts are mortised into an upper longitudinal beam, which lies close under
the rafters of the building; this upper longitudinal beam is two palms
wide and one thick. The upper posts have a slot cut out upward from a
point two feet from the bottom, and the slot is two feet high and six digits
wide. Through these upper posts a round hole is bored from one side to
the other at a point three feet one palm from the bottom, and a small iron axle
penetrates through the hole and is fastened there. Around this small iron
axle turns the second lever when it is depressed and raised. This lever is
eight feet long, and its other end is three digits wider than the rest of the
lever; at this widest point is a hole two digits wide and three high, in which
is fixed an iron ring, to which is tied the rope I have mentioned; it is five
palms long, its upper loop is two palms and as many digits wide, and the
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527
lower one is one palm one digit wide. This half of the second lever, the end
of which I have just mentioned, is three palms high and one wide; it projects
three feet beyond the slot of the post on which it turns; the other end, which
faces the back wall of the furnaces, is one foot and a palm high and a foot wide.
On this part of the lever stands and is fixed a box three and a half feet
long, one foot and one palm wide, and half a foot deep; but these measure−
ments vary; sometimes the bottom of this box is narrower, sometimes
equal in width to the top. In either case, it is filled with stones and earth
to make it heavy, but the smelters have to be on their guard and
make provision against the stones falling out, owing to the constant
motion; this is prevented by means of an iron band which is placed over
the top, both ends being wedge−shaped and driven into the lever so that the
stones can be held in. Some people, in place of the box, drive four or more
pegs into the lever and put mud between them, the required amount being
added to the weight or taken away from it.
There remains to be considered the method of using this machine. The
lower lever, being depressed by the cams, compresses the bellows, and the
compression drives the air through the nozzle. Then the weight of the box
on the other end of the upper lever raises the upper bellows−board, and the
air is drawn in, entering through the air−hole.
The machine whose cams depress the lower lever is made as follows.
First there is an axle, on whose end outside the building is a water−wheel;
at the other end, which is inside the building, is a drum made of rundles.
This drum is composed of two double hubs, a foot apart, which are five digits
thick, the radius all round being a foot and two digits; but they are double,
because each hub is composed of two discs, equally thick, fastened together
with wooden pegs glued in. These hubs are sometimes covered above and
around by iron plates. The rundles are thirty in number, a foot and two
palms and the same number of digits long, with each end fastened into a hub;
they are rounded, three digits in diameter, and the same number of digits
apart. In this practical manner is made the drum composed of rundles.
There is a toothed wheel, two palms and a digit thick, on the end
of another axle; this wheel is composed of a double disc 8 . The inner disc
is composed of four segments a palm thick, everywhere two palms and a
digit wide. The outer disc, like the inner, is made of four segments, and is
a palm and a digit thick; it is not equally wide, but where the head of the
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528
spokes are inserted it is a foot and a palm and digit wide, while on each side
of the spokes it becomes a little narrower, until the narrowest part is only
two palms and the same number of digits wide. The outer segments are joined
to the inner ones in such a manner that, on the one hand, an outer segment
ends in the middle of an inner one, and, on the other hand, the ends of the
inner segments are joined in the middle of the outer ones; there is no doubt
that by this kind of joining the wheel is made stronger. The outer segments
are fastened to the inner by means of a large number of wooden pegs. Each
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529
AAXLE. BWATER−WHEEL. CDRUM COMPOSED OF RUNDLES. DOTHER AXLE.
ETOOTHED WHEEL. FITS SPOKES. GITS SEGMENTS. HITS TEETH. ICAMS
OF THE AXLE.
segment, measured over its round back, is four feet and three palms long.
There are four spokes, each two palms wide and a palm and a digit thick; their
length, excluding the tenons, being two feet and three digits. One end of the
spoke is mortised into the axle, where it is firmly fastened with pegs; the
wide part of the other end, in the shape of a triangle, is mortised into the
outer segment opposite it, keeping the shape of the same as far as the segment
ascends. They also are joined together with wooden pegs glued in, and these
pegs are driven into the spokes under the inner disc. The parts of the spokes
in the shape of the triangle are on the inside; the outer part is simple. This
triangle has two sides equal, the erect ones as is evident, which are a palm
long; the lower side is not of the same length, but is five digits long, and a
mortise of the same shape is cut out of the segments. The wheel has sixty
teeth, since it is necessary that the rundle drum should revolve twice while
the toothed wheel revolves once. The teeth are a foot long, and project one
palm from the inner disc of the wheel, and three digits from the outer disc;
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530
they are a palm wide and two and a half digits thick, and it is necessary
that they should be three digits apart, as were the rundles.
The axle should have a thickness in proportion to the spokes and the
segments. As it has two cams to depress each of the levers, it is necessary that
it should have twenty−four cams, which project beyond it a foot and a palm and
a digit. The cams are of almost semicircular shape, of which the widest part is
three palms and a digit wide, and they are a palm thick; they are
distributed according to the four sides of the axle, on the upper, the lower
and the two lateral sides. The axle has twelve holes, of which the first
penetrates through from the upper side to the lower, the second from one
lateral side to the other; the first hole is four feet two palms distant from
the second; each alternate one of these holes is made in the same direc−
tion, and they are arranged at equal intervals. Each single cam must
be opposite another; the first is inserted into the upper part of the first
hole, the second into the lower part of the same hole, and so fixed by
pegs that they do not fall out; the third cam is inserted into that part
of the second hole which is on the right side, and the fourth into that
part on the left. In like manner all the cams are inserted into the consecutive
holes, for which reason it happens that the cams depress the levers of the
ACHARCOAL. BMORTAR−BOX. CSTAMPS.
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531
bellows in rotation. Finally we must not omit to state that this is only one
of many such axles having cams and a water−wheel.
I have arrived thus far with many words, and yet it is not unseasonable
that I have in this place pursued the subject minutely, since the smelting of all
the metals, to which I am about to proceed, could not be undertaken without
it.
The ores of gold, silver, copper, and lead, are smelted in a furnace by
four different methods. The first method is for the rich ores of gold or silver,
the second for the mediocre ores, the third for the poor ores, and the fourth
method is for those ores which contain copper or lead, whether they contain
precious metals or are wanting in them. The smelting of the first ores is
performed in the furnace of which the tap−hole is intermittently closed; the
other three ores are melted in furnaces of which the tap−holes are always
open.
First, I will speak of the manner in which the furnaces are prepared for
the smelting of the ores, and of the first method of smelting. The powder
from which the hearth and forehearth should be made is composed of char−
coal and earth (clay?). The charcoal is crushed by the stamps in a mortar−
box, the front of which is closed by a board at the top, while the charcoal,
ATUB. BSIEVE. CRODS. DBENCH−FRAME.
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532
crushed to powder, is removed through the open part below; the stamps are
not shod with iron, but are made entirely of wood, although at the lower
part they are bound round at the wide part by an iron band.
The powder into which the charcoal is crushed is thrown on to a sieve
whose bottom consists of interwoven withes of wood. The sieve is drawn
backward and forward over two wooden or iron rods placed in a triangular
position on a tub, or over a bench−frame set on the floor of the building;
the powder which falls into the tub or on to the floor is of suitable size,
but the pieces of small charcoal which remain in the sieve are emptied out
and thrown back under the stamps.
When the earth is dug up it is first exposed to the sun that it may dry.
Later on it is thrown with a shovel on to a screenset up obliquely and
supported by poles,made of thick, loosely woven hazel withes, and in this
way the fine earth and its small lumps pass through the holes of the screen, but
the clods and stones do not pass through, but run down to the ground. The
earth which passes through the screen is conveyed in a two−wheeled cart to
the works and there sifted. This sieve, which is not dissimilar to the one
ASCREEN. BPOLES. CSHOVEL. DTWO−WHEELED CART. EHAND−SIEVE.
FNARROW BOARDS. GBOX. HCOVERED PIT.
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described above, is drawn backward and forward upon narrow boards of
equal length placed over a long box; the powder which falls through the
sieve into the box is suitable for the mixture; the lumps that remain in the
sieve are thrown away by some people, but by others they are placed under
the stamps. This powdered earth is mixed with powdered charcoal, moist−
ened, and thrown into a pit, and in order that it may remain good for a long
time, the pit is covered up with boards so that the mixture may not
become contaminated.
They take two parts of pulverised charcoal and one part of powdered
earth, and mix them well together with a rake; the mixture is moistened by
pouring water over it so that it may easily be made into shapes resembling
snowballs; if the powder be light it is moistened with more water, if heavy
with less. The interior of the new furnace is lined with lute, so that the
cracks in the walls, if there are any, may be filled up, but especially in order
to preserve the rock from injury by fire. In old furnaces in which ore has
been melted, as soon as the rocks have cooled the assistant chips away, with
a spatula, the accretions which adhere to the walls, and then breaks them
up with an iron hoe or a rake with five teeth. The cracks of the furnace are
first filled in with fragments of rock or brick, which he does by passing his
hand into the furnace through its mouth, or else, having placed a ladder against
it, he mounts by the rungs to the upper open part of the furnace. To the
upper part of the ladder a board is fastened that he may lean and recline
against it. Then standing on the same ladder, with a wooden spatula, he
smears the furnace walls over with lute; this spatula is four feet long, a digit
thick, and for a foot upward from the bottom it is a palm wide, or even
wider, generally two and a half digits. He spreads the lute equally over the
inner walls of the furnace. The mouth of the copper pipe 9 should not pro−
trude from the lute, lest sows 10 form round about it and thus impede the
melting, for the furnace bellows could not force a blast through them. Then
the same assistant throws a little powdered charcoal into the pit of the fore−
hearth and sprinkles it with pulverised earth. Afterward, with a bucket
he pours water into it and sweeps this all over the forehearth pit, and with the
broom drives the turbid water into the furnace hearth and likewise sweeps
it out. Next he throws the mixed and moistened powder into the furnace,
and then a second time mounting the steps of the ladder, he introduces the
rammer into the furnace and pounds the powder so that the hearth is made
solid. The rammer is rounded and three palms long; at the bottom it is five
digits in diameter, at the top three and a half, therefore it is made in the form
of a truncated cone; the handle of the rammer is round and five feet long and
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534
AFURNACE. BLADDER. CBOARD FIXED TO IT. DHOE. EFIVE−
TOOTHED RAKE. FWOODEN SPATULA. GBROOM. HRAMMER. IRAMMER, SAME
DIAMETER. KTWO WOODEN SPATULAS. LCURVED BLADE. MBRONZE RAMMER.
NANOTHER BRONZE RAMMER. OWIDE SPATULA. PROD. QWICKER BASKET.
RTWO BUCKETS OF LEATHER IN WHICH WATER IS CARRIED FOR PUTTING OUT A CON−
FLAGRATION, SHOULD THE officina CATCH FIRE. SBRASS PUMP WITH WHICH THE WATER
IS SQUIRTED OUT. TTWO HOOKS. VRAKE. XWORKMAN BEATING THE CLAY WITH
AN IRON IMPLEMENT.
two and a half digits thick; the upper part of the rammer, where the handle
is inserted, is bound with an iron band two digits wide. There are some who,
instead, use two rounded rammers three and a half digits in diameter, the
same at the bottom as at the top. Some people prefer two wooden
spatulas, or a rammer spatula.
In a similar manner, mixed and moistened powder is thrown and pounded
with a rammer in the forehearth pit, which is outside the furnace. When
this is nearly completed, powder is again put in, and pushed with the rammer
up toward the protruding copper pipe, so that from a point a digit under the
mouth of the copper pipe the hearth slopes down into the crucible of the fore−
hearth, 11 and the metal can run down. The same is repeated until the
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535
forehearth pit is full, then afterward this is hollowed out with a curved
blade; this blade is of iron, two palms and as many digits long, three digits
wide, blunt at the top and sharp at the bottom. The crucible of the fore−
hearth must be round, a foot in diameter and two palms deep if it has to
contain a centumpondíum of lead, or if only seventy líbrae, then three palms
in diameter and two palms deep like the other. When the forehearth has
been hollowed out it is pounded with a round bronze rammer. This is
five digits high and the same in diameter, having a curved round handle
one and a half digits thick; or else another bronze rammer is used, which
is fashioned in the shape of a cone, truncated at the top, on which is
imposed another cut away at the bottom, so that the middle part of the
rammer may be grasped by the hand; this is six digits high, and five digits
in diameter at the lower end and four at the top. Some use in its place a
wooden spatula two and a half palms wide at the lower end and one palm
thick.
The assistant, having prepared the forehearth, returns to the furnace and
besmears both sides as well as the top of the mouth with simple lute. In the
lower part of the mouth he places lute that has been dipped in charcoal
dust, to guard against the risk of the lute attracting to itself the powder
of the hearth and vitiating it. Next he lays in the mouth of the furnace a
straight round rod three quarters of a foot long and three digits in diameter.
Afterward he places a piece of charcoal on the lute, of the same length and
width as the mouth, so that it is entirely closed up; if there be not at hand
one piece of charcoal so large, he takes two instead. When the mouth is thus
closed up, he throws into the furnace a wicker basket full of charcoal, and in
order that the piece of charcoal with which the mouth of the furnace is closed
should not then fall out, the master holds it in with his hand. The pieces
of charcoal which are thrown into the furnace should be of medium size, for
if they are large they impede the blast of the bellows and prevent it from
blowing through the tap−hole of the furnace into the forehearth to heat it.
Then the master covers over the charcoal, placed at the mouth of the furnace,
with lute and extracts the wooden rod, and thus the furnace is prepared.
Afterward the assistant throws four or five larger baskets full of charcoal
into the furnace, filling it right up; he also throws a little charcoal
into the forehearth, and places glowing coals upon it in order that it may
be kindled, but in order that the flames of this fire should not enter through
the tap−hole of the furnace and fire the charcoal inside, he covers the tap−hole
with lute or closes it with fragments of pottery. Some do not warm the
forehearth the same evening, but place large charcoals round the edge of it, one
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536
leaning on the other; those who follow the first method sweep out the
forehearth in the morning, and clean out the little pieces of charcoal and
cinders, while those who follow the latter method take, early in the morning,
burning firebrands, which have been prepared by the watchman of the works,
and place them on the charcoal.
At the fourth hour the master begins his work. He first inserts a
small piece of glowing coal into the furnace, through the bronze nozzle−pipe
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537
of the bellows, and blows up the fire with the bellows; thus within the space
of half an hour the forehearth, as well as the hearth, becomes warmed, and
of course more quickly if on the preceding day ores have been smelted in the
same furnace, but if not then it warms more slowly. If the hearth and
forehearth are not warmed before the ore to be smelted is thrown in, the furnace
is injured and the metals lost; or if the powder from which both are made
is damp in summer or frozen in winter, they will be cracked, and, giving
out a sound like thunder, they will blow out the metals and other substances
with great peril to the workmen. After the furnace has been warmed, the
master throws in slags, and these, when melted, flow out through the tap−
hole into the forehearth. Then he closes up the tap−hole at once with
mixed lute and charcoal dust; this plug he fastens with his hand to a
round wooden rammer that is five digits thick, two palms high, with a handle
three feet long. The smelter extracts the slags from the forehearth with a
hooked bar; if the ore to be smelted is rich in gold or silver he puts into the
forehearth a centumpondíum of lead, or half as much if the ore is poor,
because the former requires much lead, the latter little; he immediately
throws burning firebrands on to the lead so that it melts. Afterward he
performs everything according to the usual manner and order, whereby he
first throws into the furnace as many cakes melted from pyrites 12 , as he
requires to smelt the ore; then he puts in two wicker baskets full of ore
with litharge and hearth−lead 13 , and stones which fuse easily by fire of the
second order, all mixed together; then one wicker basket full of charcoal,
and lastly the slags. The furnace now being filled with all the things I
have mentioned, the ore is slowly smelted; he does not put too much of it
against the back wall of the furnace, lest sows should form around the nozzles
of the bellows and the blast be impeded and the fire burn less fiercely.
This, indeed, is the custom of many most excellent smelters, who know
how to govern the four elements 14 . They combine in right proportion the
ores, which are part earth, placing no more than is suitable in the furnaces;
they pour in the needful quantity of water; they moderate with skill the air
from the bellows; they throw the ore into that part of the fire which burns
fiercely. The master sprinkles water into each part of the furnace to dampen
the charcoal slightly, so that the minute parts of ore may adhere to it,
which otherwise the blast of the bellows and the force of the fire would agitate
and blow away with the fumes. But as the nature of the ores to be smelted
varies, the smelters have to arrange the hearth now high, now low, and to
place the pipe in which the nozzles of the bellows are inserted sometimes on a
great and sometimes at a slight angle, so that the blast of the bellows may
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538
1
539
blow into the furnace in either a mild or a vigorous manner. For those ores
which heat and fuse easily, a low hearth is necessary for the work of the
smelters, and the pipe must be placed at a gentle angle to produce a mild
blast from the bellows. On the contrary, those ores that heat and fuse
slowly must have a high hearth, and the pipe must be placed at a steep incline
in order to blow a strong blast of the bellows, and it is necessary, for this
kind of ore, to have a very hot furnace in which slags, or cakes melted from
pyrites, or stones which melt easily in the fire 15 , are first melted, so that the
ore should not settle in the hearth of the furnace and obstruct and choke up
the tap−hole, as the minute metallic particles that have been washed from
the ores are wont to do. Large bellows have wide nozzles, for if they were
narrow the copious and strong blast would be too much compressed and too
acutely blown into the furnace, and then the melted material would be
chilled, and would form sows around the nozzle, and thus obstruct the opening
into the furnace, which would cause great damage to the proprietors'
property. If the ores agglomerate and do not fuse, the smelter, mounting
on the ladder placed against the side of the furnace, divides the charge with
a pointed or hooked bar, which he also pushes down into the pipe in
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540
which the nozzle of the bellows is placed, and by a downward movement
dislodges the ore and the sows from around it.
After a quarter of an hour, when the lead which the assistant has placed
in the forehearth is melted, the master opens the tap−hole of the furnace
with a tapping−bar. This bar is made of iron, is three and a half feet long,
the forward end pointed and a little curved, and the back end hollow so that
into it may be inserted a wooden handle, which is three feet long and thick
enough to be well grasped by the hand. The slag first flows from the furnace
into the forehearth, and in it are stones mixed with metal or with the metal
adhering to them partly altered, the slag also containing earth and solidified
juices. After this the material from the melted pyrites flows out, and then the
molten lead contained in the forehearth absorbs the gold and silver. When
that which has run out has stood for some time in the forehearth, in order
to be able to separate one from the other, the master first either skims off
the slags with the hooked bar or else lifts them off with an iron fork; the
slags, as they are very light, float on the top. He next draws off the cakes of
melted pyrites, which as they are of medium weight hold the middle place;
he leaves in the forehearth the alloy of gold or silver with the lead, for these
being the heaviest, sink to the bottom. As, however, there is a difference
1
541
in slags, the uppermost containing little metal, the middle more, and the
lowest much, he puts these away separately, each in its own place, in
order that to each heap, when it is re−smelted, he may add the proper
fluxes, and can put in as much lead as is demanded for the metal in the
slag; when the slag is re−melted, if it emits much odour, there is some
metal in it; if it emits no odour, then it contains none. He puts the cakes
of melted pyrites away separately, as they were nearest in the forehearth to
the metal, and contain a little more of it than the slags; from all these
cakes a conical mound is built up, by always placing the widest of them
at the bottom. The hooked bar has a hook on the end, hence its name;
otherwise it is similar to other bars.
Afterward the master closes up the tap−hole and fills the furnace with
the same materials I described above, and again, the ores having been melted,
he opens the tap−hole, and with a hooked bar extracts the slags and the cakes
melted from pyrites, which have run down into the forehearth. He repeats
the same operation until a certain and definite part of the ore has been
smelted, and the day' s work is at an end; if the ore was rich the work is
finished in eight hours; if poor, it takes a longer time. But if the ore was
so rich as to be smelted in less than eight hours, another operation is in the
meanwhile combined with the first, and both are performed in the space of ten
hours. When all the ore has been smelted, he throws into the furnace a
basket full of litharge or hearth−lead, so that the metal which has remained
in the accretions may run out with these when melted. When he has finally
drawn out of the forehearth the slags and the cakes melted from pyrites,
he takes out, with a ladle, the lead alloyed with gold or silver and pours it into
little iron or copper pans, three palms wide and as many digits deep, but
first lined on the inside with lute and dried by warming, lest the glowing molten
substances should break through. The iron ladle is two palms wide, and in
other respects it is similar to the others, all of which have a sufficiently long
iron shaft, so that the fire should not burn the wooden part of the handle.
When the alloy has been poured out of the forehearth, the smelter foreman
and the mine captain weigh the cakes.
Then the master breaks out the whole of the mouth of the furnace with a
crowbar, and with that other hooked bar, the rabble and the five−toothed rake,
he extracts the accretions and the charcoal. This crowbar is not unlike
the other hooked one, but larger and wider; the handle of the rabble is six feet
long and is half of iron and half of wood. The furnace having cooled, the
master chips off the accretions clinging to the walls with a rectangular
1
542
spatula six digits long, a palm broad, and sharp on the front edge; it has
a round handle four feet long, half of it being of iron and half of wood. This
is the first method of smelting ores.
Because they generally consist of unequal constituents, some of which melt
rapidly and others slowly, the ores rich in gold and silver cannot be smelted as
rapidly or as easily by the other methods as they can by the first method, for
three important reasons. The first reason is that, as often as the closed
tap−hole of the furnace is opened with a tapping−bar, so often can the
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A, B, CTHREE FURNACES. AT THE FIRST STANDS THE SMELTER, WHO WITH A LADLE
POURS THE ALLOY OUT OF THE FOREHEARTH INTO THE MOULDS. DFOREHEARTH.
ELADLE. FMOULDS. GROUND WOODEN RAMMER. HTAPPING−BAR. AT THE
SECOND FURNACE STANDS THE SMELTER. WHO OPENS THE TAP−HOLE WITH HIS
TAPPING−BAR.
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smelter observe whether the ore is melting too quickly or too slowly, or
whether it is flaming in scattered bits, and not uniting in one mass; in the
first case the ore is smelting too slowly and not without great expense; in
the second case the metal mixes with the slag which flows out of the
furnace into the forehearth, wherefore there is the expense of melting it again;
in the third case, the metal is consumed by the violence of the fire. Each of
these evils has its remedy; if the ore melts slowly or does not come together,
it is necessary to add some amount of fluxes which melt the ore; or if they
melt too readily, to decrease the amount.
The second reason is that each time that the furnace is opened with a
tapping−bar, it flows out into the forehearth, and the smelter is able to test
the alloy of gold and lead or of silver with lead, which is called stannum 16 .
When the tap−hole is opened the second or third time, this test shows us
whether the alloy of gold or silver has become richer, or whether the lead is
too debilitated and wanting in strength to absorb any more gold or silver. If
it has become richer, some portion of lead added to it should renew its
strength; if it has not become richer, it is poured out of the forehearth that
it may be replaced with fresh lead.
The third reason is that if the tap−hole of the furnace is always open
when the ore and other things are being smelted, the fluxes, which are easily
melted, run out of the furnace before the rich gold and silver ores, for these
are sometimes of a kind that oppose and resist melting by the fire for a longer
period. It follows in this case, that some part of the ore is either con−
sumed or is mixed with the accretions, and as a result little lumps of ore
not yet melted are now and then found in the accretions. Therefore when
these ores are being smelted, the tap−hole of the furnace should be closed
for a time, as it is necessary to heat and mix the ore and the fluxes at the
same time; since the fluxes fuse more rapidly than the ore, when the
molten fluxes are held in the furnace, they thus melt the ore which does not
readily fuse or mix with the lead. The lead absorbs the gold or silver, just
as tin or lead when melted in the forehearth absorbs the other unmelted
metal which has been thrown into it. But if the molten matter is poured
upon that which is not molten, it runs off on all sides and consequently does
not melt it. It follows from all this that ores rich in gold or silver, when put
into a furnace with its tap−hole always open, cannot for that reason be smelted
so successfully as in one where the tap−hole is closed for a time, so that during
this time the ore may be melted by the molten fluxes. Afterward, when the
tap−hole has been opened, they flow into the forehearth and mix there with
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the molten lead. This method of smelting the ores is used by us and by the
Bohemians.
The three remaining methods of smelting ores are similar to each other
in that the tap−holes of the furnaces always remain open, so that the molten
metals may continually run out. They differ greatly from each other,
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A, BTWO FURNACES. CFOREHEARTHS. DDIPPING−POT. THE SMELTER STANDING
BY THE FIRST FURNACE DRAWS OFF THE SLAGS WITH A HOOKED BAR. EHOOKED BAR.
FSLAGS. GTHE ASSISTANT DRAWING A BUCKET OF WATER WHICH HE POURS OVER THE
GLOWING SLAGS TO QUENCH THEM. HBASKET MADE OF TWIGS OF WOOD INTERTWINED.
IRABBLE. KORE TO BE SMELTED. THE MASTER STANDS AT THE OTHER FURNACE
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however, for the tap−hole of the first of this kind is deeper in the furnace and
narrower than that of the third, and besides it is invisible and concealed.
It easily discharges into the forehearth, which is one and a half feet higher
than the floor of the building, in order that below it to the left a dipping−pot
can be made. When the forehearth is nearly full of the slags, which well up
from the invisible tap−hole of the furnace, they are skimmed off from the top
with a hooked bar; then the alloy of gold or silver with lead and the melted
pyrites, being uncovered, flow into the dipping−pot, and the latter are made into
cakes; these cakes are broken and thrown back into the furnace so that all
their metal may be smelted out. The alloy is poured into little iron moulds.
The smelter, besides lead and cognate things, uses fluxes which combine
with the ore, of which I gave a sufficient account in Book VII. The metals
which are melted from ores that fuse readily in the fire, are profitable because
they are smelted in a short time, while those which are difficult to fuse are
not as profitable, because they take a long time. When fluxes remain in the
furnace and do not melt, they are not suitable; for this reason, accretions and
slags are the most convenient for smelting, because they melt quickly. It is
necessary to have an industrious and experienced smelter, who in the first
place takes care not to put into the furnace more ores mixed with fluxes than
it can accommodate.
The powder out of which this furnace hearth and the adjoining fore−
hearth and the dipping−pot are usually made, consists mostly of equal pro−
portions of charcoal dust and of earth, or of equal parts of the same and of
ashes. When the hearth of the furnace is prepared, a rod that will reach to the
forehearth is put into it, higher up if the ore to be smelted readily fuses, and
lower down if it fuses with difficulty. When the dipping−pot and forehearth
are finished, the rod is drawn out of the furnace so that the tap−hole is open,
and through it the molten material flows continuously into the forehearth,
which should be very near the furnace in order that it may keep very hot and
the alloy thus be made purer. If the ore to be smelted does not melt easily, the
hearth of the furnace must not be made too sloping, lest the molten fluxes
should run down into the forehearth before the ore is smelted, and the metal
thus remain in the accretions on the sides of the furnace. The smelter must
not ram the hearth so much that it becomes too hard, nor make the mistake
of ramming the lower part of the mouth to make it hard, for it could not
breathe 17 , nor could the molten matter flow freely out of the furnace.
The ore which does not readily melt is thrown as much as possible to the
back of the furnace, and toward that part where the fire burns very
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fiercely, so that it may be smelted longer. In this way the smelter may direct
it whither he wills. Only when it glows at the part near the bellows' nozzle
does it signify that all the ore is smelted which has been thrown to the side of
the furnace in which the nozzles are placed. If the ore is easily melted, one
or two wicker baskets full are thrown into the front part of the furnace so that
the fire, being driven back by it, may also smelt the ore and the sows that
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A, BTWO FURNACES. CFOREHEARTH. DDIPPING−POTS. THE MASTER STANDS AT
THE ONE FURNACE AND DRAWS AWAY THE SLAGS WITH AN IRON FORK. EIRON FORK.
FWOODEN HOE WITH WHICH THE CAKES OF MELTED PYRITES ARE DRAWN OUT. GTHE
FOREHEARTH CRUCIBLE: ONE−HALF INSIDE IS TO BE SEEN OPEN IN THE OTHER FURNACE.
HTHE H OUTSIDE THE JTHE ASSISTANT THE FOR
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form round about the nozzles of the bellows. This process of smelting is very
ancient among the Tyrolese 18 , but not so old among the Bohemians.
The second method of smelting ores stands in a measure midway between
that one performed in a furnace of which the tap−hole is closed intermittently,
and the first of the methods performed in a furnace where the tap−hole is
always open. In this manner are smelted the ores of gold and silver that are
neither very rich nor very poor, but mediocre, which fuse easily and are
readily absorbed by the lead. It was found that in this way a large quantity
of ore could be smelted at one operation without much labour or great expense,
and could thus be alloyed with lead. This furnace has two crucibles, one of
which is half inside the furnace and half outside, so that the lead being put
into this crucible, the part of the lead which is in the furnace absorbs
the metals of the ores which easily fuse; the other crucible is lower, and
the alloy and the molten pyrites run into it. Those who make use of this
method of smelting, tap the alloy of gold or silver with lead from the upper
crucible once or twice if need be, and throw in other lead or litharge, and
each absorbs that flux which is nearest. This method of smelting is in use
in Styria 19 .
The furnace in the third method of smelting ores has the tap−hole like−
wise open, but the furnace is higher and wider than the others, and its bellows
are larger; for these reasons a larger charge of the ore can be thrown into
it. When the mines yield a great abundance of ore for the smelter, they
smelt in the same furnace continuously for three days and three nights,
providing there be no defect either in the hearth or in the forehearth. In this
kind of a furnace almost every kind of accretion will be found. The fore−
hearth of the furnace is not unlike the forehearth of the first furnace of all,
except that it has a tap−hole. However, because large charges of ore
are smelted uninterruptedly, and the melted material runs out and the slags
are skimmed off, there is need for a second forehearth crucible, into which the
molten material runs through an opened tap−hole when the first is full. When
a smelter has spent twelve hours' labour on this work, another always takes his
place. The ores of copper and lead and the poorest ores of gold and silver
are smelted by this method, because they cannot be smelted by the other
three methods on account of the greater expense occasioned. Yet by this
method a centumpondíum of ore containing only one or two drachmae of
gold, or only a half to one uncía of silver, 20 can be smelted; because there
is a large amount of ore in each charge, smelting is continuous, and without
expensive fluxes such as lead, litharge, and hearth−lead. In this method
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of smelting we must use only cupriferous pyrites which easily melt in the
fire, in truth the cakes melted out from this, if they no longer absorb
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552
A, BTWO FURNACES. CTAP−HOLES OF FURNACES. DFOREHEARTHS. ETHEIR
TAP−HOLES. FDIPPING−POTS. GAT THE ONE FURNACE STANDS THE SMELTER CARRYING
A WICKER BASKET FULL OF CHARCOAL. AT THE OTHER FURNACE STANDS A SMELTER WHO
WITH THE THIRD HOOKED BAR BREAKS AWAY THE MATERIAL WHICH HAS FROZEN THE
TAP−
HOLE OF THE FURNACE. HHOOKED BAR. IHEAP OF CHARCOAL. KBARROW ON
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much gold or silver, are replenished again from crude pyrites alone. If
from this poor ore, with melted pyrites alone, material for cakes cannot
be made, there are added other fluxes which have not previously been
melted. These fluxes are, namely, lead ore, stones easily fused by fire
of the second order and sand made from them, limestone, tophus, white
schist, and iron stone 21 .
Although this method of smelting ores is rough and might not seem to
be of great use, yet it is clever and useful; for a great weight of ores, in
which the gold, silver, or copper are in small quantities, may be reduced into
a few cakes containing all the metal. If on being first melted they are too
crude to be suitable for the second melting, in which the lead absorbs the
precious metals that are in the cakes, or in which the copper is melted out of
them, yet they can be made suitable if they are repeatedly roasted, some−
times as often as seven or eight times, as I have explained in the last book.
Smelters of this kind are so clever and expert, that in smelting they take out
all the gold and silver which the assayer in assaying the ores has stated to be
contained in them, because if during the first operation, when he makes the
cakes, there is a drachma of gold or half an uncia of silver lost from the ores,
the smelter obtains it from the slags by the second smelting. This method of
smelting ores is old and very common to most of those who use other methods.
Although lead ores are usually smelted in the third furnacewhose tap−
hole is always open,yet not a few people melt them in special furnaces by a
method which I will briefly explain. The Carni 22 first burn such lead ores,
and afterward break and crush them with large round mallets. Between
the two low walls of a hearth, which is inside a furnace made of and vaulted
with a rock that resists injury by the fire and does not burn into chalk, they
place green wood with a layer of dry wood on the top of it; then they throw
the ore on to this, and when the wood is kindled the lead drips down and
runs on to the underlying sloping hearth 23 . This hearth is made of pulverised
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554
charcoal and earth, as is also a large crucible, one−half of which lies under the
furnace and the other half outside it, into which runs the lead. The
smelter, having first skimmed off the slags and other things with a hoc, pours
the lead with a ladle into moulds, taking out the cakes after they have
cooled. At the back of the furnace is a rectangular hole, so that the fire
may be allowed more draught, and so that the smelter can crawl through it
into the furnace if necessity demands.
The Saxons who inhabit Gittelde, when smelting lead ore in a furnace
not unlike a baking oven, put the wood in through a hole at the back of the
furnace, and when it begins to burn vigorously the lead trickles out of the
ore into a forehearth. When this is full, the smelting being accomplished,
the tap−hole is opened with a bar, and in this way the lead, together with the
slags, runs into the dipping−pots below. Afterward the cakes of lead, when
they are cold, are taken from the moulds.
In Westphalia they heap up ten wagon−loads of charcoal on some hill−
side which adjoins a level place, and the top of the heap being made flat,
straw is thrown upon it to the thickness of three or four digits. On the top of
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555
this is laid as much pure lead ore as the heap can bear; then the charcoal is
kindled, and when the wind blows, it fans the fire so that the ore is smelted.
In this wise the lead, trickling down from the heap, flows on to the level and
forms broad thin slabs. A few hundred pounds of lead ore are kept at hand,
which, if things go well, are scattered over the heap. These broad slabs are
impure and are laid upon dry wood which in turn is placed on green wood
laid over a large crucible, and the former having been kindled, the lead is
re−melted.
The Poles use a hearth of bricks four feet high, sloping on both sides and
plastered with lute. On the upper level part of the hearth large pieces of
wood are piled, and on these is placed small wood with lute put in between;
over the top are laid wood shavings, and upon these again pure lead ore
covered with large pieces of wood. When these are kindled, the ore melts and
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AFURNACE OF THE CARNI. BLOW WALL. CWOOD. DORE DRIPPING LEAD.
ELARGE CRUCIBLE. FMOULDS. GLADLE. HSLABS OF LEAD. IRECTANGULAR
HOLE AT THE BACK OF THE FURNACE. KSAXON FURNACE. LOPENING IN THE BACK
OF THE FURNACE. MWOOD. NUPPER CRUCIBLE. ODIPPING−POT. PWESTPHALIAN
METHOD OF MELTING. QHEAPS OF CHARCOAL. RSTRAW. SWIDE SLABS.
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runs down on to the lower layer of wood; and when this is consumed by
the fire, the metal is collected. If necessity demand, it is melted over and
over again in the same manner, but it is finally melted by means of wood
laid over the large crucible, the slabs of lead being placed upon it.
The concentrates from washing are smelted together with slags (fluxes?)
in a third furnace, of which the tap−hole is always open.
It is worth while to build vaulted dust−chambers over the furnaces,
especially over those in which the precious ores are to be smelted, in order
that the thicker part of the fumes, in which metals are not wanting, may be
caught and saved. In this way two or more furnaces are combined under the
same vaulted ceiling, which is supported by the wall, against which the
furnaces are built, and by four columns. Under this the smelters of the
ore perform their work. There are two openings through which the fumes
rise from the furnaces into the wide vaulted chamber, and the wider this is the
more fumes it collects; in the middle of this chamber over the arch is an opening
three palms high and two wide. This catches the fumes of both furnaces,
which have risen up from both sides of the vaulted chamber to its arch, and
have fallen again because they could not force their way out; and they thus
pass out through the opening mentioned, into the chimney which the Greeks
call kapnodo/xh, the name being taken from the object. The chimney has
thin iron plates fastened into the walls, to which the thinner metallic sub−
stances adhere when ascending with the fumes. The thicker metallic
substances, or cadmia, 25 adhere to the vaulted chamber, and often
harden into stalactites. On one side of the chamber is a window in which
are set panes of glass, so that the light may be transmitted, but the fumes
kept in; on the other side is a door, which is kept entirely closed while the
ores are being smelted in the furnaces, so that none of the fumes may escape.
It is opened in order that the workman, passing through it, may be enabled
to enter the chamber and remove the soot and pompholyx 26 and chip off
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AFURNACES. BVAULTED ROOF. CCOLUMNS. DDUST−CHAMBER. EOPENING.
FCHIMNEY. GWINDOW. HDOOR. ICHUTE.
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the cadmía; this sweeping is done twice a year. The soot mixed with
pompholyx and the cadmia, being chipped off, is thrown down through
a long chute made of four boards joined in the shape of a rectangle,
that they should not fly away. They fall on to the floor, and are sprinkled
with salt water, and are again smelted with ore and litharge, and become
an emolument to the proprietors. Such chambers, which catch the metallic
substances that rise with the fumes, are profitable for all metalliferous
ores; but especially for the minute metallic particles collected by washing
crushed ores and rock, because these usually fly out with the fire of the
furnaces.
I have explained the four general methods of smelting ores; now I
will state how the ores of each metal are smelted, or how the metal is obtained
from the ore. I will begin with gold. Its sand, the concentrates from
washing, or the gold dust collected in any other manner, should very often
not be smelted, but should be mixed with quicksilver and washed with tepid
water, so that all the impurities may be eliminated. This method I ex−
plained in Book VII. Or they are placed in the aqua which separates
gold from silver, for this also separates its impurities. In this method we
see the gold sink in the glass ampulla, and after all the aqua has been drained
from the particles, it frequently remains as a gold−coloured residue at the
bottom; this powder, when it has been moistened with oil made from
argol 27 , is then dried and placed in a crucible, where it is melted with borax
or with saltpetre and salt; or the same very fine dust is thrown into molten
silver, which absorbs it, and from this it is again parted by aqua valens 28 .
It is necessary to smelt gold ore either outside the blast furnace in a
crucible, or inside the blast furnace; in the former case a small charge of ore
is used, in the latter a large charge of it. Rudís gold, of whatever colour
it is, is crushed with a líbra each of sulphur and salt, a third of a líbra of copper,
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and a quarter of a líbra of argol; they should be melted in a crucible on a
slow fire for three hours, then the alloy is put into molten silver that it
may melt more rapidly. Or a líbra of the same crude gold, crushed up, is
mixed together with half a líbra of stíbium likewise crushed, and put
into a crucible with half an uncía of copper filings, and heated until they
melt, then a sixth part of granulated lead is thrown into the same crucible.
As soon as the mixture emits an odour, iron−filings are added to it, or if these
are not at hand, iron hammer−scales, for both of these break the strength of
the stíbíum. When the fire consumes it, not alone with it is some strength
of the stíbíum consumed, but some particles of gold and also of silver, if it
be mixed with the gold 29 . When the button has been taken out of the
crucible and cooled, it is melted in a cupel, first until the antimony is exhaled,
and thereafter until the lead is separated from it.
Crushed pyrites which contains gold is smelted in the same way; it
and the stíbíum should be of equal weight and in truth the gold may be
made from them in a number of different ways 30 . One part of crushed
material is mixed with six parts of copper, one part of sulphur, half a part of
salt, and they are all placed in a pot and over them is poured wine distilled
by heating liquid argol in an ampulla. The pot is covered and smeared
over with lute and is put in a hot place, so that the mixture moistened with
wine may dry for the space of six days, then it is heated for three hours over
a gentle fire that it may combine more rapidly with the lead. Finally it is put
into a cupel and the gold is separated from the lead 31 .
Or else one líbra of the concentrates from washing pyrites, or other stones
to which gold adheres, is mixed with half a líbra of salt, half a líbra of argol,
a third of a líbra of glass−galls, a sixth of a libra of gold or silver slags, and a
sicílícus of copper. The crucible into which these are put, after it has been
covered with a lid, is sealed with lute and placed in a small furnace that is
provided with small holes through which the air is drawn in, and then it is
heated until it turns red and the substances put in have alloyed; this should
take place within four or five hours. The alloy having cooled, it is again
crushed to powder and a pound of litharge is added to it; then it is heated
again in another crucible until it melts. The button is taken out, purged of
slag, and placed in a cupel, where the gold is separated from the lead.
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Or to a líbra of the powder prepared from such metalliferous
concentrates, is added a libra each of salt, of saltpetre, of argol, and of
glass−galls, and it is heated until it melts. When cooled and crushed, it is washed,
then to it is added a libra of silver, a third of copper filings, a sixth of litharge,
and it is likewise heated again until it melts. After the button has been
purged of slag, it is put into the cupel, and the gold and silver are separated
from the lead; the gold is parted from the silver with aqua valens. Or else
a líbra of the powder prepared from such metalliferous concentrates,
a quarter of a libra of copper filings, and two librae of that second powder 32
which fuses ores, are heated until they melt. The mixture when cooled is again
reduced to powder, roasted and washed, and in this manner a blue powder is
obtained. Of this, and silver, and that second powder which fuses ores, a
libra each are taken, together with three librae of lead, and a quarter of a
libra of copper, and they are heated together until they melt; then the
button is treated as before. Or else a libra of the powder prepared from
such metalliferous concentrates, half a libra of saltpetre, and a quarter of a
líbra of salt are heated until they melt. The alloy when cooled is again
crushed to powder, one libra of which is absorbed by four pounds of molten
silver. Or else a líbra of the powder made from that kind of concentrates,
together with a libra of sulphur, a libra and a half of salt, a third of a libra of
salt made from argol, and a third of a líbra of copper resolved into powder
with sulphur, are heated until they melt. Afterward the lead is re−melted,
and the gold is separated from the other metals. Or else a líbra of the
powder of this kind of concentrates, together with two líbrae of salt, half a
líbra of sulphur, and one libra of litharge, are heated, and from these the
gold is melted out. By these and similar methods concentrates containing
gold, if there be a small quantity of them or if they are very rich, can be
smelted outside the blast furnace.
If there be much of them and they are poor, then they are smelted in the
blast furnace, especially the ore which is not crushed to powder, and particularly
when the gold mines yield an abundance of it 33 . The gold concentrates mixed
with litharge and hearth−lead, to which are added iron−scales, are smelted in the
blast furnace whose tap−hole is intermittently closed, or else in the first or the
second furnaces in which the tap−hole is always open. In this manner an
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alloy of gold and lead is obtained which is put into the cupellation furnace.
Two parts of roasted pyrites or cadmía which contain gold, are put with
one part of unroasted, and are smelted together in the third furnace whose
tap−hole is always open, and are made into cakes. When these cakes have
been repeatedly roasted, they are re−smelted in the furnace whose tap−
hole is temporarily closed, or in one of the two others whose tap−holes are
always open. In this manner the lead absorbs the gold, whether pure or
argentiferous or cupriferous, and the alloy is taken to the cupellation
furnace. Pyrites, or other gold ore which is mixed with much material that
is consumed by fire and flies out of the furnace, is melted with stone from
which iron is melted, if this is at hand. Six parts of such pyrites, or of gold
ore reduced to powder and sifted, four of stone from which iron is made, like−
wise crushed, and three of slaked lime, are mixed together and moistened
with water; to these are added two and a half parts of the cakes which
contain some copper, together with one and a half parts of slag. A basket−
ful of fragments of the cakes is thrown into the furnace, then the mixture
of other things, and then the slag. Now when the middle part of the
forehearth is filled with the molten material which runs down from the
furnace, the slags are first skimmed off, and then the cakes made of pyrites;
afterward the alloy of copper, gold and silver, which settles at the bottom,
is taken out. The cakes are gently roasted and re−smelted with lead, and
made into cakes, which are carried to other works. The alloy of copper,
gold, and silver is not roasted, but is re−melted again in a crucible with an
equal portion of lead. Cakes are also made much richer in copper and gold
than those I spoke of. In order that the alloy of gold and silver may be
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made richer, to eighteen líbrae of it are added forty−eight líbrae of crude
ore, three líbrae of the stone from which iron is made, and three−quarters
of a líbra of the cakes made from pyrites, and mixed with lead, all are
heated together in the crucible until they melt. When the slag and the
cakes melted from pyrites have been skimmed off, the alloy is carried to
other furnaces.
There now follows silver, of which the native silver or the lumps of rudís
silver 34 obtained from the mines are not smelted in the blast furnaces, but in
small iron pans, of which I will speak at the proper place; these lumps
are heated and thrown into molten silver−lead alloy in the cupellation furnace
when the silver is being separated from the lead, and refined. The tiny flakes
or tiny lumps of silver adhering to stones or marble or rocks, or again the
same little lumps mixed with earth, or silver not pure enough, should be
smelted in the furnace of which the tap−hole is only closed for a short time,
together with cakes melted from pyrites, with silver slags, and with stones
which easily fuse in fire of the second order.
In order that particles of silver should not fly away 35 from the lumps
of ore consisting of minute threads of pure silver and twigs of native silver,
they are enclosed in a pot, and are placed in the same furnace where the rest of
the silver ores are being smelted. Some people smelt lumps of native silver
not sufficiently pure, in pots or triangular crucibles, whose lids are sealed with
lute. They do not place these pots in the blast furnace, but arrange them in
the assay furnace into which the draught of the air blows through small holes.
To one part of the native silver they add three parts of powdered litharge, as
many parts of hearth−lead, half a part of galena 36 , and a small quantity of
salt and iron−scales. The alloy which settles at the bottom of the other
substances in the pot is carried to the cupellation furnace, and the slags are
re−melted with the other silver slags. They crush under the stamps and
wash the pots or crucibles to which silver−lead alloy or slags adhere, and
having collected the concentrates they smelt them together with the slags.
This method of smelting rudis silver, if there is a small quantity of it, is the
best, because the smallest portion of silver does not fly out of the pot or the
crucible, and get lost.
If bismuth ore or antimony ore or lead ore 37 contains silver, it is
smelted with the other ores of silver; likewise galena or pyrites, if there is
a small amount of it. If there be much galena, whether it contain a large
or a small amount of silver, it is smelted separately from the others;
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which process I will explain a little further on.
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565
Because lead and copper ores and their metals have much in common
with silver ores, it is fitting that I should say a great deal concerning them,
both now and later on. Also in the same manner, pyrites are smelted separ−
ately if there be much of them. To three parts of roasted lead or copper
ore and one part of crude ore, are added concentrates if they were made by
washing the same ore, together with slags, and all are put in the third furnace
whose tap−hole is always open. Cakes are made from this charge, which,
when they have been quenched with water, are roasted. Of these roasted
cakes generally four parts are again mixed with one part of crude pyrites
and re−melted in the same furnace. Cakes are again made from this charge,
and if there is a large amount of copper in these cakes, copper is made
immediately after they have been roasted and re−melted; if there is little
copper in the cakes they are also roasted, but they are re−smelted with a little
soft slag. In this method the molten lead in the forehearth absorbs the
silver. From the pyritic material which floats on the top of the forehearth
are made cakes for the third time, and from them when they have been
roasted and re−smelted is made copper. Similarly, three parts of roasted
cadmia 38 in which there is silver, are mixed with one part of crude pyrites,
together with slag, and this charge is smelted and cakes are made from it;
these cakes having been roasted are re−smelted in the same furnace. By this
method the lead contained in the forehearth absorbs the silver, and the silver−
lead is taken to the cupellation furnace. Crude quartz and stones which
easily fuse in fire of the third order, together with other ores in which there
is a small amount of silver, ought to be mixed with crude roasted pyrites or
cadmía, because the roasted cakes of pyrites or cadmía cannot be
profitably smelted separately. In a similar manner earths which contain
little silver are mixed with the same; but if pyrites and cadmia are not
available to the smelter, he smelts such silver ores and earths with litharge,
hearth−lead, slags, and stones which easily melt in the fire. The concentrates 39
originating from the washing of rudis silver, after first being roasted 40 until
they melt, are smelted with mixed litharge and hearth−lead, or else, after
being moistened with water, they are smelted with cakes made from pyrites
and cadmia. By neither of these methods do (the concentrates) fall
back in the furnace, or fly out of it, driven by the blast of the bellows and the
agitation of the fire. If the concentrates originated from galena they are
smelted with it after having been roasted; and if from pyrites, then with
pyrites.
Pure copper ore, whether it is its own colour or is tinged with chrysocolla
or azure, and copper glance, or grey or black rudis copper, is smelted in a
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566
furnace of which the tap−hole is closed for a very short time, or else is always
1
567
open 41 . If there is a large amount of silver in the ore it is run into the fore−
hearth, and the greater part of the silver is absorbed by the molten lead, and
the remainder is sold with the copper to the proprietor of the works in which
silver is parted from copper 42 . If there is a small amount of silver in the ore,
no lead is put into the forehearth to absorb the silver, and the above−
1
568
mentioned proprietors buy it in with the copper; if there be no silver, copper
is made direct. If such copper ore contains some minerals which do not
easily melt, as pyrites or cadmía metallíca fossilís 43 , or stone from which iron
is melted, then crude pyrites which easily fuse are added to it, together
with slag. From this charge, when smelted, they make cakes; and from
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569
these, when they have been roasted as much as is necessary and re−smelted,
the copper is made. But if there be some silver in the cakes, for which an
outlay of lead has to be made, then it is first run into the forehearth, and
the molten lead absorbs the silver.
Indeed, rudis copper ore of inferior quality, whether ash−coloured or
purple, blackish and occasionally in parts blue, is smelted in the first
furnace whose tap−hole is always open. This is the method of the Tyrolese.
To as much rudis copper ore as will fill eighteen vessels, each of which holds
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570
almost as much as seven Roman moduli 44 , the first smelterfor there are
threeadds three cartloads of lead slags, one cartload of schist, one fifth of
a centumpondium of stones which easily fuse in the fire, besides a small
quantity of concentrates collected from copper slag and accretions, all of
which he smelts for the space of twelve hours, and from which he makes six
centumpondía of primary cakes and one−half of a centumpondium of alloy.
One half of the latter consists of copper and silver, and it settles to the bottom
of the forehearth. In every centumpondium of the cakes there is half a libra
of silver and sometimes half an uncia besides; in the half of a centumpondium
1
571
of the alloy there is a bes or three−quarters of silver. In this way every week,
if the work is for six days, thirty−six centumpondia of cakes are made and
three centumpondia of alloy, in all of which there is often almost twenty−four
librae of silver. The second smelter separates from the primary cakes the
greater part of the silver by absorbing it in lead. To eighteen centumpondia
of cakes made from crude copper ore, he adds twelve centumpondia of hearth−
lead and litharge, three centumpondia of stones from which lead is smelted,
five centumpondia of hard cakes rich in silver, and two centumpondía of
exhausted liquation cakes 45 ; he adds besides, some of the slags resulting
from smelting crude copper, together with a small quantity of concentrates
made from accretions, all of which he melts for the space of twelve hours,
and makes eighteen centumpondia of secondary cakes, and twelve centum−
pondia of copper−lead−silver alloy; in each centumpondíum of the latter
there is half a libra of silver. After he has taken off the cakes with a
hooked bar, he pours the alloy out into copper or iron moulds; by this
method they make four cakes of alloy, which are carried to the works in
which silver is parted from copper. On the following day, the same smelter,
taking eighteen centumpondia of the secondary cakes, again adds twelve
centumpondia of hearth−lead and litharge, three centumpondia of stones
from which lead is smelted, five centumpondía of hard cakes rich in silver,
together with slags from the smelting of the primary cakes, and with concen−
trates washed from the accretions which are usually made at that time.
This charge is likewise smelted for the space of twelve hours, and he makes as
many as thirteen centumpondía of tertiary cakes and eleven centumpondia
of copper−lead−silver alloy, each centumpondium of which contains one−
third of a líbra and half an uncia of silver. When he has skimmed off the
tertiary cakes with a hooked bar, the alloy is poured into copper moulds, and
by this method four cakes of alloy are made, which, like the preceding four
cakes of alloy, are carried to the works in which silver is parted from copper.
By this method the second smelter makes primary cakes on alternate days
and secondary cakes on the intermediate days. The third smelter takes
eleven cartloads of the tertiary cakes and adds to them three cartloads of
hard cakes poor in silver, together with the slag from smelting the secondary
cakes, and the concentrates from the accretions which are usually made
at that time. From this charge when smelted, he makes twenty centum−
pondía of quaternary cakes, which are called "hard cakes," and also
fifteen centumpondía of those "hard cakes rich in silver," each centum−
pondium of which contains a third of a libra of silver. These latter cakes the
second smelter, as I said before, adds to the primary and secondary cakes
when he re−melts them. In the same way, from eleven cartloads of qua−
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572
ternary cakes thrice roasted, he makes the "final" cakes, of which one
centumpondinm contains only half an uncia of silver. In this operation he
also makes fifteen centumpondia of "hard cakes poor in silver," in each
centumpondium of which is a sixth of a líbra of silver. These hard cakes the
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573
third smelter, as I have said, adds to the tertiary cakes when he re−smelts
them, while from the "final" cakes, thrice roasted and re−smelted, is made
black copper 46 .
The rudis copper from which pure copper is made, if it contains little
silver or if it does not easily melt, is first smelted in the third furnace of which
the tap−hole is always open; and from this are made cakes, which after
being seven times roasted are re−smelted, and from these copper is melted
out; the cakes of copper are carried to a furnace of another kind, in which
they are melted for the third time, in order that in the copper "bottoms"
there may be more silver, while in the "tops" there may be less, which
process is explained in Book XI.
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574
Pyrites, when they contain not only copper, but also silver, are smelted
in the manner I described when I treated of ores of silver. But if they are
poor in silver, and if the copper which is melted out of them cannot easily be
treated, they are smelted according to the method which I last explained.
Finally, the copper schists containing bitumen or sulphur are roasted,
and then smelted with stones which easily fuse in a fire of the second order,
and are made into cakes, on the top of which the slags float. From
these cakes, usually roasted seven times and re−melted, are melted out
slags and two kinds of cakes; one kind is of copper and occupies the
bottom of the crucible, and these are sold to the proprietors of the works in
which silver is parted from copper; the other kind of cakes are usually
re−melted with primary cakes. If the schist contains but a small amount of
copper, it is burned, crushed under the stamps, washed and sieved, and
the concentrates obtained from it are melted down; from this are made
cakes from which, when roasted, copper is made. If either chrysocolla or azure,
or yellow or black earth containing copper and silver, adheres to the schist,
it is not washed, but is crushed and smelted with stones which easily
fuse in fire of the second order.
Lead ore, whether it be molybdaena 47 , pyrites, (galena?) or stone from
which it is melted, is often smelted in a special furnace, of which I have
spoken above, but no less often in the third furnace of which the tap−hole
is always open. The hearth and forehearth are made from powder containing
a small portion of iron hammer−scales; iron slag forms the principal flux
for such ores; both of these the expert smelters consider useful and to
the owner' s advantage, because it is the nature of iron to attract lead. If
it is molybdaena or the stone from which lead is smelted, then the lead runs
down from the furnace into the forehearth, and when the slags have been
skimmed off, the lead is poured out with a ladle. If pyrites are smelted,
the first to flow from the furnace into the forehearth, as may be seen at
Goslar, is a white molten substance, injurious and noxious to silver, for it
consumes it. For this reason the slags which float on the top having been
skimmed off, this substance is poured out; or if it hardens, then it is taken
out with a hooked bar; and the walls of the furnace exude the same substance 48 .
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575
Then the stannum runs out of the furnace into the forehearth; this is an alloy
of lead and silver. From the silver−lead alloy they first skim off the slags,
not rarely white, as some pyrites 49 are, and afterward they skim off the
cakes of pyrites, if there are any. In these cakes there is usually some copper;
but since there is usually but a very small quantity, and as the forest
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576
charcoal is not abundant, no copper is made from them. From the silver−
lead poured into iron moulds they likewise make cakes: when these cakes
have been melted in the cupellation furnace, the silver is parted from the
lead, because part of the lead is transformed into litharge and part into
hearth−lead, from which in the blast furnace on re−melting they make
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577
de−silverized lead, for in this lead each centumpondíum contains only a
drachma of silver, when before the silver was parted from it each centumpon−
dium contained more or less than three unciae of silver 50 .
The little black stones 51 and others from which tin is made, are smelted
in their own kind of furnace, which should be narrower than the other
furnaces, that there may be only the small fire which is necessary for this
ore. These furnaces are higher, that the height may compensate for the
narrowness and make them of almost the same capacity as the other furnaces.
At the top, in front, they are closed and on the other side they are open, where
there are steps, because they cannot have the steps in front on account of the
forehearth; the smelters ascend by these steps to put the tin−stone into the
furnace. The hearth of the furnace is not made of powdered earth and char−
coal, but on the floor of the works are placed sandstones which are not too
hard; these are set on a slight slope, and are two and three−quarters feet
long, the same number of feet wide, and two feet thick, for the thicker they are
the longer they last in the fire. Around them is constructed a rectangular
furnace eight or nine feet high, of broad sandstones, or of those common
substances which by nature are composed of diverse materials 52 . On the
inside the furnace is everywhere evenly covered with lute. The upper part
of the interior is two feet long and one foot wide, but below it is not so long
and wide. Above it are two hood−walls, between which the fumes ascend
from the furnace into the dust chamber, and through this they escape by a
narrow opening in the roof. The sandstones are sloped at the bed of the
furnace, so that the tin melted from the tin−stone may flow through the tap−
hole of the furnace into the forehearth. 53
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578
As there is no need for the smelters to have a fierce fire, it is not necessary
to place the nozzles of the bellows in bronze or iron pipes, but only through a
hole in the furnace wall. They place the bellows higher at the back so that
the blast from the nozzles may blow straight toward the tap−hole of the
furnace. That it may not be too fierce, the nozzles are wide, for if the fire
were fiercer, tin could not be melted out from the tin−stone, as it would be
consumed and turned into ashes. Near the steps is a hollowed stone,
in which is placed the tin−stone to be smelted; as often as the smelter
throws into the furnace an iron shovel−ful of this tin−stone, he puts on char−
coal that was first put into a vat and washed with water to be cleansed from the
grit and small stones which adhere to it, lest they melt at the same time as the
tin−stone and obstruct the tap−hole and impede the flow of tin from the
furnace. The tap−hole of the furnace is always open; in front of it is a fore−
hearth a little more than half a foot deep, three−quarters of two feet long and
one foot wide; this is lined with lute, and the tin from the tap−hole flows into it.
On one side of the forehearth is a low wall, three−quarters of a foot wider
and one foot longer than the forehearth, on which lies charcoal powder.
On the other side the floor of the building slopes, so that the slags may con−
veniently run down and be carried away. As soon as the tin begins to run
from the tap−hole of the furnace into the forehearth, the smelter scrapes
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579
down some of the powdered charcoal into it from the wall, so that the slags
may be separated from the hot metal, and so that it may be covered, lest
any part of it, being very hot, should fly away with the fumes. If after
the slag has been skimmed off, the powder does not cover up the whole of the
tin, the smelter draws a little more charcoal off the wall with a scraper. After
he has opened the tap−hole of the forehearth with a tapping−bar, in order
that the tin can flow into the tapping−pot, likewise smeared with lute, he
again closes the tap−hole with pure lute or lute mixed with powdered charcoal.
The smelter, if he be diligent and experienced, has brooms at hand with which
he sweeps down the walls above the furnace; to these walls and to the
dust chamber minute tin−stones sometimes adhere with part of the fumes.
If he be not sufficiently experienced in these matters and has melted at the
same time all of the tin−stone,which is commonly of three sizes, large,
medium, and very small,not a little waste of the proprietor' s tin results;
because, before the large or the medium sizes have melted, the small have either
been burnt up in the furnace, or else, flying up from it, they not only adhere to
the walls but also fall in the dust chamber. The owner of the works has
the sweepings by right from the owner of the ore. For the above reasons
the most experienced smelter melts them down separately; indeed, he
melts the very small size in a wider furnace, the medium in a medium−sized
furnace, and the largest size in the narrowest furnace. When he melts down
the small size he uses a gentle blast from the bellows, with the medium−sized
a moderate one, with the large size a violent blast; and when he smelts
the first size he needs a slow fire, for the second a medium one, and for the
third a fierce one; yet he uses a much less fierce fire than when he smelts
the ores of gold, silver, or copper. When the workmen have spent three
consecutive days and nights in this work, as is usual, they have finished
their labours; in this time they are able to melt out a large weight of small
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580
sized tin−stone which melts quickly, but less of the large ones which melt
slowly, and a moderate quantity of the medium−sized which holds the middle
course. Those who do not smelt the tin−stone in furnaces made sometimes
wide, sometimes medium, or sometimes narrow, in order that great loss
should not be occasioned, throw in first the smallest size, then the medium,
then the large size, and finally those which are not quite pure; and the blast
of the bellows is altered as required. In order that the tin−stone thrown
into the furnace should not roll off from the large charcoal into the forehearth
before the tin is melted out of it, the smelter uses small charcoal; first some
of this moistened with water is placed in the furnace, and then he frequently
repeats this succession of charcoal and tin−stone.
The tin−stone, collected from material which during the summer was
washed in a ditch through which a stream was diverted, and during the winter
was screened on a perforated iron plate, is smelted in a furnace a palm wider
than that in which the fine tin−stone dug out of the earth is smelted. For
the smelting of these, a more vigorous blast of the bellows and a fiercer fire
is needed than for the smelting of the large tin−stone. Whichever kind of
tin−stone is being smelted, if the tin first flows from the furnace, much of it is
made, and if slags first flow from the furnace, then only a little. It happens
that the tin−stone is mixed with the slags when it is either less pure or
ferruginousthat is, not enough roastedand is imperfect when put into
the furnace, or when it has been put in in a larger quantity than was neces−
sary; then, although it may be pure and melt easily, the ore either runs
out of the furnace at the same time, mixed with the slags, or else it settles
so firmly at the bottom of the furnace that the operation of smelting being
necessarily interrupted, the furnace freezes up.
The tap−hole of the forehearth is opened and the tin is diverted into the
dipping−pot, and as often as the slags flow down the sloping floor of the build−
ing they are skimmed off with a rabble; as soon as the tin has run out of
the forehearth, the tap−hole is again closed up with lute mixed with powdered
charcoal. Glowing coals are put in the dipping−pot so that the tin, after it
has run out, should not get chilled. If the metal is so impure that nothing
can be made from it, the material which has run out is made into cakes to be
re−smelted in the hearth, of which I shall have something to say later; if the
metal is pure, it is poured immediately upon thick copper plates, at first in
straight lines and then transversely over these to make a lattice. Each of
these lattice bars is impressed with an iron die; if the tin was melted out
of ore excavated from mines, then one stamp only, namely, that of the
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581
Magistrate, is usually imprinted, but if it is made from tin−stone collected on
the ground after washing, then it is impressed with two seals, one the
Magistrate' s and the other a fork which the washers use. Generally, three
of this kind of lattice bars are beaten and amalgamated into one mass with a
wooden mallet.
The slags that are skimmed off are afterward thrown with an iron shovel
into a small trough hollowed from a tree, and are cleansed from charcoal
1
582
AFURNACE. BITS TAP−HOLE. CFOREHEARTH. DITS TAP−HOLE. ESLAGS.
FSCRAPER. GDIPPING−POT. HWALLS OF THE CHIMNEY. IBROOM.
KCOPPER PLATE. LLATTICEWORK BARS. MIRON SEAL OR DIE. NHAMMER.
1
583
by agitation; when taken out they are broken up with a square iron mallet,
and then they are re−melted with the fine tin−stone next smelted. There
are some who crush the slags three times under wet stamps and re−melt them
three times; if a large quantity of this be smelted while still wet, little
tin is melted from it, because the slag, soon melted again, flows from the
furnace into the forehearth. Under the wet stamps are also crushed the
lute and broken rock with which such furnaces are lined, and also the
accretions, which often contain fine tin−stone, either not melted or half−
melted, and also prills of tin. The tin−stone not yet melted runs out
through the screen into a trough, and is washed in the same way as tin−
stone, while the partly melted and the prills of tin are taken from the mortar−
box and washed in the sieve on which not very minute particles remain, and
thence to the canvas strake. The soot which adheres to that part of the
chimney which emits the smoke, also often contains very fine tin−stone which
flies from the furnace with the fumes, and this is washed in the strake which
I have just mentioned, and in other sluices. The prills of tin and the partly
melted tin−stone that are contained in the lute and broken rock with which
the furnace is lined, and in the remnants of the tin from the forehearth and
the dipping−pot, are smelted together with the tin−stone.
When tin−stone has been smelted for three days and as many nights in a
furnace prepared as I have said above, some little particles of the rock from
which the furnace is constructed become loosened by the fire and fall down;
and then the bellows being taken away, the furnace is broken through at the
back, and the accretions are first chipped off with hammers, and afterward
the whole of the interior of the furnace is re−fitted with the prepared sand−
stone, and again evenly lined with lute. The sandstone placed on the bed
of the furnace, if it has become faulty, is taken out, and another is laid down
in its place; those rocks which are too large the smelter chips off and fits
with a sharp pick.
Some build two furnaces against the wall just like those I have described,
and above them build a vaulted ceiling supported by the wall and by four
pillars. Through holes in the vaulted ceiling the fumes from the furnaces
ascend into a dust chamber, similar to the one described before, except that
there is a window on each side and there is no door. The smelters, when
they have to clear away the flue−dust, mount by the steps at the side of the
furnaces, and climb by ladders into the dust chamber through the apertures
in the vaulted ceilings over the furnaces. They then remove the flue−dust
from everywhere and collect it in baskets, which are passed from one to the
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584
other and emptied. This dust chamber differs from the other described, in
the fact that the chimneys, of which it has two, are not dissimilar to those
of a house; they receive the fumes which, being unable to escape through the
upper part of the chamber, are turned back and re−ascend and release the
tin; thus the tin set free by the fire and turned to ash, and the little tin−
stones which fly up with the fumes, remain in the dust chamber or else adhere
to copper plates in the chimney.
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585
AFURNACES. BFOREHEARTHS. CTHEIR TAP−HOLES. DDIPPING−POTS. EPILLARS.
FDUST−CHAMBER. GWINDOW. HCHIMNEYS. ITUB IN WHICH THE COALS ARE
WASHED.
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586
If the tin is so impure that it cracks when struck with the hammer, it
is not immediately made into lattice−like bars, but into the cakes which I have
spoken of before, and these are refined by melting again on a hearth. This
hearth consists of sandstones, which slope toward the centre and a little
toward a dipping−pot; at their joints they are covered with lute. Dry
logs are arranged on each side, alternately upright and lengthwise, and more
closely in the middle; on this wood are placed five or six cakes of tin which
all together weigh about six centumpondia; the wood having been kindled,
AHEARTHS. BDIPPING−POTS. CWOOD. DCAKES. ELADLE. FCOPPER
PLATE. GLATTICE−SHAPED BARS. HIRON DIES. IWOODEN MALLET. KMASS
OF TIN BARS. LSHOVEL.
the tin drips down and flows continuously into the dipping−pot which
is on the floor. The impure tin sinks to the bottom of this dipping−pot
and the pure tin floats on the top; then both are ladled out by the master,
who first takes out the pure tin, and by pouring it over thick plates of copper
makes lattice−like bars. Afterward he takes out the impure tin from which
he makes cakes; he discriminates between them, when he ladles and pours,
by the ease or difficulty of the flow. One centumpondium of the lattice−like
bare sells for more than a centumpondium of cakes, for the price of the former
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587
exceeds the price of the latter by a gold coin 54 . These lattice−like bars are
lighter than the others, and when five of them are pounded and amalgamated
with a wooden mallet, a mass is made which is stamped with an iron die.
There are some who do not make a dipping−pot on the floor for the tin to run
into, but in the hearth itself; out of this the master, having removed the
charcoal, ladles the tin and pours it over the copper−plate. The dross which
adheres to the wood and the charcoal, having been collected, is re−smelted
in the furnace.
AFURNACE. BBELLOWS. CIRON DISC. DNOZZLE. EWOODEN DISC.
FBLOW−HOLE. GHANDLE. HHAFT. IHOOPS. KMASSES OF TIN.
Some of the Lusitanians melt tin from tin−stone in small furnaces. They
use round bellows made of leather, of which the fore end is a round iron disc
and the rear end a disc of wood; in a hole in the former is fixed the nozzle,
in the middle of the latter the blow−hole. Above this is the handle or haft,
which draws open the round bellows and lets in the air, or compresses it and
drives the air out. Between the discs are several iron hoops to which the
leather is fastened, making such folds as are to be seen in paper lanterns that
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588
are folded together. Since this kind of bellows does not give a vigorous blast,
because they are drawn apart and compressed slowly, the smelter is not
able during a whole day to smelt much more than half a centumpondium of
tin.
Very good iron ore is smelted 55 in a furnace almost like the cupellation
furnace. The hearth is three and a half feet high, and five feet long and
wide; in the centre of it is a crucible a foot deep and one and a half feet
wide, but it may be deeper or shallower, wider or narrower, according to whether
more or less ore is to be made into iron. A certain quantity of iron ore is
given to the master, out of which he may smelt either much or little iron.
He being about to expend his skill and labour on this matter, first throws
charcoal into the crucible, and sprinkles over it an iron shovel−ful of crushed
iron ore mixed with unslaked lime. Then he repeatedly throws on charcoal
and sprinkles it with ore, and continues this until he has slowly built up a
heap; it melts when the charcoal has been kindled and the fire violently
stimulated by the blast of the bellows, which are skilfully fixed in a pipe.
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589
He is able to complete this work sometimes in eight hours, sometimes in ten,
and again sometimes in twelve. In order that the heat of the fire should not
burn his face, he covers it entirely with a cap, in which, however, there are
holes through which he may see and breathe. At the side of the hearth is a
bar which he raises as often as is necessary, when the bellows blow too violent
a blast, or when he adds more ore and charcoal. He also uses the bar
to draw off the slags, or to open or close the gates of the sluice, through
which the waters flow down on to the wheel which turns the axle that com−
presses the bellows. In this sensible way, iron is melted out and a mass
weighing two or three centumpondia may be made, providing the iron ore
was rich. When this is done the master opens the slag−vent with the tapping−
bar, and when all has run out he allows the iron mass to cool. Afterward
he and his assistant stir the iron with the bar, and then in order to chip off
the slags which had until then adhered to it, and to condense and flatten it,
they take it down from the furnace to the floor, and boat it with large wooden
mallets having slender handles five feet long. Thereupon it is immediately
1
590
AHEARTH. BHEAP. CSLAG−VENT. DIRON MASS. EWOODEN MALLETS.
FHAMMER. GANVIL.
1
591
placed on the anvil, and repeatedly beaten by the large iron hammer that is
raised by the cams of an axle turned by a water−wheel. Not long afterward
it is taken up with tongs and placed under the same hammer, and cut up with
a sharp iron into four, five, or six pieces, according to whether it is large or
small. These pieces, after they have been re−heated in the blacksmith' s forge
and again placed on the anvil, are shaped by the smith into square bars or into
ploughshares or tyres, but mainly into bars. Four, six, or eight of these bars
weigh one−fifth of a centumpondium, and from these they make various imple−
ments. During the blows from the hammer by which it is shaped by the smith,
a youth pours water with a ladle on to the glowing iron, and this is why the
blows make such a loud sound that they may be heard a long distance from
the works. The masses, if they remain and settle in the crucible of the
furnace in which the iron is smelted, become hard iron which can only be
hammered with difficulty, and from these they make the iron−shod heads for
the stamps, and such−like very hard articles.
But to iron ore which is cupriferous, or which when heated 56 melts
with difficulty, it is necessary for us to give a fiercer fire and more labour;
because not only must we separate the parts of it in which there is metal from
those in which there is no metal, and break it up by dry stamps, but we must
also roast it, so that the other metals and noxious juices may be exhaled;
and we must wash it, so that the lighter parts may be separated from it.
Such ores are smelted in a furnace similar to the blast furnace, but much
wider and higher, so that it may hold a great quantity of ore and much
charcoal; mounting the stairs at the side of the furnace, the smelters fill
it partly with fragments of ore not larger than nuts, and partly with
charcoal; and from this kind of ore once or twice smelted they make iron
which is suitable for re−heating in the blacksmith' s forge, after it is flattened
out with the large iron hammer and cut into pieces with the sharp iron.
By skill with fire and fluxes is made that kind of iron from which steel
is made, which the Greeks call sto/mwma. Iron should be selected which
is easy to melt, is hard and malleable. Now although iron may be
smelted from ore which contains other metals, yet it is then either soft
or brittle; such (iron) must be broken up into small pieces when it is
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AFURNACE. BSTAIRS. CORE. DCHARCOAL.
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AFORGE. BBELLOWS. CTONGS. DHAMMER. ECOLD STREAM.
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hot, and then mixed with crushed stone which melts. Then a crucible
is made in the hearth of the smith' s furnace, from the same moistened
powder from which are made the forehearths in front of the furnaces in
which ores of gold or silver are smelted; the width of this crucible is
about one and a half feet and the depth one foot. The bellows are so
placed that the blast may be blown through the nozzle into the middle
of the crucible. Then the whole of the crucible is filled with the best
charcoal, and it is surrounded by fragments of rock to hold in place the pieces
of iron and the superimposed charcoal. As soon as all the charcoal
is kindled and the crucible is glowing, a blast is blown from the bellows
and the master pours in gradually as much of the mixture of iron and flux
as he wishes. Into the middle of this, when it is melted, he puts four iron
masses each weighing thirty pounds, and heats them for five or six hours in a
fierce fire; he frequently stirs the melted iron with a bar, so that the small
pores in each mass absorb the minute particles, and these particles by their
own strength consume and expand the thick particles of the masses, which they
render soft and similar to dough. Afterward the master, aided by his
assistant, takes out a mass with the tongs and places it on the anvil, where
it is pounded by the hammer which is alternately raised and dropped by
means of the water−wheel; then, without delay, while it is still hot, he
throws it into water and tempers it; when it is tempered, he places it again
on the anvil, and breaks it with a blow from the same hammer. Then at
once examining the fragments, he decides whether the iron in some part or
other, or as a whole, appears to be dense and changed into steel; if so, he seizes
one mass after another with the tongs, and taking them out he breaks them
into pieces. Afterward he heats the mixture up again, and adds a portion
afresh to take the place of that which has been absorbed by the masses. This
restores the energy of that which is left, and the pieces of the masses are again
put back into the crucible and made purer. Each of these, after having
been heated, is seized with the tongs, put under the hammer and shaped
into a bar. While they are still glowing, he at once throws them into the very
coldest nearby running water, and in this manner, being suddenly condensed,
they are changed into pure steel, which is much harder and whiter than iron.
The ores of the other metals are not smelted in furnaces. Quicksilver
ores and also antimony are melted in pots, and bismuth in troughs.
I will first speak of quicksilver. This is collected when found in pools
formed from the outpourings of the veins and stringers; it is cleansed with
vinegar and salt, and then it is poured into canvas or soft leather, through
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which, when squeezed and compressed, the quicksilver runs out into a pot or
pan. The ore of quicksilver is reduced in double or single pots. If in double
pots, then the upper one is of a shape not very dissimilar to the glass ampullas
used by doctors, but they taper downward toward the bottom, and the
lower ones are little pots similar to those in which men and women make
cheese, but both are larger than these; it is necessary to sink the lower
pots up to the rims in earth, sand, or ashes. The ore, broken up into small
pieces is put into the upper pots; these having been entirely closed up
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with moss, are placed upside down in the openings of the lower pots, where they
are joined with lute, lest the quicksilver which takes refuge in them should
be exhaled. There are some who, after the pots have been buried, do not fear
to leave them uncemented, and who boast that they are able to produce no
less weight of quicksilver than those who do cement them, but nevertheless
cementing with lute is the greatest protection against exhalation. In this
manner seven hundred pairs of pots are set together in the ground or on a
hearth. They must be surrounded on all sides with a mixture consisting of
crushed earth and charcoal, in such a way that the upper pots protrude to a
height of a palm above it. On both sides of the hearth rocks are first laid,
and upon them poles, across which the workmen place other poles transversely;
these poles do not touch the pots, nevertheless the fire heats the quick−
silver, which fleeing from the heat is forced to run down through the moss
into the lower pots. If the ore is being reduced in the upper pots, it flees
from them, wherever there is an exit, into the lower pots, but if the ore on
the contrary is put in the lower pots the quicksilver rises into the upper pot
or into the operculum, which, together with the gourd−shaped vessels, are
cemented to the upper pots.
AHEARTH. BPOLES. CHEARTH WITHOUT FIRE IN WHICH THE POTS ARE PLACED.
DROCKS. EROWS OF POTS. FUPPER POTS. GLOWER POTS.
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The pots, lest they should become defective, are moulded from the best
potters' clay, for if there are defects the quicksilver flies out in the fumes.
If the fumes give out a very sweet odour it indicates that the quicksilver is
being lost, and since this loosens the teeth, the smelters and others standing by,
warned of the evil, turn their backs to the wind, which drives the fumes in
the opposite direction; for this reason, the building should be open around
the front and the sides, and exposed to the wind. If these pots are made
of cast copper they last a long time in the fire. This process for reducing the
ores of quicksilver is used by most people.
In a similar manner the antimony ore, 57 if free from other metals, is reduced
in upper pots which are twice as large as the lower ones. Their size, however,
depends on the cakes, which have not the same weight everywhere; for in
some places they are made to weigh six librae, in other places ten, and else−
where twenty. When the smelter has concluded his operation, he extin−
guishes the fire with water, removes the lids from the pots, throws earth mixed
with ash around and over them, and when they have cooled, takes out the
cakes from the pots.
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Other methods for reducing quicksilver are given below. Big−bellied
pots, having been placed in the upper rectangular open part of a furnace,
are filled with the crushed ore. Each of these pots is covered with a lid
with a long nozzlecommonly called a campana in the shape of a bell, and
they are cemented. Each of the small earthenware vessels shaped like a
gourd receives two of these nozzles, and these are likewise cemented. Dried
APOTS. BOPERCULA. CNOZZLES. DGOURD−SHAPED EARTHENWARE VESSELS.
wood having been placed in the lower part of the furnace and kindled, the
ore is heated until all the quicksilver has risen into the operculum which is
over the pot; it then flows from the nozzle and is caught in the earthenware
gourd−shaped vessel.
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Others build a hollow vaulted chamber, of which the paved floor is made
concave toward the centre. Inside the thick walls of the chamber are the
furnaces. The doors through which the wood is put are in the outer part of the
same wall. They place the pots in the furnaces and fill them with crushed
ore, then they cement the pots and the furnaces on all sides with lute, so that
none of the vapour may escape from them, and there is no entrance to the
AENCLOSED CHAMBER. BDOOR. CLITTLE WINDOWS. DMOUTHS THROUGH THE
WALLS. EFURNACE IN THE ENCLOSED CHAMBER. FPOTS.
furnaces except through their mouths. Between the dome and the paved
floor they arrange green trees, then they close the door and the little windows,
and cover them on all sides with moss and lute, so that none of the quick−
silver can exhale from the chamber. After the wood has been kindled the
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ore is heated, and exudes the quicksilver; whereupon, impatient with the
heat, and liking the cold, it escapes to the leaves of the trees, which
have a cooling power. When the operation is completed the smelter
extinguishes the fire, and when all gets cool he opens the door and the
windows, and collects the quicksilver, most of which, being heavy, falls of
its own accord from the trees, and flows into the concave part of the floor;
if all should not have fallen from the trees, they are shaken to make it fall.
The following is the fourth method of reducing ores of quicksilver. A
larger pot standing on a tripod is filled with crushed ore, and over the ore is
put sand or ashes to a thickness of two digits, and tamped; then in
the mouth of this pot is inserted the mouth of another smaller pot and
cemented with lute, lest the vapours are emitted. The ore heated by the fire
exhales the quicksilver, which, penetrating through the sand or the ashes,
takes refuge in the upper pot, where condensing into drops it falls back into
the sand or the ashes, from which the quicksilver is washed and collected.
ALARGER POT. BSMALLER. CTRIPOD. DTUB IN WHICH THE SAND IS WASHED.
The fifth method is not very unlike the fourth. In the place of these
pots are set other pots, likewise of earthenware, having a narrow bottom
and a wide mouth. These are nearly filled with crushed ore, which is likewise
covered with ashes to a depth of two digits and tamped in. The pots are
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covered with lids a digit thick, and they are smeared over on the inside with
liquid litharge, and on the lid are placed heavy stones. The pots are set on
the furnace, and the ore is heated and similarly exhales quicksilver, which
fleeing from the heat takes refuge in the lid; on congealing there, it falls
back into the ashes, from which, when washed, the quicksilver is collected.
APOTS. BLIDS. CSTONES. DFURNACE.
By these five methods quicksilver may be made, and of these not one is
to be despised or repudiated; nevertheless, if the mine supplies a great
abundance of ore, the first is the most expeditious and practical, because a
large quantity of ore can be reduced at the same time without great expense. 58
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Bismuth 59 ore, free from every kind of silver, is smelted by various
methods. First a small pit is dug in the dry ground; into this pulverised
charcoal is thrown and tamped in, and then it is dried with burning charcoal.
Afterward, thick dry pieces of beech wood are placed over the pit, and the
bismuth ore is thrown on it. As soon as the kindled wood burns, the heated
ore drips with bismuth, which runs down into the pit, from which when cooled
the cakes are removed. Because pieces of burnt wood, or often charcoal
and occasionally slag, drop into the bismuth which collects in the pit, and
make it impure, it is put back into another kind of crucible to be melted,
so that pure cakes may be made. There are some who, bearing these things
in mind, dig a pit on a sloping place and below it put a forehearth, into
which the bismuth continually flows, and thus remains clean; then they
take it out with ladles and pour it into iron pans lined inside with lute, and
make cakes of it. They cover such pits with flat stones, whose joints are
besmeared with a lute of mixed dust and crushed charcoal, lest the joints
should absorb the molten bismuth. Another method is to put the ore in
troughs made of fir−wood and placed on sloping ground; they place small
firewood over it, kindling it when a gentle wind blows, and thus the ore is
heated. In this manner the bismuth melts and runs down from the troughs
into a pit below, while there remains slag, or stones, which are of a yellow
colour, as is also the wood laid across the pit. These are also sold.
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APIT ACROSS WHICH WOOD IS PLACED. BFOREHEARTH. CLADLE. DIRON
MOULD. ECAKES. FEMPTY POT LINED WITH STONES IN LAYERS. GTROUGHS.
HPITS DUG AT THE FOOT OF THE TROUGHS. ISMALL WOOD LAID OVER THE TROUGHS.
KWIND.
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Others reduce the ore in iron pans as next described. They lay small
pieces of dry wood alternately straight and transversely upon bricks, one and
a half feet apart, and set fire to it. Near it they put small iron pans lined
on the inside with lute, and full of broken ore; then when the wind
blows the flame of the fierce fire over the pans, the bismuth drips out of the
ore; wherefore, in order that it may run, the ore is stirred with the tongs; but
when they decide that all the bismuth is exuded, they seize the pans with
the tongs and remove them, and pour out the bismuth into empty pans, and
by turning many into one they make cakes. Others reduce the ore, when it is
not mixed with cadmía, 60 in a furnace similar to the iron furnace. In this
case they make a pit and a crucible of crushed earth mixed with pulverised
AWOOD. BBRICKS. CPANS. DFURNACE. ECRUCIBLE. FPIPE.
GDIPPING−POT.
charcoal, and into it they put the broken ore, or the concentrates from
washing, from which they make more bismuth. If they put in ore,
they reduce it with charcoal and small dried wood mixed, and if concentrates,
they use charcoal only; they blow both materials with a gentle blast from
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a bellows. From the crucible is a small pipe through which the molten
bismuth runs down into a dipping−pot, and from this cakes are made.
On a dump thrown up from the mines, other people construct a hearth
exposed to the wind, a foot high, three feet wide, and four and a half feet
long. It is held together by four boards, and the whole is thickly coated at
the top with lute. On this hearth they first put small dried sticks of fir wood,
then over them they throw broken ore; then they lay more wood over it,
and when the wind blows they kindle it. In this manner the bismuth drips
out of the ore, and afterward the ashes of the wood consumed by the fire and
the charcoals are swept away. The drops of bismuth which fall down into
the hearth are congealed by the cold, and they are taken away with the
tongs and thrown into a basket. From the melted bismuth they make
cakes in iron pans.
AHEARTH IN WHICH ORE IS MELTED. BHEARTH ON WHICH LIE DROPS OF BISMUTH.
CTONGS. DBASKET. EWIND.
Others again make a box eight feet long, four feet wide, and two feet high,
which they fill almost full of sand and cover with bricks, thus making
the hearth. The box has in the centre a wooden pivot, which turns in a hole
in two beams laid transversely one upon the other; these beams are hard and
thick, are sunk into the ground, both ends are perforated, and through
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these holes wedge−shaped pegs are driven, in order that the beams may remain
fixed, and that the box may turn round, and may be turned toward the wind
from whichever quarter of the sky it may blow. In such a hearth they put
ABOX. BPIVOT. CTRANSVERSE WOOD BEAMS. DGRATE. EITS FEET.
FBURNING WOOD. GSTICK. HPANS IN WHICH THE BISMUTH IS MELTED.
IPANS FOR MOULDS. KCAKES. LFORK. MBRUSH.
an iron grate, as long and wide as the box and threequarters of a foot high;
it has six feet, and there are so many transverse bars that they almost touch
one another. On the grate they lay pine−wood and over it broken ore, and over
this they again lay pine−wood. When it has been kindled the ore melts, out
of which the bismuth drips down; since very little wood is burned, this is the
most profitable method of smelting the bismuth. The bismuth drips through
the grate on to the hearth, while the other things remain upon the grate with
the charcoal. When the work is finished, the workman takes a stick from the
hearth and overturns the grate, and the things which have accumulated on
it; with a brush he sweeps up the bismuth and collects it in a basket, and
then he melts it in an iron pan and makes cakes. As soon as possible after
it is cool, he turns the pans over, so that the cakes may fall out, using for
this purpose a two−pronged fork of which one prong is again forked. And
immediately afterward he returns to his labours.
END OF BOOK IX.