Book VII.

If sulphur from the lye with which _sal artificiosus_ is made, is strong enough to float an egg thrown into it, and is boiled until it no longer emits fumes, and melts when placed upon glowing coals, then, if such sulphur is thrown into the melted silver, it parts the gold from it. [Illustration 453 (Parting precious metals with antimony): A--Furnace in which the air is drawn in through holes. B--Goldsmith's forge. C--Earthen crucibles. D--Iron pots. E--Block.] Silver is also parted from gold by means of _stibium_[17]. If in a _bes of_ gold there are seven, or six, or five double _sextulae_ of silver, then three parts of _stibium_ are added to one part of gold; but in order that the _stibium_ should not consume the gold, it is melted with copper in a red hot earthen crucible. If the gold contains some portion of copper, then to eight _unciae_ of _stibium_ a _sicilicus_ of copper is added; and if it contains no copper, then half an _uncia_, because copper must be added to _stibium_ in order to part gold from silver. The gold is first placed in a red hot earthen crucible, and when melted it swells, and a little _stibium_ is added to it lest it run over; in a short space of time, when this has melted, it likewise again swells, and when this occurs it is advisable to put in all the remainder of the _stibium_, and to cover the crucible with a lid, and then to heat the mixture for the time required to walk thirty-five paces. Then it is at once poured out into an iron pot, wide at the top and narrow at the bottom, which was first heated and smeared over with tallow or wax, and set on an iron or wooden block. It is shaken violently, and by this agitation the gold lump settles to the bottom, and when the pot has cooled it is tapped loose, and is again melted four times in the same way. But each time a less weight of _stibium_ is added to the gold, until finally only twice as much _stibium_ is added as there is gold, or a little more; then the gold lump is melted in a cupel. The _stibium_ is melted again three or four times in an earthen crucible, and each time a gold lump settles, so that there are three or four gold lumps, and these are all melted together in a cupel. To two _librae_ and a half of such _stibium_ are added two _librae_ of argol and one _libra_ of glass-galls, and they are melted in an earthen crucible, where a lump likewise settles at the bottom; this lump is melted in the cupel. Finally, the _stibium_ with a little lead added, is melted in the cupel, in which, after all the rest has been consumed by the fire, the silver alone remains. If the _stibium_ is not first melted in an earthen crucible with argol and glass-galls, before it is melted in the cupel, part of the silver is consumed, and is absorbed by the ash and powder of which the cupel is made. The crucible in which the gold and silver alloy are melted with _stibium_, and also the cupel, are placed in a furnace, which is usually of the kind in which the air is drawn in through holes; or else they are placed in a goldsmith's forge. Just as _aqua valens_ poured over silver, from which the sulphur has parted the gold, shows us whether all has been separated or whether particles of gold remain in the silver; so do certain ingredients, if placed in the pot or crucible "alternately" with the gold, from which the silver has been parted by _stibium_, and heated, show us whether all have been separated or not. We use cements[18] when, without _stibium_, we part silver or copper or both so ingeniously and admirably from gold. There are various cements. Some consist of half a _libra_ of brick dust, a quarter of a _libra_ of salt, an _uncia_ of saltpetre, half an _uncia_ of sal-ammoniac, and half an _uncia_ of rock salt. The bricks or tiles from which the dust is made must be composed of fatty clays, free from sand, grit, and small stones, and must be moderately burnt and very old. Another cement is made of a _bes_ of brick dust, a third of rock salt, an _uncia_ of saltpetre, and half an _uncia_ of refined salt. Another cement is made of a _bes_ of brick dust, a quarter of refined salt, one and a half _unciae_ of saltpetre, an _uncia_ of sal-ammoniac, and half an _uncia_ of rock salt. Another has one _libra_ of brick dust, and half a _libra_ of rock salt, to which some add a sixth of a _libra_ and a _sicilicus_ of vitriol. Another is made of half a _libra_ of brick dust, a third of a _libra_ of rock salt, an _uncia_ and a half of vitriol, and one _uncia_ of saltpetre. Another consists of a _bes_ of brick dust, a third of refined salt, a sixth of white vitriol[19], half an _uncia_ of verdigris, and likewise half an _uncia_ of saltpetre. Another is made of one and a third _librae_ of brick dust, a _bes_ of rock salt, a sixth of a _libra_ and half an _uncia_ of sal-ammoniac, a sixth and half an _uncia_ of vitriol, and a sixth of saltpetre. Another contains a _libra_ of brick dust, a third of refined salt, and one and a half _unciae_ of vitriol. Those ingredients above are peculiar to each cement, but what follows is common to all. Each of the ingredients is first separately crushed to powder; the bricks are placed on a hard rock or marble, and crushed with an iron implement; the other things are crushed in a mortar with a pestle; each is separately passed through a sieve. Then they are all mixed together, and are moistened with vinegar in which a little sal-ammoniac has been dissolved, if the cement does not contain any. But some workers, however, prefer to moisten the gold granules or gold-leaf instead. The cement should be placed, alternately with the gold, in new and clean pots in which no water has ever been poured. In the bottom the cement is levelled with an iron implement, and afterward the gold granules or leaves are placed one against the other, so that they may touch it on all sides; then, again, a handful of the cement, or more if the pots are large, is thrown in and levelled with an iron implement; the granules and leaves are laid over this in the same manner, and this is repeated until the pot is filled. Then it is covered with a lid, and the place where they join is smeared over with artificial lute, and when this is dry the pots are placed in the furnace. [Illustration 455 (Parting precious metals by cementation): A--Furnace. B--Pot. C--Lid. D--Air-holes.] The furnace has three chambers, the lowest of which is a foot high; into this lowest chamber the air penetrates through an opening, and into it the ashes fall from the burnt wood, which is supported by iron rods, arranged to form a grating. The middle chamber is two feet high, and the wood is pushed in through its mouth. The wood ought to be oak, holmoak, or turkey-oak, for from these the slow and lasting fire is made which is necessary for this operation. The upper chamber is open at the top so that the pots, for which it has the depth, may be put into it; the floor of this chamber consists of iron rods, so strong that they may bear the weight of the pots and the heat of the fire; they are sufficiently far apart that the fire may penetrate well and may heat the pots. The pots are narrow at the bottom, so that the fire entering into the space between them may heat them; at the top the pots are wide, so that they may touch and hold back the heat of the fire. The upper part of the furnace is closed in with bricks not very thick, or with tiles and lute, and two or three air-holes are left, through which the fumes and flames may escape. The gold granules or leaves and the cement, alternately placed in the pots, are heated by a gentle fire, gradually increasing for twenty-four hours, if the furnace was heated for two hours before the full pots were stood in it, and if this was not done, then for twenty-six hours. The fire should be increased in such a manner that the pieces of gold and the cement, in which is the potency to separate the silver and copper from the gold, may not melt, for in this case the labour and cost will be spent in vain; therefore, it is ample to have the fire hot enough that the pots always remain red. After so many hours all the burning wood should be drawn out of the furnace. Then the refractory bricks or tiles are removed from the top of the furnace, and the glowing pots are taken out with the tongs. The lids are removed, and if there is time it is well to allow the gold to cool by itself, for then there is less loss; but if time cannot be spared for that operation, the pieces of gold are immediately placed separately into a wooden or bronze vessel of water and gradually quenched, lest the cement which absorbs the silver should exhale it. The pieces of gold, and the cement adhering to them, when cooled or quenched, are rolled with a little mallet so as to crush the lumps and free the gold from the cement. Then they are sifted by a fine sieve, which is placed over a bronze vessel; in this manner the cement containing the silver or the copper or both, falls from the sieve into the bronze vessel, and the gold granules or leaves remain on it. The gold is placed in a vessel and again rolled with the little mallet, so that it may be cleansed from the cement which absorbs silver and copper. The particles of cement, which have dropped through the holes of the sieve into the bronze vessel, are washed in a bowl, over a wooden tub, being shaken about with the hands, so that the minute particles of gold which have fallen through the sieve may be separated. These are again washed in a little vessel, with warm water, and scrubbed with a piece of wood or a twig broom, that the moistened cement may be detached. Afterward all the gold is again washed with warm water, and collected with a bristle brush, and should be washed in a copper full of holes, under which is placed a little vessel. Then it is necessary to put the gold on an iron plate, under which is a vessel, and to wash it with warm water. Finally, it is placed in a bowl, and, when dry, the granules or leaves are rubbed against a touchstone at the same time as a touch-needle, and considered carefully as to whether they be pure or alloyed. If they are not pure enough, the granules or the leaves, together with the cement which attracts silver and copper, are arranged alternately in layers in the same manner, and again heated; this is done as often as is necessary, but the last time it is heated as many hours as are required to cleanse the gold. Some people add another cement to the granules or leaves. This cement lacks the ingredients of metalliferous origin, such as verdigris and vitriol, for if these are in the cement, the gold usually takes up a little of the base metal; or if it does not do this, it is stained by them. For this reason some very rightly never make use of cements containing these things, because brick dust and salt alone, especially rock salt, are able to extract all the silver and copper from the gold and to attract it to themselves. It is not necessary for coiners to make absolutely pure gold, but to heat it only until such a fineness is obtained as is needed for the gold money which they are coining. The gold is heated, and when it shows the necessary golden yellow colour and is wholly pure, it is melted and made into bars, in which case they are either prepared by the coiners with _chrysocolla_, which is called by the Moors borax, or are prepared with salt of lye made from the ashes of ivy or of other salty herbs. The cement which has absorbed silver or copper, after water has been poured over it, is dried and crushed, and when mixed with hearth-lead and de-silverized lead, is smelted in the blast furnace. The alloy of silver and lead, or of silver and copper and lead, which flows out, is again melted in the cupellation furnace, in order that the lead and copper may be separated from the silver. The silver is finally thoroughly purified in the refining furnace, and in this practical manner there is no silver lost, or only a minute quantity. There are besides this, certain other cements[20] which part gold from silver, composed of sulphur, _stibium_ and other ingredients. One of these compounds consists of half an _uncia_ of vitriol dried by the heat of the fire and reduced to powder, a sixth of refined salt, a third of _stibium_, half a _libra_ of prepared sulphur (not exposed to the fire), one _sicilicus_ of glass, likewise one _sicilicus_ of saltpetre, and a _drachma_ of sal-ammoniac.[21] The sulphur is prepared as follows: it is first crushed to powder, then it is heated for six hours in sharp vinegar, and finally poured into a vessel and washed with warm water; then that which settles at the bottom of the vessel is dried. To refine the salt it is placed in river water and boiled, and again evaporated. The second compound contains one _libra_ of sulphur (not exposed to fire) and two _librae_ of refined salt. The third compound is made from one _libra_ of sulphur (not exposed to the fire), half a _libra_ of refined salt, a quarter of a _libra_ of sal-ammoniac, and one _uncia_ of red-lead. The fourth compound consists of one _libra_ each of refined salt, sulphur (not exposed to the fire) and argol, and half a _libra_ of _chrysocolla_ which the Moors call borax. The fifth compound has equal proportions of sulphur (not exposed to the fire), sal-ammoniac, saltpetre, and verdigris. The silver which contains some portion of gold is first melted with lead in an earthen crucible, and they are heated together until the silver exhales the lead. If there was a _libra_ of silver, there must be six _drachmae_ of lead. Then the silver is sprinkled with two _unciae_ of that powdered compound and is stirred; afterward it is poured into another crucible, first warmed and lined with tallow, and then violently shaken. The rest is performed according to the process I have already explained. Gold may be parted without injury from silver goblets and from other gilt vessels and articles[22], by means of a powder, which consists of one part of sal-ammoniac and half a part of sulphur. The gilt goblet or other article is smeared with oil, and the powder is dusted on; the article is seized in the hand, or with tongs, and is carried to the fire and sharply tapped, and by this means the gold falls into water in vessels placed underneath, while the goblet remains uninjured. Gold is also parted from silver on gilt articles by means of quicksilver. This is poured into an earthen crucible, and so warmed by the fire that the finger can bear the heat when dipped into it; the silver-gilt objects are placed in it, and when the quicksilver adheres to them they are taken out and placed on a dish, into which, when cooled, the gold falls, together with the quicksilver. Again and frequently the same silver-gilt object is placed in heated quicksilver, and the same process is continued until at last no more gold is visible on the object; then the object is placed in the fire, and the quicksilver which adheres to it is exhaled. Then the artificer takes a hare's foot, and brushes up into a dish the quicksilver and the gold which have fallen together from the silver article, and puts them into a cloth made of woven cotton or into a soft leather; the quicksilver is squeezed through one or the other into another dish.[23] The gold remains in the cloth or the leather, and when collected is placed in a piece of charcoal hollowed out, and is heated until it melts, and a little button is made from it. This button is heated with a little _stibium_ in an earthen crucible and poured out into another little vessel, by which method the gold settles at the bottom, and the _stibium_ is seen to be on the top; then the work is completed. Finally, the gold button is put in a hollowed-out brick and placed in the fire, and by this method the gold is made pure. By means of the above methods gold is parted from silver and also silver from gold. Now I will explain the methods used to separate copper from gold[24]. The salt which we call _sal-artificiosus_,[25] is made from a _libra_ each of vitriol, alum, saltpetre, and sulphur not exposed to the fire, and half a _libra_ of sal-ammoniac; these ingredients when crushed are heated with one part of lye made from the ashes used by wool dyers, one part of unslaked lime, and four parts of beech ashes. The ingredients are boiled in the lye until the whole has been dissolved. Then it is immediately dried and kept in a hot place, lest it turn into oil; and afterward when crushed, a _libra_ of lead-ash is mixed with it. With each _libra_ of this powdered compound one and a half _unciae_ of the copper is gradually sprinkled into a hot crucible, and it is stirred rapidly and frequently with an iron rod. When the crucible has cooled and been broken up, the button of gold is found. The second method for parting is the following. Two _librae_ of sulphur not exposed to the fire, and four _librae_ of refined salt are crushed and mixed; a sixth of a _libra_ and half an _uncia_ of this powder is added to a _bes_ of granules made of lead, and twice as much copper containing gold; they are heated together in an earthen crucible until they melt. When cooled, the button is taken out and purged of slag. From this button they again make granules, to a third of a _libra_ of which is added half a _libra_ of that powder of which I have spoken, and they are placed in alternate layers in the crucible; it is well to cover the crucible and to seal it up, and afterward it is heated over a gentle fire until the granules melt. Soon afterward, the crucible is taken off the fire, and when it is cool the button is extracted. From this, when purified and again melted down, the third granules are made, to which, if they weigh a sixth of a _libra_, is added one half an _uncia_ and a _sicilicus_ of the powder, and they are heated in the same manner, and the button of gold settles at the bottom of the crucible. The third method is as follows. From time to time small pieces of sulphur, enveloped in or mixed with wax, are dropped into six _librae_ of the molten copper, and consumed; the sulphur weighs half an _uncia_ and a _sicilicus_. Then one and a half _sicilici_ of powdered saltpetre are dropped into the same copper and likewise consumed; then again half an _uncia_ and a _sicilicus_ of sulphur enveloped in wax; afterward one and a half _sicilici_ of lead-ash enveloped in wax, or of minium made from red-lead. Then immediately the copper is taken out, and to the gold button, which is now mixed with only a little copper, they add _stibium_ to double the amount of the button; these are heated together until the _stibium_ is driven off; then the button, together with lead of half the weight of the button, are heated in a cupel. Finally, the gold is taken out of this and quenched, and if there is a blackish colour settled in it, it is melted with a little of the _chrysocolla_ which the Moors call borax; if too pale, it is melted with _stibium_, and acquires its own golden-yellow colour. There are some who take out the molten copper with an iron ladle and pour it into another crucible, whose aperture is sealed up with lute, and they place it over glowing charcoal, and when they have thrown in the powders of which I have spoken, they stir the whole mass rapidly with an iron rod, and thus separate the gold from the copper; the former settles at the bottom of the crucible, the latter floats on the top. Then the aperture of the crucible is opened with the red-hot tongs, and the copper runs out. The gold which remains is re-heated with _stibium_, and when this is exhaled the gold is heated for the third time in a cupel with a fourth part of lead, and then quenched. The fourth method is to melt one and a third _librae_ of the copper with a sixth of a _libra_ of lead, and to pour it into another crucible smeared on the inside with tallow or gypsum; and to this is added a powder consisting of half an _uncia_ each of prepared sulphur, verdigris, and saltpetre, and an _uncia_ and a half of _sal coctus_. The fifth method consists of placing in a crucible one _libra_ of the copper and two _librae_ of granulated lead, with one and a half _unciae_ of _sal-artificiosus_; they are at first heated over a gentle fire and then over a fiercer one. The sixth method consists in heating together a _bes_ of the copper and one-sixth of a _libra_ each of sulphur, salt, and _stibium_. The seventh method consists of heating together a _bes_ of the copper and one-sixth each of iron scales and filings, salt, _stibium_, and glass-galls. The eighth method consists of heating together one _libra_ of the copper, one and a half _librae_ of sulphur, half a _libra_ of verdigris, and a _libra_ of refined salt. The ninth method consists of placing in one _libra_ of the molten copper as much pounded sulphur, not exposed to the fire, and of stirring it rapidly with an iron rod; the lump is ground to powder, into which quicksilver is poured, and this attracts to itself the gold. Gilded copper articles are moistened with water and placed on the fire, and when they are glowing they are quenched with cold water, and the gold is scraped off with a brass rod. By these practical methods gold is separated from copper. Either copper or lead is separated from silver by the methods which I will now explain.[26] This is carried on in a building near by the works, or in the works in which the gold or silver ores or alloys are smelted. The middle wall of such a building is twenty-one feet long and fifteen feet high, and from this a front wall is distant fifteen feet toward the river; the rear wall is nineteen feet distant, and both these walls are thirty-six feet long and fourteen feet high; a transverse wall extends from the end of the front wall to the end of the rear wall; then fifteen feet back a second transverse wall is built out from the front wall to the end of the middle wall. In that space which is between those two transverse walls are set up the stamps, by means of which the ores and the necessary ingredients for smelting are broken up. From the further end of the front wall, a third transverse wall leads to the other end of the middle wall, and from the same to the end of the rear wall. The space between the second and third transverse walls, and between the rear and middle long walls, contains the cupellation furnace, in which lead is separated from gold or silver. The vertical wall of its chimney is erected upon the middle wall, and the sloping chimney-wall rests on the beams which extend from the second transverse wall to the third; these are so located that they are at a distance of thirteen feet from the middle long wall and four from the rear wall, and they are two feet wide and thick. From the ground up to the roof-beams is twelve feet, and lest the sloping chimney-wall should fall down, it is partly supported by means of many iron rods, and partly by means of a few tie-beams covered with lute, which extend from the small beams of the sloping chimney-wall to the beams of the vertical chimney-wall. The rear roof is arranged in the same way as the roof of the works in which ore is smelted. In the space between the middle and the front long walls and between the second[27] and the third transverse walls are the bellows, the machinery for depressing and the instrument for raising them. A drum on the axle of a water-wheel has rundles which turn the toothed drum of an axle, whose long cams depress the levers of the bellows, and also another toothed drum on an axle, whose cams raise the tappets of the stamps, but in the opposite direction. So that if the cams which depress the levers of the bellows turn from north to south, the cams of the stamps turn from south to north. [Illustration 468 (Cupellation Furnace): A--Rectangular stones. B--Sole-stone. C--Air-holes. D--Internal walls. E--Dome. F--Crucible. G--Bands. H--Bars. I--Apertures in the dome. K--Lid of the dome. L--Rings. M--Pipes. N--Valves. O--Chains.] Lead is separated from gold or silver in a cupellation furnace, of which the structure consists of rectangular stones, of two interior walls of which the one intersects the other transversely, of a round sole, and of a dome. Its crucible is made from powder of earth and ash; but I will first speak of the structure and also of the rectangular stones. A circular wall is built four feet and three palms high, and one foot thick; from the height of two feet and three palms from the bottom, the upper part of the interior is cut away to the width of one palm, so that the stone sole may rest upon it. There are usually as many as fourteen stones; on the outside they are a foot and a palm wide, and on the inside narrower, because the inner circle is much smaller than the outer; if the stones are wider, fewer are required, if narrower more; they are sunk into the earth to a depth of a foot and a palm. At the top each one is joined to the next by an iron staple, the points of which are embedded in holes, and into each hole is poured molten lead. This stone structure has six air-holes near the ground, at a height of a foot above the ground; they are two feet and a palm from the bottom of the stones; each of these air-holes is in two stones, and is two palms high, and a palm and three digits wide. One of them is on the right side, between the wall which protects the main wall from the fire, and the channel through which the litharge flows out of the furnace crucible; the other five air-holes are distributed all round at equal distances apart; through these escapes the moisture which the earth exhales when heated, and if it were not for these openings the crucible would absorb the moisture and be damaged. In such a case a lump would be raised, like that which a mole throws up from the earth, and the ash would float on the top, and the crucible would absorb the silver-lead alloy; there are some who, because of this, make the rear part of the structure entirely open. The two inner walls, of which one intersects the other, are built of bricks, and are a brick in thickness. There are four air-holes in these, one in each part, which are about one digit's breadth higher and wider than the others. Into the four compartments is thrown a wheelbarrowful of slag, and over this is placed a large wicker basket full of charcoal dust. These walls extend a cubit above the ground, and on these, and on the ledge cut in the rectangular stones, is placed the stone sole; this sole is a palm and three digits thick, and on all sides touches the rectangular stones; if there are any cracks in it they are filled up with fragments of stone or brick. The front part of the sole is sloped so that a channel can be made, through which the litharge flows out. Copper plates are placed on this part of the sole-stone so that the silver-lead or other alloy may be more rapidly heated. A dome which has the shape of half a sphere covers the crucible. It consists of iron bands and of bars and of a lid. There are three bands, each about a palm wide and a digit thick; the lowest is at a distance of one foot from the middle one, and the middle one a distance of two feet from the upper one. Under them are eighteen iron bars fixed by iron rivets; these bars are of the same width and thickness as the bands, and they are of such a length, that curving, they reach from the lower band to the upper, that is two feet and three palms long, while the dome is only one foot and three palms high. All the bars and bands of the dome have iron plates fastened on the underside with iron wire. In addition, the dome has four apertures; the rear one, which is situated opposite the channel through which the litharge flows out, is two feet wide at the bottom; toward the top, since it slopes gently, it is narrower, being a foot, three palms, and a digit wide; there is no bar at this place, for the aperture extends from the upper band to the middle one, but not to the lower one. The second aperture is situated above the channel, is two and a half feet wide at the bottom, and two feet and a palm at the top; and there is likewise no bar at this point; indeed, not only does the bar not extend to the lower band, but the lower band itself does not extend over this part, in order that the master can draw the litharge out of the crucible. There are besides, in the wall which protects the principal wall against the heat, near where the nozzles of the bellows are situated, two apertures, three palms wide and about a foot high, in the middle of which two rods descend, fastened on the inside with plates. Near these apertures are placed the nozzles of the bellows, and through the apertures extend the pipes in which the nozzles of the bellows are set. These pipes are made of iron plates rolled up; they are two palms three digits long, and their inside diameter is three and a half digits; into these two pipes the nozzles of the bellows penetrate a distance of three digits from their valves. The lid of the dome consists of an iron band at the bottom, two digits wide, and of three curved iron bars, which extend from one point on the band to the point opposite; they cross each other at the top, where they are fixed by means of iron rivets. On the under side of the bars there are likewise plates fastened by rivets; each of the plates has small holes the size of a finger, so that the lute will adhere when the interior is lined. The dome has three iron rings engaged in wide holes in the heads of iron claves, which fasten the bars to the middle band at these points. Into these rings are fastened the hooks of the chains with which the dome is raised, when the master is preparing the crucible. On the sole and the copper plates and the rock of the furnace, lute mixed with straw is placed to a depth of three digits, and it is pounded with a wooden rammer until it is compressed to a depth of one digit only. The rammer-head is round and three palms high, two palms wide at the bottom, and tapering upward; its handle is three feet long, and where it is set into the rammer-head it is bound around with an iron band. The top of the stonework in which the dome rests is also covered with lute, likewise mixed with straw, to the thickness of a palm. All this, as soon as it becomes loosened, must be repaired. [Illustration 470 (Cupellation Furnace): A--An artificer tamping the crucible with a rammer. B--Large rammer. C--Broom. D--Two smaller rammers. E--Curved iron plates. F--Part of a wooden strip. G--Sieve. H--Ashes. I--Iron shovel. K--Iron plate. L--block of wood. M--Rock. N--Basket made of woven twigs. O--Hooked bar. P--Second hooked bar. Q--Old linen rag. R--bucket. S--Doeskin. T--Bundles of straw. V--Wood. X--Cakes of lead alloy. Y--Fork. Z--Another workman covers the outside of the furnace with lute where the dome fits on it. AA--Basket full of ashes. BB--Lid of the dome. CC--The assistant standing on the steps pours charcoal into the crucible through the hole at the top of the dome. DD--Iron implement with which the lute is beaten. EE--Lute. FF--Ladle with which the workman or master takes a sample. GG--Rabble with which the scum of impure lead is drawn off. HH--Iron wedge with which the silver mass is raised.] The artificer who undertakes the work of parting the metals, distributes the operation into two shifts of two days. On the one morning he sprinkles a little ash into the lute, and when he has poured some water over it he brushes it over with a broom. Then he throws in sifted ashes and dampens them with water, so that they could be moulded into balls like snow. The ashes are those from which lye has been made by letting water percolate through them, for other ashes which are fatty would have to be burnt again in order to make them less fat. When he has made the ashes smooth by pressing them with his hands, he makes the crucible slope down toward the middle; then he tamps it, as I have described, with a rammer. He afterward, with two small wooden rammers, one held in each hand, forms the channel through which the litharge flows out. The heads of these small rammers are each a palm wide, two digits thick, and one foot high; the handle of each is somewhat rounded, is a digit and a half less in diameter than the rammer-head, and is three feet in length; the rammer-head as well as the handle is made of one piece of wood. Then with shoes on, he descends into the crucible and stamps it in every direction with his feet, in which manner it is packed and made sloping. Then he again tamps it with a large rammer, and removing his shoe from his right foot he draws a circle around the crucible with it, and cuts out the circle thus drawn with an iron plate. This plate is curved at both ends, is three palms long, as many digits wide, and has wooden handles a palm and two digits long, and two digits thick; the iron plate is curved back at the top and ends, which penetrate into handles. There are some who use in the place of the plate a strip of wood, like the rim of a sieve; this is three digits wide, and is cut out at both ends that it may be held in the hands. Afterward he tamps the channel through which the litharge discharges. Lest the ashes should fall out, he blocks up the aperture with a stone shaped to fit it, against which he places a board, and lest this fall, he props it with a stick. Then he pours in a basketful of ashes and tamps them with the large rammer; then again and again he pours in ashes and tamps them with the rammer. When the channel has been made, he throws dry ashes all over the crucible with a sieve, and smooths and rubs it with his hands. Then he throws three basketsful of damp ashes on the margin all round the edge of the crucible, and lets down the dome. Soon after, climbing upon the crucible, he builds up ashes all around it, lest the molten alloy should flow out. Then, having raised the lid of the dome, he throws a basketful of charcoal into the crucible, together with an iron shovelful of glowing coals, and he also throws some of the latter through the apertures in the sides of the dome, and he spreads them with the same shovel. This work and labour is finished in the space of two hours. An iron plate is set in the ground under the channel, and upon this is placed a wooden block, three feet and a palm long, a foot and two palms and as many digits wide at the back, and two palms and as many digits wide in front; on the block of wood is placed a stone, and over it an iron plate similar to the bottom one, and upon this he puts a basketful of charcoal, and also an iron shovelful of burning charcoals. The crucible is heated in an hour, and then, with the hooked bar with which the litharge is drawn off, he stirs the remainder of the charcoal about. This hook is a palm long and three digits wide, has the form of a double triangle, and has an iron handle four feet long, into which is set a wooden one six feet long. There are some who use instead a simple hooked bar. After about an hour's time, he stirs the charcoal again with the bar, and with the shovel throws into the crucible the burning charcoals lying in the channel; then again, after the space of an hour, he stirs the burning charcoals with the same bar. If he did not thus stir them about, some blackness would remain in the crucible and that part would be damaged, because it would not be sufficiently dried. Therefore the assistant stirs and turns the burning charcoal that it may be entirely burnt up, and so that the crucible may be well heated, which takes three hours; then the crucible is left quiet for the remaining two hours. When the hour of eleven has struck, he sweeps up the charcoal ashes with a broom and throws them out of the crucible. Then he climbs on to the dome, and passing his hand in through its opening, and dipping an old linen rag in a bucket of water mixed with ashes, he moistens the whole of the crucible and sweeps it. In this way he uses two bucketsful of the mixture, each holding five Roman _sextarii_,[28] and he does this lest the crucible, when the metals are being parted, should break open; after this he rubs the crucible with a doe skin, and fills in the cracks. Then he places at the left side of the channel, two fragments of hearth-lead, laid one on the top of the other, so that when partly melted they remain fixed and form an obstacle, that the litharge will not be blown about by the wind from the bellows, but remain in its place. It is expedient, however, to use a brick in the place of the hearth-lead, for as this gets much hotter, therefore it causes the litharge to form more rapidly. The crucible in its middle part is made two palms and as many digits deeper.[29] There are some who having thus prepared the crucible, smear it over with incense[30], ground to powder and dissolved in white of egg, soaking it up in a sponge and then squeezing it out again; there are others who smear over it a liquid consisting of white of egg and double the amount of bullock's blood or marrow. Some throw lime into the crucible through a sieve. Afterward the master of the works weighs the lead with which the gold or silver or both are mixed, and he sometimes puts a hundred _centumpondia_[31] into the crucible, but frequently only sixty, or fifty, or much less. After it has been weighed, he strews about in the crucible three small bundles of straw, lest the lead by its weight should break the surface. Then he places in the channel several cakes of lead alloy, and through the aperture at the rear of the dome he places some along the sides; then, ascending to the opening at the top of the dome, he arranges in the crucible round about the dome the cakes which his assistant hands to him, and after ascending again and passing his hands through the same aperture, he likewise places other cakes inside the crucible. On the second day those which remain he, with an iron fork, places on the wood through the rear aperture of the dome. When the cakes have been thus arranged through the hole at the top of the dome, he throws in charcoal with a basket woven of wooden twigs. Then he places the lid over the dome, and the assistant covers over the joints with lute. The master himself throws half a basketful of charcoal into the crucible through the aperture next to the nozzle pipe, and prepares the bellows, in order to be able to begin the second operation on the morning of the following day. It takes the space of one hour to carry out such a piece of work, and at twelve all is prepared. These hours all reckoned up make a sum of eight hours. Now it is time that we should come to the second operation. In the morning the workman takes up two shovelsful of live charcoals and throws them into the crucible through the aperture next to the pipes of the nozzles; then through the same hole he lays upon them small pieces of fir-wood or of pitch pine, such as are generally used to cook fish. After this the water-gates are opened, in order that the machine may be turned which depresses the levers of the bellows. In the space of one hour the lead alloy is melted; and when this has been done, he places four sticks of wood, twelve feet long, through the hole in the back of the dome, and as many through the channel; these sticks, lest they should damage the crucible, are both weighted on the ends and supported by trestles; these trestles are made of a beam, three feet long, two palms and as many digits wide, two palms thick, and have two spreading legs at each end. Against the trestle, in front of the channel, there is placed an iron plate, lest the litharge, when it is extracted from the furnace, should splash the smelter's shoes and injure his feet and legs. With an iron shovel or a fork he places the remainder of the cakes through the aperture at the back of the dome on to the sticks of wood already mentioned. The native silver, or silver glance, or grey silver, or ruby silver, or any other sort, when it has been flattened out[32], and cut up, and heated in an iron crucible, is poured into the molten lead mixed with silver, in order that impurities may be separated. As I have often said, this molten lead mixed with silver is called _stannum_[33]. [Illustration 474 (Cupellation Furnace): A--Furnace. B--Sticks of wood. C--Litharge. D--Plate. E--The foreman when hungry eats butter, that the poison which the crucible exhales may not harm him, for this is a special remedy against that poison.] When the long sticks of wood are burned up at the fore end, the master, with a hammer, drives into them pointed iron bars, four feet long and two digits wide at the front end, and beyond that one and a half digits wide and thick; with these he pushes the sticks of wood forward and the bars then rest on the trestles. There are others who, when they separate metals, put two such sticks of wood into the crucible through the aperture which is between the bellows, as many through the holes at the back, and one through the channel; but in this case a larger number of long sticks of wood is necessary, that is, sixty; in the former case, forty long sticks of wood suffice to carry out the operation. When the lead has been heated for two hours, it is stirred with a hooked bar, that the heat may be increased. If it be difficult to separate the lead from the silver, he throws copper and charcoal dust into the molten silver-lead alloy. If the alloy of argentiferous gold and lead, or the silver-lead alloy, contains impurities from the ore, then he throws in either equal portions of argol and Venetian glass or of sal-ammoniac, or of Venetian glass and of Venetian soap; or else unequal portions, that is, two of argol and one of iron rust; there are some who mix a little saltpetre with each compound. To one _centumpondium_ of the alloy is added a _bes_ or a _libra_ and a third of the powder, according to whether it is more or less impure. The powder certainly separates the impurities from the alloy. Then, with a kind of rabble he draws out through the channel, mixed with charcoal, the scum, as one might say, of the lead; the lead makes this scum when it becomes hot, but that less of it may be made it must be stirred frequently with the bar. Within the space of a quarter of an hour the crucible absorbs the lead; at the time when it penetrates into the crucible it leaps and bubbles. Then the master takes out a little lead with an iron ladle, which he assays, in order to find what proportion of silver there is in the whole of the alloy; the ladle is five digits wide, the iron part of its handle is three feet long and the wooden part the same. Afterward, when they are heated, he extracts with a bar the litharge which comes from the lead and the copper, if there be any of it in the alloy. Wherefore, it might more rightly be called _spuma_ of lead than of silver[34]. There is no injury to the silver, when the lead and copper are separated from it. In truth the lead becomes much purer in the crucible of the other furnace, in which silver is refined. In ancient times, as the author Pliny[35] relates, there was under the channel of the crucible another crucible, and the litharge flowed down from the upper one into the lower one, out of which it was lifted up and rolled round with a stick in order that it might be of moderate weight. For which reason, they formerly made it into small tubes or pipes, but now, since it is not rolled round a stick, they make it into bars. If there be any danger that the alloy might flow out with the litharge, the foreman keeps on hand a piece of lute, shaped like a cylinder and pointed at both ends; fastening this to a hooked bar he opposes it to the alloy so that it will not flow out. [Illustration 476 (Cleansing of Silver Cakes): A--Cake. B--Stone. C--Hammer. D--Brass wire. E--Bucket containing water. F--Furnace from which the cake has been taken, which is still smoking. G--Labourer carrying a cake out of the works.] Now when the colour begins to show in the silver, bright spots appear, some of them being almost white, and a moment afterward it becomes absolutely white. Then the assistant lets down the water-gates, so that, the race being closed, the water-wheel ceases to turn and the bellows are still. Then the master pours several buckets of water on to the silver to cool it; others pour beer over it to make it whiter, but this is of no importance since the silver has yet to be refined. Afterward, the cake of silver is raised with the pointed iron bar, which is three feet long and two digits wide, and has a wooden handle four feet long fixed in its socket. When the cake of silver has been taken from the crucible, it is laid upon a stone, and from part of it the hearth-lead, and from the other part the litharge, is chipped away with a hammer; then it is cleansed with a bundle of brass wire dipped in water. When the lead is separated from the silver, more silver is frequently found than when it was assayed; for instance, if before there were three _unciae_ and as many _drachmae_ in a _centumpondium_, they now sometimes find three _unciae_ and a half[36]. Often the hearth-lead remaining in the crucible is a palm deep; it is taken out with the rest of the ashes and is sifted, and that which remains in the sieve, since it is hearth-lead, is added to the hearth-lead[37]. The ashes which pass through the sieve are of the same use as they were at first, for, indeed, from these and pulverised bones they make the cupels. Finally, when much of it has accumulated, the yellow _pompholyx_ adhering to the walls of the furnace, and likewise to those rings of the dome near the apertures, is cleared away. [Illustration 479 (Crane for cupellation furnace): A--Crane-post. B--Socket. C--Oak cross-sills. D--Band. E--Roof-beam. F--Frame. G--Lower small cross-beam. H--Upright timber. I--Bars which come from the sides of the crane-post. K--Bars which come from the sides of the upright timber. L--Rundle drums. M--Toothed wheels. N--Chain. O--Pulley. P--Beams of the crane-arm. Q--Oblique beams supporting the beams of the crane-arm. R--Rectangular iron plates. S--Trolley. T--Dome of the furnace. V--Ring. X--Three chains. Y--Crank. Z--The crane-post of the other contrivance. AA--Crane-arm. BB--Oblique beam. CC--Ring of the crane-arm. DD--The second ring. EE--Lever-bar. FF--Third ring. GG--Hook. HH--Chain of the dome. II--Chain of the lever-bar.] I must also describe the crane with which the dome is raised. When it is made, there is first set up a rectangular upright post twelve feet long, each side of which measures a foot in width. Its lower pinion turns in a bronze socket set in an oak sill; there are two sills placed crosswise so that the one fits in a mortise in the middle of the other, and the other likewise fits in the mortise of the first, thus making a kind of a cross; these sills are three feet long and one foot wide and thick. The crane-post is round at its upper end and is cut down to a depth of three palms, and turns in a band fastened at each end to a roof-beam, from which springs the inclined chimney wall. To the crane-post is affixed a frame, which is made in this way: first, at a height of a cubit from the bottom, is mortised into the crane-post a small cross-beam, a cubit and three digits long, except its tenons, and two palms in width and thickness. Then again, at a height of five feet above it, is another small cross-beam of equal length, width, and thickness, mortised into the crane-post. The other ends of these two small cross-beams are mortised into an upright timber, six feet three palms long, and three-quarters wide and thick; the mortise is transfixed by wooden pegs. Above, at a height of three palms from the lower small cross-beam, are two bars, one foot one palm long, not including the tenons, a palm three digits wide, and a palm thick, which are mortised in the other sides of the crane-post. In the same manner, under the upper small cross-beam are two bars of the same size. Also in the upright timber there are mortised the same number of bars, of the same length as the preceding, but three digits thick, a palm two digits wide, the two lower ones being above the lower small cross-beam. From the upright timber near the upper small cross-beam, which at its other end is mortised into the crane-post, are two mortised bars. On the outside of this frame, boards are fixed to the small cross-beams, but the front and back parts of the frame have doors, whose hinges are fastened to the boards which are fixed to the bars that are mortised to the sides of the crane-post. Then boards are laid upon the lower small cross-beam, and at a height of two palms above these there is a small square iron axle, the sides of which are two digits wide; both ends of it are round and turn in bronze or iron bearings, one of these bearings being fastened in the crane-post, the other in the upright timber. About each end of the small axle is a wooden disc, of three palms and a digit radius and one palm thick, covered on the rim with an iron band; these two discs are distant two palms and as many digits from each other, and are joined with five rundles; these rundles are two and a half digits thick and are placed three digits apart. Thus a drum is made, which is a palm and a digit distant from the upright timber, but further from the crane-post, namely, a palm and three digits. At a height of a foot and a palm above this little axle is a second small square iron axle, the thickness of which is three digits; this one, like the first one, turns in bronze or iron bearings. Around it is a toothed wheel, composed of two discs a foot three palms in diameter, a palm and two digits thick; on the rim of this there are twenty-three teeth, a palm wide and two digits thick; they protrude a palm from the wheel and are three digits apart. And around this same axle, at a distance of two palms and as many digits toward the upright timber, is another disc of the same diameter as the wheel and a palm thick; this turns in a hollowed-out place in the upright timber. Between this disc and the disc of the toothed wheel another drum is made, having likewise five rundles. There is, in addition to this second axle, at a height of a cubit above it, a small wooden axle, the journals of which are of iron; the ends are bound round with iron rings so that the journals may remain firmly fixed, and the journals, like the little iron axles, turn in bronze or iron bearings. This third axle is at a distance of about a cubit from the upper small cross-beam; it has, near the upright timber, a toothed wheel two and a half feet in diameter, on the rim of which are twenty-seven teeth; the other part of this axle, near the crane-post, is covered with iron plates, lest it should be worn away by the chain which winds around it. The end link of the chain is fixed in an iron pin driven into the little axle; this chain passes out of the frame and turns over a little pulley set between the beams of the crane-arm. Above the frame, at a height of a foot and a palm, is the crane-arm. This consists of two beams fifteen feet long, three palms wide, and two thick, mortised into the crane-post, and they protrude a cubit from the back of the crane-post and are fastened together. Moreover, they are fastened by means of a wooden pin which penetrates through them and the crane-post; this pin has at the one end a broad head, and at the other a hole, through which is driven an iron bolt, so that the beams may be tightly bound into the crane-post. The beams of the crane-arm are supported and stayed by means of two oblique beams, six feet and two palms long, and likewise two palms wide and thick; these are mortised into the crane-post at their lower ends, and their upper ends are mortised into the beams of the crane-arm at a point about four feet from the crane-post, and they are fastened with iron nails. At the back of the upper end of these oblique beams, toward the crane-post, is an iron staple, fastened into the lower sides of the beams of the crane-arm, in order that it may hold them fast and bind them. The outer end of each beam of the crane-arm is set in a rectangular iron plate, and between these are three rectangular iron plates, fixed in such a manner that the beams of the crane-arm can neither move away from, nor toward, each other. The upper sides of these crane-arm beams are covered with iron plates for a length of six feet, so that a trolley can move on it. The body of the trolley is made of wood from the Ostrya or any other hard tree, and is a cubit long, a foot wide, and three palms thick; on both edges of it the lower side is cut out to a height and width of a palm, so that the remainder may move backward and forward between the two beams of the crane-arm; at the front, in the middle part, it is cut out to a width of two palms and as many digits, that a bronze pulley, around a small iron axle, may turn in it. Near the corners of the trolley are four holes, in which as many small wheels travel on the beams of the crane-arm. Since this trolley, when it travels backward and forward, gives out a sound somewhat similar to the barking of a dog, we have given it this name[38]. It is propelled forward by means of a crank, and is drawn back by means of a chain. There is an iron hook whose ring turns round an iron pin fastened to the right side of the trolley, which hook is held by a sort of clavis, which is fixed in the right beam of the crane-arm. At the end of the crane-post is a bronze pulley, the iron axle of which is fastened in the beams of the crane-arm, and over which the chain passes as it comes from the frame, and then, penetrating through the hollow in the top of the trolley, it reaches to the little bronze pulley of the trolley, and passing over this it hangs down. A hook on its end engages a ring, in which are fixed the top links of three chains, each six feet long, which pass through the three iron rings fastened in the holes of the claves which are fixed into the middle iron band of the dome, of which I have spoken. Therefore when the master wishes to lift the dome by means of the crane, the assistant fits over the lower small iron axle an iron crank, which projects from the upright beam a palm and two digits; the end of the little axle is rectangular, and one and a half digits wide and one digit thick; it is set into a similar rectangular hole in the crank, which is two digits long and a little more than a digit wide. The crank is semi-circular, and one foot three palms and two digits long, as many digits wide, and one digit thick. Its handle is straight and round, and three palms long, and one and a half digits thick. There is a hole in the end of the little axle, through which an iron pin is driven so that the crank may not come off. The crane having four drums, two of which are rundle-drums and two toothed-wheels, is more easily moved than another having two drums, one of which has rundles and the other teeth. Many, however, use only a simple contrivance, the pivots of whose crane-post turn in the same manner, the one in an iron socket, the other in a ring. There is a crane-arm on the crane-post, which is supported by an oblique beam; to the head of the crane-arm a strong iron ring is fixed, which engages a second iron ring. In this iron ring a strong wooden lever-bar is fastened firmly, the head of which is bound by a third iron ring, from which hangs an iron hook, which engages the rings at the ends of the chains from the dome. At the other end of the lever-bar is another chain, which, when it is pulled down, raises the opposite end of the bar and thus the dome; and when it is relaxed the dome is lowered. [Illustration 481 (Cupellation Furnace at Freiberg): A--Chamber of the furnace. B--Its bed. C--Passages. D--Rammer. E--Mallet. F--Artificer making tubes from litharge according to the Roman method. G--Channel. H--Litharge. I--Lower crucible or hearth. K--Stick. L--Tubes.] In certain places, as at Freiberg in Meissen, the upper part of the cupellation furnace is vaulted almost like an oven. This chamber is four feet high and has either two or three apertures, of which the first, in front, is one and a half feet high and a foot wide, and out of this flows the litharge; the second aperture and likewise the third, if there be three, are at the sides, and are a foot and a half high and two and a half feet wide, in order that he who prepares the crucible may be able to creep into the furnace. Its circular bed is made of cement, it has two passages two feet high and one foot wide, for letting out the vapour, and these lead directly through from one side to the other, so that the one passage crosses the other at right angles, and thus four openings are to be seen; these are covered at the top by rocks, wide, but only a palm thick. On these and on the other parts of the interior of the bed made of cement, is placed lute mixed with straw, to a depth of three digits, as it was placed over the sole and the plates of copper and the rocks of that other furnace. This, together with the ashes which are thrown in, the master or the assistant, who, upon his knees, prepares the crucible, tamps down with short wooden rammers and with mallets likewise made of wood. [Illustration 482 (Cupellation Furnace in Poland): A--Furnace similar to an oven. B--Passage. C--Iron bars. D--Hole through which the litharge is drawn out. E--Crucible which lacks a dome. F--Thick sticks. G--Bellows.] The cupellation furnace in Poland and Hungary is likewise vaulted at the top, and is almost similar to an oven, but in the lower part the bed is solid, and there is no opening for the vapours, while on one side of the crucible is a wall, between which and the bed of the crucible is a passage in place of the opening for vapours; this passage is covered by iron bars or rods extending from the wall to the crucible, and placed a distance of two digits from each other. In the crucible, when it is prepared, they first scatter straw, and then they lay in it cakes of silver-lead alloy, and on the iron bars they lay wood, which when kindled heats the crucible. They melt cakes to the weight of sometimes eighty _centumpondia_ and sometimes a hundred _centumpondia_[39]. They stimulate a mild fire by means of a blast from the bellows, and throw on to the bars as much wood as is required to make a flame which will reach into the crucible, and separate the lead from the silver. The litharge is drawn out on the other side through an aperture that is just wide enough for the master to creep through into the crucible. The Moravians and Carni, who very rarely make more than a _bes_ or five-sixths of a _libra_ of silver, separate the lead from it, neither in a furnace resembling an oven, nor in the crucible covered by a dome, but on a crucible which is without a cover and exposed to the wind; on this crucible they lay cakes of silver-lead alloy, and over them they place dry wood, and over these again thick green wood. The wood having been kindled, they stimulate the fire by means of a bellows. [Illustration 484 (Refining Silver): A--Pestle with teeth. B--Pestle without teeth. C--Dish or tray full of ashes. D--Prepared tests placed on boards or shelves. E--Empty tests. F--Wood. G--Saw.] [Illustration 485 (Refining Silver): A--Straight knife having wooden handles. B--Curved knife likewise having wooden handles. C--Curved knife without wooden handles. D--Sieve. E--Balls. F--Iron door which the master lets down when he refines silver, lest the heat of the fire should injure his eyes. G--Iron implement on which the wood is placed when the liquid silver is to be refined. H--Its other part passing through the ring of another iron implement enclosed in the wall of the furnace. I--Tests in which burning charcoal has been thrown.] I have explained the method of separating lead from gold or silver. Now I will speak of the method of refining silver, for I have already explained the process for refining gold. Silver is refined in a refining furnace, over whose hearth is an arched chamber built of bricks; this chamber in the front part is three feet high. The hearth itself is five feet long and four wide. The walls are unbroken along the sides and back, but in front one chamber is placed over the other, and above these and the wall is the upright chimney. The hearth has a round pit, a cubit wide and two palms deep, into which are thrown sifted ashes, and in this is placed a prepared earthenware "test," in such a manner that it is surrounded on all sides by ashes to a height equal to its own. The earthenware test is filled with a powder consisting of equal portions of bones ground to powder, and of ashes taken from the crucible in which lead is separated from gold or silver; others mix crushed brick with the ashes, for by this method the powder attracts no silver to itself. When the powder has been made up and moistened with water, a little is thrown into the earthenware test and tamped with a wooden pestle. This pestle is round, a foot long, and a palm and a digit wide, out of which extend six teeth, each a digit thick, and a digit and a third long and wide, and almost a digit apart; these six teeth form a circle, and in the centre of them is the seventh tooth, which is round and of the same length as the others, but a digit and a half thick; this pestle tapers a little from the bottom up, that the upper part of the handle may be round and three digits thick. Some use a round pestle without teeth. Then a little powder is again moistened, and thrown into the test, and tamped; this work is repeated until the test is entirely full of the powder, which the master then cuts out with a knife, sharp on both sides, and turned upward at both ends so that the central part is a palm and a digit long; therefore it is partly straight and partly curved. The blade is one and a half digits wide, and at each end it turns upward two palms, which ends to the depth of a palm are either not sharpened or they are enclosed in wooden handles. The master holds the knife with one hand and cuts out the powder from the test, so that it is left three digits thick all round; then he sifts the powder of dried bones over it through a sieve, the bottom of which is made of closely-woven bristles. Afterward a ball made of very hard wood, six digits in diameter, is placed in the test and rolled about with both hands, in order to make the inside even and smooth; for that matter he may move the ball about with only one hand. The tests[40] are of various capacities, for some of them when prepared hold much less than fifteen _librae_ of silver, others twenty, some thirty, others forty, and others fifty. All these tests thus prepared are dried in the sun, or set in a warm and covered place; the more dry and old they are the better. All of them, when used for refining silver, are heated by means of burning charcoal placed in them. Others use instead of these tests an iron ring; but the test is more useful, for if the powder deteriorates the silver remains in it, while there being no bottom to the ring, it falls out; besides, it is easier to place in the hearth the test than the iron ring, and furthermore it requires much less powder. In order that the test should not break and damage the silver, some bind it round with an iron band. [Illustration 486 (Refining Silver): A--Grate. B--Brass block. C--Block of wood. D--Cakes of silver. E--Hammer. F--Block of wood channelled in the middle. G--Bowl full of holes. H--Block of wood fastened to an iron implement. I--Fir-wood. K--Iron bar. L--Implement with a hollow end. The implement which has a circular end is shown in the next picture. M--Implement, the extremity of which is bent upwards. N--Implement in the shape of tongs.] In order that they may be more easily broken, the silver cakes are placed upon an iron grate by the refiner, and are heated by burning charcoal placed under them. He has a brass block two palms and two digits long and wide, with a channel in the middle, which he places upon a block of hard wood. Then with a double-headed hammer, he beats the hot cakes of silver placed on the brass block, and breaks them in pieces. The head of this hammer is a foot and two digits long, and a palm wide. Others use for this purpose merely a block of wood channelled in the top. While the fragments of the cake are still hot, he seizes them with the tongs and throws them into a bowl with holes in the bottom, and pours water over them. When the fragments are cooled, he puts them nicely into the test by placing them so that they stand upright and project from the test to a height of two palms, and lest one should fall against the other, he places little pieces of charcoal between them; then he places live charcoal in the test, and soon two twig basketsful of charcoal. Then he blows in air with the bellows. This bellows is double, and four feet two palms long, and two feet and as many palms wide at the back; the other parts are similar to those described in Book VII. The nozzle of the bellows is placed in a bronze pipe a foot long, the aperture in this pipe being a digit in diameter in front and quite round, and at the back two palms wide. The master, because he needs for the operation of refining silver a fierce fire, and requires on that account a vigorous blast, places the bellows very much inclined, in order that, when the silver has melted, it may blow into the centre of the test. When the silver bubbles, he presses the nozzle down by means of a small block of wood moistened with water and fastened to an iron rod, the outer end of which bends upward. The silver melts when it has been heated in the test for about an hour; when it is melted, he removes the live coals from the test and places over it two billets of fir-wood, a foot and three palms long, a palm two digits wide, one palm thick at the upper part, and three digits at the lower. He joins them together at the lower edges, and into the billets he again throws the coals, for a fierce fire is always necessary in refining silver. It is refined in two or three hours, according to whether it was pure or impure, and if it is impure it is made purer by dropping granulated copper or lead into the test at the same time. In order that the refiner may sustain the great heat from the fire while the silver is being refined, he lets down an iron door, which is three feet long and a foot and three palms high; this door is held on both ends in iron plates, and when the operation is concluded, he raises it again with an iron shovel, so that its edge holds against the iron hook in the arch, and thus the door is held open. When the silver is nearly refined, which may be judged by the space of time, he dips into it an iron bar, three and a half feet long and a digit thick, having a round steel point. The small drops of silver that adhere to the bar he places on the brass block and flattens with a hammer, and from their colour he decides whether the silver is sufficiently refined or not. If it is thoroughly purified it is very white, and in a _bes_ there is only a _drachma_ of impurities. Some ladle up the silver with a hollow iron implement. Of each _bes_ of silver one _sicilicus_ is consumed, or occasionally when very impure, three _drachmae_ or half an _uncia_[41]. [Illustration 488 (Cleansing of Silver Cakes): A--Implement with a ring. B--Ladle. C--Its hole. D--Pointed bar. E--Forks. F--Cake of silver laid upon the implement shaped like tongs. G--Tub of water. H--Block of wood, with a cake laid upon it. I--Hammer. K--Silver again placed upon the implement resembling tongs. L--Another tub full of water. M--Brass wires. N--Tripod. O--Another block. P--Chisel. Q--Crucible of the furnace. R--Test still smoking.] The refiner governs the fire and stirs the molten silver with an iron implement, nine feet long, a digit thick, and at the end first curved toward the right, then curved back in order to form a circle, the interior of which is a palm in diameter; others use an iron implement, the end of which is bent directly upward. Another iron implement has the shape of tongs, with which, by compressing it with his hands, he seizes the coals and puts them on or takes them off; this is two feet long, one and a half digits wide, and the third of a digit thick. When the silver is seen to be thoroughly refined, the artificer removes the coals from the test with a shovel. Soon afterward he draws water in a copper ladle, which has a wooden handle four feet long; it has a small hole at a point half-way between the middle of the bowl and the edge, through which a hemp seed just passes. He fills this ladle three times with water, and three times it all flows out through the hole on to the silver, and slowly quenches it; if he suddenly poured much water on it, it would burst asunder and injure those standing near. The artificer has a pointed iron bar, three feet long, which has a wooden handle as many feet long, and he puts the end of this bar into the test in order to stir it. He also stirs it with a hooked iron bar, of which the hook is two digits wide and a palm deep, and the iron part of its handle is three feet long and the wooden part the same. Then he removes the test from the hearth with a shovel or a fork, and turns it over, and by this means the silver falls to the ground in the shape of half a sphere; then lifting the cake with a shovel he throws it into a tub of water, where it gives out a great sound. Or else, having lifted the cake of silver with a fork, he lays it upon the iron implement similar to tongs, which are placed across a tub full of water; afterward, when cooled, he takes it from the tub again and lays it on the block made of hard wood and beats it with a hammer, in order to break off any of the powder from the test which adheres to it. The cake is then placed on the implement similar to tongs, laid over the tub full of water, and cleaned with a bundle of brass wire dipped into the water; this operation of beating and cleansing is repeated until it is all clean. Afterward he places it on an iron grate or tripod; the tripod is a palm and two digits high, one and a half digits wide, and its span is two palms wide; then he puts burning charcoal under the tripod or grate, in order again to dry the silver that was moistened by the water. Finally, the Royal Inspector[42] in the employment of the King or Prince, or the owner, lays the silver on a block of wood, and with an engraver's chisel he cuts out two small pieces, one from the under and the other from the upper side. These are tested by fire, in order to ascertain whether the silver is thoroughly refined or not, and at what price it should be sold to the merchants. Finally he impresses upon it the seal of the King or the Prince or the owner, and, near the same, the amount of the weight. [Illustration 489 (Refining Silver): A--Muffle. B--Its little windows. C--Its little bridge. D--Bricks. E--Iron door. F--Its little window. G--Bellows. H--Hammer-chisel. I--Iron ring which some use instead of the test. K--Pestle with which the ashes placed in the ring are pounded.] There are some who refine silver in tests placed under iron or earthenware muffles. They use a furnace, on the hearth of which they place the test containing the fragments of silver, and they place the muffle over it; the muffle has small windows at the sides, and in front a little bridge. In order to melt the silver, at the sides of the muffle are laid bricks, upon which the charcoal is placed, and burning firebrands are put on the bridge. The furnace has an iron door, which is covered on the side next to the fire with lute in order that it may not be injured. When the door is closed it retains the heat of the fire, but it has a small window, so that the artificers may look into the test and may at times stimulate the fire with the bellows. Although by this method silver is refined more slowly than by the other, nevertheless it is more useful, because less loss is caused, for a gentle fire consumes fewer particles than a fierce fire continually excited by the blast of the bellows. If, on account of its great size, the cake of silver can be carried only with difficulty when it is taken out of the muffle, they cut it up into two or three pieces while it is still hot, with a wedge or a hammer-chisel; for if they cut it up after it has cooled, little pieces of it frequently fly off and are lost. END OF BOOK X. FOOTNOTES: [1] _Vile a precioso_. [2] The reagents mentioned in this Book are much the same as those of