BOOK VII.

Since the Sixth Book has described the iron tools, the vessels and the machines used in mines, this Book will describe the methods of assaying[1] ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure. Although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject. By tests of this kind miners can determine with certainty whether ores contain any metal in them or not; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it; and further, by these tests, they determine that part in which there is much metal from that part in which there is little. Unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. In the last case, they pass off with the fumes; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things. Metals, when they have been melted out, are usually assayed in order that we may ascertain what proportion of silver is in a _centumpondium_ of copper or lead, or what quantity of gold is in one _libra_ of silver; and, on the other hand, what proportion of copper or lead is contained in a _centumpondium_ of silver, or what quantity of silver is contained in one _libra_ of gold. And from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not. Further, a test of this kind shows whether coins are good or are debased; and readily detects silver, if the coiners have mixed more than is lawful with the gold; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. I will explain all these methods with the utmost care that I can. The method of assaying ore used by mining people, differs from smelting only by the small amount of material used. Inasmuch as, by smelting a small quantity, they learn whether the smelting of a large quantity will compensate them for their expenditure; hence, if they are not particular to employ assays, they may, as I have already said, sometimes smelt the metal from the ore with a loss or sometimes without any profit; for they can assay the ore at a very small expense, and smelt it only at a great expense. Both processes, however, are carried out in the same way, for just as we assay ore in a little furnace, so do we smelt it in the large furnace. Also in both cases charcoal and not wood is burned. Moreover, in the crucible when metals are tested, be they gold, silver, copper, or lead, they are mixed in precisely the same way as they are mixed in the blast furnace when they are smelted. Further, those who assay ores with fire, either pour out the metal in a liquid state, or, when it has cooled, break the crucible and clean the metal from slag; and in the same way the smelter, as soon as the metal flows from the furnace into the forehearth, pours in cold water and takes the slag from the metal with a hooked bar. Finally, in the same way that gold and silver are separated from lead in a cupel, so also are they separated in the cupellation furnace. It is necessary that the assayer who is testing ore or metals should be prepared and instructed in all things necessary in assaying, and that he should close the doors of the room in which the assay furnace stands, lest anyone coming at an inopportune moment might disturb his thoughts when they are intent on the work. It is also necessary for him to place his balances in a case, so that when he weighs the little buttons of metal the scales may not be agitated by a draught of air, for that is a hindrance to his work. [Illustration 223a (Muffle Furnace): Round assay furnace.] [Illustration 223b (Muffle Furnace): Rectangular assay furnace.] [Illustration 224 (Muffle Assay Furnace): A--Openings in the plate. B--Part of plate which projects beyond the furnace.] Now I will describe the different things which are necessary in assaying, beginning with the assay furnace, of which one differs from another in shape, material, and the place in which it is set. In shape, they may be round or rectangular, the latter shape being more suited to assaying ores. The materials of the assay furnaces differ, in that one is made of bricks, another of iron, and certain ones of clay. The one of bricks is built on a chimney-hearth which is three and a half feet high; the iron one is placed in the same position, and also the one of clay. The brick one is a cubit high, a foot wide on the inside, and one foot two digits long; at a point five digits above the hearth--which is usually the thickness of an unbaked[2] brick--an iron plate is laid, and smeared over with lute on the upper side to prevent it from being injured by the fire; in front of the furnace above the plate is a mouth a palm high, five digits wide, and rounded at the top. The iron plate has three openings which are one digit wide and three digits long, one is at each side and the third at the back; through them sometimes the ash falls from the burning charcoal, and sometimes the draught blows through the chamber which is below the iron plate, and stimulates the fire. For this reason this furnace when used by metallurgists is named from assaying, but when used by the alchemists it is named from the wind[3]. The part of the iron plate which projects from the furnace is generally three-quarters of a palm long and a palm wide; small pieces of charcoal, after being laid thereon, can be placed quickly in the furnace through its mouth with a pair of tongs, or again, if necessary, can be taken out of the furnace and laid there. The iron assay furnace is made of four iron bars a foot and a half high; which at the bottom are bent outward and broadened a short distance to enable them to stand more firmly; the front part of the furnace is made from two of these bars, and the back part from two of them; to these bars on both sides are joined and welded three iron cross-bars, the first at a height of a palm from the bottom, the second at a height of a foot, and the third at the top. The upright bars are perforated at that point where the side cross-bars are joined to them, in order that three similar iron bars on the remaining sides can be engaged in them; thus there are twelve cross-bars, which make three stages at unequal intervals. At the lower stage, the upright bars are distant from each other one foot and five digits; and at the middle stage the front is distant from the back three palms and one digit, and the sides are distant from each other three palms and as many digits; at the highest stage from the front to the back there is a distance of two palms, and between the sides three palms, so that in this way the furnace becomes narrower at the top. Furthermore, an iron rod, bent to the shape of the mouth, is set into the lowest bar of the front; this mouth, just like that of the brick furnace, is a palm high and five digits wide. Then the front cross-bar of the lower stage is perforated on each side of the mouth, and likewise the back one; through these perforations there pass two iron rods, thus making altogether four bars in the lower stage, and these support an iron plate smeared with lute; part of this plate also projects outside the furnace. The outside of the furnace from the lower stage to the upper, is covered with iron plates, which are bound to the bars by iron wires, and smeared with lute to enable them to bear the heat of the fire as long as possible. As for the clay furnace, it must be made of fat, thick clay, medium so far as relates to its softness or hardness. This furnace has exactly the same height as the iron one, and its base is made of two earthenware tiles, one foot and three palms long and one foot and one palm wide. Each side of the fore part of both tiles is gradually cut away for the length of a palm, so that they are half a foot and a digit wide, which part projects from the furnace; the tiles are about a digit and a half thick. The walls are similarly of clay, and are set on the lower tiles at a distance of a digit from the edge, and support the upper tiles; the walls are three digits high and have four openings, each of which is about three digits high; those of the back part and of each side are five digits wide, and of the front, a palm and a half wide, to enable the freshly made cupels to be conveniently placed on the hearth, when it has been thoroughly warmed, that they may be dried there. Both tiles are bound on the outer edge with iron wire, pressed into them, so that they will be less easily broken; and the tiles, not unlike the iron bed-plate, have three openings three digits long and a digit wide, in order that when the upper one on account of the heat of the fire or for some other reason has become damaged, the lower one may be exchanged and take its place. Through these holes, the ashes from the burning charcoal, as I have stated, fall down, and air blows into the furnace after passing through the openings in the walls of the chamber. The furnace is rectangular, and inside at the lower part it is three palms and one digit wide and three palms and as many digits long. At the upper part it is two palms and three digits wide, so that it also grows narrower; it is one foot high; in the middle of the back it is cut out at the bottom in the shape of a semicircle, of half a digit radius. Not unlike the furnace before described, it has in its forepart a mouth which is rounded at the top, one palm high and a palm and a digit wide. Its door is also made of clay, and this has a window and a handle; even the lid of the furnace which is made of clay has its own handle, fastened on with iron wire. The outer parts and sides of this furnace are bound with iron wires, which are usually pressed in, in the shape of triangles. The brick furnaces must remain stationary; the clay and iron ones can be carried from one place to another. Those of brick can be prepared more quickly, while those of iron are more lasting, and those of clay are more suitable. Assayers also make temporary furnaces in another way; they stand three bricks on a hearth, one on each side and a third one at the back, the forepart lies open to the draught, and on these bricks is placed an iron plate, upon which they again stand three bricks, which hold and retain the charcoal. The setting of one furnace differs from another, in that some are placed higher and others lower; that one is placed higher, in which the man who is assaying the ore or metals introduces the scorifier through the mouth with the tongs; that one is placed lower, into which he introduces the crucible through its open top. [Illustration 227 (Crucible Assay Furnace): A--Iron hoop. B--Double bellows. C--Its nozzle. D--Lever.] In some cases the assayer uses an iron hoop[4] in place of a furnace; this is placed upon the hearth of a chimney, the lower edge being daubed with lute to prevent the blast of the bellows from escaping under it. If the blast is given slowly, the ore will be smelted and the copper will melt in the triangular crucible, which is placed in it and taken away again with the tongs. The hoop is two palms high and half a digit thick; its diameter is generally one foot and one palm, and where the blast from the bellows enters into it, it is notched out. The bellows is a double one, such as goldworkers use, and sometimes smiths. In the middle of the bellows there is a board in which there is an air-hole, five digits wide and seven long, covered by a little flap which is fastened over the air-hole on the lower side of the board; this flap is of equal length and width. The bellows, without its head, is three feet long, and at the back is one foot and one palm wide and somewhat rounded, and it is three palms wide at the head; the head itself is three palms long and two palms and a digit wide at the part where it joins the boards, then it gradually becomes narrower. The nozzle, of which there is only one, is one foot and two digits long; this nozzle, and one-half of the head in which the nozzle is fixed, are placed in an opening of the wall, this being one foot and one palm thick; it reaches only to the iron hoop on the hearth, for it does not project beyond the wall. The hide of the bellows is fixed to the bellows-boards with its own peculiar kind of iron nails. It joins both bellows-boards to the head, and over it there are cross strips of hide fixed to the bellows-boards with broad-headed nails, and similarly fixed to the head. The middle board of the bellows rests on an iron bar, to which it is fastened with iron nails clinched on both ends, so that it cannot move; the iron bar is fixed between two upright posts, through which it penetrates. Higher up on these upright posts there is a wooden axle, with iron journals which revolve in the holes in the posts. In the middle of this axle there is mortised a lever, fixed with iron nails to prevent it from flying out; the lever is five and a half feet long, and its posterior end is engaged in the iron ring of an iron rod which reaches to the "tail" of the lowest bellows-board, and there engages another similar ring. And so when the workman pulls down the lever, the lower part of the bellows is raised and drives the wind into the nozzle; then the wind, penetrating through the hole in the middle bellows-board, which is called the air-hole, lifts up the upper part of the bellows, upon whose upper board is a piece of lead, heavy enough to press down that part of the bellows again, and this being pressed down blows a blast through the nozzle. This is the principle of the double bellows, which is peculiar to the iron hoop where are placed the triangular crucibles in which copper ore is smelted and copper is melted. [Illustration 228 (Muffles): A--Broad little windows of muffle. B--Narrow ones. C--Openings in the back thereof.] I have spoken of the furnaces and the iron hoop; I will now speak of the muffles and the crucibles. The muffle is made of clay, in the shape of an inverted gutter tile; it covers the scorifiers, lest coal dust fall into them and interfere with the assay. It is a palm and a half broad, and the height, which corresponds with the mouth of the furnace, is generally a palm, and it is nearly as long as the furnace; only at the front end does it touch the mouth of the furnace, everywhere else on the sides and at the back there is a space of three digits, to allow the charcoal to lie in the open space between it and the furnace. The muffle is as thick as a fairly thick earthen jar; its upper part is entire; the back has two little windows, and each side has two or three or even four, through which the heat passes into the scorifiers and melts the ore. In place of little windows, some muffles have small holes, ten in the back and more on each side. Moreover, in the back below the little windows, or small holes, there are cut away three semi-circular notches half a digit high, and on each side there are four. The back of the muffle is generally a little lower than the front. [Illustration 229 (Containers): A--Scorifier. B--Triangular crucible. C--Cupel.] The crucibles differ in the materials from which they are made, because they are made of either clay or ashes; and those of clay, which we also call "earthen," differ in shape and size. Some are made in the shape of a moderately thick salver (scorifiers), three digits wide, and of a capacity of an _uncia_ measure; in these the ore mixed with fluxes is melted, and they are used by those who assay gold or silver ore. Some are triangular and much thicker and more capacious, holding five, or six, or even more _unciae_; in these copper is melted, so that it can be poured out, expanded, and tested with fire, and in these copper ore is usually melted. The cupels are made of ashes; like the preceding scorifiers they are tray-shaped, and their lower part is very thick but their capacity is less. In these lead is separated from silver, and by them assays are concluded. Inasmuch as the assayers themselves make the cupels, something must be said about the material from which they are made, and the method of making them. Some make them out of all kinds of ordinary ashes; these are not good, because ashes of this kind contain a certain amount of fat, whereby such cupels are easily broken when they are hot. Others make them likewise out of any kind of ashes which have been previously leached; of this kind are the ashes into which warm water has been infused for the purpose of making lye. These ashes, after being dried in the sun or a furnace, are sifted in a hair sieve; and although warm water washes away the fat from the ashes, still the cupels which are made from such ashes are not very good because they often contain charcoal dust, sand, and pebbles. Some make them in the same way out of any kind of ashes, but first of all pour water into the ashes and remove the scum which floats thereon; then, after it has become clear, they pour away the water, and dry the ashes; they then sift them and make the cupels from them. These, indeed, are good, but not of the best quality, because ashes of this kind are also not devoid of small pebbles and sand. To enable cupels of the best quality to be made, all the impurities must be removed from the ashes. These impurities are of two kinds; the one sort light, to which class belong charcoal dust and fatty material and other things which float in water, the other sort heavy, such as small stones, fine sand, and any other materials which settle in the bottom of a vessel. Therefore, first of all, water should be poured into the ashes and the light impurities removed; then the ashes should be kneaded with the hands, so that they will become properly mixed with the water. When the water has become muddy and turbid, it should be poured into a second vessel. In this way the small stones and fine sand, or any other heavy substance which may be there, remain in the first vessel, and should be thrown away. When all the ashes have settled in this second vessel, which will be shown if the water has become clear and does not taste of the flavour of lye, the water should be thrown away, and the ashes which have settled in the vessel should be dried in the sun or in a furnace. This material is suitable for the cupels, especially if it is the ash of beech wood or other wood which has a small annual growth; those ashes made from twigs and limbs of vines, which have rapid annual growth, are not so good, for the cupels made from them, since they are not sufficiently dry, frequently crack and break in the fire and absorb the metals. If ashes of beech or similar wood are not to be had, the assayer makes little balls of such ashes as he can get, after they have been cleared of impurities in the manner before described, and puts them in a baker's or potter's oven to burn, and from these the cupels are made, because the fire consumes whatever fat or damp there may be. As to all kinds of ashes, the older they are the better, for it is necessary that they should have the greatest possible dryness. For this reason ashes obtained from burned bones, especially from the bones of the heads of animals, are the most suitable for cupels, as are also those ashes obtained from the horns of deer and the spines of fishes. Lastly, some take the ashes which are obtained from burnt scrapings of leather, when the tanners scrape the hides to clear them from hair. Some prefer to use compounds, that one being recommended which has one and a half parts of ashes from the bones of animals or the spines of fishes, and one part of beech ashes, and half a part of ashes of burnt hide scrapings. From this mixture good cupels are made, though far better ones are obtained from equal portions of ashes of burnt hide scrapings, ashes of the bones of heads of sheep and calves, and ashes of deer horns. But the best of all are produced from deer horns alone, burnt to powder; this kind, by reason of its extreme dryness, absorbs metals least of all. Assayers of our own day, however, generally make the cupels from beech ashes. These ashes, after being prepared in the manner just described, are first of all sprinkled with beer or water, to make them stick together, and are then ground in a small mortar. They are ground again after being mixed with the ashes obtained from the skulls of beasts or from the spines of fishes; the more the ashes are ground the better they are. Some rub bricks and sprinkle the dust so obtained, after sifting it, into the beech ashes, for dust of this kind does not allow the hearth-lead to absorb the gold or silver by eating away the cupels. Others, to guard against the same thing, moisten the cupels with white of egg after they have been made, and when they have been dried in the sun, again crush them; especially if they want to assay in it an ore of copper which contains iron. Some moisten the ashes again and again with cow's milk, and dry them, and grind them in a small mortar, and then mould the cupels. In the works in which silver is separated from copper, they make cupels from two parts of the ashes of the crucible of the cupellation furnace, for these ashes are very dry, and from one part of bone-ash. Cupels which have been made in these ways also need to be placed in the sun or in a furnace; afterward, in whatever way they have been made, they must be kept a long time in dry places, for the older they are, the dryer and better they are. [Illustration 231 (Cupel Moulds and Pestles): A--Little mould. B--Inverted mould. C--Pestle. D--Its knob. E--Second pestle.] Not only potters, but also the assayers themselves, make scorifiers and triangular crucibles. They make them out of fatty clay, which is dry[5], and neither hard nor soft. With this clay they mix the dust of old broken crucibles, or of burnt and worn bricks; then they knead with a pestle the clay thus mixed with dust, and then dry it. As to these crucibles, the older they are, the dryer and better they are. The moulds in which the cupels are moulded are of two kinds, that is, a smaller size and a larger size. In the smaller ones are made the cupels in which silver or gold is purged from the lead which has absorbed it; in the larger ones are made cupels in which silver is separated from copper and lead. Both moulds are made out of brass and have no bottom, in order that the cupels can be taken out of them whole. The pestles also are of two kinds, smaller and larger, each likewise of brass, and from the lower end of them there projects a round knob, and this alone is pressed into the mould and makes the hollow part of the cupel. The part which is next to the knob corresponds to the upper part of the mould. So much for these matters. I will now speak of the preparation of the ore for assaying. It is prepared by roasting, burning, crushing, and washing. It is necessary to take a fixed weight of ore in order that one may determine how great a portion of it these preparations consume. The hard stone containing the metal is burned in order that, when its hardness has been overcome, it can be crushed and washed; indeed, the very hardest kind, before it is burned, is sprinkled with vinegar, in order that it may more rapidly soften in the fire. The soft stone should be broken with a hammer, crushed in a mortar and reduced to powder; then it should be washed and then dried again. If earth is mixed with the mineral, it is washed in a basin, and that which settles is assayed in the fire after it is dried. All mining products which are washed must again be dried. But ore which is rich in metal is neither burned nor crushed nor washed, but is roasted, lest that method of preparation should lose some of the metal. When the fires have been kindled, this kind of ore is roasted in an enclosed pot, which is stopped up with lute. A less valuable ore is even burned on a hearth, being placed upon the charcoal; for we do not make a great expenditure upon metals, if they are not worth it. However, I will go into fuller details as to all these methods of preparing ore, both a little later, and in the following Book. For the present, I have decided to explain those things which mining people usually call fluxes[6] because they are added to ores, not only for assaying, but also for smelting. Great power is discovered in all these fluxes, but we do not see the same effects produced in every case; and some are of a very complicated nature. For when they have been mixed with the ore and are melted in either the assay or the smelting furnace, some of them, because they melt easily, to some extent melt the ore; others, because they either make the ore very hot or penetrate into it, greatly assist the fire in separating the impurities from the metals, and they also mix the fused part with the lead, or they partly protect from the fire the ore whose metal contents would be either consumed in the fire, or carried up with the fumes and fly out of the furnace; some fluxes absorb the metals. To the first order belongs lead, whether it be reduced to little granules or resolved into ash by fire, or red-lead[7], or ochre made from lead[8], or litharge, or hearth-lead, or galena; also copper, the same either roasted or in leaves or filings[9]; also the slags of gold, silver, copper, and lead; also soda[10], its slags, saltpetre, burned alum, vitriol, _sal tostus_, and melted salt[11]; stones which easily melt in hot furnaces, the sand which is made from them[12]; soft _tophus_[13], and a certain white schist[14]. But lead, its ashes, red-lead, ochre, and litharge, are more efficacious for ores which melt easily; hearth-lead for those which melt with difficulty; and galena for those which melt with greater difficulty. To the second order belong iron filings, their slag, _sal artificiosus_, argol, dried lees of vinegar[15], and the lees of the _aqua_ which separates gold from silver[16]; these lees and _sal artificiosus_ have the power of penetrating into ore, the argol to a considerable degree, the lees of vinegar to a greater degree, but most of all those of the _aqua_ which separates gold from silver; filings and slags of iron, since they melt more slowly, have the power of heating the ore. To the third order belong pyrites, the cakes which are melted from them, soda, its slags, salt, iron, iron scales, iron filings, iron slags, vitriol, the sand which is resolved from stones which easily melt in the fire, and _tophus_; but first of all are pyrites and the cakes which are melted from it, for they absorb the metals of the ore and guard them from the fire which consumes them. To the fourth order belong lead and copper, and their relations. And so with regard to fluxes, it is manifest that some are natural, others fall in the category of slags, and the rest are purged from slag. When we assay ores, we can without great expense add to them a small portion of any sort of flux, but when we smelt them we cannot add a large portion without great expense. We must, therefore, consider how great the cost is, to avoid incurring a greater expense on smelting an ore than the profit we make out of the metals which it yields. The colour of the fumes which the ore emits after being placed on a hot shovel or an iron plate, indicates what flux is needed in addition to the lead, for the purpose of either assaying or smelting. If the fumes have a purple tint, it is best of all, and the ore does not generally require any flux whatever. If the fumes are blue, there should be added cakes melted out of pyrites or other cupriferous rock; if yellow, litharge and sulphur should be added; if red, glass-galls[17] and salt; if green, then cakes melted from cupriferous stones, litharge, and glass-galls; if the fumes are black, melted salt or iron slag, litharge and white lime rock. If they are white, sulphur and iron which is eaten with rust; if they are white with green patches, iron slag and sand obtained from stones which easily melt; if the middle part of the fumes are yellow and thick, but the outer parts green, the same sand and iron slag. The colour of the fumes not only gives us information as to the proper remedies which should be applied to each ore, but also more or less indication as to the solidified juices which are mixed with it, and which give forth such fumes. Generally, blue fumes signify that the ore contains azure yellow, orpiment; red, realgar; green, chrysocolla; black, black bitumen; white, tin[18]; white with green patches, the same mixed with chrysocolla; the middle part yellow and other parts green show that it contains sulphur. Earth, however, and other things dug up which contain metals, sometimes emit similarly coloured fumes. If the ore contains any _stibium_, then iron slag is added to it; if pyrites, then are added cakes melted from a cupriferous stone and sand made from stones which easily melt. If the ore contains iron, then pyrites and sulphur are added; for just as iron slag is the flux for an ore mixed with sulphur, so on the contrary, to a gold or silver ore containing iron, from which they are not easily separated, is added sulphur and sand made from stones which easily melt. _Sal artificiosus_[19] suitable for use in assaying ore is made in many ways. By the first method, equal portions of argol, lees of vinegar, and urine, are all boiled down together till turned into salt. The second method is from equal portions of the ashes which wool-dyers use, of lime, of argol purified, and of melted salt; one _libra_ of each of these ingredients is thrown into twenty _librae_ of urine; then all are boiled down to one-third and strained, and afterward there is added to what remains one _libra_ and four _unciae_ of unmelted salt, eight pounds of lye being at the same time poured into the pots, with litharge smeared around on the inside, and the whole is boiled till the salt becomes thoroughly dry. The third method follows. Unmelted salt, and iron which is eaten with rust, are put into a vessel, and after urine has been poured in, it is covered with a lid and put in a warm place for thirty days; then the iron is washed in the urine and taken out, and the residue is boiled until it is turned into salt. In the fourth method by which _sal artificiosus_ is prepared, the lye made from equal portions of lime and the ashes which wool-dyers use, together with equal portions of salt, soap, white argol, and saltpetre, are boiled until in the end the mixture evaporates and becomes salt. This salt is mixed with the concentrates from washing, to melt them. Saltpetre is prepared in the following manner, in order that it may be suitable for use in assaying ore. It is placed in a pot which is smeared on the inside with litharge, and lye made of quicklime is repeatedly poured over it, and it is heated until the fire consumes it. Wherefore the saltpetre does not kindle with the fire, since it has absorbed the lime which preserves it, and thus it is prepared[20]. The following compositions[21] are recommended to smelt all ores which the heat of fire breaks up or melts only with difficulty. Of these, one is made from stones of the third order, which easily melt when thrown into hot furnaces. They are crushed into pure white powder, and with half an _uncia_ of this powder there are mixed two _unciae_ of yellow litharge, likewise crushed. This mixture is put into a scorifier large enough to hold it, and placed under the muffle of a hot furnace; when the charge flows like water, which occurs after half an hour, it is taken out of the furnace and poured on to a stone, and when it has hardened it has the appearance of glass, and this is likewise crushed. This powder is sprinkled over any metalliferous ore which does not easily melt when we are assaying it, and it causes the slag to exude. Others, in place of litharge, substitute lead ash,[22] which is made in the following way: sulphur is thrown into lead which has been melted in a crucible, and it soon becomes covered with a sort of scum; when this is removed, sulphur is again thrown in, and the skin which forms is again taken off; this is frequently repeated, in fact until all the lead is turned into powder. There is a powerful flux compound which is made from one _uncia_ each of prepared saltpetre, melted salt, glass-gall, and argol, and one-third of an _uncia_ of litharge and a _bes_ of glass ground to powder; this flux, being added to an equal weight of ore, liquefies it. A more powerful flux is made by placing together in a pot, smeared on the inside with litharge, equal portions of white argol, common salt, and prepared saltpetre, and these are heated until a white powder is obtained from them, and this is mixed with as much litharge; one part of this compound is mixed with two parts of the ore which is to be assayed. A still more powerful flux than this is made out of ashes of black lead, saltpetre, orpiment, _stibium_, and dried lees of the _aqua_ with which gold workers separate gold from silver. The ashes of lead[23] are made from one pound of lead and one pound of sulphur; the lead is flattened out into sheets by pounding with a hammer, and placed alternately with sulphur in a crucible or pot, and they are heated together until the fire consumes the sulphur and the lead turns to ashes. One _libra_ of crushed saltpetre is mixed with one _libra_ of orpiment similarly ground to powder, and the two are cooked in an iron pan until they liquefy; they are then poured out, and after cooling are again ground to powder. A _libra_ of _stibium_ and a _bes_ of the dried lees (_of what?_) are placed alternately in a crucible and heated to the point at which they form a button, which is similarly reduced to powder. A _bes_ of this powder and one _libra_ of the ashes of lead, as well as a _libra_ of powder made out of the saltpetre and orpiment, are mixed together and a powder is made from them, one part of which added to two parts of ore liquefies it and cleanses it of dross. But the most powerful flux is one which has two _drachmae_ of sulphur and as much glass-galls, and half an _uncia_ of each of the following,--_stibium_, salt obtained from boiled urine, melted common salt, prepared saltpetre, litharge, vitriol, argol, salt obtained from ashes of musk ivy, dried lees of the _aqua_ by which gold-workers separate gold from silver, alum reduced by fire to powder, and one _uncia_ of camphor[24] combined with sulphur and ground into powder. A half or whole portion of this mixture, as the necessity of the case requires, is mixed with one portion of the ore and two portions of lead, and put in a scorifier; it is sprinkled with powder of crushed Venetian glass, and when the mixture has been heated for an hour and a half or two hours, a button will settle in the bottom of the scorifier, and from it the lead is soon separated. There is also a flux which separates sulphur, orpiment and realgar from metalliferous ore. This flux is composed of equal portions of iron slag, white _tophus_, and salt. After these juices have been secreted, the ores themselves are melted, with argol added to them. There is one flux which preserves _stibium_ from the fire, that the fire may not consume it, and which preserves the metals from the _stibium_; and this is composed of equal portions of sulphur, prepared saltpetre, melted salt, and vitriol, heated together in lye until no odour emanates from the sulphur, which occurs after a space of three or four hours.[25] It is also worth while to substitute certain other mixtures. Take two portions of ore properly prepared, one portion of iron filings, and likewise one portion of salt, and mix; then put them into a scorifier and place them in a muffle furnace; when they are reduced by the fire and run together, a button will settle in the bottom of the scorifier. Or else take equal portions of ore and of lead ochre, and mix with them a small quantity of iron filings, and put them into a scorifier, then scatter iron filings over the mixture. Or else take ore which has been ground to powder and sprinkle it in a crucible, and then sprinkle over it an equal quantity of salt that has been three or four times moistened with urine and dried; then, again and again alternately, powdered ore and salt; next, after the crucible has been covered with a lid and sealed, it is placed upon burning charcoal. Or else take one portion of ore, one portion of minute lead granules, half a portion of Venetian glass, and the same quantity of glass-galls. Or else take one portion of ore, one portion of lead granules, half a portion of salt, one-fourth of a portion of argol, and the same quantity of lees of the _aqua_ which separates gold from silver. Or else take equal portions of prepared ore and a powder in which there are equal portions of very minute lead granules, melted salt, _stibium_ and iron slag. Or else take equal portions of gold ore, vitriol, argol, and of salt. So much for the fluxes. In the assay furnace, when it has been prepared in the way in which I have described, is first placed a muffle. Then selected pieces of live charcoals are laid on it, for, from pieces of inferior quality, a great quantity of ash collects around the muffle and hinders the action of the fire. Then the scorifiers are placed under the muffle with tongs, and glowing coals are placed under the fore part of the muffle to warm the scorifiers more quickly; and when the lead or ore is to be placed in the scorifiers, they are taken out again with the tongs. When the scorifiers glow in the heat, first of all the ash or small charcoals, if any have fallen into them, should be blown away with an iron pipe two feet long and a digit in diameter; this same thing must be done if ash or small coal has fallen into the cupels. Next, put in a small ball of lead with the tongs, and when this lead has begun to be turned into fumes and consumed, add to it the prepared ore wrapped in paper. It is preferable that the assayer should wrap it in paper, and in this way put it in the scorifier, than that he should drop it in with a copper ladle; for when the scorifiers are small, if he uses a ladle he frequently spills some part of the ore. When the paper is burnt, he stirs the ore with a small charcoal held in the tongs, so that the lead may absorb the metal which is mixed in the ore; when this mixture has taken place, the slag partly adheres by its circumference to the scorifier and makes a kind of black ring, and partly floats on the lead in which is mixed the gold or silver; then the slag must be removed from it. The lead used must be entirely free from every trace of silver, as is that which is known as _Villacense_.[26] But if this kind is not obtainable, the lead must be assayed separately, to determine with certainty that proportion of silver it contains, so that it may be deducted from the calculation of the ore, and the result be exact; for unless such lead be used, the assay will be false and misleading. The lead balls are made with a pair of iron tongs, about one foot long; its iron claws are so formed that when pressed together they are egg-shaped; each claw contains a hollow cup, and when the claws are closed there extends upward from the cup a passage, so there are two openings, one of which leads to each hollow cup. And so when the molten lead is poured in through the openings, it flows down into the hollow cup, and two balls are formed by one pouring. In this place I ought not to omit mention of another method of assaying employed by some assayers. They first of all place prepared ore in the scorifiers and heat it, and afterward they add the lead. Of this method I cannot approve, for in this way the ore frequently becomes cemented, and for this reason it does not stir easily afterward, and is very slow in mixing with the lead. [Illustration 240a (Tongs): A--Claws of the tongs. B--Iron, giving form of an egg. C--Opening.] If the whole space of the furnace covered by the muffle is not filled with scorifiers, cupels are put in the empty space, in order that they may become warmed in the meantime. Sometimes, however, it is filled with scorifiers, when we are assaying many different ores, or many portions of one ore at the same time. Although the cupels are usually dried in one hour, yet smaller ones are done more quickly, and the larger ones more slowly. Unless the cupels are heated before the metal mixed with lead is placed in them, they frequently break, and the lead always sputters and sometimes leaps out of them; if the cupel is broken or the lead leaps out of it, it is necessary to assay another portion of ore; but if the lead only sputters, then the cupels should be covered with broad thin pieces of glowing charcoal, and when the lead strikes these, it falls back again, and thus the mixture is slowly exhaled. Further, if in the cupellation the lead which is in the mixture is not consumed, but remains fixed and set, and is covered by a kind of skin, this is a sign that it has not been heated by a sufficiently hot fire; put into the mixture, therefore, a dry pine stick, or a twig of a similar tree, and hold it in the hand in order that it can be drawn away when it has been heated. Then take care that the heat is sufficient and equal; if the heat has not passed all round the charge, as it should when everything is done rightly, but causes it to have a lengthened shape, so that it appears to have a tail, this is a sign that the heat is deficient where the tail lies. Then in order that the cupel may be equally heated by the fire, turn it around with a small iron hook, whose handle is likewise made of iron and is a foot and a half long. [Illustration 240b (Hook): Small iron hook.] Next, if the mixture has not enough lead, add as much of it as is required with the iron tongs, or with the brass ladle to which is fastened a very long handle. In order that the charge may not be cooled, warm the lead beforehand. But it is better at first to add as much lead as is required to the ore which needs melting, rather than afterward when the melting has been half finished, that the whole quantity may not vanish in fumes, but part of it remain fast. When the heat of the fire has nearly consumed the lead, then is the time when the gold and silver gleam in their varied colours, and when all the lead has been consumed the gold or silver settles in the cupel. Then as soon as possible remove the cupel out of the furnace, and take the button out of it while it is still warm, in order that it does not adhere to the ashes. This generally happens if the button is already cold when it is taken out. If the ashes do adhere to it, do not scrape it with a knife, lest some of it be lost and the assay be erroneous, but squeeze it with the iron tongs, so that the ashes drop off through the pressure. Finally, it is of advantage to make two or three assays of the same ore at the same time, in order that if by chance one is not successful, the second, or in any event the third, may be certain. [Illustration 241 (Shield for Muffle Furnace): A--Handle of tablet. B--Its crack.] While the assayer is assaying the ore, in order to prevent the great heat of the fire from injuring his eyes, it will be useful for him always to have ready a thin wooden tablet, two palms wide, with a handle by which it may be held, and with a slit down the middle in order that he may look through it as through a crack, since it is necessary for him to look frequently within and carefully to consider everything. Now the lead which has absorbed the silver from a metallic ore is consumed in the cupel by the heat in the space of three quarters of an hour. When the assays are completed the muffle is taken out of the furnace, and the ashes removed with an iron shovel, not only from the brick and iron furnaces, but also from the earthen one, so that the furnace need not be removed from its foundation. From ore placed in the triangular crucible a button is melted out, from which metal is afterward made. First of all, glowing charcoal is put into the iron hoop, then is put in the triangular crucible, which contains the ore together with those things which can liquefy it and purge it of its dross; then the fire is blown with the double bellows, and the ore is heated until the button settles in the bottom of the crucible. We have explained that there are two methods of assaying ore,--one, by which the lead is mixed with ore in the scorifier and afterward again separated from it in the cupel; the other, by which it is first melted in the triangular earthen crucible and afterward mixed with lead in the scorifier, and later separated from it in the cupel. Now let us consider which is more suitable for each ore, or, if neither is suitable, by what other method in one way or another we can assay it. We justly begin with a gold ore, which we assay by both methods, for if it is rich and seems not to be strongly resistant to fire, but to liquefy easily, one _centumpondium_ of it (known to us as the lesser weights),[27] together with one and a half, or two _unciae_ of lead of the larger weights, are mixed together and placed in the scorifier, and the two are heated in the fire until they are well mixed. But since such an ore sometimes resists melting, add a little salt to it, either _sal torrefactus_ or _sal artificiosus_, for this will subdue it, and prevent the alloy from collecting much dross; stir it frequently with an iron rod, in order that the lead may flow around the gold on every side, and absorb it and cast out the waste. When this has been done, take out the alloy and cleanse it of slag; then place it in the cupel and heat it until it exhales all the lead, and a bead of gold settles in the bottom. If the gold ore is seen not to be easily melted in the fire, roast it and extinguish it with brine. Do this again and again, for the more often you roast it and extinguish it, the more easily the ore can be crushed fine, and the more quickly does it melt in the fire and give up whatever dross it possesses. Mix one part of this ore, when it has been roasted, crushed, and washed, with three parts of some powder compound which melts ore, and six parts of lead. Put the charge into the triangular crucible, place it in the iron hoop to which the double bellows reaches, and heat first in a slow fire, and afterward gradually in a fiercer fire, till it melts and flows like water. If the ore does not melt, add to it a little more of these fluxes, mixed with an equal portion of yellow litharge, and stir it with a hot iron rod until it all melts. Then take the crucible out of the hoop, shake off the button when it has cooled, and when it has been cleansed, melt first in the scorifier and afterward in the cupel. Finally, rub the gold which has settled in the bottom of the cupel, after it has been taken out and cooled, on the touchstone, in order to find out what proportion of silver it contains. Another method is to put a _centumpondium_ (of the lesser weights) of gold ore into the triangular crucible, and add to it a _drachma_ (of the larger weights) of glass-galls. If it resists melting, add half a _drachma_ of roasted argol, and if even then it resists, add the same quantity of roasted lees of vinegar, or lees of the _aqua_ which separates gold from silver, and the button will settle in the bottom of the crucible. Melt this button again in the scorifier and a third time in the cupel. We determine in the following way, before it is melted in the muffle furnace, whether pyrites contains gold in it or not: if, after being three times roasted and three times quenched in sharp vinegar, it has not broken nor changed its colour, there is gold in it. The vinegar by which it is quenched should be mixed with salt that is put in it, and frequently stirred and dissolved for three days. Nor is pyrites devoid of gold, when, after being roasted and then rubbed on the touchstone, it colours the touchstone in the same way that it coloured it when rubbed in its crude state. Nor is gold lacking in that, whose concentrates from washing, when heated in the fire, easily melt, giving forth little smell and remaining bright; such concentrates are heated in the fire in a hollowed piece of charcoal covered over with another charcoal. We also assay gold ore without fire, but more often its sand or the concentrates which have been made by washing, or the dust gathered up by some other means. A little of it is slightly moistened with water and heated until it begins to exhale an odour, and then to one portion of ore are placed two portions of quicksilver[28] in a wooden dish as deep as a basin. They are mixed together with a little brine, and are then ground with a wooden pestle for the space of two hours, until the mixture becomes of the thickness of dough, and the quicksilver can no longer be distinguished from the concentrates made by the washing, nor the concentrates from the quicksilver. Warm, or at least tepid, water is poured into the dish and the material is washed until the water runs out clear. Afterward cold water is poured into the same dish, and soon the quicksilver, which has absorbed all the gold, runs together into a separate place away from the rest of the concentrates made by washing. The quicksilver is afterward separated from the gold by means of a pot covered with soft leather, or with canvas made of woven threads of cotton; the amalgam is poured into the middle of the cloth or leather, which sags about one hand's breadth; next, the leather is folded over and tied with a waxed string, and the dish catches the quicksilver which is squeezed through it. As for the gold which remains in the leather, it is placed in a scorifier and purified by being placed near glowing coals. Others do not wash away the dirt with warm water, but with strong lye and vinegar, for they pour these liquids into the pot, and also throw into it the quicksilver mixed with the concentrates made by washing. Then they set the pot in a warm place, and after twenty-four hours pour out the liquids with the dirt, and separate the quicksilver from the gold in the manner which I have described. Then they pour urine into a jar set in the ground, and in the jar place a pot with holes in the bottom, and in the pot they place the gold; then the lid is put on and cemented, and it is joined with the jar; they afterward heat it till the pot glows red. After it has cooled, if there is copper in the gold they melt it with lead in a cupel, that the copper may be separated from it; but if there is silver in the gold they separate them by means of the _aqua_ which has the power of parting these two metals. There are some who, when they separate gold from quicksilver, do not pour the amalgam into a leather, but put it into a gourd-shaped earthen vessel, which they place in the furnace and heat gradually over burning charcoal; next, with an iron plate, they cover the opening of the operculum, which exudes vapour, and as soon as it has ceased to exude, they smear it with lute and heat it for a short time; then they remove the operculum from the pot, and wipe off the quicksilver which adheres to it with a hare's foot, and preserve it for future use. By the latter method, a greater quantity of quicksilver is lost, and by the former method, a smaller quantity. If an ore is rich in silver, as is _rudis_ silver[29], frequently silver glance, or rarely ruby silver, gray silver, black silver, brown silver, or yellow silver, as soon as it is cleansed and heated, a _centumpondium_ (of the lesser weights) of it is placed in an _uncia_ of molten lead in a cupel, and is heated until the lead exhales. But if the ore is of poor or moderate quality, it must first be dried, then crushed, and then to a _centumpondium_ (of the lesser weights) an _uncia_ of lead is added, and it is heated in the scorifier until it melts. If it is not soon melted by the fire, it should be sprinkled with a little powder of the first order of fluxes, and if then it does not melt, more is added little by little until it melts and exudes its slag; that this result may be reached sooner, the powder which has been sprinkled over it should be stirred in with an iron rod. When the scorifier has been taken out of the assay furnace, the alloy should be poured into a hole in a baked brick; and when it has cooled and been cleansed of the slag, it should be placed in a cupel and heated until it exhales all its lead; the weight of silver which remains in the cupel indicates what proportion of silver is contained in the ore. We assay copper ore without lead, for if it is melted with it, the copper usually exhales and is lost. Therefore, a certain weight of such an ore is first roasted in a hot fire for about six or eight hours; next, when it has cooled, it is crushed and washed; then the concentrates made by washing are again roasted, crushed, washed, dried, and weighed. The portion which it has lost whilst it is being roasted and washed is taken into account, and these concentrates by washing represent the cake which will be melted out of the copper ore. Place three _centumpondia_ (lesser weights) of this, mixed with three _centumpondia_ (lesser weights) each of copper scales[30], saltpetre, and Venetian glass, mixed, into the triangular crucible, and place it in the iron hoop which is set on the hearth in front of the double bellows. Cover the crucible with charcoal in such a way that nothing may fall into the ore which is to be melted, and so that it may melt more quickly. At first blow a gentle blast with the bellows in order that the ore may be heated gradually in the fire; then blow strongly till it melts, and the fire consumes that which has been added to it, and the ore itself exudes whatever slag it possesses. Next, cool the crucible which has been taken out, and when this is broken you will find the copper; weigh this, in order to ascertain how great a portion of the ore the fire has consumed. Some ore is only once roasted, crushed, and washed; and of this kind of concentrates, three _centumpondia_ (lesser weights) are taken with one _centumpondium_ each of common salt, argol and glass-galls. Heat them in the triangular crucible, and when the mixture has cooled a button of pure copper will be found, if the ore is rich in this metal. If, however, it is less rich, a stony lump results, with which the copper is intermixed; this lump is again roasted, crushed, and, after adding stones which easily melt and saltpetre, it is again melted in another crucible, and there settles in the bottom of the crucible a button of pure copper. If you wish to know what proportion of silver is in this copper button, melt it in a cupel after adding lead. With regard to this test I will speak later. Those who wish to know quickly what portion of silver the copper ore contains, roast the ore, crush and wash it, then mix a little yellow litharge with one _centumpondium_ (lesser weights) of the concentrates, and put the mixture into a scorifier, which they place under the muffle in a hot furnace for the space of half an hour. When the slag exudes, by reason of the melting force which is in the litharge, they take the scorifier out; when it has cooled, they cleanse it of slag and again crush it, and with one _centumpondium_ of it they mix one and a half _unciae_ of lead granules. They then put it into another scorifier, which they place under the muffle in a hot furnace, adding to the mixture a little of the powder of some one of the fluxes which cause ore to melt; when it has melted they take it out, and after it has cooled, cleanse it of slag; lastly, they heat it in the cupel till it has exhaled all of the lead, and only silver remains. Lead ore may be assayed by this method: crush half an _uncia_ of pure lead-stone and the same quantity of the _chrysocolla_ which they call borax, mix them together, place them in a crucible, and put a glowing coal in the middle of it. As soon as the borax crackles and the lead-stone melts, which soon occurs, remove the coal from the crucible, and the lead will settle to the bottom of it; weigh it out, and take account of that portion of it which the fire has consumed. If you also wish to know what portion of silver is contained in the lead, melt the lead in the cupel until all of it exhales. Another way is to roast the lead ore, of whatsoever quality it be, wash it, and put into the crucible one _centumpondium_ of the concentrates, together with three _centumpondia_ of the powdered compound which melts ore, mixed together, and place it in the iron hoop that it may melt; when it has cooled, cleanse it of its slag, and complete the test as I have already said. Another way is to take two _unciae_ of prepared ore, five _drachmae_ of roasted copper, one _uncia_ of glass, or glass-galls reduced to powder, a _semi-uncia_ of salt, and mix them. Put the mixture into the triangular crucible, and heat it over a gentle fire to prevent it from breaking; when the mixture has melted, blow the fire vigorously with the bellows; then take the crucible off the live coals and let it cool in the open air; do not pour water on it, lest the lead button being acted upon by the excessive cold should become mixed with the slag, and the assay in this way be erroneous. When the crucible has cooled, you will find in the bottom of it the lead button. Another way is to take two _unciae_ of ore, a _semi-uncia_ of litharge, two _drachmae_ of Venetian glass and a _semi-uncia_ of saltpetre. If there is difficulty in melting the ore, add to it iron filings, which, since they increase the heat, easily separate the waste from lead and other metals. By the last way, lead ore properly prepared is placed in the crucible, and there is added to it only the sand made from stones which easily melt, or iron filings, and then the assay is completed as formerly. You can assay tin ore by the following method. First roast it, then crush, and afterward wash it; the concentrates are again roasted, crushed, and washed. Mix one and a half _centumpondia_ of this with one _centumpondium_ of the _chrysocolla_ which they call borax; from the mixture, when it has been moistened with water, make a lump. Afterwards, perforate a large round piece of charcoal, making this opening a palm deep, three digits wide on the upper side and narrower on the lower side; when the charcoal is put in its place the latter should be on the bottom and the former uppermost. Let it be placed in a crucible, and let glowing coal be put round it on all sides; when the perforated piece of coal begins to burn, the lump is placed in the upper part of the opening, and it is covered with a wide piece of glowing coal, and after many pieces of coal have been put round it, a hot fire is blown up with the bellows, until all the tin has run out of the lower opening of the charcoal into the crucible. Another way is to take a large piece of charcoal, hollow it out, and smear it with lute, that the ore may not leap out when white hot. Next, make a small hole through the middle of it, then fill up the large opening with small charcoal, and put the ore upon this; put fire in the small hole and blow the fire with the nozzle of a hand bellows; place the piece of charcoal in a small crucible, smeared with lute, in which, when the melting is finished, you will find a button of tin. In assaying bismuth ore, place pieces of ore in the scorifier, and put it under the muffle in a hot furnace; as soon as they are heated, they drip with bismuth, which runs together into a button. Quicksilver ore is usually tested by mixing one part of broken ore with three-parts of charcoal dust and a handful of salt. Put the mixture into a crucible or a pot or a jar, cover it with a lid, seal it with lute, place it on glowing charcoal, and as soon as a burnt cinnabar colour shows in it, take out the vessel; for if you continue the heat too long the mixture exhales the quicksilver with the fumes. The quicksilver itself, when it has become cool, is found in the bottom of the crucible or other vessel. Another way is to place broken ore in a gourd-shaped earthen vessel, put it in the assay furnace, and cover with an operculum which has a long spout; under the spout, put an ampulla to receive the quicksilver which distills. Cold water should be poured into the ampulla, so that the quicksilver which has been heated by the fire may be continuously cooled and gathered together, for the quicksilver is borne over by the force of the fire, and flows down through the spout of the operculum into the ampulla. We also assay quicksilver ore in the very same way in which we smelt it. This I will explain in its proper place. Lastly, we assay iron ore in the forge of a blacksmith. Such ore is burned, crushed, washed, and dried; a magnet is laid over the concentrates, and the particles of iron are attracted to it; these are wiped off with a brush, and are caught in a crucible, the magnet being continually passed over the concentrates and the particles wiped off, so long as there remain any particles which the magnet can attract to it. These particles are heated in the crucible with saltpetre until they melt, and an iron button is melted out of them. If the magnet easily and quickly attracts the particles to it, we infer that the ore is rich in iron; if slowly, that it is poor; if it appears actually to repel the ore, then it contains little or no iron. This is enough for the assaying of ores. I will now speak of the assaying of the metal alloys. This is done both by coiners and merchants who buy and sell metal, and by miners, but most of all by the owners and mine masters, and by the owners and masters of the works in which the metals are smelted, or in which one metal is parted from another. First I will describe the way assays are usually made to ascertain what portion of precious metal is contained in base metal. Gold and silver are now reckoned as precious metals and all the others as base metals. Once upon a time the base metals were burned up, in order that the precious metals should be left pure; the Ancients even discovered by such burning what portion of gold was contained in silver, and in this way all the silver was consumed, which was no small loss. However, the famous mathematician, Archimedes[31], to gratify King Hiero, invented a method of testing the silver, which was not very rapid, and was more accurate for testing a large mass than a small one. This I will explain in my commentaries. The alchemists have shown us a way of separating silver from gold by which neither of them is lost[32]. Gold which contains silver,[33] or silver which contains gold, is first rubbed on the touchstone. Then a needle in which there is a similar amount of gold or silver is rubbed on the same touchstone, and from the lines which are produced in this way, is perceived what portion of silver there is in the gold, or what portion of gold there is in the silver. Next there is added to the silver which is in the gold, enough silver to make it three times as much as the gold. Then lead is placed in a cupel and melted; a little later, a small amount of copper is put in it, in fact, half an _uncia_ of it, or half an _uncia_ and a _sicilicus_ (of the smaller weights) if the gold or silver does not contain any copper. The cupel, when the lead and copper are wanting, attracts the particles of gold and silver, and absorbs them. Finally, one-third of a _libra_ of the gold, and one _libra_[34] of the silver must be placed together in the same cupel and melted; for if the gold and silver were first placed in the cupel and melted, as I have already said, it absorbs particles of them, and the gold, when separated from the silver, will not be found pure. These metals are heated until the lead and the copper are consumed, and again, the same weight of each is melted in the same manner in another cupel. The buttons are pounded with a hammer and flattened out, and each little leaf is shaped in the form of a tube, and each is put into a small glass ampulla. Over these there is poured one _uncia_ and one _drachma_ (of the large weight) of the third quality _aqua valens_, which I will describe in the Tenth Book. This is heated over a slow fire, and small bubbles, resembling pearls in shape, will be seen to adhere to the tubes. The redder the _aqua_ appears, the better it is judged to be; when the redness has vanished, small white bubbles are seen to be resting on the tubes, resembling pearls not only in shape, but also in colour. After a short time the _aqua_ is poured off and other is poured on; when this has again raised six or eight small white bubbles, it is poured off and the tubes are taken out and washed four or five times with spring water; or if they are heated with the same water, when it is boiling, they will shine more brilliantly. Then they are placed in a saucer, which is held in the hand and gradually dried by the gentle heat of the fire; afterward the saucer is placed over glowing charcoal and covered with a charcoal, and a moderate blast is blown upon it with the mouth and then a blue flame will be emitted. In the end the tubes are weighed, and if their weights prove equal, he who has undertaken this work has not laboured in vain. Lastly, both are placed in another balance-pan and weighed; of each tube four grains must not be counted, on account of the silver which remains in the gold and cannot be separated from it. From the weight of the tubes we learn the weight both of the gold and of the silver which is in the button. If some assayer has omitted to add so much silver to the gold as to make it three times the quantity, but only double, or two and a half times as much, he will require the stronger quality of _aqua_ which separates gold from silver, such as the fourth quality. Whether the _aqua_ which he employs for gold and silver is suitable for the purpose, or whether it is more or less strong than is right, is recognised by its effect. That of medium strength raises the little bubbles on the tubes and is found to colour the ampulla and the operculum a strong red; the weaker one is found to colour them a light red, and the stronger one to break the tubes. To pure silver in which there is some portion of gold, nothing should be added when they are being heated in the cupel prior to their being parted, except a _bes_ of lead and one-fourth or one-third its amount of copper of the lesser weights. If the silver contains in itself a certain amount of copper, let it be weighed, both after it has been melted with the lead, and after the gold has been parted from it; by the former we learn how much copper is in it, by the latter how much gold. Base metals are burnt up even to-day for the purpose of assay, because to lose so little of the metal is small loss, but from a large mass of base metal, the precious metal is always extracted, as I will explain in Books X. and XI. We assay an alloy of copper and silver in the following way. From a few cakes of copper the assayer cuts out portions, small samples from small cakes, medium samples from medium cakes, and large samples from large cakes; the small ones are equal in size to half a hazel nut, the large ones do not exceed the size of half a chestnut, and those of medium size come between the two. He cuts out the samples from the middle of the bottom of each cake. He places the samples in a new, clean, triangular crucible and fixes to them pieces of paper upon which are written the weight of the cakes of copper, of whatever size they may be; for example, he writes, "These samples have been cut from copper which weighs twenty _centumpondia_." When he wishes to know how much silver one _centumpondium_ of copper of this kind has in it, first of all he throws glowing coals into the iron hoop, then adds charcoal to it. When the fire has become hot, the paper is taken out of the crucible and put aside, he then sets that crucible on the fire and gradually heats it for a quarter of an hour until it becomes red hot. Then he stimulates the fire by blowing with a blast from the double bellows for half an hour, because copper which is devoid of lead requires this time to become hot and to melt; copper not devoid of lead melts quicker. When he has blown the bellows for about the space of time stated, he removes the glowing charcoal with the tongs, and stirs the copper with a splinter of wood, which he grasps with the tongs. If it does not stir easily, it is a sign that the copper is not wholly liquefied; if he finds this is the case, he again places a large piece of charcoal in the crucible, and replaces the glowing charcoal which had been removed, and again blows the bellows for a short time. When all the copper has melted he stops using the bellows, for if he were to continue to use them, the fire would consume part of the copper, and then that which remained would be richer than the cake from which it had been cut; this is no small mistake. Therefore, as soon as the copper has become sufficiently liquefied, he pours it out into a little iron mould, which may be large or small, according as more or less copper is melted in the crucible for the purpose of the assay. The mould has a handle, likewise made of iron, by which it is held when the copper is poured in, after which, he plunges it into a tub of water placed near at hand, that the copper may be cooled. Then he again dries the copper by the fire, and cuts off its point with an iron wedge; the portion nearest the point he hammers on an anvil and makes into a leaf, which he cuts into pieces. [Illustration 250 (Copper Mould for Assaying): A--Iron mould. B--Its handle.] Others stir the molten copper with a stick of linden tree charcoal, and then pour it over a bundle of new clean birch twigs, beneath which is placed a wooden tub of sufficient size and full of water, and in this manner the copper is broken up into little granules as small as hemp seeds. Others employ straw in place of twigs. Others place a broad stone in a tub and pour in enough water to cover the stone, then they run out the molten copper from the crucible on to the stone, from which the minute granules roll off; others pour the molten copper into water and stir it until it is resolved into granules. The fire does not easily melt the copper in the cupel unless it has been poured and a thin leaf made of it, or unless it has been resolved into granules or made into filings; and if it does not melt, all the labour has been undertaken in vain. In order that they may be accurately weighed out, silver and lead are resolved into granules in the same manner as copper. But to return to the assay of copper. When the copper has been prepared by these methods, if it is free of lead and iron, and rich in silver, to each _centumpondium_ (lesser weights) add one and a half _unciae_ of lead (larger weights). If, however, the copper contains some lead, add one _uncia_ of lead; if it contains iron, add two _unciae_. First put the lead into a cupel, and after it begins to smoke, add the copper; the fire generally consumes the copper, together with the lead, in about one hour and a quarter. When this is done, the silver will be found in the bottom of the cupel. The fire consumes both of those metals more quickly if they are heated in that furnace which draws in air. It is better to cover the upper half of it with a lid, and not only to put on the muffle door, but also to close the window of the muffle door with a piece of charcoal, or with a piece of brick. If the copper be such that the silver can only be separated from it with difficulty, then before it is tested with fire in the cupel, lead should first be put into the scorifier, and then the copper should be added with a moderate quantity of melted salt, both that the lead may absorb the copper and that the copper may be cleansed of the dross which abounds in it. Tin which contains silver should not at the beginning of the assay be placed in a cupel, lest the silver, as often happens, be consumed and converted into fumes, together with the tin. As soon as the lead[35] has begun to fume in the scorifier, then add that[36] to it. In this way the lead will take the silver and the tin will boil and turn into ashes, which may be removed with a wooden splinter. The same thing occurs if any alloy is melted in which there is tin. When the lead has absorbed the silver which was in the tin, then, and not till then, it is heated in the cupel. First place the lead with which the silver is mixed, in an iron pan, and stand it on a hot furnace and let it melt; afterward pour this lead into a small iron mould, and then beat it out with a hammer on an anvil and make it into leaves in the same way as the copper. Lastly, place it in the cupel, which assay can be carried out in the space of half an hour. A great heat is harmful to it, for which reason there is no necessity either to cover the half of the furnace with a lid or to close up its mouth. The minted metal alloys, which are known as money, are assayed in the following way. The smaller silver coins which have been picked out from the bottom and top and sides of a heap are first carefully cleansed; then, after they have been melted in the triangular crucible, they are either resolved into granules, or made into thin leaves. As for the large coins which weigh a _drachma_, a _sicilicus_, half an _uncia_, or an _uncia_, beat them into leaves. Then take a _bes_ of the granules, or an equal weight of the leaves, and likewise take another _bes_ in the same way. Wrap each sample separately in paper, and afterwards place two small pieces of lead in two cupels which have first been heated. The more precious the money is, the smaller portion of lead do we require for the assay, the more base, the larger is the portion required; for if a _bes_ of silver is said to contain only half an _uncia_ or one _uncia_ of copper, we add to the _bes_ of granules half an _uncia_ of lead. If it is composed of equal parts of silver and copper, we add an _uncia_ of lead, but if in a _bes_ of copper there is only half an _uncia_ or one _uncia_ of silver, we add an _uncia_ and a half of lead. As soon as the lead has begun to fume, put into each cupel one of the papers in which is wrapped the sample of silver alloyed with copper, and close the mouth of the muffle with charcoal. Heat them with a gentle fire until all the lead and copper are consumed, for a hot fire by its heat forces the silver, combined with a certain portion of lead, into the cupel, in which way the assay is rendered erroneous. Then take the beads out of the cupel and clean them of dross. If neither depresses the pan of the balance in which it is placed, but their weight is equal, the assay has been free from error; but if one bead depresses its pan, then there is an error, for which reason the assay must be repeated. If the _bes_ of coin contains but seven _unciae_ of pure silver it is because the King, or Prince, or the State who coins the money, has taken one _uncia_, which he keeps partly for profit and partly for the expense of coining, he having added copper to the silver. Of all these matters I have written extensively in my book _De Precio Metallorum et Monetis_. We assay gold coins in various ways. If there is copper mixed with the gold, we melt them by fire in the same way as silver coins; if there is silver mixed with the gold, they are separated by the strongest _aqua valens_; if there is copper and silver mixed with the gold, then in the first place, after the addition of lead, they are heated in the cupel until the fire consumes the copper and the lead, and afterward the gold is parted from the silver. It remains to speak of the touchstone[37] with which gold and silver are tested, and which was also used by the Ancients. For although the assay made by fire is more certain, still, since we often have no furnace, nor muffle, nor crucibles, or some delay must be occasioned in using them, we can always rub gold or silver on the touchstone, which we can have in readiness. Further, when gold coins are assayed in the fire, of what use are they afterward? A touchstone must be selected which is thoroughly black and free of sulphur, for the blacker it is and the more devoid of sulphur, the better it generally is; I have written elsewhere of its nature[38]. First the gold is rubbed on the touchstone, whether it contains silver or whether it is obtained from the mines or from the smelting; silver also is rubbed in the same way. Then one of the needles, that we judge by its colour to be of similar composition, is rubbed on the touchstone; if this proves too pale, another needle which has a stronger colour is rubbed on the touchstone; and if this proves too deep in colour, a third which has a little paler colour is used. For this will show us how great a proportion of silver or copper, or silver and copper together, is in the gold, or else how great a proportion of copper is in silver. These needles are of four kinds.[39] The first kind are made of gold and silver, the second of gold and copper, the third of gold, silver, and copper, and the fourth of silver and copper. The first three kinds of needles are used principally for testing gold, and the fourth for silver. Needles of this kind are prepared in the following ways. The lesser weights correspond proportionately to the larger weights, and both of them are used, not only by mining people, but by coiners also. The needles are made in accordance with the lesser weights, and each set corresponds to a _bes_, which, in our own vocabulary, is called a _mark_. The _bes_, which is employed by those who coin gold, is divided into twenty-four double _sextulae_, which are now called after the Greek name _ceratia_; and each double _sextula_ is divided into four _semi-sextulae_, which are called _granas_; and each _semi-sextula_ is divided into three units of four _siliquae_ each, of which each unit is called a _grenlin_. If we made the needles to be each four _siliquae_, there would be two hundred and eighty-eight in a _bes_, but if each were made to be a _semi-sextula_ or a double _scripula_, then there would be ninety-six in a _bes_. By these two methods too many needles would be made, and the majority of them, by reason of the small difference in the proportion of the gold, would indicate nothing, therefore it is advisable to make them each of a double _sextula_; in this way twenty-four needles are made, of which the first is made of twenty-three _duellae_ of silver and one of gold. Fannius is our authority that the Ancients called the double _sextula_ a _duella_. When a bar of silver is rubbed on the touchstone and colours it just as this needle does, it contains one _duella_ of gold. In this manner we determine by the other needles what proportion of gold there is, or when the gold exceeds the silver in weight, what proportion of silver. [Illustration 255 (Touch-needles)] The needles are made[40]:-- The 1st needle of 23 _duellae_ of silver and 1 _duella_ of gold. " 2nd " 22 " " 2 _duellae_ of gold. " 3rd " 21 " " 3 " " " 4th " 20 " " 4 " " " 5th " 19 " " 5 " " " 6th " 18 " " 6 " " " 7th " 17 " " 7 " " " 8th " 16 " " 8 " " " 9th " 15 " " 9 " " " 10th " 14 " " 10 " " " 11th " 13 " " 11 " " " 12th " 12 " " 12 " " " 13th " 11 " " 13 " " " 14th " 10 " " 14 " " " 15th " 9 " " 15 " " " 16th " 8 " " 16 " " " 17th " 7 " " 17 " " " 18th " 6 " " 18 " " " 19th " 5 " " 19 " " " 20th " 4 " " 20 " " " 21st " 3 " " 21 " " " 22nd " 2 " " 22 " " " 23rd " 1 " " 23 " " " 24th " pure gold By the first eleven needles, when they are rubbed on the touchstone, we test what proportion of gold a bar of silver contains, and with the remaining thirteen we test what proportion of silver is in a bar of gold; and also what proportion of either may be in money. Since some gold coins are composed of gold and copper, thirteen needles of another kind are made as follows:-- The 1st of 12 _duellae_ of gold and 12 _duellae_ of copper. " 2nd " 13 " " 11 " " " 3rd " 14 " " 10 " " " 4th " 15 " " 9 " " " 5th " 16 " " 8 " " " 6th " 17 " " 7 " " " 7th " 18 " " 6 " " " 8th " 19 " " 5 " " " 9th " 20 " " 4 " " " 10th " 21 " " 3 " " " 11th " 22 " " 2 " " " 12th " 23 " " 1 " " " 13th " pure gold. These needles are not much used, because gold coins of that kind are somewhat rare; the ones chiefly used are those in which there is much copper. Needles of the third kind, which are composed of gold, silver, and copper, are more largely used, because such gold coins are common. But since with the gold there are mixed equal or unequal portions of silver and copper, two sorts of needles are made. If the proportion of silver and copper is equal, the needles are as follows:-- Gold. Silver. Copper. The 1st of 12 _duellae_ 6 _duellae_ 0 _sextula_ 6 _duellae_ 0 _sextula_ " 2nd " 13 " 5 " 1 " 5 " 1 " " 3rd " 14 " 5 " 5 " " 4th " 15 " 4 " 1 " 4 " 1 " " 5th " 16 " 4 " 4 " " 6th " 17 " 3 " 1 " 3 " 1 " " 7th " 18 " 3 " 3 " " 8th " 19 " 2 " 1 " 2 " 1 " " 9th " 20 " 2 " 2 " " 10th " 21 " 1 " 1 " 1 " 1 " " 11th " 22 " 1 " 1 " " 12th " 23 " 1 " " 13th " pure gold. Some make twenty-five needles, in order to be able to detect the two _scripula_ of silver or copper which are in a _bes_ of gold. Of these needles, the first is composed of twelve _duellae_ of gold and six of silver, and the same number of copper. The second, of twelve _duellae_ and one _sextula_ of gold and five _duellae_ and one and a half _sextulae_ of silver, and the same number of _duellae_ and one and a half _sextulae_ of copper. The remaining needles are made in the same proportion. Pliny is our authority that the Romans could tell to within one _scripulum_ how much gold was in any given alloy, and how much silver or copper. Needles may be made in either of two ways, namely, in the ways of which I have spoken, and in the ways of which I am now about to speak. If unequal portions of silver and copper have been mixed with the gold, thirty-seven needles are made in the following way:-- Gold. Silver. Copper. _Duellae_. _Duellae_ _Duellae_ _Sextulae_ _Sextulae_ _Siliquae_. _Siliquae_. The 1st of 12 9 0 0 3 0 0 " 2nd " 12 8 0 0 4 0 0 " 3rd " 12 7 5 " 4th " 13 8 1/2 2 1/2 " 5th " 13 7 1/2 4 3 1 8 " 6th " 13 6 1/2 8 4 1 4 " 7th " 14 7 1 2 1 " 8th " 14 6 1 8 3 1/2 4 " 9th " 14 5 1-1/2 4 4 8 " 10th " 15 6 1-1/2 2 1/2 " 11th " 15 6 3 " 12th " 15 5 1/2 3 1-1/2 " 13th " 16 6 2 " 14th " 16 5 1/2 4 2 1 8 " 15th " 16 4 1 8 3 1/2 4 " 16th " 17 5 1/2 0 1 1-1/2 " 17th " 17 4 1 8 2 1/2 4 " 18th " 17 4 4 2 1-1/2 8 " 19th " 18 4 1 1 1 " 20th " 18 4 0 2 " 21st " 18 3 1 2 1 " 22nd " 19 2 1-1/2 1 1/2 " 23rd " 19 3 1/2 4 1 1 8 " 24th " 19 2 1-1/2 8 2 4 " 25th " 20 3 1 " 26th " 20 2 1 8 1 1/2 4 " 27th " 20 2 1/2 4 1 1 8 " 28th " 21 2 1/2 1-1/2 " 29th " 21 2 1 " 30th " 21 1 1-1/2 1 1/2 " 31st " 22 1 1 1 " 32nd " 22 1 1/2 4 0 1 8 " 33rd " 22 1 8 1-1/2 4 " 34th " 23 1-1/2 1/2 " 35th " 23 1 8 1/2 4 " 36th " 23 1 4 1/2 8 " 37th " pure gold. Since it is rarely found that gold, which has been coined, does not amount to at least fifteen _duellae_ gold in a _bes_, some make only twenty-eight needles, and some make them different from those already described, inasmuch as the alloy of gold with silver and copper is sometimes differently proportioned. These needles are made:-- Gold. Silver. Copper. _Duellae_. _Duellae_ _Duellae_ _Sextulae_ _Sextulae_ _Siliquae_. _Siliquae_. The 1st of 15 6 1 8 2 1/2 4 " 2nd " 15 6 4 2 1-1/2 8 " 3rd " 15 5 1/2 3 1-1/2 " 4th " 16 6 1/2 1 1-1/2 " 5th " 16 5 1 8 2 1/2 4 " 6th " 16 4 1-1/2 8 3 4 " 7th " 17 5 1 4 1 1/2 8 " 8th " 17 5 4 1 1-1/2 8 " 9th " 17 4 1 4 2 1/2 8 " 10th " 18 4 1 1 1 " 11th " 18 4 2 " 12th " 18 3 1 2 1 " 13th " 19 3 1-1/2 4 1 8 " 14th " 19 3 1/2 4 1 1 8 " 15th " 19 2 1-1/2 4 2 8 " 16th " 20 3 1 " 17th " 20 2 1 1 " 18th " 20 2 2 " 19th " 21 2 1/2 4 1 8 " 20th " 21 1 1-1/2 4 1 8 " 21st " 21 1 1 8 1 1/2 4 " 22nd " 22 1 1 8 1/2 4 " 23rd " 22 1 1 1 " 24th " 22 1 1/2 4 1 8 " 25th " 23 1-1/2 4 8 " 26th " 23 1-1/2 1/2 " 27th " 23 1 8 1/2 4 " 28th " pure gold Next follows the fourth kind of needles, by which we test silver coins which contain copper, or copper coins which contain silver. The _bes_ by which we weigh the silver is divided in two different ways. It is either divided twelve times, into units of five _drachmae_ and one _scripulum_ each, which the ordinary people call _nummi_[41]; each of these units we again divide into twenty-four units of four _siliquae_ each, which the same ordinary people call a _grenlin_; or else the _bes_ is divided into sixteen _semunciae_ which are called _loths_, each of which is again divided into eighteen units of four _siliquae_ each, which they call _grenlin_. Or else the _bes_ is divided into sixteen _semunciae_, of which each is divided into four _drachmae_, and each _drachma_ into four _pfennige_. Needles are made in accordance with each method of dividing the _bes_. According to the first method, to the number of twenty-four half _nummi_; according to the second method, to the number of thirty-one half _semunciae_, that is to say a _sicilicus_; for if the needles were made to the number of the smaller weights, the number of needles would again be too large, and not a few of them, by reason of the small difference in proportion of silver or copper, would have no significance. We test both bars and coined money composed of silver and copper by both scales. The one is as follows: the first needle is made of twenty-three parts of copper and one part silver; whereby, whatsoever bar or coin, when rubbed on the touchstone, colours it just as this needle does, in that bar or money there is one twenty-fourth part of silver, and so also, in accordance with the proportion of silver, is known the remaining proportion of the copper. The 1st needle is made of 23 parts of copper and 1 of silver. " 2nd " " 22 " " 2 " " 3rd " " 21 " " 3 " " 4th " " 20 " " 4 " " 5th " " 19 " " 5 " " 6th " " 18 " " 6 " " 7th " " 17 " " 7 " " 8th " " 16 " " 8 " " 9th " " 15 " " 9 " " 10th " " 14 " " 10 " " 11th " " 13 " " 11 " " 12th " " 12 " " 12 " " 13th " " 11 " " 13 " " 14th " " 10 " " 14 " " 15th " " 9 " " 15 " " 16th " " 8 " " 16 " " 17th " " 7 " " 17 " " 18th " " 6 " " 18 " " 19th " " 5 " " 19 " " 20th " " 4 " " 20 " " 21st " " 3 " " 21 " " 22nd " " 2 " " 22 " " 23rd " " 1 " " 23 " " 24th of pure silver. The other method of making needles is as follows:-- Copper. Silver. _Semunciae_ _Sicilici._ _Semunciae_ _Sicilici._ The 1st is of 15 1 " 2nd " " 14 1 1 1 " 3rd " " 14 2 " 4th " " 13 1 2 1 " 5th " " 13 3 " 6th " " 12 1 3 1 " 7th " " 12 4 " 8th " " 11 1 4 1 " 9th " " 11 5 " 10th " " 10 1 5 1 " 11th " " 10 6 " 12th " " 9 1 6 1 " 13th " " 9 7 " 14th " " 8 1 7 1 " 15th " " 8 8 " 16th " " 7 1 8 1 " 17th " " 7 9 " 18th " " 6 1 9 1 " 19th " " 6 10 " 20th " " 5 1 10 1 " 21st " " 5 11 " 22nd " " 4 1 11 1 " 23rd " " 4 12 " 24th " " 3 1 12 1 " 25th " " 3 13 " 26th " " 2 1 13 1 " 27th " " 2 14 " 28th " " 1 1 14 1 " 29th " " 1 15 " 30th " " 1 15 1 " 31st of pure silver. So much for this. Perhaps I have used more words than those most highly skilled in the art may require, but it is necessary for the understanding of these matters. I will now speak of the weights, of which I have frequently made mention. Among mining people these are of two kinds, that is, the greater weights and the lesser weights. The _centumpondium_ is the first and largest weight, and of course consists of one hundred _librae_, and for that reason is called a hundred weight. The various weights are:-- 1st = 100 _librae_ = _centumpondium_. 2nd = 50 " 3rd = 25 " 4th = 16 " 5th = 8 " 6th = 4 " 7th = 2 " 8th = 1 _libra_. This _libra_ consists of sixteen _unciae_, and the half part of the _libra_ is the _selibra_, which our people call a _mark_, and consists of eight _unciae_, or, as they divide it, of sixteen _semunciae_:-- 9th = 8 _unciae_. 10th = 8 _semunciae_. 11th = 4 " 12th = 2 " 13th = 1 _semuncia_. 14th = 1 _sicilicus_. 15th = 1 _drachma_. 16th = 1 _dimidi-drachma_. [Illustration 262 (Weights for Assay Balances)] The above is how the "greater" weights are divided. The "lesser" weights are made of silver or brass or copper. Of these, the first and largest generally weighs one _drachma_, for it is necessary for us to weigh, not only ore, but also metals to be assayed, and smaller quantities of lead. The first of these weights is called a _centumpondium_ and the number of _librae_ in it corresponds to the larger scale, being likewise one hundred[42]. The 1st is called 1 _centumpondium_. " 2nd " 50 _librae_. " 3rd " 25 " " 4th " 16 " " 5th " 8 " " 6th " 4 " " 7th " 2 " " 8th " 1 " " 9th " 1 _selibra_. " 10th " 8 _semunciae_. " 11th " 4 " " 12th " 2 " " 13th " 1 " " 14th " 1 _sicilicus_. The fourteenth is the last, for the proportionate weights which correspond with a _drachma_ and half a _drachma_ are not used. On all these weights of the lesser scale, are written the numbers of _librae_ and of _semunciae_. Some copper assayers divide both the lesser and greater scale weights into divisions of a different scale. Their largest weight of the greater scale weighs one hundred and twelve _librae_, which is the first unit of measurement. 1st = 112 _librae_. 2nd = 64 " 3rd = 32 " 4th = 16 " 5th = 8 " 6th = 4 " 7th = 2 " 8th = 1 " 9th = 1 _selibra_ or sixteen _semunciae_. 10th = 8 _semunciae_. 11th = 4 " 12th = 2 " 13th = 1 " As for the _selibra_ of the lesser weights, which our people, as I have often said, call a _mark_, and the Romans call a _bes_, coiners who coin gold, divide it just like the greater weights scale, into twenty-four units of two _sextulae_ each, and each unit of two _sextulae_ is divided into four _semi-sextulae_ and each _semi-sextula_ into three units of four _siliquae_ each. Some also divide the separate units of four _siliquae_ into four individual _siliquae_, but most, omitting the _semi-sextulae_, then divide the double _sextula_ into twelve units of four _siliquae_ each, and do not divide these into four individual _siliquae_. Thus the first and greatest unit of measurement, which is the _bes_, weighs twenty-four double _sextulae_. The 2nd = 12 double _sextulae_. " 3rd = 6 " " " 4th = 3 " " " 5th = 2 " " " 6th = 1 " " " 7th = 2 _semi-sextulae_ or four _semi-sextulae_. " 8th = 1 _semi-sextula_ or 3 units of 4 _siliquae_ each. " 9th = 2 units of four _siliquae_ each. " 10th = 1 " " " Coiners who mint silver also divide the _bes_ of the lesser weights in the same way as the greater weights; our people, indeed, divide it into sixteen _semunciae_, and the _semuncia_ into eighteen units of four _siliquae_ each. There are ten weights which are placed in the other pan of the balance, when they weigh the silver which remains from the copper that has been consumed, when they assay the alloy with fire. The 1st = 16 _semunciae_ = 1 _bes_. " 2nd = 8 " " 3rd = 4 " " 4th = 2 " " 5th = 1 " or 18 units of 4 _siliquae_ each. " 6th = 9 units of 4 _siliquae_ each. " 7th = 6 " " " 8th = 3 " " " 9th = 2 " " " 10th = 1 " " The coiners of Nuremberg who mint silver, divide the _bes_ into sixteen _semunciae_, but divide the _semuncia_ into four _drachmae_, and the _drachma_ into four _pfennige_. They employ nine weights. The 1st = 16 _semunciae_. " 2nd = 8 " " 3rd = 4 " " 4th = 2 " " 5th = 1 " For they divide the _bes_ in the same way as our own people, but since they divide the _semuncia_ into four _drachmae_, the 6th weight = 2 _drachmae_. " 7th " = 1 _drachma_ or 4 _pfennige_. " 8th " = 2 _pfennige_. " 9th " = 1 _pfennig_. The men of Cologne and Antwerp[43] divide the _bes_ into twelve units of five _drachmae_ and one _scripulum_, which weights they call _nummi_. Each of these they again divide into twenty-four units of four _siliquae_ each, which they call _grenlins_. They have ten weights, of which the 1st = 12 _nummi_ = 1 _bes_. " 2nd = 6 " " 3rd = 3 " " 4th = 2 " " 5th = 1 " = 24 units of 4 _siliquae_ each. " 6th = 12 units of 4 _siliquae_ each. " 7th = 6 " " " 8th = 3 " " " 9th = 2 " " " 10th = 1 " " And so with them, just as with our own people, the _mark_ is divided into two hundred and eighty-eight _grenlins_, and by the people of Nuremberg it is divided into two hundred and fifty-six _pfennige_. Lastly, the Venetians divide the _bes_ into eight _unciae_. The _uncia_ into four _sicilici_, the _sicilicus_ into thirty-six _siliquae_. They make twelve weights, which they use whenever they wish to assay alloys of silver and copper. Of these the 1st = 8 _unciae_ = 1 _bes_. " 2nd = 4 " " 3rd = 2 " " 4th = 1 " or 4 _sicilici_. " 5th = 2 _sicilici_. " 6th = 1 _sicilicus_. " 7th = 18 _siliquae_. " 8th = 9 " " 9th = 6 " " 10th = 3 " " 11th = 2 " " 12th = 1 " Since the Venetians divide the _bes_ into eleven hundred and fifty-two _siliquae_, or two hundred and eighty-eight units of 4 _siliquae_ each, into which number our people also divide the _bes_, they thus make the same number of _siliquae_, and both agree, even though the Venetians divide the _bes_ into smaller divisions. This, then, is the system of weights, both of the greater and the lesser kinds, which metallurgists employ, and likewise the system of the lesser weights which coiners and merchants employ, when they are assaying metals and coined money. The _bes_ of the larger weight with which they provide themselves when they weigh large masses of these things, I have explained in my work _De Mensuris et Ponderibus_, and in another book, _De Precio Metallorum et Monetis_. [Illustration 265 (Balances): A--First small balance. B--Second. C--Third, placed in a case.] There are three small balances by which we weigh ore, metals, and fluxes. The first, by which we weigh lead and fluxes, is the largest among these smaller balances, and when eight _unciae_ (of the greater weights) are placed in one of its pans, and the same number in the other, it sustains no damage. The second is more delicate, and by this we weigh the ore or the metal, which is to be assayed; this is well able to carry one _centumpondium_ of the lesser weights in one pan, and in the other, ore or metal as heavy as that weight. The third is the most delicate, and by this we weigh the beads of gold or silver, which, when the assay is completed, settle in the bottom of the cupel. But if anyone weighs lead in the second balance, or an ore in the third, he will do them much injury. Whatsoever small amount of metal is obtained from a _centumpondium_ of the lesser weights of ore or metal alloy, the same greater weight of metal is smelted from a _centumpondium_ of the greater weight of ore or metal alloy. END OF BOOK VII. FOOTNOTES: [1] We have but little record of anything which could be called "assaying" among the Greeks and Romans. The fact, however, that they made constant use of the touchstone (see note 37, p. 252) is sufficient proof that they were able to test the purity of gold and silver. The description of the touchstone by Theophrastus contains several references to "trial" by fire (see note 37, p. 252). They were adepts at metal working, and were therefore familiar with melting metals on a small scale, with the smelting of silver, lead, copper, and tin ores (see note 1, p. 353) and with the parting of silver and lead by cupellation. Consequently, it would not require much of an imaginative flight to conclude that there existed some system of tests of ore and metal values by fire. Apart from the statement of Theophrastus referred to, the first references made to anything which might fill the _role_ of assaying are from the Alchemists, particularly Geber (prior to 1300), for they describe methods of solution, precipitation, distillation, fusing in crucibles, cupellation, and of the parting of gold and silver by acid and by sulphur, antimony, or cementation. However, they were not bent on determining quantitative values, which is the fundamental object of the assayer's art, and all their discussion is shrouded in an obscure cloak of gibberish and attempted mysticism. Nevertheless, therein lies the foundation of many cardinal assay methods, and even of chemistry itself. The first explicit records of assaying are the anonymous booklets published in German early in the 16th Century under the title _Probierbuechlein_. Therein the art is disclosed well advanced toward maturity, so far as concerns gold and silver, with some notes on lead and copper. We refer the reader to Appendix B for fuller discussion of these books, but we may repeat here that they are a collection of disconnected recipes lacking in arrangement, the items often repeated, and all apparently the inheritance of wisdom passed from father to son over many generations. It is obviously intended as a sort of reminder to those already skilled in the art, and would be hopeless to a novice. Apart from some notes in Biringuccio (Book III, Chaps. 1 and 2) on assaying gold and silver, there is nothing else prior to _De Re Metallica_. Agricola was familiar with these works and includes their material in this chapter. The very great advance which his account represents can only be appreciated by comparison, but the exhaustive publication of other works is foreign to the purpose of these notes. Agricola introduces system into the arrangement of his materials, describes implements, and gives a hundred details which are wholly omitted from the previous works, all in a manner which would enable a beginner to learn the art. Furthermore, the assaying of lead, copper, tin, quicksilver, iron, and bismuth, is almost wholly new, together with the whole of the argument and explanations. We would call the attention of students of the history of chemistry to the general oversight of these early 16th Century attempts at analytical chemistry, for in them lie the foundations of that science. The statement sometimes made that Agricola was the first assayer, is false if for no other reason than that science does not develop with such strides at any one human hand. He can, however, fairly be accounted as the author of the first proper text-book upon assaying. Those familiar with the art will be astonished at the small progress made since his time, for in his pages appear most of the reagents and most of the critical operations in the dry analyses of gold, silver, lead, copper, tin, bismuth, quicksilver, and iron of to-day. Further, there will be recognised many of the "kinks" of the art used even yet, such as the method of granulation, duplicate assays, the "assay ton" method of weights, the use of test lead, the introduction of charges in leaf lead, and even the use of beer instead of water to damp bone-ash. The following table is given of the substances mentioned requiring some comment, and the terms adopted in this book, with notes for convenience in reference. The German terms are either from Agricola's Glossary of _De Re Metallica_, his _Interpretatio_, or the German Translation. We have retained the original German spelling. The fifth column refers to the page where more ample notes are given:-- Terms Latin. German. Remarks. Further adopted. Notes. Alum _Alumen_ _Alaun_ Either potassium p. 564 or ammonia alum Ampulla _Ampulla_ _Kolb_ A distillation jar Antimony _Stibium_ _Spiesglas_ Practically always p. 428 antimony sulphide _Aqua valens_ _Aqua valens_ _Scheidewasser_ Mostly nitric acid p. 439 or _aqua_ Argol _Feces vini _Die Crude tartar p. 234 siccae_ weinheffen_ Ash of lead _Nigrum Artificial lead p. 237 plumbum sulphide cinereum_ Ash of musk ivy _Sal ex _Salalkali_ Mostly potash p. 560 (Salt made anthyllidis from) cinere factus_ Ashes which _Cineres quo Mostly potash p. 559 wool-dyers use infectores lanarum utuntur_ Assay _Venas experiri_ _Probiren_ Assay furnace _Fornacula_ _Probir ofen_ "Little" furnace Azure _Caeruleum_ _Lasur_ Partly copper p. 110 carbonate (azurite) partly silicate Bismuth _Plumbum _Wismut_ _Bismuth_ p. 433 Cinereum_ Bitumen _Bitumen_ _Bergwachs_ p. 581 Blast furnace _Prima fornax_ _Schmeltzofen_ Borax _Chrysocolla ex _Borras; Tincar_ p. 560 nitro confecta; chrysocolla quam boracem nominant_ Burned alum _Alumen coctum_ _Gesottener Probably p. 565 alaun_ dehydrated alum _Cadmia_ (1) Furnace p. 112 (see note accretions (2) 8, p. 112) Calamine (3) Zinc blende (4) Cobalt arsenical sulphides Camphor _Camphora_ _Campffer_ p. 238 Chrysocolla called borax (see borax) Chrysocolla _Chrysocolla_ _Berggruen und Partly p. 110 (copper Schifergruen_ chrysocolla, mineral) partly malachite Copper filings _Aeris scobs _Kupferfeilich_ Apparently finely p. 233 elimata_ divided copper metal Copper flowers _Aeris flos_ _Kupferbraun_ Cupric oxide p. 538 Copper scales _Aeris squamae_ _Kupfer Probably cupric hammerschlag oxide oder kessel braun_ Copper minerals (see note 8, p. 109) Crucible _Catillus _Dreieckicht- See illustration p. 229 (triangular) triangularis_ schirbe_ Cupel _Catillus _Capelle_ cinereus_ Cupellation _Secunda _Treibherd_ furnace fornax_ Flux _Additamentum_ _Zusetze_ p. 232 Furnace _Cadmia _Mitlere und accretions fornacum_ obere offenbrueche_ Galena _Lapis _Glantz_ Lead sulphide p. 110 plumbarius_ Glass-gall _Recrementum _Glassgallen_ Skimmings from p. 235 vitri_ glass melting Grey antimony or _Stibi_ or _Spiesglas_ Antimony sulphide, p. 428 stibium _stibium_ stibnite Hearth-lead _Molybdaena_ _Herdplei_ The saturated p. 476 furnace bottoms from cupellation Hoop (iron) _Circulus _Ring_ A forge for p. 226 ferreus_ crucibles Iron filings _Ferri scobs _Eisen feilich_ Metallic iron elimata_ Iron scales _Squamae ferri_ _Eisen Partly iron oxide hammerschlag_ Iron slag _Recrementum _Sinder_ ferri_ Lead ash _Cinis plumbi _Pleiasche_ Artificial lead p. 237 nigri_ sulphide Lead granules _Globuli _Gekornt plei_ Granulated lead plumbei_ Lead ochre _Ochra _Pleigeel_ Modern massicot p. 232 plumbaria_ (PbO) Lees of _aqua_ _Feces aquarum _Scheidewasser Uncertain p. 234 which separates quae aurum ab heffe_ gold from argento silver secernunt_ Dried lees of _Siccae feces _Heffe des Argol p. 234 vinegar aceti_ essigs_ Dried lees of _Feces vini _Wein heffen_ Argol p. 234 wine siccae_ Limestone _Saxum calcis_ _Kalchstein_ Litharge _Spuma argenti_ _Glette_ Lye _Lixivium_ _Lauge durch Mostly potash p. 233 asschen gemacht_ Muffle _Tegula_ _Muffel_ Latin, literally "Roof-tile" Operculum _Operculum_ _Helm oder Helmet or cover alembick_ for a distillation jar Orpiment _Auripigmentum_ _Operment_ Yellow sulphide p. 111 of arsenic (As_{2}S_{3}) Pyrites _Pyrites_ _Kis_ Rather a genus p. 112 of sulphides, than iron pyrite in particular Pyrites (Cakes _Panes ex _Stein_ Iron or Copper p. 350 from) pyrite matte conflati_ Realgar _Sandaraca_ _Rosgeel_ Red sulphide of p. 111 arsenic (AsS) Red lead _Minium_ _Menning_ Pb_{3}O_{4} p. 232 Roasted copper _Aes ustum_ _Gebrandt Artificial p. 233 kupffer_ copper sulphide (?) Salt _Sal_ _Saltz_ NaCl p. 233 Salt (Rock) _Sal fossilis_ _Berg saltz_ NaCl p. 233 _Sal _Sal A stock flux? p. 236 artificiosus_ artificiosus_ Sal ammoniac _Sal _Salarmoniac_ NH_{4}Cl p. 560 ammoniacus_ Saltpetre _Halinitrum_ _Salpeter_ KNO_{3} p. 561 Salt (refined) _Sal facticius NaCl purgatus_ _Sal tostus_ _Sal tostus_ _Geroest saltz_ Apparently p. 233 simply heated or melted common salt _Sal _Sal _Geroest saltz_ p. 233 torrefactus_ torrefactus_ Salt (melted) _Sal _Geflossen Melted salt or p. 233 liquefactus_ saltz_ salt glass Scorifier _Catillus _Scherbe_ fictilis_ Schist _Saxum fissile_ _Schifer_ Silver minerals (see note 8, p. 108) Slag _Recrementum_ _Schlacken_ Soda _Nitrum_ Mostly soda from p. 558 Egypt, Na_{2}CO_{3} Stones which _Lapides qui _Flues_ Quartz and p. 380 easily melt facile igni fluorspar liquescunt_ Sulphur _Sulfur_ _Schwefel_ p. 579 _Tophus_ _Tophus_ _Topstein_ Marl(?) p. 233 Touchstone _Coticula_ _Goldstein_ Venetian glass _Venetianum vitrum_ Verdigris _Aerugo _Gruenspan_ Copper p. 440 oder sub-acetate Spanschgruen_ Vitriol _Atramentum _Kupferwasser_ Mostly FeSO_{4} p. 572 sutorium_ White schist _Saxum fissile _Weisser p. 234 album_ schifer_ Weights (see Appendix). [2] _Crudorum_,--unbaked? [3] This reference is not very clear. Apparently the names refer to the German terms _probier ofen_ and _windt ofen_. [4] _Circulus_. This term does not offer a very satisfactory equivalent, as such a furnace has no distinctive name in English. It is obviously a sort of forge for fusing in crucibles. [5] _Spissa_,--"Dry." This term is used in contra-distinction to _pingue_, unctuous or "fatty." [6] _Additamenta_,--"Additions." Hence the play on words. We have adopted "flux" because the old English equivalent for all these materials was "flux," although in modern nomenclature the term is generally restricted to those substances which, by chemical combination in the furnace, lower the melting point of some of the charge. The "additions" of Agricola, therefore, include reducing, oxidizing, sulphurizing, desulphurizing, and collecting agents as well as fluxes. A critical examination of the fluxes mentioned in the next four pages gives point to the Author's assertion that "some are of a very complicated nature." However, anyone of experience with home-taught assayers has come in contact with equally extraordinary combinations. The four orders of "additions" enumerated are quite impossible to reconcile from a modern metallurgical point of view. [7] _Minium secundarium_. (_Interpretatio_,--_menning_. Pb_{3}O_{4}). Agricola derived his Latin term from Pliny. There is great confusion in the ancient writers on the use of the word _minium_, for prior to the Middle Ages it was usually applied to vermilion derived from cinnabar. Vermilion was much adulterated with red-lead, even in Roman times, and finally in later centuries the name came to be appropriated to the lead product. Theophrastus (103) mentions a substitute for vermilion, but, in spite of commentators, there is no evidence that it was red-lead. The first to describe the manufacture of real red-lead was apparently Vitruvius (VII, 12), who calls it _sandaraca_ (this name was usually applied to red arsenical sulphide), and says: "White-lead is heated in a furnace and by the force of the fire becomes red lead. This invention was the result of observation in the case of an accidental fire, and by the process a much better material is obtained than from the mines." He describes _minium_ as the product from cinnabar. Dioscorides (V, 63), after discussing white-lead, says it may be burned until it becomes the colour of _sandaracha_, and is called _sandyx_. He also states (V, 69) that those are deceived who consider cinnabar to be the same as _minium_, for _minium_ is made in Spain out of stone mixed with silver sands. Therefore he is not in agreement with Vitruvius and Pliny on the use of the term. Pliny (XXXIII, 40) says: "These barren stones (apparently lead ores barren of silver) may be recognised by their colour; it is only in the furnace that they turn red. After being roasted it is pulverized and is _minium secundarium_. It is known to few and is very inferior to the natural kind made from those sands we have mentioned (_cinnabar_). It is with this that the genuine _minium_ is adulterated in the works of the Company." This proprietary company who held a monopoly of the Spanish quicksilver mines, "had many methods of adulterating it (_minium_)--a source of great plunder to the Company." Pliny also describes the making of red lead from white. [8] _Ochra plumbaria_. (_Interpretatio_,--_pleigeel_; modern German,--_Bleigelb_). The German term indicates that this "Lead Ochre," a form of PbO, is what in the English trade is known as _massicot_, or _masticot_. This material can be a partial product from almost any cupellation where oxidation takes place below the melting point of the oxide. It may have been known to the Ancients among the various species into which they divided litharge, but there is no valid reason for assigning to it any special one of their terms, so far as we can see. [9] There are four forms of copper named as re-agents by Agricola: Copper filings _Aeris scobs elimata._ Copper scales _Aeris squamae._ Copper flowers _Aeris flos._ Roasted copper _Aes ustum._ The first of these was no doubt finely divided copper metal; the second, third, and fourth were probably all cupric oxide. According to Agricola (_De Nat. Fos._, p. 352), the scales were the result of hammering the metal; the flowers came off the metal when hot bars were quenched in water, and a third kind were obtained from calcining the metal. "Both flowers (_flos_) and hammer-scales (_squama_) have the same properties as _crematum_ copper.... The particles of flower copper are finer than scales or _crematum_ copper." If we assume that the verb _uro_ used in _De Re Metallica_ is of the same import as _cremo_ in the _De Natura Fossilium_, we can accept this material as being merely cupric oxide, but the _aes ustum_ of Pliny--Agricola's usual source of technical nomenclature--is probably an artificial sulphide. Dioscorides (V, 47), who is apparently the source of Pliny's information, says:--"Of _chalcos cecaumenos_, the best is red, and pulverized resembles the colour of cinnabar; if it turns black, it is over-burnt. It is made from broken ship nails put into a rough earthen pot, with alternate layers of equal parts of sulphur and salt. The opening should be smeared with potter's clay and the pot put in the furnace until it is thoroughly heated," etc. Pliny (XXXIV, 23) states: "Moreover Cyprian copper is roasted in crude earthen pots with an equal amount of sulphur; the apertures of the pots are well luted, and they are kept in the furnace until the pot is thoroughly heated. Some add salt, others use _alumen_ instead of sulphur, others add nothing, but only sprinkle it with vinegar." [10] The reader is referred to note 6, p. 558, for more ample discussion of the alkalis. Agricola gives in this chapter four substances of that character: Soda (_nitrum_). Lye. "Ashes which wool-dyers use." "Salt made from the ashes of musk ivy." The last three are certainly potash, probably impure. While the first might be either potash or soda, the fact that the last three are mentioned separately, together with other evidence, convinces us that by the first is intended the _nitrum_ so generally imported into Europe from Egypt during the Middle Ages. This imported salt was certainly the natural bicarbonate, and we have, therefore, used the term "soda." [11] In this chapter are mentioned seven kinds of common salt: Salt _Sal._ Rock salt _Sal fossilis._ "Made" salt _Sal facticius._ Refined salt _Sal purgatius._ Melted salt _Sal liquefactus._ And in addition _sal tostus_ and _sal torrefactus_. _Sal facticius_ is used in distinction from rock-salt. The melted salt would apparently be salt-glass. What form the _sal tostus_ and _sal torrefactus_ could have we cannot say, however, but they were possibly some form of heated salt; they may have been combinations after the order of _sal artificiosus_ (see p. 236). [12] "Stones which easily melt in hot furnaces and sand which is made from them" (_lapides qui in ardentibus fornacibus facile liquescunt arenae ab eis resolutae_). These were probably quartz in this instance, although fluorspar is also included in this same genus. For fuller discussion see note on p. 380. [13] _Tophus_. (_Interpretatio_, _Toffstein oder topstein_). According to Dana (Syst. of Min., p. 678), the German _topfstein_ was English potstone or soapstone, a magnesian silicate. It is scarcely possible, however, that this is what Agricola meant by this term, for such a substance would be highly infusible. Agricola has a good deal to say about this mineral in _De Natura Fossilium_ (p. 189 and 313), and from these descriptions it would seem to be a tufaceous limestone of various sorts, embracing some marls, stalagmites, calcareous sinter, etc. He states: "Generally fire does not melt it, but makes it harder and breaks it into powder. Tophus is said to be a stone found in caverns, made from the dripping of stone juice solidified by cold ... sometimes it is found containing many shells, and likewise the impressions of alder leaves; our people make lime by burning it." Pliny, upon whom Agricola depends largely for his nomenclature, mentions such a substance (XXXVI, 48): "Among the multitude of stones there is _tophus_. It is unsuitable for buildings, because it is perishable and soft. Still, however, there are some places which have no other, as Carthage, in Africa. It is eaten away by the emanations from the sea, crumbled to dust by the wind, and washed away by the rain." In fact, _tophus_ was a wide genus among the older mineralogists, Wallerius (_Meditationes Physico-Chemicae De Origine Mundi_, Stockholm, 1776, p. 186), for instance, gives 22 varieties. For the purposes for which it is used we believe it was always limestone of some form. [14] _Saxum fissile album._ (_The Interpretatio_ gives the German as _schifer_). Agricola mentions it in _Bermannus_ (459), in _De Natura Fossilium_ (p. 319), but nothing definite can be derived from these references. It appears to us from its use to have been either a quartzite or a fissile limestone. [15] Argol (_Feces vini siccae_,--"Dried lees of wine." Germ. trans. gives _die wein heffen_, although the usual German term of the period was _weinstein_). The lees of wine were the crude tartar or argols of commerce and modern assayers. The argols of white wine are white, while they are red from red wine. The white argol which Agricola so often specifies would have no special excellence, unless it may be that it is less easily adulterated. Agricola (_De Nat. Fos._, p. 344) uses the expression "_Fex vini sicca_ called _tartarum_"--one of the earliest appearances of the latter term in this connection. The use of argol is very old, for Dioscorides (1st Century A.D.) not only describes argol, but also its reduction to impure potash. He says (V, 90): "The lees (_tryx_) are to be selected from old Italian wine; if not, from other similar wine. Lees of vinegar are much stronger. They are carefully dried and then burnt. There are some who burn them in a new earthen pot on a large fire until they are thoroughly incinerated. Others place a quantity of the lees on live coals and pursue the same method. The test as to whether it is completely burned, is that it becomes white or blue, and seems to burn the tongue when touched. The method of burning lees of vinegar is the same.... It should be used fresh, as it quickly grows stale; it should be placed in a vessel in a secluded place." Pliny (XXIII, 31) says: "Following these, come the lees of these various liquids. The lees of wine (_vini faecibus_) are so powerful as to be fatal to persons on descending into the vats. The test for this is to let down a lamp, which, if extinguished, indicates the peril.... Their virtues are greatly increased by the action of fire." Matthioli, commenting on this passage from Dioscorides in 1565, makes the following remark (p. 1375): "The precipitate of the wine which settles in the casks of the winery forms stone-like crusts, and is called by the works-people by the name _tartarum_." It will be seen above that these lees were rendered stronger by the action of fire, in which case the tartar was reduced to potassium carbonate. The _weinstein_ of the old German metallurgists was often the material lixiviated from the incinerated tartar. Dried lees of vinegar (_siccae feces aceti_; _Interpretatio_, _die heffe des essigs_). This would also be crude tartar. Pliny (XXIII, 32) says: "The lees of vinegar (_faex aceti_); owing to the more acrid material are more aggravating in their effects.... When combined with _melanthium_ it heals the bites of dogs and crocodiles." [16] Dried lees of _aqua_ which separates gold and silver. (_Siccae feces aquarum quae aurum ab argento secernunt_. German translation, _Der scheidwasser heffe_). There is no pointed description in Agricola's works, or in any other that we can find, as to what this material was. The "separating _aqua_" was undoubtedly nitric acid (see p. 439, Book X). There are two precipitates possible, both referred to as _feces_,--the first, a precipitate of silver chloride from clarifying the _aqua valens_, and the second, the residues left in making the acid by distillation. It is difficult to believe that silver chloride was the _feces_ referred to in the text, because such a precipitate would be obviously misleading when used as a flux through the addition of silver to the assays, too expensive, and of no merit for this purpose. Therefore one is driven to the conclusion that the _feces_ must have been the residues left in the retorts when nitric acid was prepared. It would have been more in keeping with his usual mode of expression, however, to have referred to this material as a _residuus_. The materials used for making acid varied greatly, so there is no telling what such a _feces_ contained. A list of possibilities is given in note 8, p. 443. In the main, the residue would be undigested vitriol, alum, saltpetre, salt, etc., together with potassium, iron, and alum sulphates. The _Probierbuechlin_ (p. 27) also gives this re-agent under the term _Toden kopff das ist schlam oder feces auss dem scheydwasser_. [17] _Recrementum vitri_. (_Interpretatio_, _Glassgallen_). Formerly, when more impure materials were employed than nowadays, the surface of the mass in the first melting of glass materials was covered with salts, mostly potassium and sodium sulphates and chlorides which escaped perfect vitrification. This "slag" or "_glassgallen_" of Agricola was also termed _sandiver_. [18] The whole of this expression is "_candidus, candido_." It is by no means certain that this is tin, for usually tin is given as _plumbum candidum_. [19] _Sal artificiosus_. These are a sort of stock fluxes. Such mixtures are common in all old assay books, from the _Probierbuechlin_ to later than John Cramer in 1737 (whose Latin lectures on Assaying were published in English under the title of "Elements of the Art of Assaying Metals," London, 1741). Cramer observes (p. 51) that: "Artificers compose a great many fluxes with the above-mentioned salts and with the reductive ones; nay, some use as many different fluxes as there are different ores and metals; all which, however, we think needless to describe. It is better to have explained a few of the simpler ones, which serve for all the others, and are very easily prepared, than to tire the reader with confused compositions: and this chiefly because unskilled artificers sometimes attempt to obtain with many ingredients of the same nature heaped up beyond measure, and with much labour, though not more properly and more securely, what might have been easily effected, with one only and the same ingredient, thus increasing the number, not at all the virtue of the things employed. Nevertheless, if anyone loves variety, he may, according to the proportions and cautions above prescribed, at his will chuse among the simpler kinds such as will best suit his purpose, and compose a variety of fluxes with them." [20] This operation apparently results in a coating to prevent the deflagration of the saltpetre--in fact, it might be permitted to translate _inflammatur_ "deflagrate," instead of kindle. [21] The results which would follow from the use of these "fluxes" would obviously depend upon the ore treated. They can all conceivably be successful. Of these, the first is the lead-glass of the German assayers--a flux much emphasized by all old authorities, including Lohneys, Ercker and Cramner, and used even yet. The "powerful flux" would be a reducing, desulphurizing, and an acid flux. The "more powerful" would be a basic flux in which the reducing action of the argols would be largely neutralised by the nitre. The "still more powerful" would be a strongly sulphurizing basic flux, while the "most powerful" would be a still more sulphurizing flux, but it is badly mixed as to its oxidation and basic properties. (See also note 19 on _sal artificiosus_). [22] Lead ash (_Cinis Plumbi_. Glossary, _Pleyasch_).--This was obviously, from the method of making, an artificial lead sulphide. [23] Ashes of lead (_Nigri plumbi cinis_). This, as well as lead ash, was also an artificial lead sulphide. Such substances were highly valued by the Ancients for medicinal purposes. Dioscorides (V, 56) says: "Burned lead (_Molybdos cecaumenos_) is made in this way: Sprinkle sulphur over some very thinnest lead plates and put them into a new earthen pot, add other layers, putting sulphur between each layer until the pot is full; set it alight and stir the melted lead with an iron rod until it is entirely reduced to ashes and until none of the lead remains unburned. Then take it off, first stopping up your nose, because the fumes of burnt lead are very injurious. Or burn the lead filings in a pot with sulphur as aforesaid." Pliny (XXXIV., 50) gives much the same directions. [24] Camphor (_camphora_). This was no doubt the well-known gum. Agricola, however, believed that camphor (_De Nat. Fossilium_, p. 224) was a species of bitumen, and he devotes considerable trouble to the refutation of the statements by the Arabic authors that it was a gum. In any event, it would be a useful reducing agent. [25] Inasmuch as orpiment and realgar are both arsenical sulphides, the use of iron "slag," if it contains enough iron, would certainly matte the sulphur and arsenic. Sulphur and arsenic are the "juices" referred to (see note 4, p. 1). It is difficult to see the object of preserving the antimony with such a sulphurizing "addition," unless it was desired to secure a regulus of antimony alone from a given antimonial ore. [26] The lead free from silver, called _villacense_, was probably from Bleyberg, not far from Villach in Upper Austria, this locality having been for centuries celebrated for its pure lead. These mines were worked prior to, and long after, Agricola's time. [27] This method of proportionate weights for assay charges is simpler than the modern English "assay ton," both because of the use of 100 units in the standard of weight (the _centumpondium_), and because of the lack of complication between the Avoirdupois and Troy scales. For instance, an ore containing a _libra_ of silver to the _centumpondium_ would contain 1/100th part, and the same ratio would obtain, no matter what the actual weight of a _centumpondium_ of the "lesser weight" might be. To follow the matter still further, an _uncia_ being 1/1,200 of a _centumpondium_, if the ore ran one "_uncia_ of the lesser weight" to the "_centumpondium_ of the lesser weight," it would also run one actual _uncia_ to the actual _centumpondium_; it being a matter of indifference what might be the actual weight of the _centumpondium_ upon which the scale of lesser weights is based. In fact Agricola's statement (p. 261) indicates that it weighed an actual _drachma_. We have, in some places, interpolated the expressions "lesser" and "greater" weights for clarity. This is not the first mention of this scheme of lesser weights, as it appears in the _Probierbuechlein_ (1500? see Appendix B) and Biringuccio (1540). For a more complete discussion of weights and measures see Appendix C. For convenience, we repeat here the Roman scale, although, as will be seen in the Appendix, Agricola used the Latin terms in many places merely as nomenclature equivalents of the old German scale. Ozs. dwts. Troy gr. Grains. per short ton. 1 _Siliqua_ 2.87 Per _Centumpondium_ 0 3 9 6 _Siliquae_ = 1 _Scripulum_ 17.2 " " 1 0 6 4 _Scripula_ = 1 _Sextula_ 68.7 " " 4 1 0 6 _Sextulae_ = 1 _Uncia_ 412.2 " " 24 6 2 12 _Unciae_ = 1 _Libra_ 4946.4 " " 291 13 8 100 _Librae_ = 1 _Centumpondium_ 494640.0 However Agricola may occasionally use 16 _Unciae_ = 1 _Libra_ 6592.0 (?) 100 _Librae_ = 1 _Centumpondium_ 659200.0 (?) Also Oz. dwts. gr. per short ton. 1 _Scripulum_ 17.2 Per _Centumpondium_ 1 0 6 3 _Scripula_ = 1 _Drachma_ 51.5 " " 3 0 19 2 _Drachmae_ = 1 _Sicilicus_ 103.0 " " 6 1 15 4 _Sicilici_ = 1 _Uncia_ 412.2 " " 24 6 12 8 _Unciae_ = 1 _Bes_ 3297.6 " " 194 12 0 [28] The amalgamation of gold ores is fully discussed in note 12, p. 297. [29] For discussion of the silver ores, see note 8, p. 108. _Rudis_ silver was a fairly pure silver mineral, the various coloured silvers were partly horn-silver and partly alteration products. [30] It is difficult to see why copper scales (_squamae aeris_--copper oxide?) are added, unless it be to collect a small ratio of copper in the ore. This additional copper is not mentioned again, however. The whole of this statement is very confused. [31] This old story runs that Hiero, King of Syracuse, asked Archimedes to tell him whether a crown made for him was pure gold or whether it contained some proportion of silver. Archimedes is said to have puzzled over it until he noticed the increase in water-level upon entering his bath. Whereupon he determined the matter by immersing bars of pure gold and pure silver, and thus determining the relative specific weights. The best ancient account of this affair is to be found in Vitruvius, IX, Preface. The story does not seem very probable, seeing that Theophrastus, who died the year Archimedes was born, described the touchstone in detail, and that it was of common knowledge among the Greeks before (see note 37). In any event, there is not sufficient evidence in this story on which to build the conclusion of Meyer (Hist. of Chemistry, p. 14) and others, that, inasmuch as Archimedes was unable to solve the problem until his discovery of specific weights, therefore the Ancients could not part gold and silver. The probability that he did not want to injure the King's jewellery would show sufficient reason for his not parting these metals. It seems probable that the Ancients did part gold and silver by cementation. (See note on p. 458). [32] The Alchemists (with whose works Agricola was familiar--_vide_ preface) were the inventors of nitric acid separation. (See note on p. 460). [33] Parting gold and silver by nitric acid is more exhaustively discussed in Book X. and note 10, p. 443. [34] The lesser weights, probably. [35] Lead and Tin seem badly mixed in this paragraph. [36] It is not clear what is added. [37] HISTORICAL NOTE ON TOUCHSTONE. (_Coticula_. _Interpretatio_,--_Goldstein_). Theophrastus is, we believe, the first to describe the touchstone, although it was generally known to the Greeks, as is evidenced by the metaphors of many of the poets,--Pindar, Theognis, Euripides, etc. The general knowledge of the constituents of alloys which is implied, raises the question as to whether the Greeks did not know a great deal more about parting metals, than has been attributed to them. Theophrastus says (78-80): "The nature of the stone which tries gold is also very wonderful, as it seems to have the same power with fire; which is also a test of that metal. Some people have for this reason questioned the truth of this power in the stone, but their doubts are ill-founded, for this trial is not of the same nature or made in the same manner as the other. The trial by fire is by the colour and by the quantity lost by it; but that by the stone is made only by rubbing the metal on it; the stone seeming to have the power to receive separately the distinct particles of different metals. It is said also that there is a much better kind of this stone now found out, than that which was formerly used; insomuch that it now serves not only for the trial of refined gold, but also of copper or silver coloured with gold; and shows how much of the adulterating matter by weight is mixed with gold; this has signs which it yields from the smallest weight of the adulterating matter, which is a grain, from thence a colybus, and thence a quadrans or semi-obolus, by which it is easy to distinguish if, and in what degree, that metal is adulterated. All these stones are found in the River Tmolus; their texture is smooth and like that of pebbles; their figure broad, not round; and their bigness twice that of the common larger sort of pebbles. In their use in the trial of metals there is a difference in power between their upper surface, which has lain toward the sun, and their under, which has been to the earth; the upper performing its office the more nicely; and this is consonant to reason, as the upper part is dryer; for the humidity of the other surface hinders its receiving so well the particles of metals; for the same reason also it does not perform its office as well in hot weather as in colder, for in the hot it emits a kind of humidity out of its substance, which runs all over it. This hinders the metalline particles from adhering perfectly, and makes mistakes in the trials. This exudation of a humid matter is also common to many other stones, among others, to those of which statues are made; and this has been looked on as peculiar to the statue." (Based on Hill's trans.) This humid "exudation of fine-grained stones in summer" would not sound abnormal if it were called condensation. Pliny (XXXIII, 43) says: "The mention of gold and silver should be accompanied by that of the stone called _coticula_. Formerly, according to Theophrastus, it was only to be found in the river Tmolus but now found in many parts, it was found in small pieces never over four inches long by two broad. That side which lay toward the sun is better than that toward the ground. Those experienced with the _coticula_ when they rub ore (_vena_) with it, can at once say how much gold it contains, how much silver or copper. This method is so accurate that they do not mistake it to a scruple." This purported use for determining values of _ore_ is of about Pliny's average accuracy. The first detailed account of touch-needles and their manner of making, which we have been able to find, is that of the _Probierbuechlein_ (1527? see Appendix) where many of the tables given by Agricola may be found. [38] _De Natura Fossilium_ (p. 267) and _De Ortu et Causis Subterraneorum_ (p. 59). The author does not add any material mineralogical information to the quotations from Theophrastus and Pliny given above. [39] In these tables Agricola has simply adopted Roman names as equivalents of the old German weights, but as they did not always approximate in proportions, he coined terms such as "units of 4 _siliquae_," etc. It might seem more desirable to have introduced the German terms into this text, but while it would apply in this instance, as we have discussed on p. 259, the actual values of the Roman weights are very different from the German, and as elsewhere in the book actual Roman weights are applied, we have considered it better to use the Latin terms consistently throughout. Further, the obsolete German would be to most readers but little improvement upon the Latin. For convenience of readers we set out the various scales as used by Agricola, together with the German:-- ROMAN SCALE. OLD GERMAN SCALE. 6 _Siliquae_ = 1 _Scripulum_ 3 _Grenlin_ = 1 _Gran_ 4 _Scripula_ = 1 _Sextula_ 4 _Gran_ = 1 _Krat_ 2 _Sextulae_ = 1 _Duella_ 24 _Kratt_ = 1 _Mark_ 24 _Duellae_ = 1 _Bes_ or 24 _Grenlin_ = 1 "_Nummus_" 12 "_Nummi_" = 1 _Mark_ Also the following scales are applied to fineness by Agricola:-- 3 _Scripula_ = 1 _Drachma_ 4 _Pfennige_ = 1 _Quintlein_ 2 _Drachmae_ = 1 _Sicilicus_ 4 _Quintlein_ = 1 _Loth_ 2 _Sicilici_ = 1 _Semuncia_ 16 _Loth_ = 1 _Mark_ 16 _Semunciae_ = 1 _Bes_ The term "_nummus_," a coin, given above and in the text, appears in the German translation as _pfennig_ as applied to both German scales, but as they are of different values, we have left Agricola's adaptation in one scale to avoid confusion. The Latin terms adopted by Agricola are given below, together with the German:-- Number in one Value in Roman Term. German Term. Mark or Bes. _Siliquae_. _Siliqua_ 1152 1 "Unit of 4 _Siliquae_" _Grenlin_ 288 4 _Pfennig_ 256 -- _Scripulum_ _Scruple_ (?) 192 6 _Semi-sextula_ _Gran_ 96 12 _Drachma_ _Quintlein_ 64 18 _Sextula_ _Halb Krat_ 48 24 _Sicilicus_ _Halb Loth_ 32 36 _Duella_ _Krat_ 24 48 _Semuncia_ _Loth_ 16 72 "_Unit of 5 Drachmae "_Nummus_" 12 96 & 1 Scripulum_" _Uncia_ _Untzen_ 8 144 _Bes_ _Mark_ 1 1152 While the proportions in a _bes_ or _mark_ are the same in both scales, the actual weight values are vastly different--for instance, the _mark_ contained about 3609.6, and the _bes_ 3297 Troy Grains. Agricola also uses: _Selibra_ _Halb-pfundt_ _Libra_ _Pfundt_ _Centumpondium_ _Centner_. As the Roman _libra_ contains 12 _unciae_ and the German _pfundt_ 16 _untzen_, the actual weights of these latter quantities are still further apart--the former 4946 and the latter 7219 Troy grains. [40] There are no tables in the Latin text, the whole having been written out _in extenso_, but they have now been arranged as above, as being in a much more convenient and expressive form. [41] See note 39 above. [42] See note 27, p. 242, for discussion of this "Assay ton" arrangement. [43] _Agrippinenses_ and _Antuerpiani_.