The foreman of the works, according to the different proportions of silver in each centumpondium of copper, alloys it with lead, without which he could not separate the silver from the copper.[10] If there be a moderate amount of silver in the copper, he alloys it fourfold; for instance, if in three-quarters of a centumpondium of copper there is less than the following proportions, i.e.: half a libra of silver, or half a libra and a sicilicus, or half a libra and a semi-uncia, or half a libra and semi-uncia and a sicilicus, then rich lead—that is, that from which the silver has not yet been separated—is added, to the amount of half a centumpondium or a whole centumpondium, or a whole and a half, in such a way that there may be in the copper-lead alloy some one of the proportions of silver which I have just mentioned, which is the first alloy. To this "first" alloy is added such a weight of de-silverized lead or litharge as is required to make out of all of these a single liquation cake that will contain approximately two centumpondia of lead; but as usually from one hundred and thirty librae of litharge only one hundred librae of lead are made, a greater proportion of litharge than of de-silverized lead is added as a supplement. Since four cakes of this kind are placed at the same time into the furnace in which the silver and lead is liquated from copper, there will be in all the cakes three centumpondia of copper and eight centumpondia of lead. When the lead has been liquated from the copper, it weighs six centumpondia, in each centumpondium of which there is a quarter of a libra and almost a sicilicus of silver. Only seven unciae of the silver remain in the exhausted liquation cakes and in that copper-lead alloy which we call "liquation thorns"; they are not called by this name so much because they have sharp points as because they are base. If in three-quarters of a centumpondium of copper there are less than seven uncia and a semi-uncia or a bes of silver, then so much rich lead must be added as to make in the copper and lead alloy one of the proportions of silver which I have already mentioned. This is the "second" alloy. To this is again to be added as great a weight of de-silverized lead, or of litharge, as will make it possible to obtain from that alloy a liquation cake containing two and a quarter centumpondia of lead, in which manner in four of these cakes there will be three centumpondia of copper and nine centumpondia of lead. The lead which liquates from these cakes weighs seven centumpondia, in each centumpondium of which there is a quarter of a libra of silver and a little more than a sicilicus. About seven unciae of silver remain in the exhausted liquation cakes and in the liquation thorns, if we may be allowed to make common the old name (spinae = thorns) and bestow it upon a new substance. If in three-quarters of a centumpondium of copper there is less than three-quarters of a libra of silver, or three-quarters and a semi-uncia, then as much rich lead must be added as will produce one of the proportions of silver in the copper-lead alloy above mentioned; this is the "third" alloy. To this is added such an amount of de-silverized lead or of litharge, that a liquation cake made from it contains in all two and three-quarters centumpondia of lead. In this manner four such cakes will contain three centumpondia of copper and eleven centumpondia of lead. The lead which these cakes liquate, when they are melted in the furnace, weighs about nine centumpondia, in each centumpondium of which there is a quarter of a libra and more than a sicilicus of silver; and seven unciae of silver remain in the exhausted liquation cakes and in the liquation thorns. If, however, in three-quarters of a centumpondium of copper there is less than ten-twelfths of a libra or ten-twelfths of a libra and a semi-uncia of silver, then such a proportion of rich lead is added as will produce in the copper-lead alloy one of the proportions of silver which I mentioned above; this is the "fourth" alloy. To this is added such a weight of de-silverized lead or of litharge, that a liquation cake made from it contains three centumpondia of lead, and in four cakes of this kind there are three centumpondia of copper and twelve centumpondia of lead. The lead which is liquated therefrom weighs about ten centumpondia, in each centumpondium of which there is a quarter of a libra and more than a semi-uncia of silver, or seven unciae; a bes, or seven unciae and a semi-uncia, of silver remain in the exhausted liquation cakes and in the liquation thorns.
The smelter, when he alloys copper with lead, with his hand throws into the heated furnace, first the large fragments of copper, then a basketful of charcoal, then the smaller fragments of copper. When the copper is melted and begins to run out of the tap-hole into the forehearth, he throws litharge into the furnace, and, lest part of it should fly away, he first throws charcoal over it, and lastly lead. As soon as he has thrown into the furnace the copper and the lead, from which alloy the first liquation cake is made, he again throws in a basket of charcoal, and then fragments of copper are thrown over them, from which the second cake may be made. Afterward with a rabble he skims the "slag" from the copper and lead as they flow into the forehearth. Such a rabble is a board into which an iron bar is fixed; the board is made of elder-wood or willow, and is ten digits long, six wide, and one and a half digits thick; the iron bar is three feet long, and the wooden handle inserted into it is two and a half feet long. While he purges the alloy and pours it out with a ladle into the copper mould, the fragments of copper from which he is to make the second cake are melting. As soon as this begins to run down he again throws in litharge, and when he has put on more charcoal he adds the lead. This operation he repeats until thirty liquation cakes have been made, on which work he expends nine hours, or at most ten; if more than thirty cakes must be made, then he is paid for another shift when he has made an extra thirty.
At the same time that he pours the copper-lead alloy into the copper mould, he also pours water slowly into the top of the mould. Then, with a cleft stick, he takes a hook and puts its straight stem into the molten cake. The hook itself is a digit and a half thick; its straight stem is two palms long and two digits wide and thick. Afterward he pours more water over the cakes. When they are cold he places an iron ring in the hook of the chain let down from the pulley of the crane arm; the inside diameter of this ring is six digits, and it is about a digit and a half thick; the ring is then engaged in the hook whose straight stem is in the cake, and thus the cake is raised from the mould and put into its place.
The copper and lead, when thus melted, yield a small amount of "slag"[12] and much litharge. The litharge does not cohere, but falls to pieces like the residues from malt from which beer is made. Pompholyx adheres to the walls in white ashes, and to the sides of the furnace adheres spodos.
In this practical manner lead is alloyed with copper in which there is but a moderate portion of silver. If, however, there is much silver in it, as, for instance, two librae, or two librae and a bes, to the centumpondium,—which weighs one hundred and thirty-three and a third librae, or one hundred and forty-six librae and a bes,[13]—then the foreman of the works adds to a centumpondium of such copper three centumpondia of lead, in each centumpondium of which there is a third of a libra of silver, or a third of a libra and a semi-uncia. In this manner three liquation cakes are made, which contain altogether three centumpondia of copper and nine centumpondia of lead.[14] The lead, when it has been liquated from the copper, weighs seven centumpondia; and in each centumpondium—if the centumpondium of copper contain two librae of silver, and the lead contain a third of a libra—there will be a libra and a sixth and more than a semi-uncia of silver; while in the exhausted liquation cakes, and in the liquation thorns, there remains a third of a libra. If a centumpondium of copper contains two librae and a bes of silver, and the lead a third of a libra and a semi-uncia, there will be in each liquation cake one and a half librae and a semi-uncia, and a little more than a sicilicus of silver. In the exhausted liquation cakes there remain a third of a libra and a semi-uncia of silver.
