De Re Metallica, Translated from the First Latin Edition of 1556

by Georg Agricola

The copper "bottoms" are alloyed in three different ways with lead.[17] First, five-eighths of a centumpondium of copper and two and three-quarters centumpondia of lead are taken; and since one liquation cake is made from this, therefore two and a half centumpondia of copper and eleven centumpondia of lead make four liquation cakes. Inasmuch as in each centumpondium of copper there is a third of a libra of silver, there would be in the whole of the copper ten-twelfths of a libra of silver; to these are added four centumpondia of lead re-melted from "slags," each centumpondium of which contains a sicilicus and a drachma of silver, which weights make up a total of an uncia and a half of silver. There is also added seven centumpondia of de-silverized lead, in each centumpondium of which there is a drachma of silver; therefore in the four cakes of copper-lead alloy there is a total of a libra, a sicilicus and a drachma of silver. In each single centumpondium of lead, after it has been liquated from the copper, there is an uncia and a drachma of silver, which alloy we call "poor" argentiferous lead, because it contains but little silver. But as five cakes of that kind are placed together in the furnace, they liquate from them usually as much as nine and three-quarters centumpondia of poor argentiferous lead, in each centumpondium of which there is an uncia and a drachma of silver, or a total of ten unciae less four drachmae. Of the liquation thorns there remain three centumpondia, in each centumpondium of which there are three sicilici of silver; and there remain four centumpondia of exhausted liquation cakes, each centumpondium of which contains a semi-uncia or four and a half drachmae. Inasmuch as in a centumpondium of copper "bottoms" there is a third of a libra and a semi-uncia of silver, in five of those cakes there must be more than one and a half unciae and half a drachma of silver.

Then, again, from another two and a half centumpondia of copper "bottoms," together with eleven centumpondia of lead, four liquation cakes are made. If in each centumpondium of copper there was a third of a libra of silver, there would be in the whole of the centumpondia of base metal five-sixths of a libra of the precious metal. To this copper is added eight centumpondia of poor argentiferous lead, each centumpondium of which contains an uncia and a drachma of silver, or a total of three-quarters of a libra of silver. There is also added three centumpondia of de-silverized lead, in each centumpondium of which there is a drachma of silver. Therefore, four liquation cakes contain a total of a libra, seven unciae, a sicilicus and a drachma of silver; thus each centumpondium of lead, when it has been liquated from the copper, contains an uncia and a half and a sicilicus of silver, which alloy we call "medium" silver-lead.

Then, again, from another two and a half centumpondia of copper "bottoms," together with eleven centumpondia of lead, they make four liquation cakes. If in each centumpondium of copper there were likewise a third of a libra of silver, there will be in all the weight of the base metal five-sixths of a libra of the precious metal. To this is added nine centumpondia of medium silver-lead, each centumpondium of which contains an uncia and a half and a sicilicus of silver; or a total of a libra and a quarter and a semi-uncia and a sicilicus of silver. And likewise they add two centumpondia of poor silver-lead, in each of which there is an uncia and a drachma of silver. Therefore the four liquation cakes contain two and a third librae of silver. Each centumpondium of lead, when it has been liquated from the copper, contains a sixth of a libra and a semi-uncia and a drachma of silver. This alloy we call "rich" silver-lead; it is carried to the cupellation furnace, in which lead is separated from silver. I have now mentioned in how many ways copper containing various proportions of silver is alloyed with lead, and how they are melted together in the furnace and run into the casting pan.

From the vicinity of the furnaces in which copper is mixed with lead and the "slags" are re-melted, to the third long wall, are likewise ten furnaces, in which silver mixed with lead is separated from copper. If this space is eighty feet and two palms long, and the third long wall has in the centre a door three feet and two palms wide, then the spaces remaining at either side of the door will be thirty-eight feet and two palms; and if each of the furnaces occupies four feet and a palm, then the interval between each furnace and the next one must be a foot and three palms; thus the width of the five furnaces and four interspaces will be twenty-eight feet and a palm. Therefore, there remain ten feet and a palm, which measurement is so divided that there are five feet and two digits between the first furnace and the transverse wall, and as many feet and digits between the fifth furnace and the door; similarly in the other part of the space from the door to the sixth furnace, there must be five feet and two digits, and from the tenth furnace to the seventh transverse wall, likewise, five feet and two digits. The door is six feet and two palms high; through it the foreman of the officina and the workmen enter the store-room in which the silver-lead alloy is kept.

The passage under the plates between the rectangular stones is a foot wide at the back, and a foot and a palm wide at the front, for it gradually widens out. The hearth, which is between the sole-stones, is covered with a bed of hearth-lead, taken from the crucible in which lead is separated from silver. The rear end is the highest, and should be so high that it reaches to within six digits of the plates, from which point it slopes down evenly to the front end, so that the argentiferous lead alloy which liquates from the cakes can flow into the receiving-pit. The wall built against the third long wall in order to protect it from injury by fire, is constructed of bricks joined together with lute, and stands on the copper plates; this wall is two feet, a palm and two digits high, two palms thick, and three feet, a palm and three digits wide at the bottom, for it reaches across both of them; at the top it is three feet wide, for it rises up obliquely on each side. At each side of this wall, at a height of a palm and two digits above the top of it, there is inserted in a hole in the third long wall a hooked iron rod, fastened in with molten lead; the rod projects two palms from the wall, and is two digits wide and one digit thick; it has two hooks, the one at the side, the other at the end. Both of these hooks open toward the wall, and both are a digit thick, and both are inserted in the last, or the adjacent, links of a short iron chain. This chain consists of four links, each of which is a palm and a digit long and half a digit thick; the first link is engaged in the first hole in a long iron rod, and one or other of the remaining three links engages the hook of the hooked rod. The two long rods are three feet and as many palms and digits long, two digits wide, and one digit thick; both ends of both of these rods have holes, the back one of which is round and a digit in diameter, and in this is engaged the first link of the chain as I have stated; the hole at the front end is two digits and a half long and a digit and a half wide. This end of each rod is made three digits wide, while for the rest of its length it is only two digits, and at the back it is two and a half digits. Into the front hole of each rod is driven an iron bar, which is three feet and two palms long, two digits wide and one thick; in the end of this bar are five small square holes, two-thirds of a digit square; each hole is distant from the other half a digit, the first being at a distance of about a digit from the end. Into one of these holes the refiner drives an iron pin; if he should desire to make the furnace narrower, then he drives it into the last hole; if he should desire to widen it, then into the first hole; if he should desire to contract it moderately, then into one of the middle holes. For the same reason, therefore, the hook is sometimes inserted into the last link of the chain, and sometimes into the third or the second. The furnace is widened when many cakes are put into it, and contracted when there are but few, but to put in more than five is neither usual nor possible; indeed, it is because of thin cakes that the walls are contracted. The bar has a hump, which projects a digit on each side at the back, of the same width and thickness as itself. These humps project, lest the bar should slip through the hole of the right-hand rod, in which it remains fixed when it, together with the rods, is not pressing upon the furnace walls.