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BOOK IX.

of the alloy there is a bes or three-quarters of silver. In this way every week,if the work is for six days, thirty-six centumpondia of cakes are made andthree centumpondia of alloy, in all of which there is often almost twenty-fourlibrae of silver. The second smelter separates from the primary cakes thegreater part of the silver by absorbing it in lead. To eighteen centumpondiaof cakes made from crude copper ore, he adds twelve centumpondia of hearth-lead and litharge, three centumpondia of stones from which lead is smelted,five centumpondia of hard cakes rich in silver, and two centumpondia ofexhausted liquation cakes 45 ; he adds besides, some of the slags resultingfrom smelting crude copper, together with a small quantity of concentratesmade from accretions, all of which he melts for the space of twelve hours,and makes eighteen centumpondia of secondary cakes, and twelve centum-pondia of copper-lead-silver alloy; in each centumpondium of the latterthere is half a libra of silver. After he has taken off the cakes with ahooked bar, he pours the alloy out into copper or iron moulds ; by thismethod they make four cakes of alloy, which are carried to the works inwhich silver is parted from copper. On the following day, the same smelter,taking eighteen centumpondia of the secondary cakes, again adds twelvecentumpondia of hearth-lead and litharge, three centumpondia of stonesfrom which lead is smelted, five centumpondia of hard cakes rich in silver,together with slags from the smelting of the primary cakes, and with concen-trates washed from the accretions which are usually made at that time.This charge is likewise smelted for the space of twelve hours, and he makes asmany as thirteen centumpondia of tertiary cakes and eleven centumpondiaof copper-lead-silver alloy, each centumpondium of which contains one-third of a libra and half an uncia of silver. When he has skim m ed off thetertiary cakes with a hooked bar, the alloy is poured into copper moulds, andby this method four cakes of alloy are made, which, like the preceding fourcakes of alloy, are carried to the works in which silver is parted from copper.By this method the second smelter makes primary cakes on alternate daysand secondary cakes on the intermediate days. The third smelter takeseleven cartloads of the tertiary cakes and adds to them three cartloads ofhard cakes poor in silver, together with the slag from smelting the secondarycakes, and the concentrates from the accretions which are usually madeat that time. From this charge when smelted, he makes twenty centum-pondia of quaternary cakes, which are called “ hard cakes,” and alsofifteen centumpondia of those “ hard cakes rich in silver,” each centum-pondium of which contains a third of a libra of silver. These latter cakes thesecond smelter, as I said before, adds to the primary and secondary cakeswhen he re-melts them. In the same way, from eleven cartloads of qua-ternary cakes thrice roasted, he makes the “ final ” cakes, of which onecentumpondium contains only half an uncia of silver. In thk operation healso makes fifteen centumpondia of “ hard cakes poor in silver,” in eachcentumpondium of which is a sixth of a libra of silver. These hard cakes the

46 Exhausted liquation cakes (panes aerei fathiscentes). This is the copper sponge resultingfrom the first liquation of lead, and still contains a considerable amount of lead. The liquationprocess is discussed in great detail in Book XI.