BOOK IX.

401

Because lead and copper ores and their metals have much in commonwith silver ores, it is fitting that I should say a great deal concerning them,both now and later on. Also in the same manner, pyrites are smelted separ-ately if there be much of them. To three parts of roasted lead or copperore and one part of crude ore, are added concentrates if they were made bywashing the same ore, together with slags, and all are put in the third furnacewhose tap-hole is always open. Cakes are made from this charge, which,when they have been quenched with water, are roasted. Of these roastedcakes generally four parts are again mixed with one part of crude pyritesand re-melted in the same furnace. Cakes are again made from this charge,and if there is a large amount of copper in these cakes, copper is madeimmediately after they have been roasted and re-melted ; if there is littlecopper in the cakes they are also roasted, but they are re-smelted with a littlesoft slag. In this method the molten lead in the forehearth absorbs thesilver. From the pyritic material which floats on the top of the forehearthare made cakes for the third time, and from them when they have beenroasted and re-smelted is made copper. Similarly, three parts of roastedcadmia 38 in which there is silver, are mixed with one part of crude pyrites,together with slag, and this charge is smelted and cakes are made from it ;these cakes having been roasted are re-smelted in the same furnace. By thismethod the lead contained in the forehearth absorbs the silver, and the silver-lead is taken to the cupellation furnace. Crude quartz and stones whicheasily fuse in fire of the third order, together with other ores in which thereis a small amount of silver, ought to be mixed with crude roasted pyrites orcadmia, because the roasted cakes of pyrites or cadmia cannot beprofitably smelted separately. In a similar manner earths which containlittle silver are mixed with the same; but if pyrites and cadmia are notavailable to the smelter, he smelts such silver ores and earths with litharge,hearth-lead, slags, and stones which easily melt in the fire. The concentrates 39originating from the washing of rudis silver, after first being roasted 40 untilthey melt, are smelted with mixed litharge and hearth-lead, or else, afterbeing moistened with water, they are smelted with cakes made from pyritesand cadmia. By neither of these methods do (the concentrates) fallback in the furnace, or fly out of it, driven by the blast of the bellows and theagitation of the fire. If the concentrates originated from galena they aresmelted with it after having been roasted ; and if from pyrites, then withPyrites.

Pure copper ore, whether it is its own colour or is tinged with chrysocollaor azure, and copper glance, or grey or black rudis copper, is smelted in afurnace of which the tap-hole is closed for a very short time, or else is always

* 8 The term cadmia is used in this paragraph without the usual definition. Whetherit was cadmia fornacis (furnace accretions) or cadmia metallica (cobalt-arsenic-blende mixture)is uncertain. We believe it to be the former.

^Ramentum si loiura ex argento rudi. This expression is generally used by the authorto indicate concentrates, but it is possible that in this sentence it means the tailings afterwashing rich silver minerals, because the treatment of the rudis silver has been alreadydiscussed above.

i 0 Ustum. This might be rendered “burnt.” In any event, it seems that the materialis sintered.