386 BOOK IX. 



however, for the tap-hole of the first of this kind is deeper in the furnace and 

 narrower than that of the third, and besides it is invisible and concealed. 

 It easily discharges into the forehearth, which is one and a half feet higher 

 than the floor of the building, in order that below it to the left a dipping-pot 

 can be made. When the forehearth is nearly full of the slags, which well up 

 from the invisible tap-hole of the furnace, they are skimmed off from the top 

 with a hooked bar ; then the alloy of gold or silver with lead and the melted 

 pyrites, being uncovered, flow into the dipping-pot, and the latter are made into 

 cakes ; these cakes are broken and thrown back into the furnace so that all 

 their metal may be smelted out. The alloy is poured into little iron moulds. 



The smelter, besides lead and cognate things, uses fluxes which combine 

 with the ore, of which I gave a sufficient account in Book VII. The metals 

 which are melted from ores that fuse readily in the fire, are profitable because 

 they are smelted in a short time, while those which are difficult to fuse are 

 not as profitable, because they take a long time. When fluxes remain in the 

 furnace and do not melt, they are not suitable ; for this reason, accretions and 

 slags are the most convenient for smelting, because they melt quickly. It is 

 necessary to have an industrious and experienced smelter, who in the first 

 place takes care not to put into the furnace more ores mixed with fluxes than 

 it can accommodate. 



The powder out of which this furnace hearth and the adjoining fore- 

 hearth and the dipping-pot are usually made, consists mostly of equal pro- 

 portions of charcoal dust and of earth, or of equal parts of the same and of 

 ashes. When the hearth of the furnace is prepared, a rod that will reach to the 

 forehearth is put into it, higher up if the ore to be smelted readily fuses, and 

 lower down if it fuses with difficulty. When the dipping-pot and forehearth 

 are finished, the rod is drawn out of the furnace so that the tap-hole is open, 

 and through it the molten material flows continuously into the forehearth, 

 which should be very near the furnace in order that it may keep very hot and 

 the alloy thus be made purer. If the ore to be smelted does not melt easily, the 

 hearth of the furnace must not be made too sloping, lest the molten fluxes 

 should run down into the forehearth before the ore is smelted, and the metal 

 thus remain in the accretions on the sides of the furnace. The smelter must 

 not ram the hearth so much that it becomes too hard, nor make the mistake 

 of ramming the lower part of the mouth to make it hard, for it could not 

 breathe 17 , nor could the molten matter flow freely out of the furnace. 

 The ore which does not readily melt is thrown as much as possible to the 

 back of the furnace, and toward that part where the fire burns very 

 fiercely, so that it may be smelted longer. In this way the smelter may direct 

 it whither he wills. Only when it glows at the part near the bellows' nozzle 

 does it signify that all the ore is smelted which has been thrown to the side of 

 the furnace in which the nozzles are placed. If the ore is easily melted, one 

 or two wicker baskets full are thrown into the front part of the furnace so that 

 the fire, being driven back by it, may also smelt the ore and the sows that 



"Expirare, to exhale or blow out. 



I 



