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BOOK IX.

these, when they have been roasted as much as is necessary and re-smelted,the copper is made. But if there be some silver in the cakes, for which anoutlay of lead has to be made, then it is first run into the forehearth, andthe molten lead absorbs the silver.

Indeed, rudis copper ore of inferior quality, whether ash-coloured orpurple, blackish and occasionally in parts blue, is smelted in the firstfurnace whose tap-hole is always open. This is the method of the Tyrolese.To as much rudis copper ore as will fill eighteen vessels, each of which holds

“ men pour cold water on it, the copper spits and throws off the flowers.” He gives the firstdescription of vitriol (see note n, p. 572), and describes the pieces as “ shaped like dice whichstick together in bunches like grapes.” Altogether, from Dioscorides we learn for the firsttime of copper made from sulphide ores, and of the recovery of zinc oxides from furnacefumes ; and he gives us the first certain description of making brass, and finally the firstnotice of blue vitriol.

The next author we have who gives any technical detail of copper work is Pliny (23-79A.D.), and while his statements carry us a little further than Dioscorides, they are not ascomplete as the same number of words could have afforded had he ever had practical contactwith the subject, and one is driven to the conclusion that he was not himself much of a metal-lurgist. Pliny indicates that copper ores were obtained from veins by underground mining.He gives the same minerals as Dioscorides, but is a good deal confused over chrysocolla andchalcitis. He gives no description of the shapes of furnaces, but frequently mentions thebellows, and speaks of the cadmia and pompholyx which adhered to the walls and arches ofthe furnaces. He has nothing to say as to whether fluxes are used or not. As to fuel, he says(xxxiii, 30) that “ for smelting copper and iron pine wood is the best.” The following (xxxiv,20) is of the greatest interest on the subject:—“ Cyprian copper is known as coronarium and“ regulare ; both are ductile. ... In other mines are made that known as regulare and“ caldarium. These differ, because the caldarium is only melted, and is brittle to the hammer ;“ whereas the regulare is malleable or ductile. All Cyprian copper is this latter kind. But“ in other mines with care the difference can be eliminated from caldarium, the impurities being“ carefully purged away by smelting with fire, it is made into regulare. Among the remaining“ kinds of copper the best is that of Campania, which is most esteemed for vessels and utensils.“ This kind is made in several ways. At Capua it is melted with wood, not with charcoal,“ after which it is sprinkled with water and washed through an oak sieve. After it is melted“ a number of times Spanish plumbum argentum (probably pewter) is added to it in pro-“ portion of ten pounds of the lead to one hundred pounds of copper, and thereby it is“ made pliable and assumes that pleasing colour which in other kinds of copper is effected“ by oil and the sun. In many parts of the Italian provinces they make a similar kind" of metal; but there they add eight pounds of lead, and it is re-melted over charcoal“ because of the scarcity of wood. Very different is the method carried on in Gaul, par-“ ticularly where the ore is smelted between red hot stones, for this burns the metal and renders“ it black and brittle. Moreover, it is re-melted only a single time, whereas the oftener this“ operation is repeated the better the quality becomes. It is well to remark that all copper" fuses best when the weather is intensely cold.” The red hot stones in Gaul were prob-ably as much figments of imagination as was the assumption of one commentator thatthey were a reverberatory furnace. Apart from the above, Pliny says nothing very direct onrefining copper. It is obvious that more than one melting was practised, but that anythingwas known of the nature of oxidation by a blast and reduction by poling is uncertain. Weproduce the three following statements in connection with some bye-products used for medicinalpurposes, which at least indicate operations subsequent to the original melting. As to whetherthey represent this species of refining or not, we leave it to the metallurgical profession (xxxiv,24):—“ The flowers of copper are used in medicine; they are made by fusing copper and moving“ it to another furnace, where the rapid blast separates it into a thousand particles, which“ are called flowers. These scales are also made when the copper cakes are cooled in water“ (xxxiv, 35). Smega is prepared in the copper works ; when the metal is melted and“ thoroughly smelted charcoal is added to it and gradually kindled ; after this, being blown“ upon by a powerful bellows, it spits out, as it were, copper chaff (xxxiv, 37). There is“ another product of these works easily distinguished from smega, which the Greeks call“ diphrygum. This substance has three different origins. . . A third way of making it

“ is from the residues which fall to the bottom in copper furnaces. The difference between“ the different substances (in the furnace) is that the copper itself flows into a receiver ; the“ slag makes its escape from the furnace ; the flowers float on the top (of the copper ?), and“ the diphrygum remains behind. Some say that in the furnace there are certain masses of“ stone which, being smelted, become soldered together, and that the copper fuses around it,“ the mass not becoming liquid unless it is transferred to another furnace. It thus forms a“ sort of knot, as it were, in the metal.”