265. Theognis (6th century B.C.) and Hippocrates (5th century B.C.) are

frequently referred to as mentioning the refining of gold with lead; an inspection of the passages fails to corroborate the importance which has been laid upon them. Among literary evidences upon lead metallurgy of later date, Theophrastus (300 B.C.) describes the making of white-lead with lead plates and vinegar. Diodorus Siculus (1st century B.C.), in his well-known quotation from Agatharchides (2nd century B.C.) with regard to gold mining and treatment in Egypt, describes the refining of gold with lead. (See note 8, p. 279.) Strabo (63 B.C.-24 A.D.) says (III, 2, 8): "The furnaces for silver are constructed lofty in order that the vapour, which is dense and pestilent, may be raised and carried off." And again (III, 2, 10), in quoting from Polybius (204-125 B.C.): "Polybius, speaking of the silver mines of New Carthage, tells us that they are extremely large, distant from the city about 20 stadia, and occupy a circuit of 400 stadia; that there are 40,000 men regularly engaged in them, and that they yield daily to the Roman people (a revenue of) 25,000 drachmae. The rest of the process I pass over, as it is too long; but as for the silver ore collected, he tells us that it is broken up and sifted through sieves over water; that what remains is to be again broken, and the water having been strained off it is to be sifted and broken a third time. The dregs which remain after the fifth time are to be melted, and the lead being poured off, the silver is obtained pure. These silver mines still exist; however, they are no longer the property of the State, neither these nor those elsewhere, but are possessed by private individuals. The gold mines, on the contrary, nearly all belong to the State. Both at Castlon and other places there are singular lead mines worked. They contain a small proportion of silver, but not sufficient to pay for the expense of refining" (Hamilton's Trans.). Dioscorides (1st century A.D.), among his medicines, describes several varieties of litharge, their origin, and the manner of making white-lead (see on pp. 465, 440), but he gives no very tangible information on lead smelting. Pliny, at the same period in speaking of silver, (XXXIII, 31), says: "After this we speak of silver, the next folly. Silver is only found in shafts, there being no indications like shining particles as in the case of gold. This earth is sometimes red, sometimes of an ashy colour. It is impossible to melt it except with lead ore (_vena plumbi_), called _galena_, which is generally found next to silver veins. And this the same agency of fire separates part into lead, which floats on the silver like oil on water." (We have transferred lead and silver in this last sentence, otherwise it means nothing.) Also (XXXIV, 47) he says: "There are two different sources of lead, it being smelted from its own ore, whence it comes without the admixture of any other substance, or else from an ore which contains it in common with silver. The metal, which flows liquid at the first melting in the furnace, is called _stannum_ that at the second melting is silver; that which remains in the furnace is _galena_, which is added to a third part of the ore. This being again melted, produces lead with a deduction of two-ninths." We have, despite some grammatical objections, rendered this passage quite differently from other translators, none of whom have apparently had any knowledge of metallurgy; and we will not, therefore, take the several pages of space necessary to refute their extraordinary and unnecessary hypotheses. From a metallurgical point of view, two facts must be kept in mind,--first, that _galena_ in this instance was the same substance as _molybdaena_, and they were both either a variety of litharge or of lead carbonates; second, that the _stannum_ of the Ancients was silver-lead alloy. Therefore, the metallurgy of this paragraph becomes a simple melting of an argentiferous lead ore, its subsequent cupellation, with a return of the litharge to the furnace. Pliny goes into considerable detail as to varieties of litharge, for further notes upon which see p. 466. The Romans were most active lead-silver miners, not only in Spain, but also in Britain. There are scores of lead pigs of the Roman era in various English museums, many marked "_ex argent_." Bruce (The Roman Wall, London, 1852, p. 432) describes some Roman lead furnaces in Cumberland where the draught was secured by driving a tapering tunnel into the hills. The Roman lead slag ran high in metal, and formed a basis for quite an industry in England in the early 18th century (Hunt, British Mining, London, 1887, p. 26, etc.). There is nothing in mediaeval literature which carries us further with lead metallurgy than the knowledge displayed by Pliny, until we arrive at Agricola's period. The history of cupellation is specially dealt with in note on p. 465. [25] _Cadmia_. In the German Translation this is given as _kobelt_. It would be of uncertain character, but no doubt partially furnace calamine. (See note on p. 112.) [26] _Pompholyx_. (_Interpretatio_ gives the German as _Weisser huetten rauch als ober dem garherde und ober dem kupfer ofen_). This was the impure protoxide of zinc deposited in the furnace outlets, and is modern "tutty." The ancient products, no doubt, contained arsenical oxides as well. It was well known to the Ancients, and used extensively for medicinal purposes, they dividing it into two species--_pompholyx_ and _spodos_. The first adequate description is by Dioscorides (V, 46): "_Pompholyx_ differs from _spodos_ in species, not in genus. For _spodos_ is blacker, and is often heavier, full of straws and hairs, like the refuse that is swept from the floors of copper smelters. But _pompholyx_ is fatty, unctuous, white and light enough to fly in the air. Of this there are two kinds--the one inclines to sky blue and is unctuous; the other is exceedingly white, and is extremely light. White _pompholyx_ is made every time that the artificer, in the preparation and perfecting of copper (brass?) sprinkles powdered _cadmia_ upon it to make it more perfect, for the soot which rises being very fine becomes _pompholyx_. Other _pompholyx_ is made, not only in working copper (brass?), but is also made from _cadmia_ by continually blowing with bellows. The manner of doing it is as follows:--The furnace is constructed in a two-storied building, and there is a medium-sized aperture opening to the upper chamber; the building wall nearest the furnace is pierced with a small opening to admit the nozzle of the bellows. The building must have a fair-sized door for the artificer to pass in and out. Another small building must adjoin this, in which are the bellows and the man who works them. Then the charcoal in the furnace is lighted, and the artificer continually throws broken bits of _cadmia_ from the place above the furnace, whilst his assistant, who is below, throws in charcoals, until all of the _cadmia_ inside is consumed. By this means the finest and lightest part of the stuff flies up with the smoke to the upper chamber, and adheres to the walls of the roof. The substance which is thus formed has at first the appearance of bubbles on water, afterward increasing in size, it looks like skeins of wool. The heaviest parts settle in the bottom, while some fall over and around the furnaces, and some lie on the floor of the building. This latter part is considered inferior, as it contains a lot of earth and becomes full of dirt." Pliny (XXXIV, 33) appears somewhat confused as to the difference between the two species: "That which is called _pompholyx_ and _spodos_ is found in the copper-smelting furnaces, the difference between them being that _pompholyx_ is separated by washing, while _spodos_ is not washed. Some have called that which is white and very light _pompholyx_, and it is the soot of copper and _cadmia_; whereas _spodos_ is darker and heavier. It is scraped from the walls of the furnace, and is mixed with particles of metal, and sometimes with charcoal." (XXXIV, 34.) "The Cyprian _spodos_ is the best. It is formed by fusing _cadmia_ with copper ore. This being the lightest part of the metal, it flies up in the fumes from the furnace, and adheres to the roof, being distinguished from the soot by its whiteness. That which is less white is immature from the furnace, and it is this which some call '_pompholyx_.'" Agricola (_De Natura Fossilium_, p. 350) traverses much the same ground as the authors previously quoted, and especially recommends the _pompholyx_ produced when making brass by melting alternate layers of copper and calamine (_cadmia fossilis_). [27] _Oleo, ex fece vini sicca confecto_. This oil, made from argol, is probably the same substance mentioned a few lines further on as "wine," distilled by heating argol in a retort. Still further on, salt made from argol is mentioned. It must be borne in mind that this argol was crude tartrates from wine vats, and probably contained a good deal of organic matter. Heating argol sufficiently would form potash, but that the distillation product could be anything effective it is difficult to see. [28] _Aqua valens_. No doubt mainly nitric acid, the preparation of which is explained at length in Book X, p. 439. [29] _Quod cum ignis consumit non modo una cum eo, quae ipsius stibii vis est, aliqua auri particula, sed etiam argenti, si cum auro fuerit permistum, consumitur._ The meaning is by no means clear. On p. 451 is set out the old method of parting silver from gold with antimony sulphide, of which this may be a variation. The silver combines with sulphur, and the reduced antimony forms an alloy with the gold. The added iron and copper would also combine with the sulphur from the antimony sulphide, and no doubt assist by increasing the amount of free collecting agent and by increasing the volume of the matte. (See note 17, p. 451.) [30] There follow eight different methods of treating crude bullion or rich concentrates. In a general way three methods are involved,--1st, reduction with lead or antimony, and cupellation; 2nd, reduction with silver, and separation with nitric acid; 3rd, reduction with lead and silver, followed by cupellation and parting with nitric acid. The use of sulphur or antimony sulphide would tend to part out a certain amount of silver, and thus obtain fairly pure bullion upon cupellation. But the