this is laid as much pure lead ore as the heap can bear ; then the charcoal is
kindled, and when the wind blows, it fans the fire so that the ore is smelted.
In this wise the lead, trickling down from the heap, flows on to the level and
forms broad thin slabs. A few hundred pounds of lead ore are kept at hand,
which, if things go well, are scattered over the heap. These broad slabs are
impure and are laid upon dry wood which in turn is placed on green wood
laid over a large crucible, and the former having been kindled, the lead is
re-melted.
The Poles use a hearth of bricks four feet high, sloping on both sides and
plastered with lute. On the upper level part of the hearth large pieces of
wood are piled, and on these is placed small wood with lute put in between ;
over the top are laid wood shavings, and upon these again pure lead ore
covered with large pieces of wood. When these are kindled, the ore melts and
" silver are constructed lofty in order that the vapour, which is dense and pestilent,
" may be raised and carried off." And again (in, 2, io), in quoting from Polybius (204125 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 suver 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 (ist 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.
