solidified material is afterwards broken up into pieces of the desired size, and classified according to the completeness with which the roasting has been effected, as indicated by the presence or absence of unroasted sulphide. It is then smelted down in the Pilz furnaces, in admixture with coke and brown coal. Large quantities of iron are present in the material charged into the furnace, and cold blast has therefore to be employed to prevent too great a reduction of that metal and the consequent formation of unfused masses of reduced iron in the furnace. The products of this smelting are (1) lead; (2) a regulus, or mixture of fused sulphides of lead and copper; (3) a slag; and (4) a lead fume. A small quantity of speise, containing nickel and cobalt, is also occasionally obtained. The lead produced contains the greater part of the precious metals originally present in the charge, together with some copper and other impurities. Such lead has always to be subjected to a refining process before being desilverised by the method in use at the works, and, if very impure, a secondary refining process of liquation has also to be used. To avoid the necessity of this the charge is usually maintained as free from impurities as possible, the percentage of the copper being at the same time kept low. The slag from the ore-smelting always contains lead in too large a quantity to admit of its being thrown away. It has therefore to be retreated, and, as the lead obtained from this source is always very impure, any impure materials that it may be necessary to deal with are generally treated simultaneously with the slag, provided they are not too rich in the precious metals. The percentage of copper admissible in the furnace charge for this slagsmelting is also greater than in that for the treatment of the ore. The ore-slag is treated in admixture with materials poor in silver and in lead, in a manner similar to the method adopted when smelting the ore. The products are the same as before-lead, speise, regulus, slag, and fume. The lead, however, is much less in relative quantity, and more impure than that obtained from the ore-smelting; speise is a more frequent product, the regulus obtained is richer in copper, and the slag is so poor in silver and lead that it may be thrown away.

The further treatment of these various products is as follows:Lead. The slag-lead, and occasionally the ore-lead, is first submitted to a liquation process, which consists in melting the lead at as low a temperature as possible, on the sloping bed of an ordinary reverberatory furnace in a deoxidising atmosphere. By this means the lead melts and flows into a sump or hollow at the foot of the sloping bed of the furnace, leaving the greater por

tion of the copper it originally contained, together with iron and other impurities, the melting-points of which exceed that of lead, on the furnace-bed. Nearly all the silver present in the lead charged into the furnace, and with it the gold, passes into the liquated product, owing to the low melting-points of the silverlead and gold-lead alloys there present. This liquated lead, together with the ore-lead, is then submitted to an oxidising fusion in a reverberatory furnace, the result being that the arsenic, antimony, tin, and other impurities present, which had failed to be eliminated by the liquation process, are oxidised, and a portion of the lead being simultaneously oxidised and fused, they pass into this oxide scum, and can be removed with it. Owing to the varying degree of oxidisability of the several impurities, the fused litharge obtained at different stages of this process contains relatively larger or smaller quantities of the various impurities. These litharges, after removal from the furnace, are kept separate, and are known by the name of the more important impurity they contain. Each of them is afterwards reduced by itself in a small blast-furnace, the product being in each case a readily-marketable hard lead, the impure litharge being first fused with a small percentage of carbon to reduce a portion of the lead, and in this way to collect any silver that may be present in the reduced lead formed. Any copper, too, that may have passed into the liquated lead is also oxidised, but the bismuth remains with the lead. Small quantities of the precious metals always pass into the fused oxide -layer on the surface of the lead, but by far the larger proportion of that originally charged into the furnace remains with the purified lead. This lead is then treated by the ordinary Pattinson process, the lead being first melted at a low temperature and then allowed to cool gradually, the lead crystals poor in silver being separated from the richer molten portion. This treatment is repeated in the ordinary manner until the lead contains 0.1 per cent. of silver. Instead of continuing to treat this lead by the Pattinson process, the Parkes process of desilverisation by the aid of zinc is employed for the purpose of extracting the remaining silver and gold, the lead from this treatment -being dezincified by an oxidising fusion, after which it is ladled into moulds and is ready for the market. The rich Pattinsonised lead is cupelled in cupellation-furnaces of the German type, with non-absorbent marl beds. The cupellation is so conducted that the lead, being charged into a hearth of large size, is oxidised until the residual material contains about 80 per

cent. of the precious metals. This requires a higher temperature for its further treatment, and it is therefore removed from the large furnace to a similar but much smaller one, in which the remaining portion of the lead is eliminated, the fused gold and silver being granulated by pouring into water, the granules dried, and the gold and silver parted by the aid of sulphuric acid. The litharge, if of a yellow colour, is reduced to the metallic state by a reducing-fusion in a small Pilz furnace, but any red litharge that is produced is sold as such. The beds of both the large and the small cupellation-furnaces show green spots at the places where the final products, rich in gold and silver, collected; the bismuth, not being removed by oxidation until nearly all the lead has been oxidised, passes into these portions of the marl-beds, colouring them green. These green patches are carefully removed, dissolved in hydrochloric acid, and the bismuth oxychloride is precipitated by dilution with water. This is either sold as such after purification, or else is reduced to the metallic state by fusion in crucibles with iron. The other portions of the marl cupellation beds, being rich in lead, are on this account added to the various smelting-charges.

Zinc.-The argentiferous zinc ores are roasted, the sulphurous anhydride evolved being collected and converted into sulphuric acid. The desulphurised ore is then mixed with charcoal, and placed in the retorts, which are heated in a regenerative furnace by gaseous fuel. The zinc distils over, and is collected in fire-clay receivers, and, after refining in a special reverberatory furnace, is sent to market. The residues left in the retorts contain the precious metals, and are charged into the Pilz furnaces with the lead-ores.

The zinc rich in silver and gold obtained by the Parkes process is distilled in an ordinary Morgan furnace, which consists of a hooded crucible contained in a wind-furnace. This completes the lead-smelting process proper, both the gold and silver present in the original materials treated having been collected, and the desilverised lead obtained in a form in which it is ready for the market.

The cupriferous regulus resulting from the ore-smelting contains usually but a few per cent. of copper, and consists chiefly of the sulphides of iron and lead. It may be mentioned that it is necessary to have considerable quantities of iron present in the furnace-charge, partly on account of the desulphurising action of the reduced metal, and partly because considerable quantities of zinc are usually present, and the zinc-oxide, passing into the slag,

would render it exceedingly pasty and difficult to fuse, were it not for the counteracting influence of large quantities of ferrous oxide.

This regulus, if its composition is such that this treatment is admissible, is roasted in kilns, the sulphurous anhydride produced being utilised in the manufacture of sulphuric acid. When roasted the regulus is added to the slag-smelting charge; the greater portion of the lead-oxide contained in the roasted regulus is then reduced to the metallic state, and a second regulus is produced, which is poorer in lead but richer in copper than was the one resulting from the ore-smelting. This regulus is too rich in copper to admit of its being roasted in kilns, the tendency of the pieces of regulus to clot together during the roasting being too great; it is therefore roasted in "stalls" which are built of brick, and much resemble ordinary cattle-stalls; they are roofless, with low surrounding walls and a slightly sloping bed. On this bed wood is placed, the regulus to be roasted being piled up on it, and then covered over with a compact layer of finely divided roasted pyrites or regulus. The stalls are placed in rows side by side, and back to back, a tunnel being left between every two such rows. Into this tunnel the gases resulting from the roasting are drawn through perforations in the back walls of the stalls, and are led away to the sulphuric-acid chambers. The combustion is started by lighting a small fire in a grate outside the stall; this kindles the wood, the heat evolved by the combustion of the sulphur in the regulus being afterwards sufficient to continue the process without the addition of any other fuel. This roasted second regulus is then treated as before, until a regulus is produced which contains about 35 per cent. of copper.

Instead of this repeated roasting and treatment with the slagcharge, the regulus, after having been roasted, may be treated in a cupola, together with lead-slags and other fluxing and reducing additions. The product is a comparatively rich regulus, the lead originally present being reduced to the metallic state, taking with it the silver, the enriched regulus retaining but little of the precious metals. When enriched to the degree mentioned above, the regulus is brought, by a single roasting in an ordinary Welsh reverberatory furnace, to a white 66 or pimple" metal containing about 75 to 80 per cent. of copper. This is not further treated at the Müldenhütte, the principal works at Freiberg, but is sent to the Halsbrücke works, where it is roasted sweet, and the copper converted into copper sulphate by treating the roasted material with sulphuric acid. Any lead and gold that

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