The total loss of lead varies according to the weather (which has an influence on the process), the quality of the fuel, &c., between 3.8 and 6.6 per cent. By reducing the fuel to the weight of charcoal, and supposing a yield of 20 per cent of coal from wood, I part in weight of coal is used for every 2 to 35 parts of ore. The consumption of iron varies between 2'4 and 3 per cent. According to Rivot, I ton of ore yields 0.470 ton of crude lead, containing 9 ozs. of silver; and 0324 ton of residues, containing o'123 ton of lead and 1'75 ounces of silver. The yield in reverberatory furnaces is 71 per cent of the lead contained in the ore; about 20 per cent remains in the residues, whilst nearly all the silver will be found in the crude lead.

The expense on I ton of ore amounts to

The loss of lead per ton of ore amounts to o'067 ton, valued at £1 6s. 6d. ; the loss of silver, to o'0123 lb., valued at Is.; together £1 7s. 6d.

The process at Poullaouen requires more fuel than the English process, on account of the employment of wood and the length of the roasting period. It also produces less lead in a metallic state, and the loss of metal is greater.

The composition of lead slag from Poullaouen resulting from galena containing blende is—

At Pesey, in Savoy, the French process is employed, but the hearth is of larger dimensions, and furnished with a partition wall having a communication between the two partitions. The reduction takes place in the nearer part, situated close to the fire-bridge, and the roasting goes on in the back part; by this arrangement a larger production is gained, and there is less loss of lead, and a smaller consump

tion of fuel.

Efforts have been made to introduce this process at the Clausthal lead works, but without success, on account of the large amount of silica contained in the ores of the Hartz.

At Corfali, in Belgium, charges of 26 cwts. of calcareous galena, containing pyrites and blende, are worked in 16 hours; 6 hours for roasting, and the remaining 10 hours for the reduction of the oxide of lead by stirring it up with wood. 14 cubic feet of coal and 51 cubic feet of wood are used in this process; the yield of lead is from 50 to 60 per cent. The residues of this process are worked in a reverberatory furnace with an inclined hearth, and with the addition of cast iron. To assist the formation of slag I cwt. of limestone is spread out upon the sole of the furnace, and 5 cwts. of residues, 5 cwts. of poor earthy ores, and 1 cwts. of iron are placed on it. After 5 hours the resulting lead is tapped off, and the furnace charged again. The consumption of coal for one charge amounts to 8 cubic feet.

In 31 days, 760 cwts. of lead (= 67·62 per cent), and 170 cwts. of residues containing 51 cwts. of lead, were produced from 1,112 cwts. of lead ore, giving a total yield of 72 per cent. 617 cubic feet of coal and 3,410 cubic feet of wood were required for this result.

In Vienne furnaces 540 cwts. of residues and 320 cwts. of poor ore (galena) were smelted in 20 days, consuming 900 cubic feet of coal, 106 cwts. of scrap iron, and 35 cwts. of wrought iron, and producing 238 cwts. (=28'65 per cent) of

* DUMAS, angêw, Ch., iv., 240. LELIVEC, Journ. d. Min., xx, 419. BERTHIER, Ann. d. Min., 1 sér., iii., 549. REPLAT, Ann. des Min., 3 sér., xviii., 161; 4 sér., iv., 331. BERTHIER, Met. analyt. Chem., ii., 629, 647. COTTA, Erzlagerstätten, ii., 331.

+ KERL, Oberharzer Schmelzprocesse, 1860, p. 581. KERL, B. u. h. Ztg., 1854, p. 217, No. 25.

lead. It is more advantageous to smelt the residue, together with ores and iron refinery cinders, in cupola furnaces, 3.66 metres high above the tuyere.

A mixture consisting of—

20 cwts. Residues of the reverberatory containing 39 per

furnace

White lead ore

Iron refinery cinders

cent of lead.

Furnace ends containing 20 per cent of lead

was smelted with 8 to 9 per cent of coke. The loss of lead amounted to 2 per cent, per cent of which was contained in the slags, and 2 per cent was collected in the condensing chambers.

The ores used in the lead works at Bleiberg and Binsfeldhammer, in the neighbourhood of Stolberg, near Aix-laChapelle, are either free from copper, or contain only traces of it; but they have more or less antimony, which makes it necessary to refine the raw lead previous to its treatment by Pattinson's process.

The galena occurring at the lead works at Bleiberg* consists chiefly of very pure ore with small quantities of associated minerals, namely, quartz (from 4 to 1 per cent), blende, pyrites, and, in rare cases, limestone. It contains 82 per cent of lead, per cent of antimony, and 4 ounces of silver to the ton. Reverberatory furnaces with a fire-place on each side are used for smelting the ore. They are represented by Figs. 19, 20,

FIG. 19.

FIG. 20.

21, and 22. a is the grate; b, the fire bridge; c, hearth; d, lead sump; e, working doors; f, outside basin for receiving the metal; g, opening for charging the fuel; m, flues; n, chimney. The hearth slopes from the fire-bridge towards the middle, where it forms a sump, which likewise slopes from one broad side of the furnace to the other, and communicates with the outside basin. The two working doors at the extremities of each long side of the furnace are used for manipulating on the hearth, which is formed either of slags got from smelting the residues of the reverberatory process, or of other slags, from 1 to 2 feet thick, smelted upon a sole of bricks; an addition of lime is made to stiffen the mass and render it more refractory.

As soon as the furnace is properly cooled, the workmen. charge it with two tons of ore, which occupies about 30 minutes; the ore is then heated from of an hour to 1 hour

until red hot, whilst the working doors are closed; it is then turned over with iron rabbles every half-hour, for 7 or 8 minutes, both workmen commencing at opposite working doors, and working on to the middle of the furnace. In about 5 hours from the commencement, the roasting mass having become fat under the influence of the gradually increased temperature, begins to smoke, and easily fusible alloys of antimony and lead flow out in small quantity from the sump into the outside basin, before the real reaction of the sulphate of lead upon the sulphide commences. As soon as a sufficient quantity of that alloy is produced, glowing coal and coal slack are thrown into the basin and stirred in it, causing a separation of slag from the lead alloy, which is removed and put back into the furnaces.

When the roasting mass upon the hearth begins to become pasty, some shovels-full of coal slack are mixed up with it in order to give it a stiffer consistence. About 8 hours after charging, a copious extraction of lead begins at the higher temperature, but less slag is separated in the outside basin; this slag is crumbly-from other reasons than the first formed slag-and becomes stiff very quickly: whilst cooling, drops of lead are still running out of it.

After about 10 or 11 hours the whole process is finished, and from an hour to an hour and a half's time is allowed for cooling the furnace. From the ore containing 82 per cent of lead, about 60 per cent of lead is produced, and this lead contains at first 8 ounces, and later 5 ounces of silver in the ton. The residues often contain as much as 70 per cent of lead, besides a considerable quantity of antimony. The consumption of coal in 24 hours amounts to 53 cubic feet, and the loss of lead is about 5 or 6 per cent; this, however, is notably lessened by working up the contents of the very extensive condensation chambers.

Smelting the Residues.-The raw lead is refined by Pattinson's process. The residues are worked in cupola furnaces about 5 metres high, having a sump inside the furnace for collecting the metal; they are mixed with 60 per cent of iron refinery cinders, 18 per cent of lime and broken bricks, and 6 per cent of impure slags, and are smelted.