Ordinary Method.—Roast-reduction. Cost per 1000 kg. of crude ore:

1. Roasting in reverberatory furnace:
Labor$0.70
Fuel1.50
Repairs and supplies.05
$2.25
2. Smelting in water-jacket:
Labor$1.01
Fuel2.20
Repairs and supplies.03
Fluxes.50
3.74
Total $5.99

Bormettes Method.—Agglomeration with slag, pneumatic desulphurization and smelting in water-jacket:

1. Agglomeration and desulphurization:
Labor$0.42
Repairs and supplies0.05
$0.47
2. Smelting in water-jacket:
Labor$0.90
Fuel1.91
Repairs and supplies.03
Fluxes.42
3.26
Total $3.73

This shows a difference in favor of the new method of $2.26 per ton of ore, without taking into account the savings realized by a much more speedy handling of the operation, which would further reduce the cost to approximately $2.50 per ton.

Fig. 22.—Details of Transfer Cars.

In the above figures, no account has been taken of general expenses, which per ton of ore are reduced because of the greater rapidity of the process, enabling a larger quantity of ore to be smelted in a given time. Making allowance for this, the saving will amount to an average of $2.40 per 1000 kg., a figure which will naturally vary according to the prices for fuel, labor, and the quantity of matte which it may be necessary to re-treat. If the quantity of matte does not exceed 10 per cent. of the weight of the ore, it can be desulphurized by admixture with the ore, without use of other fuel. If, however, the proportion of matte rises to 20 parts per 100 parts of ore (a maximum which ought not to be reached in good working), it is necessary to roast a portion of it. Under unfavorable conditions, consequently, the saving effected by this process may be reduced to $2 @ $2.20 per 1000 kg., and even to as little as $1.40 @ $1.60. The above reckonings are, however, without taking any account of the higher extraction of lead and silver, which is one of the great advantages of the Bormettes process.

Fig. 23.—Latest Form of Converter. (Section on A B.)