| Month | Hand Roasters | Brown-O’Harra Mechanical Furnaces | ||||||
|---|---|---|---|---|---|---|---|---|
| Total Tons Roasted Per Day | Tons Roasted Per Day | Labor | Coal | General Expense | Labor | Coal | General Expense | |
| January | 5,691 | 184 | $1.47 | $0.53 | $0.80 | $0.92 | $0.80 | $1.32 |
| February | 5,677 | 203 | 1.44 | 0.44 | 0.99 | 0.72 | 0.58 | 1.01 |
| March | 5,821 | 188 | 1.51 | 0.53 | 0.64 | 0.76 | 0.64 | 0.62 |
| April | 5,472 | 182 | 1.47 | 0.47 | 0.71 | 0.80 | 0.69 | 0.87 |
| May | 5,444 | 176 | 1.55 | 0.51 | 0.84 | 0.80 | 0.69 | 0.81 |
| June | 4,859 | 162 | 1.58 | 0.48 | 0.71 | 0.90 | 0.68 | 1.17 |
| July | 5,691 | 184 | 1.59 | 0.48 | 0.75 | 0.72 | 0.56 | 0.64 |
| August | 5,910 | 191 | 1.55 | 0.46 | 0.83 | 0.72 | 0.55 | 0.75 |
| September | 5,677 | 189 | 1.55 | 0.45 | 0.74 | 0.73 | 0.55 | 0.67 |
| October | 6,254 | 202 | 1.48 | 0.49 | 0.72 | 0.65 | 0.50 | 0.60 |
| November | 6,291 | 213 | 1.42 | 0.47 | 0.80 | 0.66 | 0.53 | 0.70 |
| December | 5,874 | 198 | 1.45 | 0.48 | 0.78 | 0.79 | 0.63 | 0.81 |
| Average | $1.50 | $0.48 | $0.77 | $0.76 | $0.62 | $0.83 | ||
| Total | 2.75 | 2.21 | ||||||
Cost of Smelting.—The lead-ore mixtures of the United States, in addition to lead, contain gold, silver and generally copper, and are treated to save these metals. The total cost of smelting is made up of a large number of items. The questions of locality and transportation, fuel, fluxes and labor are the principal factors, to which must be added the handling of the material to and from the furnace; the furnace itself, its size, shape, and method of smelting, the volume and pressure of blast, etc. The following table of costs, from 1887 to 1898, shows in a general way the great advance that has been made in the development of smelting, and the consequent reduction in cost per ton of ore treated:
AVERAGE COST OF SMELTING, PER TON
| 1887 | $4.644 | 1891 | 4.170 | 1895 | 2.786 |
| 1888 | 4.530 | 1892 | 4.906 | 1896 | 2.750 |
| 1889 | 4.480 | 1893 | 3.375 | 1897 | 2.520 |
| 1890 | 4.374 | 1894 | 3.029 | 1898 | 2.260 |
In connection with this table of smelting cost should be considered the changes developed during the interval 1887-1889, outlined as follows:
CONDITIONS OF SMELTING IN 1886 AND 1899 CONTRASTED TO SHOW THE PROGRESS OF DEVELOPMENT
| Area of Furnace at Tuyeres, In. | Height of Charge from Tuyeres, Ft. | Blast Pressure, Lb. per Sq. In. | Fore Hearth Capacity, Cu. Ft. | Slag Settled | Fuel | Slag Removed, Lb. per Trip | Matte Removed, Lb. per Trip | |
|---|---|---|---|---|---|---|---|---|
| 1886 | 30 × 100 | 11 | 1 | 6 | In pots | Charcoal | By hand 280 | By hand 200 |
| 1899 | 42 × 140 | 16 | 3 to 4 | 128 | In furnaces | Coke | By locomotive 3000-6000 | By horse 2000-3000 |
I believe that there is room for further improvement in the substitution of mechanical transportation within the works for hand labor, and that the fuel cost can be materially reduced by replacing the coke, which at present contains 16 to 22 per cent. of ash, by a fuel of purer and better quality.
Cost of Refining by the Parkes Process.—In general it may be stated that the average cost of refining base bullion is from $3 to $5 a ton. This amount is based on the cost of labor, spelter, coal, coke, supplies, repairs and general expenses. When the additional items of interest, expressage, brokerage and treatment of by-products are considered, which go to make up the total refining cost, the amount may be stated approximately as $10 per ton of bullion treated.