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Detail Holywell Stiper-stones Tarnowitz Tarnowitz Desloge Hearth length, ft. 12.00 9.75 11.75 16.00 16.00 Hearth width, ft. 9.50 9.50 10.83 8.83 11.00 Grate length, ft. 4.50 4.50 8.00 8.00 8.00 Grate width, ft. 2.50 2.50 1.67 1.67 3.00 Grate area: hearth area 1:8 1:6⅔ 1:10 1:10 1:7-1/3 Charges per 24 hr., 3 3 2 2 3 Ore smelted per 24 hr., lb. 7,050 7,050 8,800 16,500 10,500 Assay of ore, % Pb 75-80 77.5 70-74 70-74 70 Gray slag, % of charge 12 15 30 27 Gray slag, % Pb 55 38.8 56 38 Men per 24 hr. 6 4 4 6 6 Coal used per ton ore 0.57-0.76 0.56 0.46 0.50 0.90

The regular furnace charge at Desloge was 3500 lb. The working of three charges per 24 hours gave a daily capacity of 10,500 lb. per furnace. These figures refer to the wet weight of the concentrate, which was smelted just as delivered from the mill. Its size was 9 mm. and finer. Assuming its average moisture content to be 5 per cent., the daily capacity per furnace was about 10,000 lb. (5 tons) of dry ore.

The metallurgical result is indicated by the figures for two months of operation in 1900. The quantity of ore smelted was 1012 tons, equivalent to approximately 962 tons dry weight. The pig lead produced was 523.3 tons, or 54.4 per cent. of the weight of the ore. The gray slag produced was 262.25 tons, or about 27 per cent. of the weight of the ore. The assay of the ore was approximately 70 per cent. lead, giving a content of 673.4 tons in the ore smelted. The gray slag assayed approximately 38 per cent. lead, giving a content of 99.66 tons. Assuming that 90 per cent. of the lead in the gray slag be recoverable in the subsequent smelting in the blast furnace, or 89.7 tons, the total extraction of lead in the process was 523.3 + 89.7 ÷ 673.4 = 91 per cent. The metallurgical efficiency of the process was, therefore, reasonably high, especially in view of the absence of dust chambers.