The volume of air forced into this furnace was 15,000 cub. ft. per min., or as much as was used elsewhere for furnaces of more than twice the capacity. The results obtained were sur prising. Considering the cubic capacity of the furnace, the rate of driving was certainly excessive, and that the results on fuel were so low, as compared with the subsequent con sumption on larger furnaces where the same practice was employed, is mainly due to the nar row furnace-stack. These fuel results were much lower than any obtained from the larger furnaces in the next five years.
The second furnace erected at these works had general dimensions as follows: Ileig,ht. SO ft. ; diameter of bosh. 20 ft.; diameter of hearth, 11 ft.; cubical capacity, 17,868 cub. ft. The stock was distributed at the top by a double bell, in which the central cone remained station ary ; while the outer conical ring. being lowered, cast the stock toward the wall and center of the furnace. One feature of this construction, differing from that of other furnaces then using coke for fuel, was the large hearth, providing more space for combustion. The in-walls of the hearth were straight, and the diameter 11 ft. There was an increased number of tuyeres, eight being used, and an increased elevation of tnyeres above the hearth-level, all of which were necessary for rapid driving and large yields. No American furnace up to that time had been constructed with so large a hearth as this one at the Edgar Thomson works. In another respect this furnace was well prepared by its designers for a high productive ca pacity. viz., in its equipment. Fire-brick stoves of the most approved type were erected. Substantially built blowing engines were provided, and they were rendered efficient by an ample supply of boilers—a point in which other furnaces were then sadly lacking. At the same time, all the flues and mains were constructed sufficiently large. and in the most sub stantial way. In fact. no furnace previously erected had been planned on such a liberal basis; consequently, large yields were to be expected. The furnace was put in blast in April, 1880. In the following month an output of 3,718 tons was made, and the next month showed 4,318 tons; thus fully justifying the claims of its designers by eclipsing all previous records. The weight of limestone was 23 per cent of the weight of the ore. An analysis of the cinder showed : silica, per cent ; alumina, per cent.
The limestone contained a very small quantity of magnesia. The blast entered the fur nace through eight bronze tuyeres of 5+ in. diameter, and was heated to a temperature of 1,100°.
The silicon in the iron averaged about 2 per cent. The rapid wear of the furnace-walls, through the use of such a large volume of air, gradually increased the consumption of coke to over 3.000 lbs. per ton of iron. At the end of the first 12 full months the output. was 48. 179 tons, on an average coke consumption of 2,839 lbs. per ton of iron. The second year showed an average consumption of 3,200 lbs. of coke, with a decrease in yield. The furnace was blown out after a blast of two years and five months, having made a total product of 112,000 tons, on an average coke consumption of 3,149 lbs. per ton of iron. The results ob tanned in this blast determined several important changes in construction. The crinoline structure was torn down and replaced by an iron jacket ; the bosh-walls were protected so as to preserve as far as possible the original lines. and the hearth was surrounded with c•ooled plates. The double bell was also found to possess no special advantage, and was aban doned, The practice of rapid driving, begun on furnace -A." and further developed on this one, had an important effect on the general practice of this country. The great outputs obtained from this furnace by the use a large volume of air, was a matter of common knowledge; the practice of fast driving soon became the accepted one, and with our national ardor it was prosecuted enthusiastically. In every direction engines that had been running along for years at a methodical gait were oiled up and started off at a livelier pace ; new boilers were added ; the old iron hot-blast stoves, not supplying, sufficient heat, were torn down and re placed by the more efficient lire-brick stoves. At many works rapid driving degenerated into excessive driving. True, thw outputs increased; so also did the consumption of fuel. and that at a surprising rate, until it was thought well-nigh impossible to produce a ton of iron with 2,000 lbs. of coke, Although the practice of rapid driving, has been much decried. yet in many ways it has resulted beneficially. It has brought in an equipment of hot-blast stoves. boilers, engines. etc., sufficient to accomplish a large amount of work without a constant strain on every part—a condition very rare prior to 1880; and it has also developed a con struction of the furnace-stack by which larger outputs from a single lining can be obtained with less irregularity in the working.