CHAP. XIII. FROM THE YEAR 1830 to 1840. ARRIVING now at the final chapters, the arrangement, as laid down in the concluding paragraph of the Introduction, will be carried out. The history of the home manufacture from 1830 up to the present period, with remarks upon its state and prospects, and the surprising extent of improvements in the mode of operations, will occupy attention. The rapidity with which skill, under the tuition of science, is advancing production, is not less striking than the novel and valuable application of iron to innumerable purposes unheard of anterior to the enormous supply now always attainable in the British market. The great and increasing importance of the iron trade to this country, caused theory and practice to be brought into play to discover the best means of improving both the quantity and the quality of the iron, and the blast furnace underwent almost every variety of form, with the exception of those which have been found most beneficial in the present day. The old charcoal furnaces, from 12 to 18 feet high, or where a good water power existed, even 28 feet, gave place to coke furnaces of 40, 50, 60, and even, in one instance, 70 feet, of which height a furnace was erected in South Wales*, but, after in vain attempting to work it, they were obliged to reduce it, which they did to the extent of 30 feet by cutting a hole in the side, narrowing the mouth, and throwing in the materials at 40 feet instead of 70. The width of the boshes also varied from 10 to 15 feet, and an experiment was tried at Muirkirk, in Scotland, where they reduced the width of Rees' Cyclopædia. : the boshes from 10 feet to 8; the height of the furnace being 40 feet but it was soon found that with the same volume of blast, which was formerly applied to the ten-feet furnace, very inferior effects were now produced. The combustion, apparently, was carried to too great an extent, and the materials, owing to this circumstance, entered into fusion before the iron had imbibed a sufficient dose of the coally principle from the fuel. Another great evil which resulted from this diminution of diameter, was a friction, or retardation of the descent of the materials upon the lining of the furnace. This evil was increased, and the materials made more buoyant, by the usual volume of air elevating itself in a cone not much more than half its former area. The consequences were, that the whole mixture of coke, ironstone, and limestone, would frequently hang for an hour together, or until the blast had cleared the hearth and boshes of materials, a slip would then ensue, and bring with it a large proportion of newly-introduced matter. The introduction of this into the fusing point, before being properly heated, and long before any affinity had been established betwixt the particles of metal and the carbon of the furnace, invariably changed the quality of the metal, and caused frequent and sudden alterations from grey to white iron.* But the general average height and width of the furnaces, about thirty years back, may be taken at 40 feet from the upper surface of the hearth bottom, 11 feet across the boshes, and 3 of the tunnel head, or furnace mouth. been the custom to blow the furnace with one tuyere; they now, however, at some works began to blow with two, and the beneficial effects being soon experienced, they became very generally introduced. No material alteration took place for some years, when accident in some degree discovered what now constitutes one of our greatest improvements. One of the Blendare Furnaces †, near Pontypool, built as usual, with a narrow top, carrying but little burden, and making neither quantity nor quality, by some chance gave way in the top, so *Rees' Cyclopædia. feet for the diameter Till that time it had † Mushet's Papers on Iron and Steel. far as to widen the filling place to 9 or 10 feet. This accident was immediately followed by a cooler top, a better quality of iron, and a greater weekly quantity; and this accidental alteration furnished a model for the construction of other furnaces at the same works. Changes of this kind are not brought about rapidly, by reasoning or knowledge of principle, but by a series of slow observations and chance circumstances. The subject is, however, now better understood, and within the last five or six years the mouth or filling place of the furnace has been very generally enlarged; and, instead of 3, 3, or 4 feet, are now from 8 to 11 feet, and in some few instances larger. One of the most striking varieties in the modern form of the furnace, and from which the greatest quantities of iron have been run, is the cylindrical form. Furnaces of this description are erected in many places, and amongst others at the Govan Works in Scotland, of which the following is an account of a fortnight's work: No. 1. Furnace,-15 feet 8 inches in diameter, 45 feet high, cylindrical, from the boshes to within a few feet of the charging plate, where it is rapidly brought in to a convenient diameter for the tunnel head. Blown in 21st November, 1840. Two weeks, ending December 12th, produced1st week 140 tons 1 cwt. f No. 1. Į 1st week 2nd do. 145 6 1 iron. I stopped 12 hours. Blown with hot air, and 5 tuyeres, pillar of blast-3 lbs. per square inch, at tuyere pipes. وو No. 2. Furnace,-15 feet diameter, cylindrical, 45 feet high. 1st week 128 tons 15 cwt. I stopped 12 hours, 2nd do. 150 } No. 1. iron. No. 3. Furnace, Out of blast, being enlarged. No. 4. Furnace, -11 feet diameter, 45 feet high, and cylindrical: 1st week 75 tons I stopped 12 hours, 2nd do. 77 13 cwt. J No. 4. iron. وو No. 5. Furnace,-15 feet diameter, 45 feet high, and cylindrical: 1st week 95 tons وو } No. 4. iron 2nd do 116 13 cwt. J stopped 12 hours These furnaces were all blown with heated air, and have, within these few years, been erected by the proprietor, Mr. William Dixon, who made a series of experiments at the Calder Iron Works, the results of which satisfied him of the superiority of the cylindrical form, which he has here adopted. And the make is a good proof of the advantage of this form of furnace; but from 90 to 100 tons per week from a furnace is now by no means unusual; in fact, throughout most of the works of South Wales the average make is seldom below 80 tons per week, but more generally as above stated. But the boldest and most successful alteration in the form of the blast furnace was made by Mr. John Gibbons, of Corbyn's Hall. The account of his furnace was published by himself in a small pamphlet, and circulated amongst his friends. Mr. Gibbons' furnace is considered the best in Staffordshire, for the duration of the hearth and boshes, working to good yields, making good iron, and greatest quantity. The duration of the hearth and boshes appears to arise from the fact of the hearth being put in wider than they generally are, and consequently giving more room for the blast to act. The boshes commence a little above the tuyeres, and have nearly the same inclination as the curve of the furnace; the boshes, in fact, running 30 feet high; at which height is the widest part of the furnace, it being there 14 feet. Mr. Gibbons, an eminent ironmaster, a gentleman having ample opportunities of watching the blast furnace in its operations, observes, that he acquired the habit of observing with much attentive interest the changes effected by fire in its inner form; his attention was first more particularly directed to the very rapid destruction that takes place in the hearth and boshes during the early period of the furnace being worked: "at the end of six months it may, I believe, be safely stated as a general fact, that both of them have been carried away to the extent of at least a third of their substance. From thi time, or about this time (for exact accuracy cannot be obtained on such a subject), the destruction becomes gradual, and proceeds more or less slowly, till the boshes, either in some part of their circle, or the whole of it, are obliterated; and this may be called the natural death of the furnace it will carry on its operations no longer." "The hearth may be replaced or repaired from without for an indefinite period, but the boshes are beyond our reach, and when they are gone, the case is hopeless-the furnace must be blown out." Mr. Gibbons' observations extend in the second place to the upper part of the furnace. He states, that it appeared to him, if he at once made the room which the furnace makes for itself by a rougher operation, "I might probably preserve thereby a considerable portion of my hearth and boshes. I put in my hearth stones as wide asunder as the pillars of the stack would allow; I cut them upwards from the tuyeres to their junction with the boshes in a diagonal line, so as to bring them into the same, or nearly the same angle with the boshes, and I certainly found that my purpose was thus far answered.* The furnace lasted longer, the hearth did not call for repairs so soon; and there was this additional advantage, I arrived at my full burden and average make for months before the accustomed period." The second alteration Mr. Gibbons considers of even more importance:From the appearance of the lining bricks, it was evident that in the old form of furnace, the heat in the upper part had little intensity, the fire-bricks were barely glazed. With the view, therefore, of accumulating heat in this hitherto useless part, instead of building the interior of his furnace in a straight diagonal, or nearly so, from the top of the boshes to the filling hole, or tunnel head, "I scooped it outwards, so far as I could do so with safety to its structure; this gave me much room upward, the effect was unequivocal, particularly in my *Till this time the hearth stones were put in, forming a square of 21 to 2 feet at the bottom, and running up about 7 or 8 feet; and even to the present day there is a prejudice that the fire had better form its own hearth, but Mr. Gibbons very justly observes, " If the stones melted, it would be true to the full extent; but they do not melt, they shatter, and detach themselves in fragments of irregular shape and size, according to their natural clefts or fissures. If he were to build a new stack, he would place the pillars wide enough asunder to admit a five-feet hearth." |