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without reference to the special application of which we are treating, this method is of paramount importance at the present moment to the iron trade of the whole world.

As this method is but the last of a number of successive improvements which have been effected in different countries and by different persons, it may not be uninteresting to our readers to trace the progress of these improvements.

The first mode of economising the waste gases of furnaces was that of Faber du Faur, who placed a ring of flues all round the inside of the furnace, at about one-third of the height of the body from the top. These flues passed upwards through the brick work, and the hot gases were then conducted away by a descending pipe to the points where they were required. This method had the disadvantage of drawing off not merely the waste gases, but even the actual flame, so that a large portion of the heat was wasted; and when used in heating the blast, or for similar purposes, the heat produced was so excessive that the apparatus was often burned through. Mr. James Palmer Budd, of Ystal-y-Fera, in Wales, to whom the honour belongs of having first attempted to utilize the waste gases in Great Britain, modified the method of Du Faur, by tapping the gases at a part only three feet below the throat of the furnace. As the same quantity of the gases would not enter flues at that point as lower down, and as they would get mixed with air, Mr. Budd, by making an upright flue, 25 feet higher than the platforms of his furnaces, and provided at top with a kind of damper, was enabled to suck, as it were, any quantity of the hot gases, and make them pass under boilers and heat the blast, &c., before finally passing off through a high chimney. It is unnecessary to remark, that in Mr. Budd's arrangement for heating the hot blast, the gases were not burned, except in the case of the steam boilers, under which we believe the gas was burned; it was only the high temperature at which they issued from the furnace that was taken advantage of.

The next modification worthy of notice is the mode in use at the Dundyvan Works, in Scotland. The furnace is 42 feet high, and is 12 feet in diameter at 8 feet from the top; from this point it narrows to 8 feet at the filling place. Just below the point at which the narrowing commences is a ring of 8 flues, 4 feet high and 18 inches in diameter, all of which open into an annular flue surrounding the top of the furnace, from near the top of which the gas is conducted away. A similar plan is adopted at Pontypool, the width of the furnace in this case, below the ring of flues, being 13 feet, and narrowing to 9 feet 6 inches.

Another plan, and one indeed adopted at a very early period, was to introduce a cylinder somewhat smaller in diameter than the throat of the furnace, and open at both ends, into it, and having a projecting flange on its upper end, which rests on the top of the furnace. There was formed an annular chamber, in which the gas collected, and into which the flues or ports opened. By keeping the central cylinder full of fuel and ore, a certain resistance was offered to the passage of the gas, which accordingly passed off by the flues in the inclosed space. This plan, which was first employed on the Continent, has also been tried in Great Britain, and

among other places we believe at Dundyvan, in connection with the system of flues just described.

In all the preceding cases only a portion of the gases was economised, whilst the rest escaped into the air. To utilize the whole it would obviously be necessary to completely close the furnace, and accordingly one of the earliest attempts was that made at the great iron works of Le Creusot, in France. This method, which is, we believe, still used in seven furnaces there, is represented in fig. 1. C is a conical iron cylinder, which

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has exactly the same inclination as the walls of the furnace, S, and therefore as it were a continuation of it. Just below the cylinder, C, the wall of the furnace is beveled off for a short distance, and then goes up parallel with the cylinder, C, forming an annular space exactly like that described above. D is a double cover, hinged on at s, and which may be lifted by means of the lever, h, with the counterpoise, g. This cover has a flange all round it, seen at dd, which fits into an annular box or groove, in which water or sand may be put to form a tight joint. The gas, as it ascends, passes into the annular space around C, from which it is carried off by the gas duct, R, having a throttle valve, v, for regulating its supply as may be required. Independent of the fact that by this plan the furnace can be completely closed down, the cylinder, C, being in a line with the walls of the body of the furnace, S, allows the charge to descend with the same regularity as if the furnace were open; whilst with the cylinder before described, the materials went too much towards the centre, which is a great evil, as it is of great importance to have a column of blast in the centre of the furnace, while the ore and flux should lie towards the sides. This last object is still more perfectly attained in the next modification of importance with which we are acquainted. This plan, which is represented in fig. 2, was, we believe, first adopted by Mr. Levick, of the Cwm

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Celyn Works, near Abergavenny, in Wales, and a model of it was exhibited at the Great Exhibition of 1851, in connection, if we recollect aright, with a model of a blast furnace contributed by Mr. John James, of Blaina Works, which belong to Messrs. Crutwell, Allies, & Co., who are also the proprietors of the Cwm Celyn Works. The upper part of the body of the furnace, for a distance of about 5 feet below the mouth, M, is cylindrical. At the junction of this cylindrical part with the conical body, S, is a double cross, a, formed of iron bars let into the masonry; upon the centre of this cross is placed the cast iron cone, A, the apex of which is in the axis of the furnace, and whose base is about 2 feet all around from the wall of the furnace. Upon the same cross bars rests the hollow annular cast iron cylinder, B, open at its lower end, which diminishes the mouth of the furnace, m n, to the space, o p. The lower edge, q r, of the inner wall of the cylinder, B, is about 14 feet from the base of the cone, A, so that an opening of 18 inches wide exists all around the cone into the body of the furnace. This opening can be closed by means of the cylinder, C, open at both ends, which fits on the inner wall of the cylinder, B, like the tubes of a telescope, and may be drawn up or let down by the rods, k h. When the cylinder, C, is let down upon the cone, A, the furnace is completely closed, and the whole of the gas will pass off by the duct, D. If in this case the internal cylindrical space over the cone is filled with fuel, ore, and flux, and the cylinder, C, be lifted to the level of the dotted line, G, the whole charge will fall into the furnace, and under the best conditions, for the central column of blast will remain undisturbed. The duct, D, can be closed, in case it may require closing, by the damper, d; in such case, the pipe, b, which is closed by a cap, admits of the escape of the gases. By this plan all the gases could be economised, except merely what passed off while the charge was being allowed to fall into the furnace.

The next important improvement with which we are acquainted was that effected at the Ebbw Vale Works, near Abergavenny, and is manifestly an improvement upon the plan followed at the neighbouring Cwm Celyn Works just described. This method will be at once understood by a reference to fig. 3. In this case a hopper, in the shape of an inverted truncated cone, B, is fitted into the mouth of the furnace, corresponding to the internal cylinder in fig. 2, and by making the cone B movable, the cylinder, C, in fig. 2, is dispensed with.

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Fig. 3.

When the cone is drawn up by the chain and lever shown in the figure, the furnace is perfectly closed, and the whole gas is forced to pass off by the pipe, C.

Fig. 4.

Fig. 4 represents a modification of this plan adopted by Mr. Blackwall, either in Derbyshire or South Staffordshire, in which, however, there is no feature of novelty. A is a vent closed with a cap upon the main gas duct B; D is a smaller duct leading to the conducting pipe C, which is also provided with a cap to facilitate cleaning.

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There is a great difference of opinion relative to the economy of closing down furnaces; some assert that it is not so great as was anticipated, whilst others say that only white iron can be made with closed furnaces. Into this question we shall not now enter, but we may as well say that the plan shown in fig. 3, and a model of which was exhibited at the Great Exhibition of London, already was in such successful operation in the previous year (1850) at the Ebbw Vale Company's works, that out of 25 boilers required to work 5 blowing machines, which supplied air to 11 high furnaces, 19 were fired with gas alone.

It will no doubt be interesting to mention here the nature of the gas generators used at Ilsenburg, in the Harz, for iron puddling, to which allusion has already been made. These generators are made either with a round or square section, both forms having been found equally well adapted for the object required, and work by the ordinary draught of air, no blast being used. There is first an ash-pit, 2 feet deep and 2 feet 6 inches square. Over this is placed a grating of fire-bars, resting upon two iron bars 3 inches square; above the grating is the hearth, 9 inches high. The ash-pit and hearth would, in fact, constitute, if the fire-bars were removed

a hearth similar to that of an iron furnace. Above the hearth is formed a small boshes, 1 foot high, with its greatest diameter 3 feet 6 inches, which again diminishes at the top of the cone or body to 2 feet. The height of the body to the gas duct is only 3 feet 6 inches, and the gas duct is 18 inches high and 18 inches wide, so that the whole height of the cone is only between 5 and 6 feet.

The filling of this small high furnace takes place by means of an iron cylindrical hopper placed on top, 7 feet 9 inches high, and 1 foot 6 inches in diameter. This hopper is closed by means of a lid, and has a sliding damper or valve 3 feet below the top. When this valve is closed the the lid on the top may be opened and the fuel introduced, so as to fill the three feet of the cylinder or hopper above the valve; the latter is then drawn out like a damper and the charge allowed to fall into the furnace. In a subsequent article I will return to this subject of gas puddling, and then have an opportunity of giving some details respecting the cost of fuel, quantity of iron puddled, and other matters which would now occupy too much space.

The great disadvantage attending all the methods which we have described, with the exception of that used at Ilsenburg, is, that every time that a charge is introduced into the furnace, there is a momentary diminution of the quantity of gas passing into the respective flame beds, owing to the top of the furnace being opened. This is not of so much consequence in iron furnaces worked with coke, where the charges are larger and are not, comparatively speaking, very frequent; but it is very different in the case of a peat works like that which we are describing, for peat is so bulky, that even with a large hopper each charge is very small, and then the waste gases should be so fully economized that even the momentary diminution of the regular flow of gas would produce serious inconvenience. Hence the necessity, not alone of closing the furnace itself, but also of closing the hopper in the manner described. In this alone it differs from the system at Ebbw Vale, upon which it is evidently an improvement, but though slight yet in our opinion an important one.

We shall now return to the description of the arrangement of the Peat Works, which we broke off in order to shew what had been done in other places towards effecting the shutting down of iron furnaces.

The air blown in by the tuyeres a a, comes in contact with incandescent charcoal on the hearth, a combination ensues, the oxygen of the former, in presence of an excess of carbon, is resolved into carbonic oxide, which, in an intensely heated state, passes up with four times its volume of similarly heated nitrogen, the residue of the air after the abstraction of the oxygen, through the body of the furnace, until it meets with the fresh charge of peat, which it heats sufficiently to allow of complete distillation taking place. The results of this distillation are: water containing, as already several times remarked, ammonia, naphtha, &c.; tar, and gas, consisting chiefly of carbo-hydrogen. From the high heat of the ascending gases, the tar and aqueous products are produced in the state of vapour, and are carried along with the gas, and conveyed away by the outlet pipes C, of which there are two to each furnace; these pipes issue from near the top of the furnace, and consist of a short ascending branch and a long descending one,

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