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Smoke and soot came up the upcast. The flame had travelled all through the mine and 100 yards up the shaft. Naked lights were used and shots were fired.

Apedale (27th March, 1878). 40 men killed. Depth (?). Smoke and flame came up the shaft. The workings were set on fire.

Haydock (7th June, 1878). 195* men killed. Depth of the workings 750 feet. Smoke and dust were ejected from the shafts. The mine was dry and dusty. It was not possible to say how or where the explosion had occurred. Locked safety lamps were used and no shots were fired in the district where the explosion happened.

Abercarne (11th September, 1878). 264 men killed. Depth (?). A flash of flame and a column of black smoke ascended high into the air above the mouth of the shaft. The workings were set on fire. This mine was well ventilated, and no accumulations of gas of any consequence were known to exist in it. The workings were unusually dry and contained much very fine coal-dust. Locked safety lamps were used and no shots were fired.

Dinas (13th January, 1879). 63 men killed. Depth of the shaft, 1,218 feet. The workings extended under high ground, where they were from 1,500 to 1,800 feet below the surface; they were very dry and dusty. Small accumulations of explosive gas were sometimes formed in them, but not of sufficient magnitude to account for the disaster. The bottom of the principal shaft was filled up with rubbish in consequence of the timber which supported the entrance to the workings being blown away by the explosion. This obstruction has not yet been removed at the time I write, and the workings have not been entered, nor the bodies got out. I had visited this mine several times during the two or three years preceding the accident, and knew its general condition well. The return air coming from the working places, and therefore filling nearly one-half of the existing open space, contained always more than 2 per cent. of fire-damp. In this respect it did not materially differ from the return air of most of the steam coal collieries in the district, being better than some and worse than others. If there had been no coal-dust present I should have considered it to be comparatively safe. As it was, I strongly and repeatedly urged the manager to water the roadways so as to keep them always damp or moist, and he actually had two water-carts made for that purpose. On the occasion of my last visit before the explosion, however, I found they were not being employed, and I had no power to enforce my views. The result has been exactly what might have been anticipated, and what is liable to happen any day in every mine similarly circumstanced. It is quite plain that, with 2 per

*The official reports are not yet published, and in some cases the number of men killed may not be quite correct, as they are taken from the reports in the Times.

cent. of fire-damp in the return air, the slightest puff of a local firedamp explosion, or of a blown-out shot, will raise sufficient dust to increase the amount of inflammable matter a hundred fold, and produce all the phenomena that have been observed in this and similar cases. Locked safety lamps were used, and shots were fired. The cause of this explosion, like that of the preceding ones, will in all probability never be ascertained.

When smoke and soot are produced; or dust is ejected from the shafts; or the coal, stone, and timber have a charred appearance, due to a deposit of coked coal-dust on their surface; or, lastly, when large superficies of the sides of the galleries are found to be on fire immediately after the event, we may safely conclude that coal-dust has played an important, if not a predominant, part in the explosion. The manner in which coal-dust operates in setting fire to coal and timber is probably as follows:-The air is travelling rapidly in one direction along a gallery, throwing a continuous shower of dust, small pieces of coal, &c., against all surfaces that deflect it or obstruct its course; at the instant the flame traverses it, however, the coal-dust is melted; it then assumes the properties of flaming pitch, adheres to the surfaces against which it is thrown, and rapidly accumulates until it forms a crust of greater or less thickness, according to the length of time the air continues to travel in the same direction. If it is thick enough to retain its high temperature, and is supplied with fresh air immediately, it continues to burn, and the flame soon communicates itself to the body of the coal or timber; but if it is thin, or if the surrounding atmosphere cannot support combustion, it becomes extinguished. In the second case, the surface covered with the crust or layer of coke is vulgarly said to be charred.

During the course of the past year I have been enabled to make a considerable number of experiments with mixtures of coal-dust, air, and fire-damp; thanks to the liberality of the Lords of the Committee of Council on Education, who acted upon the recommendation of the Government Grant Committee in affording me pecuniary aid; and thanks also to the kind co-operation of Mr. Archibald Hood, managing director of Llwynypia Colliery, and his two sons, Messrs. Robert and William Hood, whose assistance has been quite invaluable to me. The two experiments I propose now to describe were made at Llwynypia Colliery with the coal-dust and fire-damp, whose analyses are given at pp. 357 and 358 of the "Proceedings," No. 168, 1876.

In order to test the truth of the hypothesis that the return air of a mine in which a considerable amount of fire-damp is emitted by the coal may be rendered inflammable by the addition of coal-dust, I had an apparatus constructed at Llwynypia Colliery, and placed close to the ventilating fan in such a position that a current of the return air from the upcast shaft could be made to pass through it at pleasure.

Referring to fig. 1, which represents the whole arrangement, e, f, g, h is the chimney of a Guibal fan, through which all the air from the

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workings, amounting to about 80,000 cubic feet per minute, is ejected into the atmosphere. a, b, c, d is a bent pipe partly made up of square wooden boxes, partly of round sheet iron pipes; at the end, a, it overhangs, and partly dips into, the chimney of the fan; and at the other end the part c, d, runs along the surface of the ground. k is a branch of the same area in cross section as the other wooden parts of the apparatus; it is covered on the top, but is provided with a hopper 1, having a wooden plug m, through which coal-dust can be introduced, v is a valve by means of which the velocity of the current can be regulated, and n is a door.

When the regulating valve is full open a strong current of return air, amounting to 1,251 cubic feet per minute, passes through the apparatus, and makes its escape at d. This air is not only saturated with

water, but it contains innumerable globules of water floating in it. On the 5th of October last its temperature was 69°3 F. An oil lamp, having a good large flame, was placed inside the door n, so that the flame was in the centre of the current, and it was then found that the temperature of the air had increased to 74°.5. The temperature, quantity, and quality of the various currents of return air in this colliery were, on the 11th of April, 1878, as follows:

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The elevation of temperature due to placing the lamp inside the apparatus is, therefore, not abnormal. The hopper having been filled with coal-dust the plug was raised somewhat and stirred about so as to determine the entry of dust into the chamber k. The immediate result was the appearance of a large and very hot red flame at the mouth of the pipe d. The length of the visible part of the flame varied from 6 to 8 feet, and its greatest diameter from 2 to 23 feet; and it was accompanied by large volumes of black smoke and dust. The pipe d soon became so hot that it could not be approached closely. The second experiment is intended to illustrate the effects of an explosion of fire-damp in a dry mine containing coal-dust. One part of the apparatus represents a gallery with coal-dust lying on its floor as well as on the horizontal timbers, the buildings, and other rough surfaces at its top and sides; another part represents a cavity in the roof containing an explosive mixture of fire-damp and air. When the explosive gas is ignited the flame sweeps down into the gallery, the disturbance raises the coal-dust and the results are exactly those that have been foreseen. Figs. 2 to 6 show all that is necessary for underFIG. 2.

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standing the apparatus and the experiment. In all the figures, A represents the cavity in the roof: it is a galvanized sheet-iron cylinder, 4 feet long by 15 inches in diameter, covered at the top and open at the bottom. There is a stuffing-box in its cover which allows a thin spindle to pass through it in an air-tight manner. At its lower end the spindle carries a fan which consists of a thin metallic disk 11 inches in diameter, having a hole 4 inches in diameter in its centre, and with radial blades 1 inches high on its upper surface. When the fan revolves, the blades, which are nearly touching the cover of the cylinder, throw out the air centrifugally and draw in new supplies through the hole in the disk. Immediately below the

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