by 2 p.m., the conditions for the work being extremely favourable except in the return airway where there was delay for a short time on account of thick smoke. As soon as this had been partially cleared away by short circuiting the air current at the separation doors between intake and return, men wearing rescue apparatus were able to get to work and soon erected a temporary stopping sufficiently adequate to allow other men without apparatus to complete the stopping. All persons were then withdrawn from the mine and it was decided not to approach the stoppings for a period of 30 hours. In accordance with this arrangement, an inspection of the stoppings was made at 8 o'clock on Sunday evening when they were found undisturbed, and there was only a slight smell of burning timber at the return dip stopping. The stoppings in the West level and air heading beyond the Dirt Jig" (see Plates 1 and 2) were also inspected and found to be in satisfactory condition. 66 Arrangements were then made for strengthening the dip stoppings, the intake one with brickwork and the return one with sand packing. Another inspection was made on Monday morning when it was agreed that the mine was safe for the re-admission of workmen. The report required by the General Regulations of the 30th July, 1920, Nos. 9 (i) and (ii), was posted and coal drawing was resumed on Tuesday morning. In the meantime plans had been set on foot for exploring the explosion area and recovering the bodies. For the purpose of this report it will suffice to mention that these operations were commenced on 4th January, 1926, by three of the colliery rescue brigades working inside an airlock. This was first installed in the West level between the tops of the intake and return dips, and later advanced to the airheading which was originally the return from Kelsall's dip. The operations were completed on 1st April, 1926. The recovery work to be performed was probably more hazardous and arduous than any previously recorded in the annals of mining in this country, but it was carried through persistently and methodically in the face of great difficulties without a hitch or accident of any description. To enter into the great detail necessary to do justice to the subject of these recovery operations is beyond the scope of this report. But it is most desirable that the facts should be made fully known to the coal mining industry, and I venture to hope that in the near future they will be published in the form of a paper read before one of the Institutions of Mining Engineers. The greatest credit is due to all the members of the brigades who took part in the operations and I am glad to have this opportunity of paying tribute to them. At the same time I feel sure that they will agree with me that great credit is also due to the Agent, Mr. Allott, and his staff of officials, whose careful organisation, clear plans of procedure and keen and ceaseless supervision inspired confidence and made success possible. VI. SEAT AND CAUSE OF THE EXPLOSION AND POINT OF IGNITION. The most important evidence as to the seat of the explosion is that of the fireman, Amos Whalley, quoted above at page 11, and of Edgar Threadgold, hooker-on, who was working at the bottom of Kelsall's dip at the moment of the explosion and who described his experience in the following words : 378. Q. Shortly before quarter to five where were you-at the bottom of Kelsall's Dip?-A. Yes. 379. Q. You are a hooker on ?-A. Yes. 380. Q. Which way were you facing ?-A. I was facing towards the level. 381. Q. You were facing the gob?-A. Yes. 382. Q. Did you notice anything different to the usual?-A. When I first went in? 383. Q. No, just about this time before the explosion?-A. There was a wind first; a slight wind. 384. Q. Did you turn round?-A. Yes, it was followed by a big rush. 409. Q. Had you got another tub hooked on?—Yes. 410. Q. When you had your face in the direction of the gob and felt the rush of air? A. Yes. 414. Q. When you got the rush of air from the gob you turned your face outwards?-A. Yes; I turned to go then. 415. Q. And you found the direction of the air current had changed and was again hitting you in the face as you went out? -A. Yes. This evidence in my opinion definitely establishes that the seat of the explosion was somewhere in the goaf beyond the pillars on the left hand side of Kelsall's dip. How far beyond the pillars it is impossible to suggest, except that it was probably some yards beyond the area over which the ventilating current normally passed. Accepting this as being the seat of the explosion the field for discussion of its possible causes is materially curtailed. Blasting, electricity, the haulage brake wheels* and defective lamps are ruled out at once. To make assurance doubly sure in respect of the safety lamps, they were all submitted to examination and test by the Testing Officer whose report proved that generally they were in safe condition. Some of them were damaged, but the damage was such as to indicate that it had resulted from the explosion and * Brake wheels are mentioned because a serious fire was caused in this mine some years ago by heat generated by friction at a brake wheel. was not likely to have been the cause of it. Further, in support of that conclusion, we have evidence to the effect that, as far as is known, there was not an inflammable mixture of firedamp and air in any of the working places, The possible sources of ignition are therefore narrowed down to : (1) Matches in the waste. (2) Frictional sparking from rock falling in the waste. (1) Matches in the waste.-The possibility of the presence of matches cannot be dismissed, but it is no more than a bare possibility and the character of the seam and other considerations lead one to look for some more likely cause. (2) Frictional sparking from rock falling in the waste.--This possible source of ignition was referred to by several witnesses but was not stressed. It is quite possible, indeed it is almost inevitable, that sparks are produced by falls of rock of the hard nature of the rock forming the roof of the Seven Feet Banbury Seam. Although no first hand evidence of such sparks was adduced, it can be accepted that flashes have been seen on occasions when heavy falls have occurred. Experiments on an extensive scale with this rock have failed, however, to demonstrate that firedamp can be ignited by such transitory sparks. In this connection I desire to quote the following statement by Professor Wheeler, who was good enough to give us the benefit of his wide experience on the matter: 3523. Q. Mr. Wynne: On the particular point of the possibility of fire being caused by rock falling?-A. I would not care to say that it is impossible, but I regard it as very unlikely and perhaps I might explain the reason why I regard it as very unlikely. It is possible, experimentally, to obtain ignition of firedamp and air mixtures by rubbing a piece of rock on another piece of rock. That ignition takes place not by the sparks which are produced when you rub a piece of rock like the rock in this seam on another piece of rock, but by a hot spot which is formed at the point of contact between the two rocks. To explain in detail the manner in which that experiment is made, you can make a wheel like a grindstone wheel out of the rock from this seam, and when that is revolving rapidly and you press a small portion of rock up against this wheel with considerable pressure-equal to about 30 or 40 lbs. pressure-you will get a stream of sparks. Those sparks will not ignite a mixture of firedamp and air, but as you continue to press the piece of rock, the piece of rock you are pressing becomes hot, and when hot enough, namely, red hot at a temperature of about 800 degrees Centigrade, then it can ignite any mixture of methane and air within the limits of inflammability. But this operation of producing a hot spot spot on a piece of rock is a matter sometimes of minutes. We have never in our experiments been able to obtain an ignition under a few seconds at least. It is not instantaneous. That is the point I chiefly want to make. There has to be so much work put into the operation of rubbing one piece of rock against the other that I cannot conceive of that happening in actual practice in mining; not, I mean, under the conditions which obtained in this pit. It may happen where there is mechanical coal cutting, a matter which I do not want to go into just now. So that in general, although, as I say, I would not like to regard it as impossible for ignition of firedamp and air to take place by heat engendered by one rock striking on another, I think it unlikely. Another point suggested in the evidence, by inference, has been that you might possible cause ignition of paper, if you cannot cause ignition of fire damp. On that I can say definitely so far as our experiments go at all events-and I think they are very stringent experiments which will correspond with the most that can happen underground-we have not been able to ignite paper by sparks produced by rock on rock. You can do so by metal on rock, but not by rock on rock. That completes my statement, Sir. 3524. Q. What about ignition of coal dust?-A. Coal dust is much more difficult to ignite than a mixture of firedamp and air. 3525. Q. Can you say anything about the possibilities of igniting say resin exuding from timber?-A. The manner in which these ignitions are obtained is by a completely mobile medium moving round a hot piece of rock. You must have a gaseous mixture. Coal dust to be readily inflammable has to be mixed with air-you have to presume a dust cloud formed all round this hot spot, and a dust cloud is more difficult to ignite than firedamp and air, and you would in some way have to have a dust cloud of resin and air in order to cause ignition at that hot spot. 3526. Q. Would it be feasible to suggest that a spark such as you have described momentarily dashing on to a little exudation of resin could ignite that resin ?-A. I do not think so. We could not light such an easily lightable thing as tissue paper by such sparks. We can ignite it by metal sparks, but not by sparks from rock on rock. 3527. Q. Would the same apply to possible exudations of mineral oil? A. Yes, mineral oil is not as easily lightable as firedamp. Experiments of this kind are of course purely empirical but so far as they go they show that the ignition of firedamp by sparks produced by rock falling upon rock is a very remote possibility. A transient spark is insufficient in itself for the purpose. A prolonged spark or series of sparks concentrated at one point for an appreciable period of time might ignite firedamp if present in the air in ignitable quantity, but even this is open to doubt. Experiments show that continued friction at one stationary spot will produce ignition after some time, but it is difficult to see this happening under such conditions as arise when rock falls in a steeply inclined goaf. (3) Heat from spontaneous combustion.-The jury arrived at the conclusion that firedamp was ignited from heat from spontaneous combustion. I agree with them. In view of the character of the seam and its previous history in respect of heatings, it appears to be the reasonable conclusion to reach. The only cause for hesitation in arriving at this conclusion is the alleged absence, prior to the explosion, of any of the usual indications of incipient heating. To those who have had experience of gob fires unmistakable indications are generally manifest when incipient heating is going on. As a rule such heating results in gob stink, a smell which in its early stages may be faint and indistinct, but which, as the oxidation becomes more active, should leave no doubt as to its cause. This is not an invariable rule, but there appear to be few cases on record to the contrary. In this instance, were such indications entirely wanting? I do not think they were. In my opinion, the unusual smell which Forrester noticed in the return airway emanated from the goaf in Wakefield's district of the Seven Feet Banbury and was a faint gob stink. Neither Forrester nor Hughes would admit that they smelt gob stink but there is no doubt, I think, that they strongly suspected it. In justice to them and to Lowe and Wilcox I must say that I accept their statements that later on, the smell, whatever it was due to, had disappeared. At the same time it is. difficult to account for the fact that no smell was ever noticed by the day fireman or any of the workmen in the district, most, or at any rate some, of whom one would expect to be fully alert for it and fully alive to its significance. It is quite possible, indeed, in view of the evidence, it seems to be established that there never was any smell in the working places. It is also quite possible that the smell was barely more than momentary in the return airway where Forrester and Hughes detected it. Some disturbance in the goaf, such as a fall or a slip of debris may for an instant or two have projected gases from a heating into the sweep of an air current by which they would be carried into the return without touching the main current in the working places. In no other way can I account for the appearance of the smell in the one place and its absence from the other. A glance at the plan leads one to suspect leakage at the stoppings in the two roadways at the right hand top corner of the area of goaf (see Plates 1 and 2) but against this is the evidence of Forrester and Wilcox that they got no smell at all at these stoppings, although they detected it in the thirling known as the "Dirt Jig," a short distance outbye thereof. It is to be regretted that a more definite conclusion |