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Possible Causes Of The Explosion.

In the absence of any direct or conclusive evidence as to the cause of the explosion it only remains to review all possible causes and then eliminate those which are improbable. There is no doubt in our minds that the chief element, in at any rate extending the explosion, was coal dust, but we are of the opinion that the explosion itself was initiated by the ignition of firedamp.

Presence of Firedamp. — It is hardly conceivable that "gas" could be present on the main intake haulage road in such quantity as to constitute an explosive mixture, for the main air current of 23,260 cubic feet of air was passing along, this road. A reference to the plan of the workings (Plan No. 1) will show, however, that there existed two large goaves on the low side of the main engine plane, which, provided they had not been rendered tight by heaving up of the floor or pressing down of the roof, might constitute reservoirs of gas ready to be liberated on a reduction of atmospheric pressure. Owing to the soft thill (floor) of the Harvey Seam and the facility with which the roads and goaf "heave" close, it was at first considered that there would be little or no open goaf space when the coal had been extracted several years previously. At the time of the explosion the atmospheric pressure was fairly steady, and the mercurial column of the barometer stood at a medium height of 29.05 inches. On a subsequent occasion, on March 19th, after an abnormal fall in pressure amounting to one inch in 15 hours (28.42), Mr. Hay (Junior Inspector of Mines) examined the edges of these goaves, and also the airway between them and the main engine plane. At this time both roads were acting as intake airways, and in spite of the fact that a current of 2,000 cubic feet of air per minute was passing along the low road nearest the goaf, gas was detected at the demolished old south air-crossing, in the return air-way from this district at the regulator, and, in fact, at all the open holings from these goaves to the air-way. At the time of the explosion this road was not looked upon as a return air-way, and a current of only about 2,000 cubic feet per minute was allowed to pass along it through a regulator at. the point R (see Plan No. 1) which was kept about three inches open. The conditions existing at the time of this examination (on March 19th, 1913) were, of course, very different from those on October 27th, 1912, but the results are interesting as proving that there was a gas space existing in these old goaves. It should also be borne in mind that owing to the position of the regulators and the feeble current of air in this road there was nothing to prevent gas ascending from the goaves towards the engine plane stoppings. Assuming the firedamp to be present in an explosive mixture on the date of the explosion there are several ways in which it might be the means of initiating an explosion.

By Sparks caused by the Friction of Rocks. — The Harvey Seam roof in this area is frequently formed of strong sandstone, and there is the possibility, perhaps remote, that asses of this rock in falling in the goaf might by friction cause sparks sufficient to explode a mixture of firedamp and air. There are several authentic cases of sparks having been so produced in other mines. No evidence has been found to suggest this as a probable cause of the explosion.

By Matches. — There is always the possibility of flames from matches which may, in order to avoid detection, have been thrown into the goaf at some remote period. It is probably only a coincidence, but the point where the explosion on the engine plane commenced - if the deduction from the evidences of force is correct — was the place where the workmen daily left a portion of their clothing after getting out of the set or train which brought them inbye to their work from the shaft. Jackets and other portions of clothing were usually placed on the rough pack wall at this point. However, no remains of matches or match boxes have been discovered though a most careful search has been made from time to time since the explosion. If they were present at the time they might have been destroyed by the force of the explosion.