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Conclusions and Remarks

The explosion was due to firedamp accumulating in Bailey's place consequent, in all probability, upon a derangement of the brattice doors across the road known as the "Brake". If the firedamp accumulated in Bailey's place from this cause, it is difficult to understand why Cowan did not discover it unless he examined the place before charging the hole and not immediately before firing. In this connection there is the evidence of James McGlennon that at two minutes to eight Cowan appeared to have been charging the shot-hole.

The practice of making an examination prior to charging a shothole is not an uncommon one. It is a very proper practice but, to comply with Clause 6 (f) (i) of the Explosives in Coal Mines Order, it must be supplemented by an examination "immediately before the shot is to be fired".

The ignition of this firedamp was due either (1) to a spark within the exploder or across the conductors of the firing cable or (2) to sparks or heat caused by the friction of the Cardox cartridge when it struck and penetrated the end of the steel tub.

The first mentioned cause was proved to be possible, but experiments carried out by the staff of the Safety in Mines Research Board have not yet resulted in the ignition of firedamp by sparks or heat caused by the friction of steel pressing upon steel except where the point of contact was enveloped by a shroud of metal. wood or other material.*

The reason why an exploder was used of such power as would give a spark capable of igniting fire damp was the failure of a smaller powered exploder always to fire the shot.

It is true that following a report** by a Sub-Committee of the Explosives in Mines Research Committee exploders which fire shots but will not ignite firedamp have been designed and that such exploders are in use in various collieries in the country. It is also true that some of such exploders have not been found in use to retain their safety qualities. This matter is being given further attention and on being solved, the use of such exploders should be made compulsory.

The Cardox cartridge was ejected from the shothole at the right side of Bailey's place because that shothole was not well placed, or, in other words, the cartridge was given more work than it could do — the "burden" was too great.

Cartridges were not infrequently ejected from shotholes in another district of the mine. The cause, in such cases, is as stated, and is one which can be remedied.

The explosion was spread throughout the district because of dampness causing the limestone dust to bind and not rise and intermingle with the fine coal dust which lay upon it.

The stonedusting regulations in force in the Dortmund area of Germany require that the incombustible dust used shall be capable of retaining its "loose" condition when in the mine, and alternative tests for "looseness" are prescribed as follows

In either case, if at the end of the period the dust can be blown away in a cloud by lightly blowing on it with the mouth, the test has been satisfied. Some such test would appear to be necessary in respect of incombustible dusts used in the mines of this country.

I desire to record my deep appreciation of the courtesy and restraint shown by the representatives of the parties to the Inquiry and by all those who attended the Inquiry.

I have the honour to be,

Sir,

Your obedient Servant,

HENRY WALKER.

* S.M.R.B. Paper No. 54.

** S.M.R.B. Paper No. 11.