4. Coal Dust. — The Ten Quarters seam does not produce a great amount of coal dust, and such dust as existed was rendered more or less inert by the stone dust created in brushing the shale roof and stowing the debris.

With a view to carrying out the General Regulations made under the Coal Mines Act, 1911, as to Precautions against Coal Dust, stone-dusting was done on the main roadways and on some of the levels. Samples of the dust lying on these roadways were taken during the months of September, October and November, 1922, and on analysis were found to contain less than 50 per cent, of combustible matter, thus complying with the requirements of the General Regulations.

I attribute the localisation of the explosion and the absence of propagation of flame by coal dust to the fact that the stone dust produced by the brushing debris sufficed to neutralise the dangerous character of the coal dust, i.e., this is another instance in which a high percentage of incombustible matter (exceeding 50 per cent.) in the mine dust prevented coal dust from propagating a gas explosion. It is also evidence in favour of "artificial" stone-dust treatment where the natural conditions do not supply the quantity of inert matter requisite to render coal dust innocuous. It should be mentioned that, while none of the dust samples referred to above was actually taken in Dixon's road, I believe the. coal dust there to have been naturally diluted by the working conditions of the seam. I consider that when collecting dust samples for analysis managers of mines should be careful to take samples from any places where blasting operations are contemplated, in order to ascertain whether or not special treatment is necessary to render these places safe before shot firing. I have previously drawn attention to this point in my reports on the Whitehaven and East Plean disasters.

5. Responsibility for the explosion. — The primary cause of the disaster was, I am convinced, the firing of a top brushing shot by the Deputy Johnstone when firedamp was present in the vicinity. That shot was the last of three fired by him. It was in my view an unnecessary shot, and at the same time overcharged, with the result that it emitted flame which caused the explosion.

It was stated that he had been warned by the Overman not to fire a certain shot, the first of the three, until the 2 per cent, of gas which had been found in the top brushing had been removed. That shot was, as a matter of fact, fired without any mishap; but it was followed by others without, I fear, the same care being exercised in regard to the clearing away of firedamp, and regardless of the requirements of Clause 5 (g) of the Explosives in Coal Mines Order, which stipulates that an inspection must be made and that the place must be found clear of inflammable gas before each shot is fired. But while saying that this failure was the primary cause of the disaster, I cannot regard the Management as being wholly free from responsibility in the matter.

There had been a temporary cessation of blasting operations in the Ten Quarters Seam owing to firedamp on previous occasions, and if similar foresight had been exercised in regard to the large cavity in Dixon's Level and the break leading therefrom, which could not be thoroughly examined with a safety lamp, the disaster would have been avoided.

In any case, if blasting operations were deemed to be absolutely necessary, those operations should have been sparingly carried on between shifts, when coal getting was not in progress, and only then with the exercise of the greatest caution.

With regard to the general question of blasting in a fiery mine such as this, operations are undoubtedly fraught with some risk unless the Regulations are most rigidly observed by all concerned. But there is always the human element to be borne in mind, for instance, the possibility of failure on the part of a Deputy to make the careful examination required and to see that a place is clear of gas, or of neglect on the part of some other person to see that adequate steps are taken to render coal dust innocuous, and it therefore behoves those responsible for the safety of the workers, not only to restrict blasting operations as much as possible by employing other means to the same end, but also to arrange for such shot-firing as may be necessary to be done at such times and under such conditions as will entail a minimum of risk.

In no case should blasting be done near breaks or cavities which cannot be examined for the presence of gas and near to which the air is liable to be vitiated with 2 per cent, of firedamp; further, when more shots than one are fired in the same road or place, a sufficient interval of time should be allowed to elapse after each shot to enable a careful examination of the place to be made before another shot is fired.

6. Other points raised at the Inquiry. — In course of the evidence given by, and the cross-examination of witnesses, the following matters not already discussed in this Report were referred to

The question of overtime by Deputies arose at the Haig Pit Inquiry, when it was contended, as at St. Helens, that no one knows a district so well as the regular Deputies assigned to that district, and that it is safer to allow one of the regular staff to work overtime than to put on another man who is less familiar with the district. There is something in this argument, of course, but the objection would be met if the person designated as spare Deputy were ordinarily employed in the same district on other duties, whereby he would have an opportunity to become acquainted with the district.

I have the honour to be,

Sir,

Your obedient Servant.

THOMAS H. MOTTRAM.