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Summary And Conclusions.

The Point of Origin and Cause of the Explosion. — An examination of the plans on which are given the indication as to the direction of force conclusively proves that the point of origin of the main explosion was at or within ten yards on either side of the joint box marked J on the plans. The explosion was without doubt in the main a coal-dust explosion, and although it cannot be positively ascertained we are convinced that it was initiated by a previous explosion of firedamp and air. All direct physical evidence of such an initial explosion was subsequently destroyed by the principal explosion. As to the igniting cause we are at a loss to explain it, but we think that by a process of elimination the most probable was spontaneous combustion in the low side goaf.

Ventilation. — If the air road on the low side of the Main Engine Plane had been utilised as a regular return airway, and a considerable quantity of air allowed to pass along it, instead of simply a scale of 2,000 cubic feet per minute, throttled down by means of a regulator only three inches open, any likelihood of gas discharged from the low side goaves being able to rise up to the engine plane stoppings would have been removed.

Coal Dust. — The Harvey Seam Main Engine Plane had been used for many years for hauling coal at high speeds. There was therefore considerable dust on certain portions of the road, notably in old pack walls, which the means adopted were insufficient adequately to cope with. Cleaning up was resorted to and watering by means of pipes laid along the engine plane. But once an explosion was started, there was ample dust to carry it on with increasing intensity. The explosion never passed more than a few yards into the returns, and in the case of the inbye portion of the North Crosscut Engine Plane soon died out on reaching the area where bottom had recently been taken up. These facts in our opinion point to the advisability of dusting with inert stone-dust the floor, sides, and roof of the haulage roads, and such other parts of the mine where coal dust is liable or likely to accumulate, as well as of removing the dust from time to time. On the question of the proportion of stone to coal-dust which is necessary to render the latter innocuous, as this matter is still under consideration by the Departmental Committee on Coal-dust and Colliery Explosions, we forbear to make any suggestions.

Joint Boxes. — The occurrence of the flashing at the joint box at Black Boy and the vapourization of the compound inside the box serves to remind us that the joint boxes may be regarded as more likely to break down under abnormal conditions such as a sudden rise of pressure than the cable itself. To meet such a danger, we suggest that all joint boxes should be securely built in with brickwork and well filled with sand. This has been done at several large collieries in the county.

In conclusion we wish to express our appreciation of the considerable assistance voluntarily afforded to us by Mr. S. Hare, Agent for Messrs. Bolckow, Vaughan & Co., Ltd., and Mr. J. C. Hall, Manager of Auckland Park Colliery, in supplying all the information available to them, and in other ways contributing to the investigation of this mysterious explosion. Our thanks are also due to Mr. Douglas Hay, H.M. Junior Inspector of Mines, for his zeal in assisting to elucidate the cause of the explosion, and for his detailed work in preparing the plans illustrating this Report.

We have the honour to be

Sir,

Your obedient Servants,

R. A. S. Redmayne,

Arthur D. Nicholson.