SOURCES OF THE COAL DUST.

The roads affected could not be said to be specially dusty. After the explosion over their entire length there was indeed evidence of coal dust in considerable quantity, and all the exposed surfaces were blackened, and there would be more coal dust before the explosion, as part had been consumed and part was blown into the return air ways and side roads. The question as to where the dust came from is worth earnest examination, as in the answer may lie possible remedies.

The coal dust caused in the driving of' the roads may be dismissed, as it would be small in quantity, and had no fresh sources of dust existed the intake and haulage roads would have been almost as free from it as the return air ways were found to be.

The important and permanent sources of coal dust on such roads are three –

The first condition necessary to the existence of coal dust on roads in a mine is sufficient dryness; the air in the Low Main seam was not particularly dry, yet the following observations made after the explosion indicate a sufficient degree of dryness to allow of the accumulation of dry coal dust. The air current, when these observations were made, was probably somewhat below its normal amount, and when also, owing to the damage in the downcast shaft not having been repaired, probably more moisture or water than usual was present in the shaft to saturate the air in its descent.

It will be observed that on the 22nd October, there was a difference of 2¼°F., and on the 29th October a difference of 2½° F., and on the 9th November a difference of only ½° F. between the dry and wet bulbs at the point where the shot was fired; this difference, although much less than has often been observed on the intake air ways in collieries, is nevertheless indicative, so far as the observations on the 22nd and 29th October are concerned, of a sufficient degree of dryness to allow of the existence of dry coal dust at the point.

As already stated, the screening plant for the Five Quarter and Low Main seams was near the upcast shaft. Little, if any, dust from this plant would come within the scope of the air descending the downcast shaft, as the coal in the first place did not produce much dust, and the tipplers or points where the tubs were emptied and the screens or belts where the coal was sized and cleaned were enclosed in a separate building some distance from that shaft. In the raising of the coal from these seams in the upcast shaft not much dust would be blown from the tubs as they were moving with the air current and any dust coming from them during transit in the shaft would also be whirled upwards and lost as dust be coming in contact with the moisture and exhaust steam.

At the downcast shaft the state of matters was different: the driest and most dusty coal from the Hutton and Harvey seams was screened here, and both the tipplers where the tubs were emptied and the screens were within the influence of the air descending the downcast shaft, particularly if the wind was from the East. The loaded tubs raised against the descending air in the shaft would no doubt part with some dust during the journey. Much of the dust from the screens on the surface and from the tubs in the shaft would be caught by such moisture as was present and fall with it into the sump at the Harvey seam and be lost as dust, but that some was carried in-bye by the air cannot he doubted. The onsetter at the Harvey seam stated to one of us before the inquest that dust came down the shaft and passed him and a quantity roughly proportional to the amount of air entering the Low Main seam would be carried into the intakes in that seam.

These considerations lead to the somewhat singular conclusion that some, and possibly most, of the coal dust on the upper parts of the haulage roads for some distance from the downcast shaft in the Low Main seam was dust from the coal of the underlying Hutton and Harvey seams.

There are, however, certain difficulties to account for before this view can be accepted ; if the dust from the screens and from the tubs in the shaft reached the Low Main seam why was it not seen in the Main Coal and Hutton seams, which were ventilated by currents from the same downcast shaft and the intakes of winch were found after the explosion to be free from any considerable or apparently dangerous quantity of coal dust ? Even had coal dust in dangerous quantity been present on the intake (there was only one) in the Hutton seam the explosion would not in all probability have extended into it, as the damp condition of the downcast shaft and return staples arrested its progress both downwards and upwards by these, the only routes, and the same reason led to the Harvey seam escaping entirely, the intakes of which were more dusty than the intakes in the Low Main seam.

The routes to the Main Coal seam above, which, as already stated, was in turn connected with the Five Quarter seam, included one, the drop staple, which had apparently been sufficiently dusty to extend the explosion upwards to the Main Coal seam, but it had not extended in that seam any considerable distance a way from the staple top, but might have done so had the roads in the Main Coal seam been dusty.

The only explanation the under manager could give when questioned on the point at the inquest was that much less air left the shaft at the Main Coal and Hutton seams than at the Low Main and Harvey seams and that as regards the Hutton seam it had only recently been re-opened after standing with the ventilation largely reduced for some years. In addition to these considerations it should be. stated that as the depth to the Main Coal seam was not great it would be more moist, and the roof stone being of a soft nature small falls were constantly occurring, exposing new and clean surfaces, particularly in the summer time when warm saturated air descending the downcast shaft was cooled in its passage in-bye and deposited moisture.

The principal source of the fine dust on the upper surfaces of the main haulage and intake air ways in the Low Main seam may have been dust blown from the loaded tubs drawn out-bye by a rope at a speed of about 8 miles per hour against the ingoing air current, but against this view is the fact that the coal from the Low Main seam does not produce much dust, and outside the probable influence of the screen dust there was little fine coal dust to be observed on the upper surfaces of the intake air ways and mechanical haulage roads in that seam.

Whatever the source of the dust there was no doubt of its existence as fine dust, adhering to the timber roof and sides of the road and lying on the bottom mixed with coarser particles and debris, in parts of both the Low Main and Harvey seam haulage roads.

CONTRAVENTIONS OF THE LAW.

The cause of the explosion was the firing of a charge of geloxite, a permitted explosive, on the main haulage road under conditions involving the following contraventions.

It was not alleged, and we do not think it likely that any official of the mine had authorised Maddison to use any explosive at the point where he was directed to work.

The abstract of the Coal Mines Regulation Acts and the Special Rules are posted up at the Colliery, and it was stated that a copy of the Special Rules was handed to each authorised shot-firer when his licence was given him. It was suggested at the inquest by Mr. Ruegg that detailed information as to the conditions under which shots can be fired should be printed on the licence, and this the manager agreed to do, and he has since decided, as an extra precaution, that each shot-firer shall sign a book acknowledging receipt of the Special Rules.