13. So far nothing has been considered except the indications which are furnished by the observed effects of the explosion. But in attempting to form a conclusion as to the place of origin there are two other elements for consideration, namely, how the presence of explosive matter can be accounted for, and what means of ignition existed at either of the points so indicated.

14. It has been stated that at none of the points in question, all of them points in the main intakes and near the downcast shaft, can the presence of gas in sufficient quantity to account for an explosion of the ordinary kind be accounted for by an ordinary issue, blower, accumulation, or leakage. It was indeed suggested that the arrangements for ventilation at the Main Coal Staple ("D"), and in that portion of the Maudlin engine plane which is nearest to the Curve were such as made it possible that there might be an occasional balancing or partial stagnation of air at those points, but none of the witnesses connected with the mine thought that any such balancing or stagnation ever happened in fact; nor could a sufficient accumulation of gas easily occur in this way to account of itself for what occurred. The great volume of air sweeping the intakes at all the points in question would require a large quantity of gas to bring it to an explosive condition under ordinary circumstances.

The witnesses called for the proprietors concurred in adopting a suggestion which fits in with their opinion of the point of explosion as indicated by its observed effects. Their suggestion was as follows :— Among the many falls of roof which were found after the explosion in various parts of the area affected, one was found in the No. 1 Hutton intake at a point about 550 yards south of the downcast, and a few yards north of the point "C" in the neighbourhood of the Polka doors. These witnesses suggested that this fall possibly occurred immediately before the explosion and liberated a bag or reservoir of compressed gas which did the mischief, and they pointed to the fact that the fall was in the neighbourhood of a trouble, and that a number of fissures or "jacks" occurred in the roof in the same neighbourhood, as showing a faulty condition of the strata. The great objection to this suggestion is that it is a pure assumption based on no evidence whatever. There was nothing to indicate that this particular fall had occurred before the explosion, or in any way tending to show that this particular fall differed in character, cause, or time from any of the numerous other falls found in other parts of the mine. The gallery was about 25 years old, and no fall producing gas had been known by Mr. Stratton to have occurred in it at any time. The fall was at some distance from the actual trouble, which was not affected. The fissures or "jacks" which existed in the neighbourhood might be expected to have operated as escapes, by which any old accumulation of gas would have long since drained away. When a large quantity of gas conies off at a fall it is usual to find some continuance or remains of gas for hours or days afterwards; but nothing of the sort could be found in this case. Further, according to the evidence of Mr. Forman, on behalf of the miners, which no witness was called to contradict, and on which he was not cross-examined, the timbers which supported the roof of the site of the fall were not broken or crushed, and were actually blown out of their places southwards, not from, but towards the lamp at which according to the proprietors view the gas must have exploded. If this is correct, it appears to show nearly conclusively that the fall followed instead of preceding the explosion; and the only suggestion by which gas was attempted to be accounted for being negatived, the explosion would be entirely inexplicable.

This difficulty was at an early stage of the explorations understood by the miners, who then began to suggest that the coal dust, which, as has been stated, existed in large quantities in sonic parts of the mine, and especially at the Curve, might have had something to do with the explosion. Their suggestion, at first put forward in the probably untenable form that coal dust, when suspended in the air of a mine, may of itself, without any gas, suffice to produce all the phenomena of a violent explosion, was referred to Professor Abel for consideration, and in his hands it received certain modifications, and as so modified it has assumed great importance. His report in full is annexed to the special report of Mr. Inspector Bell, which will be separately published, and it is unnecessary at this place to do more than state the general effect. As the result of numerous experiments (added to many which had been previously made by former observers, and in particular by Mr. Galloway and Mr. Frere Marreco), he found that whereas mere coal dust suspended in a current of air in a closed gallery and there brought in contact with a flame was not shown to be capable of doing more than extending the flame, if a small per-centage of gas were added (a per-centage much less than in the absence of dust would form an explosive mixture with the air) this weak mixture might be rendered highly explosive by the presence of the dust. Even wholly uninflammable kinds of dust, such as magnesia, have this power, but very inflammable coal dust in a dry and finely powdered state possesses it in a much higher degree; and the chances of explosion may be much increased by the velocity of the current, the nature of the flame with which it is brought in contact, and other circumstances. The experiments further showed that when an explosion is once started by dust and a small per-centage of gas, its effects may be greatly extended and intensified by dust alone without any further admixture of gas. The proportion of gas to air which is required for an explosion in the absence of dust is about seven to eight per cent. The proportion which will suffice with the aid of certain kinds of dust under favourable circumstances may range as low as 2½ per cent., or even 1¾ per cent., or possibly less. The presence of gas in such small proportions is discoverable with the greatest difficulty, or not at all, by any of the ordinary tests. When it is remembered that gas is probably, to some extent, continually evolved from nearly every part of the galleries and workings of a colliery, and that the laws which govern its diffusion through the atmospheric currents of a mine are very imperfectly known, it is obvious that an element of danger much greater than has been hitherto understood exists in every colliery in which gas is given off and dust is present in a dry condition.

In the present case, however, the solution thus suggested is open in some degree to a similar objection to that which has been raised against the proprietor's theory of an issue of gas from the fall near the point "C." One objection to that theory was that it was a pure assumption not supported by any evidence leading to an inference that gas had come off, or was likely to come off at the fall, or that the fall had preceded the explosion. So with regard to the dust, it cannot be said that there is any evidence of the presence of gas, even in the small proportion which might, with the aid of the dust, suffice for what occurred, and it is very difficult, if not impossible, to account for the presence of even two per cent. of gas in the main intakes where the air is fresh from the downcast shaft. It therefore cannot be said that in the present state of knowledge this suggestion furnishes more than a possible solution of the difficulty; especially as shots had been frequently fired in or near the same places for years without any ill result.

15. It remains to be considered in what way, assuming the existence of explosive matter at either of the probable or possible places of origin of the explosion, ignition may have occurred.

If the place of origin was near the point "C," as the witnesses for the proprietors suggest, the ignition must, in all probability, have taken place at Ramshaw's Clanny lamp, the fragments of which were found scattered about that point. There was no other lamp or light about that point. It is one of the objections raised by the Inspectors against these witnesses theory, that in order to account for ignition they are obliged to assume that it took place in the lamp, which there is no ground for supposing to have been open or imperfectly put together, and in a current which the Inspectors calculate did not exceed seven feet a second, but which Mr. Stratton put at 10 to 11 feet. If, however, Ramshaw was moving against this current at a rate of three miles an hour, this would bring up the relative velocity of the air past the lamp, even on the Inspectors calculation, to about 11½ feet a second, a rate quite high enough to be dangerous with a Clanny lamp in an explosive mixture.

If the place of origin was at the main coal staple the ignition may have taken place either at a naked light which was there or at Venner's shot "A," which was probably fired about the moment of the explosion. This shot, however, appeared to have done its work and not to have been blown out.

If the place of origin was not at either of the above-mentioned places, it was probably at Brown's shot ("B"). There is very strong evidence that the firing of this shot and the occurrence of the explosion were absolutely coincident in time. The boring tools were found standing against the wall as they would have been placed just before firing the shot, and, the bodies of Brown and his companions were found just at the places in which they would naturally have sought shelter on either side of the shot at the moment of firing. It will be remembered that this shot was fired in the immediate neighbourhood of the Curve, the most dusty portion of the whole mine. It had, however, done its work, and had not been blown out.

16. The principal considerations with respect to —

have now been stated; and it will have been seen that there are no sufficient grounds for a decided opinion in favour of either of the explanations which have been suggested. It appears to me that there is some preponderance of evidence and argument in favour of the view that the explosion commenced at Brown's shot and gathered fresh strength from clouds of coal dust raised in its passage along the Curve in one direction and towards No. 3 Hutton on the other. It is remarkable that an explosion which occurred in this colliery about 10 years ago is said also to have been coincident in time with the, firing of a shot in the No. 3 Hutton where that explosion began. In the present case it appears to me that the exact coincidence in time of Brown's shot with the explosion is a circumstance to which great weight ought to be attached, and that the immunity from damage of the immediate neighbourhood of Brown's shot, natural on this hypothesis, but hardly explicable on any other, is also of importance. No other considerations of equal weight appear to be forthcoming in favour of either of the other suggestions. On the other hand there is the especial difficulty of accounting for any gas at all at this place, and the fact that the shot was not blown out but had done its work, so that any considerable issue of flame is improbable. It would certainly not have occurred to any one before this inquiry that there could be any possibility of danger in firing a successful shot at this point, any more than (as Mr. Lindsay Wood put it) in firing a shot on the rocks in the harbour; and, as has been stated, shots had frequently during a long period been fired with safety at or near the same place.

It is to be hoped rather than expected that the opening of the Maudlin and of the travelling way and engine plane which lead to it may throw some further light on the matter. It is possible that some fall may have occurred in the Maudlin either near the fault or elsewhere just before the explosion at such a place as to derange the ventilation; but it appears useless to enter into conjectures upon the subject.

17. Notwithstanding the failure to arrive at any clear conclusion as to the place or cause of this disaster, the inquiry has been by no means barren of results. Professor Abel's experiments and reasoning have given a greatly increased importance to the questions already stated and illustrated by Mr. Galloway, Mr. Frere Marreco, Mr. Lindsay Wood, and other gentlemen with respect to the dangers of coal dust; and it is to be hoped that further attention will be given to this subject.

Further, the Seaham disaster adds another warning to those emphatically given by previous explosions, but still disregarded, on two points of the highest importance in colliery management. If the view of the proprietors as to the place of origin of the explosion is correct, this disaster is another instance, following that of the Risca explosion, of the extreme unsafety of the Clanny lamp — the Davy is even less safe — in a rapid ventilation when gas is present. If the other view is correct, this disaster is another instance of the urgent necessity for prohibiting the firing of shots when any large numbers of men are underground.

29th April 1881.