368^ Mr. W. Galloway on the Influence [Mar. 2, 



Similarly, in the case of the Llan explosion, I found that, at a distance 

 of 15 yards or so beyond the point where the principal air-current was 

 met (k, fig. 2), the traces of coked coal-dust on the timber began to grow 

 fainter ; and although they could be found here and there to a distance 

 of 70 yards further towards e, they were indistinct for the last 40 yards, 

 and resembled sparsedly scattered grains of gunpowder. Let the plane 

 on which figure 2 is described be elevated, so that the line a c dips towards 

 e at an angle of 10° while fO'" is level; then each line on the drawing 

 represents a gallery about 8 feet wide by 5 feet high with solid coal on 

 each side and rock above and below. O'"/ is the level referred to formerly ; 

 the roof had fallen so as to fill up most of the gallery (h i), and several of 

 the places (ss 1 &c.) were also partially or wholly filled up. O is the only 

 working-place shown ; the others were in the pillars immediately above 

 the level. All the galleries terminate as shown in the figure, except a, b, 

 c, d, and e, which may be supposed to continue indefinitely. Bends of no 

 consequence from our present point of view are omitted. Those galleries 

 and parts of galleries in which traces of coked coal-dust were found are 

 shown by means of plain lines, and the others by dotted lines. There 

 was a trap-door in the gallery a and a stopping in b where the traces ter- 

 minate; both were blown out; there was also a stopping at g. The 

 arrow-heads show the direction in which the air was evidently travelling 

 when the coke was deposited on the timbers. 



Before leaving this part of the subject it may not be out of place to 

 make a few remarks on the influence of blasting-shots in giving rise to 

 explosions in mines. I have already had the honour of submitting a 

 paper on the same subject to this Society, published in No. 154 of 

 the ' Proceedings ' for 1874. In that paper experiments were described 

 which showed that an intense sound-wave, such as that originated by a 

 blown-out shot, was able to pass the flame through the wire-gauze of a 

 safety-lamp burning in an explosive mixture. The two hypotheses ad- 

 vanced in the reports of the Inspectors of Mines to account for the simul- 

 taneousness of explosions of firedamp with the firing of shots were also 

 mentioned (p. 443) ; and I purpose again to refer to one of these, namely, 

 that which supposes the firedamp to be ignited directly by the flame of 

 the shot. 



There can be no doubt that the gases which issue from a shot-hole have 

 a sufficiently high temperature to ignite an explosive mixture of firedamp 

 and air if they pass into it immediately. I exploded such a mixture of 

 coal-gas and air many times by firing a pistol-shot into it when making 

 experiments at the Meteorological Office in the beginning of the year 

 1873. It seems exceedingly doubtful, however, whether the gases even 

 from a heavily-charged shot which blows out the tamping will retain a 

 sufficiently high temperature to ignite a mixture of this kind at a distance 

 of a few yards, if they have to pass through a space filled with pure air 

 before reaching it. On the other hand, it may be reasonably supposed 



