1882.] on Some of the Dangerous Properties of Dusts, 107 



powder where the men were burned, in both directions in the cross 

 workings, in the accident above cited. The influence of coal dust in 

 increasing the distance to which the flame from a blown-out shot will 

 extend in mine-workings is therefore conclusively demonstrated by a 

 comparison of the effects of those accidents with the foregoing experi- 

 mental data. On the other hand, the important circumstance noticed 

 by Mr. Hall that no signs of burning on the props in the mine were 

 visible at greater distances than a yard or two beyond the spots where 

 the men were waiting, although there were open workings in both direc- 

 tions for some considerable distance, and although the flame was 

 sufficiently extensive at those spots to injure the men severely, proved 

 conclusively that coal dust had not the power, in these two instances, 

 to carry on the flame to a great distance from the source of fire. Had 

 there been any gas in the air of the mine the flame would doubtless 

 have extended much farther, and perhaps throughout the adjacent 

 workings. The amount of dust raised by the blown-out shots may, 

 however, have been less considerable than in other similar occur- 

 rences, and the dust itself may not have been so highly inflammable, 

 or otherwise of so suitable a character for carrying on flame, as that 

 existing in other mines where undoubtedly dust has played an important 

 part in enhancing the magnitude of explosions. At any rate these 

 results demonstrate the necessity for the exercise of caution in drawing 

 conclusions of too sweeping a nature with regard to the causes and 

 the extent of such coal-mine explosions as cannot be quite clearly 

 ascribed to fire-damp. A few experiments have been made, in the 

 largest gallery (Caponier) at Chatham, to test the power of coal dust 

 to carry on the flame from a blo^Ti-out shot. A large quantity of 

 very fine and inflammable coal dust, from Seaham collieries, was 

 suspended in the air by employment of sufiicient mechanical con- 

 trivances, and clouds of the same dust were also blown into the 

 gallery in the direction of the shot, and immediately in front of it, 

 just when it was fired. One of the frame-screens was placed across 

 the gallery where the pier jutted out (at a distance of 31: feet from 

 the shot), and pieces of guncotton were attached to nails driven in 

 the wall along the short narrow part of the straight gallery and to 

 some distance round the curve. In every one of the experiments 

 tried (three) with 1^ lb. of powder, fired when dust was thickly sus- 

 pended and carried along in the air, the flame burned a number of 

 pieces of guncotton on the screen ; in two experiments guncotton 

 was burned at a further distance of 1 ft. 6 in., but not beyond ; in the 

 third, some flame travelled to the end of the straight gallery, and to 

 a distance of 4 ft. 8 in. beyond the curve, but guncotton was not 

 inflamed beyond that point. In this case, therefore, flame reached 

 rather more than, and in the others not quite, double the distance 

 with dust thickly suspended in the air, to what it did in the absence 

 of dust. Experiments will be continued in the long narrow galleries 

 which have been spoken of. 



It must now be accepted as beyond question that very few, if 



