1882.] on Some of the Dangerous Properties of Dusts. 99 



working of a mine, tlirougli its agency, in the complete absence of fire- 

 damp. The effects of transmission of flame in this way would be 

 decidedly different, and much inferior in violence, to those produced 

 by an explosion of fire-damp and air, or of a mixture of these 

 with coal dust ; the comparative suddenness of the gas explosion 

 would produce greater destruction and less burning effects than the 

 comparatively gradual explosion, or the rapid burning of a dust-and- 

 air-mixture. In the latter case, the coal dust will generally be con- 

 siderably in excess of the air needed for its combustion, so that, 

 however finely divided, much will escape being burned, and may be 

 only very partially coked, and it is conceivable that, as suggested by 

 Mr. Galloway, a second rapid burning or semi- explosion may be caused 

 by the inrush of air, following the first explosion, into the workings, 

 which may be thick with heated and only partially burned dust, 

 some of which may still be incandescent. 



Considering that, since first Faraday and Lyell directed attention 

 to the dangers of coal dust in mines, its behaviour has been made the 

 subject of many series of experiments and published reports here and 

 abroad, it is remarkable that in most instances of coal-mine explosions, 

 until quite recently, the probable effect of coal dust in increasing their 

 magnitude does not appear to have received the serious attention 

 which it merits at the hands of mine owners and of those in authority 

 connected with coal mines. When the Eoyal Commission on Accidents 

 in Mines was appointed, it collected evidence from H.M. inspectors 

 of mines, from experienced colliery owners and mining engineers, and 

 from selected j)itmen, with respect to the causes of accidents, and that 

 evidence included several statements regarding the possible influence 

 of coal dust in aggravating explosions, but the preponderance of 

 opinion of H.M. inspectors was against the view that explosions could 

 originate with, or be to any great extent propagated by coal dust in 

 the absence of fire-damp. The only experiment on a practical scale 

 bearing upon the subject which appears to have been made until quite 

 recently is that of Mr. H. Hall, Mine Inspector of the N. Wales, &c., 

 District, who, in firing charges of 4 lb. of powder from a cannon in 

 an adit driven about 50 yards from the surface in a coal seam on the 

 dij), coal dust being sprinkled uj)on the floor, obtained flame extending 

 to distances of 30 to 60 yards, while without the dust the flame of the 

 shot did not extend more than 6 or 7 yards.* Some decided ojnnions 

 were expressed that the suj)posed influence of coal dust in aggravating 

 explosions was over-rated, and that it would certainly not lead to 

 explosions in the absence of gas. On the other hand, Mr. Galloway 

 expressed a strong opinion that some of the most extensive of recent 

 explosions, such as those at Llan and Abercarne, were at any 

 rate largely contributed to by coal dust, and more recently, on the 

 occasion of the inquiry into the Penygraig explosion, he gave evidence 



* Mr. Hall stated that the air iu this adit was " practically " free from gas, 

 but did not maintain its absolute freedom. 



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