1881.] of Coal-dust in Colliery Explosions. 455 



September, and the lOtli of December respectively, and they cost the 

 lives of no fewer than 385 persons in all — Risca, 120 ; Seaham. 164 ; 

 and Penygraig, 101. 



For the purposes of the present paper I visited Risca Colliery on 

 the 24th of October, and Seaham Colliery on the 24th of November, 

 and I have had the rare opportunity of becoming thoroughly conver- 

 sant with every circumstance connected with the Penygraig explosion, 

 and with the events which immediately preceded and accompanied its 

 occurrence. 



A careful consideration of all the preceding details has irresistibly 

 convinced me that, whatever may be the results of experiments with 

 coal-dust made on a small scale, this is not a mere question of " adding 

 fuel to the flame," of " aggravating the consequences of an explosion," 

 of " spreading an explosion," or of " lengthening out the flame of 

 firedamp," or that of a blown-out shot. Expressions of that kind not 

 only fail to convey a true idea of the actual state of matters, but they 

 are apt to be misleading. I might describe the impression upon my 

 own mind to be somewhat as follows : — Given a well-ventilated or 

 badly-ventilated dry mine, with moderately clean fine dry coal-dust 

 lying everywhere all over the workings, and of any quality varying 

 from a long-flaming house coal, like that of Blantyre, on the one hand, 

 to a semi-bituminous steam coal, like that of Penygraig, on the other 

 hand. Then if an explosion be begun at any point in one of the only 

 three possible ways (1. By the coal-dust being raised and ignited by a 

 blown-out or other shot ; 2. By an explosive accumulation of fire- 

 damp and air being ignited by a blown-out or other shot ; 3. By an 

 explosive accumulation being ignited accidentally by a defective or 

 other safety lamp, or in any other manner), and if it accumulates a 

 certain degree of force without dying out, that force will go on increas- 

 ing, and the explosion will inevitably extend to every open space in 

 the workings, whatever may be their extent or ramifications. I make 

 no mention of firedamp as necessary to the attainment of this result, 

 with the exception of the comparatively small quantity required to 

 create the first disturbance. It must not be imagined, however, that 

 I lose sight of the latent firedamp contained in the air of every mine 

 of this class. On the contrary, I am satisfied that that firedamp plays 

 a most important part in every great explosion, and I have endeavoured 

 strongly to urge this view in both of my previous papers. 



XXVI. "The Molecular Volume of Solids/' By E. Wilson. 

 Communicated by Professor G. G. Stokes, Sec. R.S. Re- 

 ceived May 19, 1881. 



[Publication deferred.] 

 VOL. XXXII. 2 K 



