96 Mr. F. A. Ahel [April 28, 



small scale for tlie purpose of ascertaining whether, and to what extent, 

 the flame from a small charge of powder was lengthened, when pro- 

 jected, like the flame from a blown-out shot, into air containing fine 

 coal dust in suspension, M. Vital concluded that very fine coal dust, 

 very rich in volatile (inflammable) constituents, will take fire when 

 raised by an explosion, and that portions of the coal are successively 

 decomposed, yielding explosive mixtures with the air, whereby the 

 fire is carried along ; the intensity or violence of the burning being 

 much influenced by the physical characters (fineness, &c.) of the 

 dust. He also pointed out that an explosion of fire-damp, while 

 taking place almost instantaneously, inflames or decomposes a small 

 quantity of coal dust raised thereby ; explosive action being thus 

 propagated after the fire-damp explosion has ceased. Soon after 

 M. Vital's investigation of the subject, Mr. W. Galloway commenced a 

 series of valuable experiments upon a larger scale, with the view of 

 investigating the influence of coal dust in colliery explosions, and the 

 results were communicated by him to the Eoyal Society in two papers 

 in 1876 and 1879. The conclusions to which Mr. Galloway was led 

 by the experiments described in his first paper, were to the effect that 

 a mixture of air and a particular coal dust which had been made the 

 subject of chemical examination and practical experiment was not 

 inflammable at the ordinary pressure and temperature, but that the 

 presence of a very small proportion of fire-damp in the air, the exist- 

 ence of which could not be detected with the Davy lamp by the most 

 experienced observer, rendered this dust inflammable, and caused it 

 to burn freely with a red, smoky flame. From this it was inferred 

 that an explosion, when originated in any way whatever in a dry and 

 dusty mine, may extend itself to remote parts of the workings, where 

 the presence of fire-damp was quite unsuspected. 



In his second paper, Mr. Galloway shows that the return air of a 

 fiery mine which, though furnishing no indication of the presence of 

 gas when examined in the usual way (by means of a Davy safety 

 lamp), might in his opinion contain from 2 to 2*5 per cent., may 

 be rendered inflammable by suspending coal dust in it. He also 

 described experiments by which it appeared to be demonstrated that 

 the flame produced by the explosion of fire-damp in a particular part 

 of a mine might be propagated, at any rate to some extent, by coal- 

 dust raised by the explosion and suspended in the air travelling through 

 the mine, even in the complete absence of fire-damp in the air. The 

 apparatus used by Mr. Galloway was constructed on a somewhat exten- 

 sive scale. In connection with the channel or gallery through which 

 a current of air, with or without coal dust in suspension was passed, was 

 a receptacle in which a mixture of pit gas (from Llwynpia Colliery) 

 and of air was prepared and exploded. The direct communication 

 between the gas vessel and the gallery (representing a mine way) was 

 only interrupted by a diaphragm composed of from two to six leaves 

 of newspaper ; this separator being burst through by the explosion of 

 a mixture of nearly two cubic feet of fire-damp with the requisite pro- 



