On the Influence of Coal-dust in Colliery Explosions. 495 



given off at a more or less uniform rate along the face of the solid 

 coal. From observations made at the time I estimated that the air- 

 current, which would receive a certain proportion of gas from each 

 working place through which it passed in succession, would, on leaving 

 the last working place nearest the upcast shaft, always contain rather 

 more than 2 per cent, of fire-damp ; and I have no doubt whatever 

 that this latent fire-damp, acting in conjunction with the coal-dust, was 

 a most important factor in promoting and intensifying the explosion. 



