126 THE CHEMISTEY OF COLLIERY EXPLOSIONS 



coal-dust on the floor of the tunnels, and the lumps in the 

 wagons had been subjected to dry distillation, not 

 combustion. These effects upon coal, horses, men, and calico 

 bags disclose the fact that the atmospheric oxygen in the 

 tunnels of the mine was, at most, not more than adequate to 

 supply the requirem.ents of the hydrogen in the educts of 

 the coal undergoing distillation ; consequently there was no 

 oxygen available for the chemical requirements of other 

 combustible bodies, as the timber, coal, clothes and food bags, 

 and they could only exhibit the effects of gaseous water 

 upon them. 



Another effect of the oxidation of the hydrogen is indicated 

 at Timsbury collieries. In the path of the explosions, three 

 tunnels branched off at right angles into extensive old 

 workings, which had an indirect connection with the down- 

 cast shaft. The entrances of these branches were filled up 

 by dry stone walls in two cases ; the third, being a large 

 place, was closed up with a wall of masonry. These vertical 

 walls were erected to prevent the air current leaking into 

 the old workings, and in the ordinary operations of the 

 mine they retained their positions, the atmospheric pressure 

 being equal on both sides. After the explosion, all three 

 walls were found thrown down into the path of the explo- 

 sion, indicating that the pressure of the air in the old 

 workings behind them was at the moment of their dis- 

 placement greater than the pressure iu the tunnels. In 

 the combustion of the hydrogen in the educts of the coal, 

 one-fifth of the volume of air in the tunnel would be taken 

 to form twice the volume of water vapour, which would 

 undergo instantaneous condensation, the enclosing walls of 

 the tunnel being at a temperature of not more than 15° C. 

 The volume of permanent gases in the tunnel would thereby 

 be reduced by one-fifth, forming a partial vacuum of 3 lbs. 



