114 THE CHEMISTRY OF COLLIERY EXPLOSIONS 



observed, and the supporters of the hypothesis of a continuous 

 blast designate it as " conflictiDg evidence of the direction 

 of force,'' and caused by a " return blast." Professor 

 Dixon's explanation is that the phenomenon is "due to a 

 wave of air propagated backwards when the explosion has 

 again gathered strength, or to one of those oscillations of 

 flame which are seen in laboratory experiments." ^ 



This shattering and displacement of wagons exhibited 

 the effects of ignition of highly explosive mixtures ; con- 

 sequently no second mixture of this nature could have re- 

 mained at these places, nor in juxtaposition, for a second 

 or return blast. It is difficult to understand how a wave 

 of air propagated backwards, or an oscillation of flame, could 

 displace and carry away ponderous bodies, including masses 

 of iron. If a wave of air, or the flame, were capable of 

 moving the train of wagons referred to, it must have 

 carried the train in one direction ; therefore the primary 

 wave would leave all the wagons in the eastern entrance 

 of the siding. The " wave of air backwards " must then 

 have passed over the first half of the train without me- 

 chanical effect, but on reaching the centre, suddenl}^ de- 

 veloped propulsive energy to hurl the remaining half away 

 to the western entrance, leaving the antecedent part at rest, 

 which is also difficult to understand. 



The hypothesis of the combustion of a mixture of coal- 

 dust and air, continuous or instantaneous, through the field 

 of disaster, was opposed by the phenomena of the disrup- 

 tions ; and no attempt was made to elucidate the chemical 

 and physical activities in the propagations through thou- 

 sands of 3^ards of tunnels beyond the point of origin. 



The small quantity of heat disengaged in the explosion of 

 charges of less than one pound of blasting powder, or of a 

 * Report, Albion Colliery Explosion, p. 2. 



