128 THE CHEMISTRY OF COLLIERY EXPLOSIONS 



oxygen to be 2,810 metres, or 9,219 feet, per second, and 

 Professor Dixon has recently arrived at almost identical 

 figures. 



The origin and propagation of the explosive wave was 

 also investigated by Berthelot, who observes that the wave 

 developed in an explosive mixture consists of chemical 

 actions transformed into calorific and mechanical energies, 

 and when once originated, propagates itself without diminu- 

 tion of force, because the chemical and physical actions that 

 develop it regenerate its energy throughout the matter 

 undergoing transformation. The explosive wave, he con- 

 tinues to say, propagates itself in the substance which 

 explodes by virtue of a series of shocks incessantly repro- 

 duced, which regenerate its energy. 



Propagation of the explosive wave in intermediate sub- 

 stances as air, whose nature is not changed, is purely 

 physical, and is effected solely by virtue of the energy of 

 the last shock, an energy which is no longer regenerated 

 and which rapidly weakens by distance. 



Propagation of the explosive wave ceased when the 

 theoretical temperature of the compounds formed with free 

 oxygen fell below 2000° C, for hydrogen associated with 

 nitrogen ; also when the products of combustion amounted 

 to less than a quarter of the total volume of the final 

 mixture, and no propagation was observed below 1,000 

 metres, or 3,281 feet per second. 



Propagation only occurs when the inflamed molecules 

 preserve almost in its entirety the heat developed by 

 chemical action ; consequently the maximum velocity and 

 maximum translating energy. 



These researches show that the explosive wave developed 

 in the gaseous mixture in the mine possessed a velocity that 

 explains the shattered effects observed in the disruption, as 



