DUE TO GAS DERIVED FROM COAL-DUST. 129 



well as its local character, inasmuch as the wave was not 

 propagated beyond the immediate vicinity of that mixture, 

 because its energy was no longer regenerated, and the 

 conditions of temperature and products necessary to propa- 

 gation had ceased. The disruption is consequently followed 

 by quiescent conditions, in which a second explosive gaseous 

 mixture is formed, and a second local explosion occurs where 

 it is ignited. 



The experimental researches of Berthelot into the be- 

 haviour of explosive mixtures upon ignition are therefore in 

 agreement with the phenomenon of local explosions at in- 

 tervals along the paths of coal-dust. 



These explosions along the paths of coal-dust were 

 arrested in air that had already ventilated other parts of 

 the mine, and was consequently poor in oxygen ; also in 

 small currents of air of limited resources and in receding 

 currents, the oxygen of which was being constantly ex- 

 hausted. In these conditions, there was inadequate oxygen 

 to burn a sufficient quantity of hydrogen to maintain the 

 temperature of the distillation, and the chemical changes 

 stopped with the failure of the supply of heat. Where wet 

 surfaces intervened in the path of coal-dust, the conditions 

 of instantaneous condensation were perfect, the product of 

 the hydrogen and oxygen surrendered its heat with the 

 rapidit}^ observed in a steam condenser, and distillation 

 was again arrested by want of heat. 



Propagation of the hydrogen explosions, therefore, failed in 

 wet places, and where atmospheric oxygen was insufficient 

 to sustain the chemical actions. 



The principal phenomena of the explosions at the 

 Camerton and Timsbury collieries have now been referred 

 to, and the examination has led to suggestions of their 

 causes, which enable the proposed rationale to be shortly 

 stated as follows : — 



