CHAPTER VII. 



THE EXPLOSIVE WAVE. 



1, GENERAL CHARACTERISTICS. 1 



1. THE study of the various modes of decomposition of 

 explosive substances, and especially that of detonation as com- 

 pared with combustion, and of explosions by influence, leads to 

 the admission of the existence of a wave motion peculiar to and 

 characteristic of explosive phenomena; this is the explosive 

 wave. It will be more accurately and completely denned by 

 showing how it is propagated in gaseous systems. The results 

 of the experiments which the author undertook in conjunction 

 with M. Vieille led to the examination of the rate of propagation 

 of the explosion in gases, the physical constitution of which 

 gives to these researches a peculiar theoretical interest. In the 

 experiments the conditions of the phenomena, the pressure of 

 the gases, their nature and relative proportion, and the form, 

 dimensions and nature of the vessels in which they are con- 

 tained, were varied. They confirmed the existence of a new 

 kind of wave motion of a compound nature, i.e. produced by 

 a certain concordance between the physical and chemical 

 impulses in the matter undergoing transformation. The wave 

 motion once produced is then propagated from layer to layer 

 throughout the whole mass, in accordance with the successive im- 

 pulses of the gaseous molecules brought to a more intense state 

 of vibration by the heat given off in their combination and 

 transformed with but very slight displacement of their original 

 position. Similar phenomena may be developed in explosive 

 solids and liquids. 



Such effects are comparable to those of a sound wave, but 

 with this important difference, that the sound wave is transmitted 

 onwards by degrees with little active energy, a very small excess 

 of pressure, and with a velocity which depends solely on the 



1 " Comptes Rendus des stances de l'Acade*mie des Sciences," torn, xciii. 

 p. 21 ; torn. xciv. pp. 101, 149, 822 ; torn. xcv. pp. 151 and 199. 



