4 Jones and Bower, Explosion Wave Pressures. 



increase of pressure on collision of two explosion waves — . 

 a conclusion which Professor Dixon recognised to be 

 hardly consistent with his own theory of gaseous explo- 

 sions, according to which the explosion wave may be 

 regarded as an intense sound wave in the burning gases. 

 The evidence from other sources was sufficiently cogent 

 to make him still retain his belief in the theory, and we 

 have now had the pleasure of removing this seeming 

 contradiction. 



An actual increase of pressure on collision of two 

 explosion waves has been proved, and also an explanation 

 arrived at concerning the cause of the previous inability 

 to demonstrate this fact. 



Two distinct theories have been advanced to bring all 

 the rates of combustion of the various gaseous explosive 

 mixtures under one general formula : — Dixon's and 

 Berthelot's. 



Berthelot assumes the instantaneous pressure-motion 

 of the wave to be due to the forward movement of burnt 

 molecules, i.e.^ of molecules produced by the completion 

 of the chemical reaction ; thus each wave front, on 

 collision, would act as a dead wall to the other, the mole- 

 cules merely exchanging energies, and there would be 

 no reason to expect any abnormal increase of pressure 

 above that due to the stoppage and reversal of the waves. 



From Dixon's theory it seemed possible — if the wave 

 is piopagated partly by movement of heated yet unburnt 

 molecules in the wave front — that these molecules meeting 

 "end-on" would cause a measurable increase of tempera- 

 ture and pressure at the moment of collision, over and 

 above the natural increase due to the impact ol two 

 pressure waves. On either theory an increase of pressure 

 would be expected. 



The means of measurement was that first suggested 

 by Le Chatelier and applied by Dixon and Cain. 



