Manchester Memoirs, Vol. xlh. ( 1 898), No. 7. 7 



explosion waves meet, with that of the colh'sion of the 

 waves whilst in the recouping period after a partial 

 stoppage (see fig. 2), shews that, in the former case, 

 the rebound waves are less luminous and travel much 

 more slowly than the explosion waves ; whilst, in the 

 latter case, the rebound waves are more luminous and 

 travel faster than the recouping explosion waves, 



A sound wave, similar to those obtained on the 

 collision of two explosion waves, is produced when an 

 explosion takes place in a glass tube closed at one end, 

 rebounding from the end surface and travelling back along 

 the tube. 



The fifth figure gives an illustration of the phenomenon 

 just mentioned. Notice that the angle which the rebound 

 wave makes with the horizontal diminishes, thus indicating 

 that the rate becomes faster. The dark vertical line, used 

 for purposes of measurement, is caused by a small black 

 band placed on the explosion tube. 



Comparison of the rate of this rebound with that of 

 each of the rebounds produced when two explosion waves 

 meet shows the former to be slower. 



The ratio of the two rates is about 10 to 13. 



Thus we have indirect evidence of the increase of 

 pressure when two explosion waves come into collision. 



This is again confirmed by the increased intensity and 

 longer duration of the light which the photograph displays 

 at the point of collision. 



The evidence from the actual measurements, the rates 

 of the rebounds, and the luminosity, taken together, seem 

 to establish beyond a doubt the increase of pressure on 

 collision of two explosion waves. 



