1902.] 



of the Flame in the Explosion of Gases. 



479 



rubber) which gave to a shock caused a retardation ; when the glass 

 was firmly cemented to the metal no retardation occurred. The 

 anomalies met with in our collision experiments were thus accounted 

 for, and the examination of collisions between true detonation-waves 

 was proceeded with. 



When two detonation- waves come into collision the tube remains 

 brightly luminous at the point of contact for some time, and two 

 reflected waves are sent backwards with velocities which increase at 

 first, owing to the movement of the gas through which they are pro- 

 pagated. 



A comparison of all the photographs shows that the gases are more 

 luminous after a collision than when the explosion-wave strikes a flat 

 surface of metal fastened at the end of the tube. The reflected waves 

 in the two cases are similar in character, but the reflection generated 

 by collision with another detonation-wave seems always to travel 

 slightly faster. If we were dealing only with waves produced me- 

 chanically, the reflected waves would be exact copies of the incident 

 waves with velocities reversed — in both cases. But in the detonation- 

 wave we have chemical as well as mechanical action, while the reflected 

 wave is mainly mechanical. We should expect therefore the reflected 

 waves to travel more slowly than the incident waves, but we should also 

 expect the reflected waves to travel with the same velocity whether 

 they were produced by collision with a rigid diaphragm or with a 

 similar and equal wave travelling in the opposite direction — unless there 

 was some chemical difference involved in the two kinds of collision. 



Our photographs have shown that the wave of detonation has 

 certain characteristics by which it may readily be recognised : — 



(1.) It starts suddenly, throwing back a strongly luminous wave 

 through the burning gases, and leaving a dark space where it started. 



(2.) It travels with constant velocity unless it traverses a junction 

 not rigidly attached ; after being damped down by such an obstacle it 

 recoups itself and again starts with abruptness. 



(3.) On collision with a similar detonation-wave moving in the 

 opposite direction, or with a rigid diaphragm, it sends back a reflected 

 wave not so rapid as itself, and as a rule not so luminous. 



In the case of the more luminous explosions, e.g., those of cyanogen, 

 acetylene, and carbon disulphide mixtures, the reflected waves were 

 less luminous than the detonation-wave; but in the case of the less 

 luminous explosions, e.g., those of hydrogen and carbonic oxide, which 

 depend largely for their light on the particles detached from the tubes, 

 the waves reflected from a collision were sometimes more luminous 

 than the detonation-waves themselves. 



