OF THE FLAME IN THE EXPLOSION OF GASES. 
341 
from right to left in the second tube, and sends back a wave of retonation when it 
reaches the end of the tube. The retonation and detonation-waves are apparently 
jDarallel. 
As regards the dark space formed at the point where the detonation and retona- 
tion-waves originate, it is no doubt a space of cooler gas. It persists for some time, 
and its damping effect on the passage of the collision-wave can be observed in seveial 
of the ^photographs. In fig. 31 tliis effect is evident just before the collision-wave 
cuts the black reference line on the right of the picture. 
In 1898, a few of our photographs showing the point of detonation and the collision 
and reflexion of waves in explosion were published in the ‘Manchester Memoirs.’ 
Attention was drawn to the wave of retonation and the dark space. It was pointed 
out that the detonation “ was represented by the straight and inteiisely-luminous 
line as distinct from the curved and less luminous line of the recouping period.” 
“ Further, a new and very luminous wave is observed starting from the point of 
re-determination of the explosive-wave proper, and travelling in the opposite direction 
with a speed almost, if not quite, equal to that of the explosive-wave itself.” 
In June, 1900, Le Chatelier published'^ an account of liis photographs of the 
development and propagation of the detonation-wave '(taken on a moving plate) 
Without knowing of our work, he observed and recorded the “ wave of retonation ” ami 
the “ dark space” formed in the explosion of acetylene with oxygen, and the waves 
reflected from the end of the tube and at the point of collision of two waves :— 
“ 1. An moment du developpement spontane de londe explosive une onde condensee 
retrograde est toujours lancee en arriere dans les gaz deja brides ; 
“ 2. L’arret complet ou partiel de I’onde explosive centre I’extremite fermee (on 
dans une region etranglee) d’un tube lance en arriere une onde condensee rejiechie ; 
“ 3. All point de rencontre d’ondes explosives alluniees simultanement en difterentes 
parties d’une masse gazeuse, leur extinction simultanee donne naissance a des ondes 
condensees qui progressent dans la meme direction que les ondes explosives 
auxquelles elles succedent.” 
For the velocities of these waves in the mixture -f- Go Le Chatelier gives 
the following values :— 
M ave. 
Pates, metres per second. 
L’onde explosive (detonation-wave). 
29901 
L’onde retrograde (retonation-wave). 
2300 
L’onde refiechie (reflexion-wave). 
2250 
L’onde prolongee (collision-wave). 
2050 
* ‘Comptes Kendus,’ vol. 130, p. 1755. 
t I found the rate of detonation in the mixture CjIL + Og to be 29G1 metres per second, by measurements 
in a long tube (‘Phil. Trans.,’ 1893, A, p. 161), a rate in close agreement with Le Chatelier’s number. 
