PEOFESSOR H. B, DIXON OX THE MOVEMENTS 
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OO^ 
It will be seen that the temperature calculated for the first sound-wave (4100°) is 
in close accordance with that calculated from the reflexion-wave in the same mixture 
(4200°) given in Table III. 
The experiment was next varied hy the introduction of a thin iron membrane 
between the air and the ex 2 )losive mixture. The shock transmitted through the air 
from the fulminate struck the flexible jflate, and so jU'ojiagated a wave of small 
displacement through the explosive mixture. This wave had verv little effect on the 
movements of the gas in the wake of the detonation-wave, but its j^assage through 
the luminous gas was jDlainly marked. The gases were ignited as before, the lengths 
of the tubes being so adjusted that the first sound-wave met the detonation-wave 
about 1 metre from the membrane. Several of these sound-waves (produced by echo 
in the bomb) are seen in fig. 20 traversing tbe flame jn’oduced Ipv the exjflosion of 
cyanogen with its own volume of oxygen ; these sound-waves apparently increase in 
velocity owing to the movements of the gas througli which they pass. 
It is not so easy to measure the angles of tliese faintly-marked sound-waves, but 
three johotographs have given as the mean of several independent measurements 
made on each iDhotograph the velocity of the sound-wave in the stationary gas as 
1250 metres jDer second. This velocity corres^Donds to a temj)erature of 3460° 
(y = 1‘41); a number in very fair agreement with that calculated from the reflexion- 
waves, viz., 3330° (Table III.). This agreement indicates that the reflexion-waves 
really travel with a velocity apjDroximately ecpial to that of sound. 
Similar sound-waves are shown in fig. 21, where the mixture was C'S^ 20^. 
Some other exiDeriments were also made in which a compression-wave was made to 
follow closely behind a detonation-wave, both moving in the same direction. 
A leaden tube had a by-pass inserted so that the explosion travelled both along 
the straight piece a c and along the curved jjiece a h c. When the flame travelling 
hy the straight road reached the second opening of the by- 2 :)ass a, it joenetrated this 
o^Dening and came into collision with the exiflosion travelling by the longer road. 
The reflected wave so jDroduced followed the main detoiiation-wave into the glass 
tube (I, where the two were 23hotograjDhed al)out 1 metre from the jjoint c. The 
reflected wave is assisted by the forward movement of the gas, and consequently its 
apparent velocity is much greater than the sound-waves or reflexion-waves measured 
in stationary gas. 
Fig. 22. Apparatus to make a sottnd-wave follov a detoiiation-Avave. 
In fig. 23, which shows the two waves iit the ex^^losion ot cyanogen with two 
volumes of oxygen, the comi^ression-wave is seen running alongside the detonation- 
