This series of papers has so far dealt mainly with non-maintained or partially maintained atmospheric shock waves, and only incidentally with the fully maintained "detonation" wave. It is generally accepted that the detonation wave in an explosive gas mixture is a shock wave produced by the rapid combustion of the mixture, sufficiently intense to cause almost instantaneous ignition of the gas through which it passes, and continuous maintained by the combustion thereby started. An account of some preliminary experiments, using the "wave-speed" camera to record the movement of the flame and of the invisible shock waves in front of the flame in gas mixtures prior to detonation, has already been given by one of us. Those experiments related mainly to hydrogen-oxygen and methane-oxygen mixtures whose aptitude to detonate may be regarded as moderate, for the continuation of the work, mixtures with oxygen have again been used, but a more readily detonating gas, ethylene, was chosen. Experiments were also made with carbon monoxide, because the flame usually requires a comparatively long run before detonation is established. These two gases have the advantage, not shared by hydrogen and methane, that their predetonation flames are sufficiently actinic for good records to be obtained by direct photography for comparison with corresponding "wave-speed" records. All gas mixtures used were saturated with water vapour.
Explosion waves and shock waves III-The initiation of detonation in mixtures of ethylene and oxygen and of carbon monoxide and oxygen
