EXTENSIVE study of gaseous detonation has been made by a number of investigators, but in spite of this fact the phenomenon is as yet not well understood. In presenting this paper, therefore, we will not attempt to explain all the phenomena with which it deals. The object of the paper is'to discuss the bearing of this factor on the operation of internalcombustion engines, and to describe the progress that has been made in controlling it by chemical means.Results of Early Study of Gaseous Detonation r In] 1881 Bertholet2 and LeChatelier3 independently discovered that the propagation of flame through mixtures of some combustible gases with air, and through mixtures of practically all combustible gases with oxygen in proper proportions, results in setting up a detonation wave.These results were confirmed by II. B. Dixon,4 who has carried out quite an extensive investigation of this subject. Mallard and LeChatelier5 noted that the development of the detonation wave is not progressive, but always instantaneous. They noted further that the detonation wave is characterized, not only by its great velocity of movement, but also by its intense luminosity. Dixon6 was also impressed by the sharpness with which luminosity is set up when detonation occurs.Bertholet and Vieille7 and also Dixon4 showed that the velocity of the detonation wave is constant, and Dixon advanced the theory that during detonation the flame travels at the same speed as sound at the temperature of the burning gases. Mallard and LeChatelier7 found that very large pressures are developed by detonation waves, but that such pressures exist only for an exceedingly brief period. This finding was confirmed by Dixon,4 who worked on the principle that, if a pressure is produced in a glass container greater than the glass will vrithstand, the vessel will be broken, although the pressure may endure only for a very short interval of time. Dixon gave a range of from 25 to 78 atmospheres for the magnitude of these pressures for various gases. He showed further that these instantaneous pressures are approximately four times the maximum "effective pressure" developed by the explosion.Gaseous Detonation an Important Factor in Internal CombustionExcept for some comparatively recent work, practically all the study of gaseous. detonation that has been made has been conducted in atmospheric tubes, or under other conditions that did not simulate those of internal combustion. From an economic standpoint, however, the detonation that occurs in internalcombustion engines is of great importance.8 Nearly everyone

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MEANS of an apparatus developed especially for the purpose, photographs have been taken of combustion in the gasoline engine as it appeared through a narrow quartz window that extended over the entire length of the combustion chamber. A simultaneous record of the changes in pressure in the engine cylinder was also obtained by photographic means.The flame records, which were taken on moving films, consist essen-