THERE is probably no one among those listening to me this evening who does not know, or who has not realised through personal experience, the importance of the problem of detonation in internal combustion engine technique. Indeed, since petrol engines have been working on the Beau do Rochas cycle, the phenomenon of “knocking” has been an obstacle—which has gradually been driven into the background, it is true, but which is really insurmountable—to the increase in compression which is recommended by thermodynamics and which experience has shown to produce an increase in output equal to, and even slightly in excess of, the calculated theoretical value.