IN a recent paper Gaydon and Wolfhard1 state: “In stationary pre-mixed flames of hydrocarbons at pressures between 1 atm. and a few mm. of mercury . . . the flame speed is independent of pressure". Reference is made to determinations by Wolfhard2 of the effect of pressure on the burning velocities of acetylene/air, acetylene/oxygen and acetylene/oxygen/argon mixtures and also of butane/air mixtures. Some experiments of ours and various recorded measurements of the effect of pressure on burning velocity, excluding those in tubes, had led us to a different view.