RECENT experiments carried out here lead to the conclusion that the vortex tube of Georges Ranque1 may form an extremely useful compact combustion chamber and also a possible research tool for the investigation of cool flames. Many applications of the vortex tube have appeared during the past fifteen years, as shown by Westley2, but, so far as it has been possible to ascertain, the nearest approach to the burner described here is due to Moore and Martin3 and Martin (private communication). Moore and Martin, using a single-outlet vortex tube made of ‘Pyrex’ glass, discovered the peculiar behaviour of premixed propane-air flames in this burner, together with the extreme flame stability obtained over a wide range of ratios of air to fuel. Owing to the limitations of their air supply, and to the size of the glass tube, they were apparently unable to obtain the rates of flow needed for some of the behaviour described here.