From the July 18, 1931, issue
By Science News
AIR VIBRATIONS IN ORGAN PIPES REVEALED BY PATTERN IN SMOKE
Making smoke rings in organ pipes, to show up the little cyclones that whirl in them when obstacles are placed in the openings, is the curious mode of research adopted by a London physicist, Prof. E.N. da C. Andrade of University College. These little cyclones, or vortices, have important effects on the tones of the pipes. By photographing them in smoke, Prof. Andrade is able to check the accuracy of mathematically calculated theories never before tested.