Smoke-jets by Intermittent Vision

In the second series of these observations (Phil. Mag. 1879 [vol. I. p. 406]) I proved that when stationary sonorous waves occupy the region surrounding a sensitive flame, the action of sound in causing the flame to flare manifests itself when the burner is situated at a loop, but not when the burner is situated at a node; from which we infer that the effects are due to a lateral disturbance causing the issuing jet to bend from its course. During the same year I made a stroboscopic examination of a jet of phosphorus-smoke issuing from a drawn-out glass nozzle, and disturbed by the neighbourhood of a vibrating tuning-fork of pitch 256. So much light is necessarily lost in this method of observation that some precaution is required in illuminating the jet. Two points should be especially attended to. In the first place, the eye must be so situated that the scattered light by which the jet is seen is but slightly deflected from its original course; and, secondly, the background must be thoroughly dark. By carrying out adequately this system of illumination, and by so choosing the revolving disk that the apertures bore a not too small proportion to the entire circumference, I was able to see tolerably well by the light of a good gas-flame. When the coincidence of periods was nearly approached, the serpentine motion of the jet previous to rupture was clearly observable.