384 MR. C. A. BELL ON THE SYMPATHETIC VIBRATIONS OF JETS. 
From his experiments Savart concluded that periodic movements of the jet exist 
independently of communicated vibrations, and that these movements are not due 
to vibrations of the edges of the orifice, nor to friction of the liquid against these 
edges. He attributed them rather to periodic oscillations of the entire mass of fluid 
behind the orifice, and concluded that the vibrations excited by impact of the jet 
against any solid, when conducted back to the orifice, assist and intensify these 
normal vibrations. External vibrations act in a similar way, but such external vibra¬ 
tions may sometimes alter the normal period of the jet vibrations. 
In a later paper * * * § Savart showed that the jet vibrations are preserved in the 
“ nappe,” or thin sheet of liquid formed when the jet strikes normally on a small 
surface. 
In a paper published after his death! Savart endeavoured to show, by some very 
beautiful experiments, that periodic oscillations of the mass of fluid behind the orifice 
did actually take place. Filling large glass tubes with water, and allowing the 
liquid to escape through circular openings in flat plates which closed their lower 
ends, he found that the tubes emitted musical sounds, the intensity of which passed 
alternately through certain maxima and minima as the level of the liquid sank within 
them. Savart established the following law :—The pitch of the tone produced is 
independent of the diameter of the tube-reservoir, but varies directly as the square 
root of the height of the liquid therein, and inversely as the diameter of the orifice. 
In the year 1852 Sondhauss J imitated some of Sav art’s experiments with jets of 
air rendered visible by mixture with smoke. Using a circular orifice, and a pressure 
equal to one inch of water, he demonstrated that an air-jet, like a wafer-jet, presents 
a continuous arid a troubled portion. In the experiment described the continuous 
portion was about one inch in length, and beyond this the jet showed protuberances 
analogous to those observed in liquid jets. Sondhauss also showed that an air-jet, 
projected against a surface, spreads out from the point of impact in the form of a 
“ nappe.” He does not appear to have observed the phenomenon of the sensitive air- 
jet, possibly because the pressure he employed was too high. 
In 1853 Masson § in an elaborate paper described an extended series of experi¬ 
ments on the tones produced by efflux of air. In some of these the jet was allowed 
to escape from a circular orifice into free air, and for this case he established the fol¬ 
lowing laws :— 
The flow of air through an orifice in a metallic plate is not continuous ; it varies 
periodically, and the orifice is the seat of a vibratory movement which gives rise to 
sound when communicated to the external air : 
* Anna!, de Chimie, vol. 54 (1833), pp. 55 and 113 ; Poggend. Annal., vol. 29 (1833), p. 356. 
t Poggend. Annal., vol. 90 (1853), p. 389; Comptes Rendus, vol. 37 (1853), p. 208; Phil. Mag., ser. 4, 
vol. 7 (1854), p. 186. 
1 Poggend. Annal., vol. 85 (1852), p. 58. 
§ Annal. de Cliemie, ser. 3, vol. 40 (1854), p. 333; Phil. Mag., ser. 4, vol. 6 (1853), p. 449. 
