MR. C. A. BELL ON THE SYMPATHETIC VIBRATIONS OF JETS. 
385 
The number of vibrations of the air at the orifice varies directly as the square root 
of the pressure in the reservoir, or as the velocity of efflux ; but is independent of the 
diameter of the orifice. 
The first part of the law regulating the number of vibrations holds also for liquids, 
as pointed out by Savart. 
Masson’s experiments were made with large orifices, and, with few exceptions, at 
comparatively high pressures. By calculation from his results he determined the rate 
of vibration corresponding to a pressure of 1 mm. of water to be 626^ per second. 
In the great majority of his experiments the sounds of the jet were reinforced, as he 
supposed, by placing over the orifice tubes of various diameters and shapes. 
About the same time Sondhauss, ^ apparently having no knowledge of Masson’s 
work, also published experiments on sounds produced by the efflux of air. He found 
that a jet of air, at a pressure of I or 2 mm. of water, gave no sound ; but a “ rushing 
noise” was produced when the pressure was increased. At a pressure of from 5 to 
30 mms. of water, a jet, although spontaneously emitting no sound, was capable of 
being thrown into vibration when an organ pipe was made to speak in its neigh¬ 
bourhood. The tone emitted by the jet was usually, but not always, an octave lower 
than that of the pipe. The pitch of the tone to which a jet would respond rose 
in general through the scale as the pressure was increased ; but the jet was more 
powerfully affected by some tones than by others. Sondhauss expressly claimed the 
discovery of these sympathetic tones in air-jets. 
He further found that an otherwise silent jet was caused to “sing” by placing in 
front of it an edge, a point, or an orifice in a plate. The pitch of the tone produced 
in this way, he concluded, varies directly as the velocity of efflux, and inversely as the 
distance between the orifice and receiving plate. He thought that the vibrations 
of the jet were due to friction of the air against the edges of the orifice, and compared 
the jet to a solid vibrating rod. His experiments were made with a number of orifices 
of various shapes. 
In a note on this paper, Masson! disputed the supposed analogy between the jet 
and a vibrating rod; and expressed the opinion that the vibrations of air jets arise at 
the orifice in the same way as those of liquid jets. 
In 1865 Sondhauss | obtained with water-jets results very similar to those 
previously obtained with air. He found that such jets could also be set in vibration 
by allowing them to strike against an edge or a plate. According to his observations 
the pitch of the tone produced rises with the velocity of efflux, but falls as the 
distance of the receiving plate from the orifice is increased. Here again, Sondhauss 
regarded the jet as an elastic rod, thrown into vibration by friction against the edges 
of the orifice. 
* Poggend. Annal., vol. 91 (1854), pp. 126 and 214. 
f Annal. de Chimie, ser. 3, vol. 41 (1854), p. 176. 
t Poggend. Anna!., vol. 124 (1865), pp. 1 and 235. 
3 D 
MDCCCLXXXVI. 
