XI. On the Sympathetic Vibrations of Jets . 
By Chichester A. Bell, M.B. 
Communicated by Professor A. W. Williamson, F.R.S. 
Received April 28,— Read May 13, 1886. 
In the year 1833 Felix Sayart published a remarkable memoir* on the structure 
of liquid jets from circular orifices, in which he demonstrated the following facts :— 
A vertical jet of liquid from a circular orifice presents in general two distinct 
portions—an upper continuous or rod-like portion, and a lower or troubled portion ; 
the relative lengths of these two regions being approximately the same in air as 
in a vacuum. 
The lower or troubled portion consists of separate drops, as proved by the fact that 
objects may be viewed through it, even when the jet is composed of an opaque 
liquid like mercury. 
The troubled portion of a jet which is not perfectly insulated from accidental 
vibrations, or from the vibrations produced by its impact against a solid body, pre¬ 
sents swellings at regular intervals, these swellings ( ventres ) being the result of 
certain longitudinal and transverse changes of shape, of regular period, executed by 
each drop during its fall; but a jet from a carefully insulated orifice does not exhibit 
these swellings, but only slight irregularities which continually change their position. 
In the upper half of the first of these regular swellings the drops are not yet 
completely detached from the main stream, but only become so in the lower half. 
A jet which is allowed to strike against a stretched membrane at a certain dis¬ 
tance from the orifice, gives out a musical sound of definite pitch, or some sound 
related thereto ; its continuous portion at the same time becomes shortened, and 
resolution into drops occurs higher up in the stream. 
The pitch of the characteristic sound depends neither on the nature nor the 
temperature of the liquid, but is determined solely by the velocity of the stream 
and the diameter of the orifice. 
A jet which is exposed to the action of external vibrations may also have its 
continuous portion shortened, and may reproduce the impressed vibrations by impact 
against a membrane; but the musical sounds which have this effect must either be 
related to the characteristic of the jet or not differ from it widely in pitch. 
* Annal. de Chimie, vol. 53 (1833), p. 337, and Poggend. Annal., vol. 29 (1833), p. 353, and vol. 33 
(1834), pp. 451 and 520. 
