MR. C. A. BELL ON THE SYMPATHETIC VIBRATIONS OF JETS. 
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points that seem to me to have been overlooked or not sufficiently dwelt upon in 
treating of these phenomena hitherto, and point out certain analogies which may 
at least serve as guides to further experiment, even if they answer no other purpose. 
Briefly stated, the facts to be accounted for are the following :— 
An impulse given to the fluid at a jet orifice, or to the orifice itself, gives rise to 
some kind of disturbance which probably moves forward with the mean velocity of 
the stream, and therefore involves always the originally disturbed particles, or those 
immediately adjoining them. If the velocity were different for different disturbances, 
accurate reproduction of complex sounds at a distance from the orifice would be 
impossible. 
Fig. 11. 
The disturbance produced by an impulse in the direction of the jet, or by a sound 
impulse, is circular and symmetrical with respect to the jet axis, and retains its 
symmetrical form throughout. This is not the case when the impulse is mechanical, 
and in a direction inclined to the jet axis, or when the orifice is not perfectly circular. 
These conclusions are arrived at by inspection of instantaneous photographs of jets 
disturbed by sounds and by vibrating tuning-forks, &c. 
A sound vibration of a simple nature conveyed to the jet orifice causes disturbance 
of a certain length of the column, which disturbance takes the form of a swelling and 
a contraction. Both swelling and contraction become more pronounced as the fluid 
travels away from the orifice ; but at any given distance within the continuous portion 
successive sections of the jet represent the form of the impressed vibration. This 
statement, however, requires qualification ; for a jet of given size and at any particular 
pressure, can reproduce at a distance from the orifice only a certain range of tones. 
But the upper limit of this range is not sharply defined, the tones lying in its 
