398 
MR. C. A. BELL ON THE SYMPATHETIC VIBRATIONS OF JETS. 
varying impact of the cool jet; or possibly to the ring-shaped waves of air (if they 
may be so called) leaving the incandescent surface with a higher temperature and of 
greater volume than they possessed when approaching it. 
The foregoing experiments obviously admit of many variations, which it is un¬ 
necessary to mention here. 
A remarkable fact is that the vibrations set up in a jet by sound seem to be inde¬ 
pendent of the direction of the sound, and copy only its form. It is quite true that 
powerful impulses, such as those produced by a vibrating tuning-fork held close to the 
orifice, will cause the jet to divide or branch, and the direction of this branching will 
depend on the position of the tuning fork. But, so far as I have observed, small 
disturbances of the gas at the orifice exert the same influence, from whatever direc¬ 
tion they may arrive. 
Such disturbances may be other than of a mechanical nature. Thus electric strains 
at the orifice may act as disturbances to the jet. A very effective way to demonstrate 
this, is to include a battery and a microphone or rheotome in the primary circuit of 
an induction coil, and to connect either of the secondary terminals with a brass-jet 
nozzle, mounted on the end of an insulating ebonite or glass tube ; while the remain¬ 
ing secondary terminal is either grounded or attached to a conductor held close to the 
jet orifice. On talking to the microphone the words spoken may be heard from the 
jet in the usual way. Also by coating a glass jet tube inside and outside with 
platinum near the orifice, but not at the orifice, and connecting these coatings with 
the induction coil secondary terminals, we can get an arrangement capable of taking 
the place of the ordinary receiving telephone. 
It would not serve the purpose of this paper to describe at length the great number 
of experiments made with jets of air and other gases. Most of them have only a 
secondary interest. One other fact, however, is worthy of notice. It is not only at 
the orifice that jets are easily affected. In fact it is easy, especially by mechanical 
means, to produce disturbances at a distance from the orifice. But the intensity of 
the effect on the jet diminishes as the distance of the point of application of the dis¬ 
turbance from the orifice increases. 
At a very early stage in this investigation the question naturally presented itself: 
Would jets of water and other liquids exhibit the same properties as gaseous jets ? 
Referring to the historical notice at the beginning of this paper, it will be seen that 
much more had been done in the way of reliable experiment with liquid than with 
gaseous jets ; probably because the phenomena of such jets appeal to two senses, sight 
and hearing, and are therefore more easily studied. A few simple experiments sufficed 
to show that all the results obtained with gaseous jets may also be obtained with liquid 
jets, and in a more marked and satisfactory way. 
As even the lightest known liquid has a very high density compared with air, we 
should naturally not expect liquid jets to exhibit the same sensitiveness to sound that 
gaseous jets do. Nor do they in fact; while to purely mechanical disturbances they 
