422 MR. C. A. BELL ON THE SYMPATHETIC VIBRATIONS OF JETS. 
of the vibratory changes. We have an extreme case of this kind of action in jets of 
mercury, which are not only highly sensitive, but break very easily under the 
influence of sound. This may be seen by letting the jet fall into a basin of mercury, 
and including it in circuit with a battery and coil. Viewing it in a dark room, sparks 
will then appear wherever breaks occur, and may frequently be seen quite close to the 
orifice when the jet is disturbed by moderately loud sounds. The vibrations of a 
mercury jet become much more regular when it is surrounded by water. 
In the foregoing I have given the outlines of a new theory of jet vibrations. 
Treading on somewhat unfamiliar ground, I have endeavoured to base it, as far as 
possible, on purely experimental considerations. It would be useless to deny that 
there are many points in which the theory, taken as a whole, is deficient; and my 
hope is that others, who have made a special study of vortex motion, may be able 
to supply what is wanting. The strongest claim to attention that can be urged 
for it is certainly that it refers the otherwise very similar phenomena of gaseous 
and liquid jets to conditions of motion which may be experimentally demonstrated 
in fluids of both kinds. Whether or not the theory can stand the test of 
mathematical treatment remains to be seen. But even should it ultimately prove 
to have no more solid foundation than analogy, the experimental part of the inquiry 
which has led to it may still have some value as a contribution to our knowledge of 
an exceedingly interesting, if somewhat obscure, class of phenomena. Many lines 
of thought and experiment are already suggested, and on some of these I hope to 
report at an early date. 
