TRANSACTIONS OF THE SECTIONS. 
13 
fact has been assigned. Mr. Challis thinks it may be shown mathe¬ 
matically that the aerial vibrations, excited at the extremity of the 
tube, and propagated along its interior, will put it into the state of 
vibration, which, as appears from the foregoing results, will produce 
an effect the same in kind as that observed. But to what degree the 
phsenomenon may be attributed to this cause, can be learnt only from 
experiment, by ascertaining whether the vibrations of the tube have 
any considerable influence on the intensity of the musical sounds. 
The following fact seems to favour the idea of a sensible influence. 
A sound produced under glass, (for instance, the ticking of a French 
clock under a glass covering,) is louder than when the glass is re¬ 
moved, plainly by reason of the internal reflexions and the propa¬ 
gation of the vibrations along its surface, which cause it to vibrate 
so as to act with increased effect on the external air. It is not easy 
to discern that the glass vibrates, but the increase of sound is proved 
to be owing to this cause, when, on pressing the glass with the palms 
of the hands, the intensity is diminished. This experiment may 
suggest the means of detecting the induence of the vibration of a 
solid, in other instances of a similar nature. 
Case of Interference of Sound. By Robert Kane, M.D ., 
M.R.I.A., &c. 
Among the experimental proofs of the neutralization of tvaves, 
suggested by Sir John Herschel in his interesting paper on the ab¬ 
sorption of light, is one which consists in transmitting through a 
system of canals, waves of sound, emanating from one origin, and 
reuniting after that by the route of one having been rendered more 
circuitous than that of the other, when the difference in the lengths of 
the paths has become such as to qualify, them for interference. It 
occurred to Professor Kane to ascertain whether Sir J. Herschel’s 
idea could be verified in practice, and in certain cases the result has 
been found satisfactory. 
A system of tubes w T as constructed in which the lengths of the 
paths were as two to three. Thus in the annexed figures (which, 
notwithstanding the difference of shape, 
produced precisely the same results,) the 
shorter path a. c. d. is as 10 inches and the 
longer a . b. d. 15 inches in length. The 
waves of sound were generated by the lan- 
guette mechanism of an organ-pipe applied 
at a. or d., and the series obtained first for 
each tube separately, and then from the sy¬ 
stem of both. The series of the shorter 
tube was found E'.E". B". E'"., and that 
of the longer tube A. A'. E". A". C " f . E'". 
When the tubes were sounded together, the latter series was ob¬ 
tained complete, and the notes of the shorter tube completely sup- 
