British Association for the Advancement of Science. 301 



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 influence 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 waves, 

 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 was 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 



m 



of the longer tube A. A'. E". A". C '". E 

 When the tubes were sounded together, the latter series was ob- 

 tained complete, and the notes of the shorter tube completely sup- 

 pressed. It was found, however, that the sounds of the longer tube, 

 which also belong to the series of the shorter, were obtained with 

 superior clearness, as E". E'". and A", and B". appeared to break 

 into each other. 



Other experiments having shown that systems of tubes may, 

 by certain methods of vibration, be forced to produce sounds not 



* Siv John Herschel's paper here referred to was published in Lond. and 

 Edinb. Phil. Mag., vol. iii. p. 401. — Edit. 



