15 



n_, 



the ear. The sound of an open 

 tube is, therefore, ceteris paribus, 

 much stronger than that of a 

 closed tube, as there are two 

 waves in place of one. 

 That the office of closed tubes, when resonant, is to de- 

 stroy a portion of the sound of the original vibrating body, 

 and of the open tubes to afford, in addition to that, a new 

 centre of a wave of the same phase as that which remains, 

 may be exhibited in many ways. Thus, Mr. Adams shewed 

 long since, that when two closed tubes are placed at right 

 angles to each other, they interfere when made to speak to 

 a tuning fork, and for this effect no explanation has hitherto 

 been given. But it is evident that the tubes being at right 

 angles to each other, the waves destroyed are in opposite 

 phases, and those which remain are in opposite phases also, 

 so that the effect is the same as if no tubes were present at 

 all. The same effect may be produced 

 by a single tube, bent so that its aper- 

 tures may be at right angles to each other ; 

 the — and -}- waves, d and c, meeting in 

 the tube, produce neutralization, and the 

 waves A and b, also -|- and — , which re- 

 main, interfere also, and hence no sound 

 results. In an open tube bent into a circle, 

 as in the figure, the two waves destroyed (a c) are of the 



same phase, and also those which 

 remain, (b d,) and hence, such a 

 tube sounds with nearly double the 

 power of an ordinary open tube. 

 That it is the sound of the waves 

 which do not go into the tube, 

 and not that of the waves in the 

 tube, we hear, may be shewn by applying two closed tubes, as 

 in the next figure. When the two — waves are absorbed 



