272 Prof. A. M. Mayer's Researches in Acoustics. 



brought neatly together and cemented to one and the same point 

 of the membrane, while the other ends of these fibres were at- 

 tached to tuning-forks mounted on their resonant boxes, as 

 shown in fig. 1. In the experiment which I will now describe 



Fig. 1. 



eight forks were thus connected with one point of the membrane. 

 The fundamental tone of the pipe was Ut 2 , of 128 vibrations per 

 second ; and the pipe was brought into accurate unison with a 

 fork giving this sound*. The forks connected with the mem- 

 brane were the harmonic series of Ut 2 , Ut 3 , Sol 3 , Ut 4 , Mi 4 , Sol 4 , 

 Bj - , Ut 5 . In the first stage of the experiment we will suppose 

 that the fibres are but slightly stretched ; then, on sounding the 

 pipe, all the fibres at once break up into exquisite combinations 

 of ventral segments. If the sunshine fall upon a vibrating fibre 

 and we look on it obliquely in the direction of its length, we 

 shall see ventral segments superimposed on ventral segments in 

 beautiful and changing combinations. On gradually tightening 

 the fibres, we diminish the number of their nodes ; and on reach- 

 ing a certain dgeree of tension with fibres 1 m. long, I have seen 

 them all vibrating with single ventral segments. On increasing 

 the tension, the amplitudes of these single segments gradually 

 diminish and at last disappear entirely, so far as the unaided 

 eye can discern; and then we have reached the conditions re- 

 quired in our experimental confirmation. 



The point of the membrane to which the fibres are attached 

 is actuated by a motion which is the resultant of all of the 

 elementary pendulum-vibrations existing in the composite 

 sonorous wave ; and the composite vibrations of this point are 



* Since the number of beats per second given by any harmonic (of a 

 pipe out of tune with its harmonic series of forks) will be as the order of 

 the harmonic, it is better to tune a reed to unison with a fork giving one of 

 its higher harmonics. I generally used the Sol 3 fork, or the 3rd harmonic. 



