300 AVERS. [Vol, VI. 



timbre of a tone is due to the sequence of certain simple tones, 

 and not on the form of the wave compounded of them. 



Or, as Bernstein states it, " the sensation of a note is caused 

 by the irritation of a certain fibre of the nerve of the cochlea, 

 which is produced by the fundamental tone, and also by the 

 more or less feeble irritation of certain other nerve fibres, the 

 terminal organs of which have been irritated by the harmonics." 

 On the supposition, of course, that each hair cell received from 

 its supporting basilar membrane fibres stimuli due to a given 

 frequency. 



Koenig has, I think, conclusively proven that timbre is due to 

 the presence of what he calls the sounds of subdivision (Helm- 

 holtz's " oberpartialtone," translated by Tyndall into "over- 

 tones "), which are not identical with the " harmonics." These 

 subdivisional sounds are produced by ;2^;2-periodic as well as 

 periodic waves, and hence the quality, pleasing or otherwise, of 

 the tone may be due to non-periodic undulations as well as the 

 periodic, to which alone Helmholtz restricted them. Helmholtz 

 was led by experimental results to hold the view that timbre 

 was due to the form of the sonorous wave, and that in the suc- 

 cession of upper and lower partial tones or tones of subdivision, 

 the form of these wavelets must necessarily remain constant. 

 Koenig has shown that Helmholtz's error lay primarily in the 

 apparatus which he used, and that as a fact, altJioiigh the form 

 of the zvavelets is constantly cJianging, the ear nevertheless does 

 tinder normal conditions ^^ group the result as a unitary sensa- 

 tion!' These experiments of Koenig's prove the correctness 

 of the view I had already arrived at ; viz. that there are in reality 

 but two conditioning physical relations of the tone wave, — its 

 rapidity and its kinetic energy. 



The sound wave, strictly speaking, has no form ; it is not a 

 discrete thing, but only a condition of the matter gaseous, 

 liquid, or solid, which in all cases partakes in the physical basis 

 of sound. And from the external vibrating body to the nerve 

 end cell the vibration is transmitted without assuming form : 

 such, at least, is true of all the acoustic undulations which pro- 

 duce the sensation of sound in the brain of man. It is demon- 

 strable, as Helmholtz claims, that two notes of the same pitch 

 and intensity, but from different sources {e.g. middle C from 

 the piano and violin) reaching the ear simultaneously, do not 



