HELMHOLTZ IN BONN 



the series of simple tones which correspond with these 

 simple vibrations. 



The interesting question now arises, whether the ear, 

 having to deal with waves varying almost infinitely in 

 form, is differently affected by such waves, according as 

 their form represents various modes of pressure (pushes 

 and pulls) on the drumhead and conducting mechanism ? 

 When we sound the harmonic series of forks from 

 Ut to Ut 5 , we hear a rich harmonious sound, and we 

 can analyse the sensation, and pick out the tone of any 

 particular partial, more especially if it is slightly 

 strengthened by a touch of the bow. By varying the 

 order and intensity of the partials, we can produce a 

 very large number of wave-forms, but the general 

 character of the harmonious sound remains the same. 

 In other words, waves may differ much in form, but 

 if they contain the same harmonic constituents, the, 

 sensational effect will be the same. This would 

 appear to indicate that the ear takes no cognisance 

 of phase. Helmholtz invented a special apparatus 

 to investigate this question. This costly apparatus 

 was presented to him by King Maximilian of 

 Bavaria. It consists of a harmonic series of forks, 

 electrically driven, and so arranged that they can be 

 sounded in any order and with various intensities, 

 according to changes produced in the size of the 

 orifices of their appropriate resonators. 1 The resona- 



1 A figure of the apparatus is given in M'Kendrick's Physiology, vol. 

 ii., p. 691. 



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