Prof. A. M. Mayer's Researches in Acoustics. 361 



or quickly enough, to prevent two sounds from succeeding each 

 other so rapidly without blending. 



" This fact proves, besides, that there should be in the ear dif- 

 ferent parts which are set in vibration by sounds of different height, 

 and which give the sensations of these sounds. Some may imagine 

 that the mass of the vibratile elements of the ear, comprising the 

 tympanic membrane, the ossicles, and the liquid of the internal 

 ear, can vibrate, and that it is on this property of this mass that 

 depends the impossibility of sonorous vibrations ceasing with 

 the same rapidity in the ear. But this hypothesis does not suf- 

 fice to explain the known facts. 



" When, in fact, an elastic body enters into vibration under 

 the influence of an exterior sound, it takes the number of vibra- 

 tions of the latter; but as soon as the exciting sound ceases, it 

 vibrates with the number of vibrations which belongs to it when 

 vibrating freely. This fact, which is a consequence of theory, 

 can be very neatly proved for tuning-forks by means of the vibra- 

 tion-microscope. 



" Therefore, if the ear vibrate as an entire system, 7P and is 

 capable of prolonging notably its vibrations, this prolongation 

 should depend on the number of its own free vibrations, which 

 is altogether independent of the number of vibrations of the 

 exterior sound which excited the vibratory motion. It at 

 once follows that it will be as difficult to trill among the high 

 notes as among those of the bass, and, also, that the two 

 sounds of the trill will blend, not with each other, but with a 

 third sound belonging to the ear itself. We have already 

 made known one of the sounds in the preceding chapter : it is 

 the fa 6 *. In these circumstances, consequently, the result 

 should be altogether different from that given us by the obser- 

 vation of the facts."" 



If we extend our law downward and upward, throughout 

 the range of audible sounds, we have for forty vibrations per 



* I here adopt, as I always do, the French notation, which is used by 

 Konig. Those who use the French translation of Helmholtz's work should 

 be on their guard to observe that the translator has lowered all of his nota- 

 tion one unit below that used in France, and he thus gives all of Helm- 

 holtz's notes too low by an octave. Thus the translator's Ut 2 should read 

 Ut 3 . 



The fact to which Helmholtz refers above is that the human ear is tuned, 

 by resonance, to the/a 6 of 2730 complete vibrations ; so that the vibrations 

 of this note and of those near it cause piercing sensations in our ears. If 

 a short tube be adapted to the external auditory canal, these disagreeable 

 sensations disappear, as the canal can no longer resound to the above note ; 

 but the same piercing sensation will now reappear on sounding a lower 

 note. Mad. E. Seiler, now of Philadelphia, has shown that dogs are pecu- 

 liarly sensitive to the acute mi of the violin. 



