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



second a residual sensation lasting ^o °f a se cond ; while for 

 40,000 vibrations per second we have a residual sensation en- 

 during only -ji— of a second. If we apply the law to vibra- 

 tions below forty per second, when they do not produce a con- 

 tinuous sound, but explosive sensations in the ear, we reach a 

 remarkable result. Thus the residual sensation corresponding 

 to thirty vibrations per second should remain in the ear - 1 — of 

 a second after the vibrations outside the ear have ceased; then 

 we at once ask why is it, if the residual sensation lasts _L of a 

 second, that thirty beats or pulses per second do not blend? 

 This abrupt breaking down of the law can only be explained 

 by the highly probable supposition that covibrating bodies in 

 the ear, tuned to vibrations below forty per second, do not 

 exist, and therefore, as there are no bodies in the inner ear to 

 covibrate and keep up these oscillations after the cause which 

 would have set them in motion has ceased to exist, it follows 

 that when the ear receives less than forty vibrations per second 

 it can only vibrate en masse, and the durations of these oscilla- 

 tions of the ear, as a whole, are far too short to remain the ^ 

 of a second. The last supposition, as to the vibration of the 

 ear as a mass, may serve to explain why the higher notes 

 (far beyond those used in the musical scale) produce conti- 

 nuous sensations ; for, to these very high sounds we can hardly 

 imagine corresponding tuned bodies ; yet they produce conti- 

 nuous sensations. But may it not be imagined that the ear with 

 them does also only vibrate as one mass, and that the duration 

 of this vibration is sufficient to give continuous sensations from 

 pulses following at the rate of several thousand per second ? 

 But for notes thus perceived (without the intervention of cor- 

 responding covibrating parts in the inner ear) differences of 

 pitch should be difficult, even impossible, to distinguish ; and 

 this we find to be the case. 



The fact that the durations of the residual sensations dimin- 

 ish as the numbers of vibrations producing the sounds in- 

 crease, leads to the knowledge of a new and curious phenome- 

 non in the physiology of audition, viz. that the timbre of a 

 composite sound begins to change at the instant the vibra- 

 tions outside the ear have ceased ; for from that instant the 

 residual sensation becomes more and more simple in its cha- 

 racter, until at last only the simple sound of the fundamental 

 harmonic remains in the ear; and soon after, this sensation also 

 vanishes. Thus, after the vibrations of an Ut 2 reed-pipe con- 

 taining twenty harmonics have ceased, the residual sensation of 

 the twentieth harmonic, or that highest in pitch, disappears in 

 the qt— °f a second ; but the sensation of the fundamental or 

 lowest harmonic remains in the ear jj of a second after the 



