A. M. Mayer — Researches in Acoustics. 7 



nipple of the resonator takes place rapidly and that the nipple 

 remains fully opened from 4 to 8 ; that is, during one-third 

 the time that the opening in the disk takes to traverse the 

 opening in the resonator. The advantages gained by this 

 mode of experimenting are considerable. The periods of 

 sound and of silence are sharply marked and, as we shall now 

 show, the fact that the hole in the resonator has half the 



5 — — — — — :: 



a /- 



6 -J- 



L ^ 



Fie;. 5. 



Fig. 6. 



diameter of the hole in the disk gives us the means of ap- 

 proaching nearer to the measure of the veritable time during 

 which we have an after- sensation of uniform intensity. 



In fig. 6, R represents the opening in the nipple of the 

 resonator, supposed to pass over the opening D in the disk. 

 In this case, as in fig. 2, the 

 space A to B in which sound 

 traverses the revolving disk is 

 equal to the space B to C in 

 which silence supervenes, for 

 the distance separating two 

 holes on the disk equals twice the diameter of a hole, or, four 

 times the diameter of the hole in the nipple of the resonator. 

 But in this form of the experiment we are again in doubt as 

 to what space should be taken as measuring the duration of 

 the uniform residual sensation. The period from the full 

 opening of the resonator in one position to the full opening in 

 the succeeding one is equal to the time the disk takes to go 

 from G- to H, which is equal to the distance D to E between 

 the center of the openings in the disk minus the diameter of 

 the opening in the resonator, or, to DE minus ^ DE. This 

 distance, G- to H, evidently measures the periods between 

 maximum and maximum intensities of succeeding sound 

 pulses, and we have taken this distance, in terms of velocity of 

 rotation, as the measure of the period of uniform residual 

 sound sensation because we have no certain knowledge of the 

 relative durations of the residual sensations corresponding to 



