Dr. A. M. Mayer's Researches in Acoustics. 263 



undiminished residual sensation the time that the centre of 

 the tube, R, takes to go from the centre of D to the centre 

 ofE. 



In this illustration I have, for simplicity and conciseness, 

 supposed the tube E to move over the openings D and E. 

 In the actual experiments D and E are two of several holes 

 in a disk, arranged in a circle, and the disk rotates while the 

 tube E is fixed. Another tube placed in the prolongation 

 of the tube E, on the other side of the disk, conveys the 

 interrupted sound to the ear. 



Evidently the manner in which the tube conveying the 

 sound to the disk is open and closed by the revolving disk 

 has to be considered in researches made with this apparatus. 



two cases whose discussion has led me to modifj^ 



» 



Fig. 3. 



I give 



with marked efficiency, the apparatus, shown in fig. 3, which 

 was used in the researches published in this Journal in 1875. 

 In that apparatus the interruptions of sound were made 

 by a perforated disk revolving in front of the mouth of a 

 resonator, while the interrupted sound was conveyed to the 

 ear by a tube attached to the small opening in the nipple 

 of the resonator. 



This mode of obtaining the interruptions of the sound is 

 objectionable because the resonator is not in tune with the 

 fork except when the former is fully opened, and also because 



T2 



