270 



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



Experiments made with this apparatus gave the same 

 results as those made with apparatus [A] , but the sounds given 

 are so feeble compared with those coming from the resonator 

 (fig. 7), that the periods of sound and silence (or, rather, of 

 sound and much diminished sound) are not sharply separated. 

 It followed that the judgment of a continuous sensation on 

 the ear could not be so neatly made with the use of the 

 resonant tubes as when the resonators were employed. 



[C] To obtain sharper demarcation of sound and silence 

 by having no aperture for the lateral escape of sound between 

 the rotating disk and the nipple of the resonator and be- 

 tween the disk and the tube conveying the sound to the 

 ear, I made the following apparatus (fig. 9) . I turned disks 

 of brass flat and of uniform thickness. These disks were 

 revolved on a rotator driven by gear wheels made of 

 " fiberoid," so that the movement should be noiseless. The 

 number of teeth on the wheels and holes in the disks were 

 such that I was enabled to make three determinations corre- 

 sponding in the number of interruptions of sound to those 

 already obtained with apparatus [A] . 



Two brass tubes, T and T', fig. 9, one having an interior 

 diameter of | centim., the other an interior diameter of 

 1 centim., slid accurately and with little friction in two tubes, 



Fis-. 9. 



T 



P 



1 



> 



p 



t' 















^1 

 f 



il 







A and B, with flanges on their ends. These flanges were 

 pressed against the surfaces of the disk D by two delicate 

 helical springs fitting over the tubes at S and S', between the 

 flanges of A and B and the standards P and P'. The tubes 

 T and T' were as close as possible to the disk while it rotated. 

 The flanges A and B were of such diameter that no sound 



