xz 



A. M. Mayer — Researches in Acoustics. 11 



Sound passes through mahogany and other woods even 

 when a centimeter in thickness. Sound also passes through 

 card-board but not so readily as through wood. I found that 

 by placing card-board on wood I formed a screen of hetero- 

 geneous materials which presented an effective obstruction to 

 the passage of sound. 



(B) In the second form of 

 apparatus I replaced the H 



.resonators by resonant tubes _L 

 as shown in fig. 8, where F ' — 

 is the fork, T, the tube with 

 a tube of larger diameter, 

 A, sliding on T, so that the 

 air in the tube could be ad- 

 justed to vibrate with the 

 fork. On the other side of 

 the disk D, is the tube T' Fig. 8. 



to which is attached a tube 



of caoutchouc which leads to the ear. This arrangement is 

 like that used by Dr. R. Kcenig and described on page 140 of 

 his " Quelques Experiences d'Acoustique," Paris, 1882, and 

 used by him for the observation of the sounds produced by 

 interruptions of continuous sounds. 



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 resonators (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 between 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 one interior 

 diameter of |- cm , the other an interior diameter of l cm , slid 

 accurately and with little friction in two tubes, A and B, with 

 flanges on their ends. These flanges were pressed against the 



