Dr. A. M. Mayer's Researches in Acoustics. 269 



and cardboard disks exactly coincided. The circle of holes 

 in the disks was placed 5 centim. from its border. The 

 rotator and disks were so carefully made that the nipple of 

 the resonator was only j 3 q millim. from the surface of the 

 revolving disk. The mouth of the tube conveying the inter- 

 rupted sounds to the ear was about the same distance from 

 the surface of the other side of the disk. The disks were 

 clamped on the axis of the rotator between smaller flat disks 

 of brass, not shown in the figure. 



The diameter of the holes in the disk, and of the interior of 

 the tube conveying the sounds to the ear, was 1 centim. The 

 diameter of the opening in the nippies of the resonators was 

 J centim. 



The disks were made of mahogany which had been in my 

 possession for thirty years. It was well seasoned and had 

 nearly the thickness required for the disks. This wood was 

 used because it holds the form given it better than any wood 

 1 have had experience with. 



Sound passes through mahogany and other woods even 

 when a centimetre in thickness. Sound also passes through 

 cardboard, but not so readily as through wood. I found 

 that by placing cardboard on wood I formed a screen of hetero- 

 geneous materials which presented an effective obstruction to 

 the passage of sound. 



Fio-. 8. 



D 



T 



[B.] In the second form of apparatus I replaced the re- 

 sonator by resonant tubes 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 adjusted to vibrate 

 with the fork. On the other side of the disk D is the tube T', 

 to which is attached the tube of caoutchouc which leads to the 

 ear. This arrangement is like that used bv Dr. R. Koeniof, 

 and described on page 140 of his Quelques Experiences 

 d'Acoustigue, Paris, 1882, and used by him for the obser- 

 vation of the sounds produced by interruptions of continuous 

 sounds. 



