Dr. A. M. Mayer's Researches in Acoustics. 265 



marked 8 Y shows the full area of opening when the circles 

 of the tube of the resonator and of the disk coincide. It will 

 be observed that the tube is opened and closed slowly, and is 

 only instantaneously fully opened at 8. 



Second Case. The openings in the disk remain 1 centim. in 

 diameter, but the opening in the nipple of the resonator is 

 ^ centim. in diameter. Fig. 5 shows the relations between 

 the areas of opening of the nipple of the resonator and the 



f r> 







- 







Fig. 5. 



Y 













g 









































































































fl 



























path A to B (fig. 6) of this opening, R, as it is supposed to 

 move across the opening D in the disk. Fig. 5 is to be 

 studied in connexion with fig. 6. Fig. 5 shows that the 

 opening and closing of the nipple of the resonator take 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 con- 

 siderable. 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 diameter of the hole in the disk gives 

 us the means of approaching nearer to the measure of the 

 veritable time during which we have an after-sensation of 

 uniform intensity. 



Fm. 6. 



C H 



In fig. 6 E, 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 in the disk equals twice the diameter of a hole, or four 



