﻿Air fyc.for Pure Notes of different Pitch 



251 



and distinctly found by using the flat side of the bare prong. 

 Some of the earliest readings were taken with the resonance- 

 box ; but I soon laid it aside, as the strong resonance of the 

 box obscured too much the maximum of resonance of the tube. 



Fig. 1. 



Fig. 2. 



In a tube like that represented in fig. 1 the air-column can 

 resonate in two different ways. In the one case a loop forms 

 at the side-piece A, and a minimum of intensity is heard 

 through the tubing A C. The distance of the loop from the 

 reflecting surface of the swimmer is then an odd multiple of 

 a quarter wave-length. Raise the swimmer through a dis- 

 tance equal to the length A 0, increased by the amount of 

 Rayleigh's correction* for open pipes, then a loop forms at 0, 

 a greater change of density takes place at A, and a maximum 

 of intensity is heard through AC. The distance of the 



+ 0-82 x radius of the pipe. Vide Lord Rayleigh's 'Sound,' vol.ii. 



§ 307, and Appendix A. 



S2 



