Lord Rayleigh : Acoustical Notes. 321 



improves up to complete withdrawal of the finger, the aperture 

 may still be too small. Before finally enlarging the aperture 

 it may be well to ascertain that the resonance is improved by 

 a partial use of the one next in order. 



The second resonator was constructed entirely of metal. 

 It consists of an elliptical box of sheet zinc, with top and 

 bottom also of zinc and slightly dished for the sake of en- 

 hanced rigidity (fig. 1). The capacity (S) is about 140 c.c. 



Fiff. 1. 



The apertures for the fundamental tone (F) and for the 

 octave L(th) are formed of brass tubing soldered into position. 

 The other passages are simple perforations in the wall and 

 in the top of the box. E represents a short length of brass 

 tubing over which is slipped an india-rubber attachment 

 passing to the ear. To sound the fundamental tone of about 

 128 vibrations per second (B of my harmonium), F, about 

 8 mm. in diameter and 20 mm. long, is alone open. For the 

 octave tone L(th), 11 mm. in diameter and 53 mm. long, is 

 opened in addition. R 3 then gives the twelfth, R 2 the double 

 octave, UL 1 the higher third, L 3 the sixth component (octave 4- 

 twelt'th), L 2 the harmonic seventh, and finally L x the triple 

 octave. The diameter of R 3 is about 5 mm. and that of L : 

 (the largest aperture) say 13 mm. The letters are intended 

 to indicate the fingering. Thus L 1? L 2 , L 3 denote the first, 

 second, and third fingers of the left hand; R 1? R 2 , R3 the 

 corresponding fingers of the right hand. The octave tube 

 L(th) is closed with the thumb of the left hand. 



Phil. Mag. S. 6. Vol. 13. No. 75. March 1907. 2 A 



