116 
THE HON. J. W. STRUTT ON THE THEORY OP RESONANCE. 
Some experiments were next made with the moderator globe and two openings. The 
theoretical formulae are 
n 
a /] 
— 7r\/ - 
'°-k v S 
ttK 2 
€ — ■ 
Table III. 
No. of 
I experiment. 
s, 
in cub. 
centims. 
> 
in inches. 
c 2 , 
ill inches. 
. C l.+ C 2 > 
in inches. 
n, 
by calcula- 
tion. 
n, 
by observa- 
tion. 
Difference, 
in mean 
semitones. 
23 
3240 
2-00 
1-95 
3-95 
303-4 
320 
•92 
24 
32 40 
2-00 
1-01 
3-01 
264-8 
282 
1-09 
25 
3-40 
•715 
1-01 
1-725 
200-4 
204 
•31 
In 23 both holes of the globe were clear, and in 24, 25 they were covered with wooden 
faces carrying holes of various diameters. The error in 23, 24 is to be ascribed to the 
same cause as in 15 and 22 above. 
The last experiment that I shall describe was made in order to test the theory of 
double resonance, but is not quite satisfactory, for the same reason as 15, 22, 23, 24. 
Two moderator globes were cemented together so as to form two chambers communi- 
cating with each other and with the external air. The natural openings were used clear, 
and the resonance (which was not very good) was estimated by means of a tube con- 
necting the ear with one of them. The observations gave for the values of n, 
High note = 384,'[ 
Low note =213.] 
The result of calculation from the dimensions of the globes and openings by means of 
the formulae of Parts I. and II. was 
High note= 360,1 
Low note =212.J 
The error in the high note is about a semitone. 
[The two moderator globes were fitted up again as a double resonator, only with 
bored wooden disks over the holes, so as to lower the note and render the theory more 
strictly applicable. The pitch was much better defined than before, and gave 
Low note =152 ‘5,^ 
Lligh note = 240. J 
c 1 =c 3 =1 , 008; <?,=• 7152. 
«=1133 ( 70 ° F.) 
