THE HOX. J. W. STEUTT OX THE THEORY OF RESOXAXCE. 
115 
(61). In 9, 13, 14 the reservoir consisted of the body of a flask whose neck had been 
cut off close, and which was fitted with a small tube for insertion in the ear. In 9 and 
13 there was a short glass or tin tube fitted into the opening*, while in 14 the mouth 
was covered (air-tight) with a piece of sheet gutta percha pierced by a cork borer ; 11 
was a small globe treated in the same way. 15 to 22 were all experiments with a globe 
of a moderator-lamp, which also had a tube for the ear, one opening being closed by a 
piece of plate glass cemented over it. Sometimes a little water was poured in for 
greater convenience in determining the pitch, whence the slightly differing values of S. 
In 15 the opening was clear, and in 16 fitted with a brass tube; in 17 it was covered 
with a gutta-percha face, in 18, 19, 21 with a Avooden face bored by a centre-bit, and 
in 20 with a piece of tin plate carrying a circular hole ; 22 contains the result when the 
other opening of the globe was used clear. 
On inspection of Table II. it appears that the discrepancy between theory and obser- 
vation is decidedly greater than in Table I., in fact about double, whether we consider 
the maximum or the mean error. The cause of some of the large errors may, I think, 
be traced. 13 and 16 had necks of just the length for which the correction - E may not 
be quite applicable. A decided flow back round the edge of the outer end must take 
place with the effect of diminishing the value of «. In order to test this explanation, a 
piece of millboard Avas placed over the outer end of the tube in 16 to represent the 
infinite plane. A new estimation of n, as honest as possible, gaA r e n= 137, which would 
considerably diminish the error. I fancied that I could detect a decided difference in 
the resonance according as the millboard Avas in position or not ; but when the theo- 
retical result is known, the difficulty is great of making an independent observation. 
In 15 and 22, where the apertures of the globe were used clear, the error is, I believe, 
due to an insufficient fulfilment of the condition laid down at the commencement of this 
paper. Thus in 15 the wave-length =112 3 -^227 = 4-9 feet ; or ±\=V2 feet, Avhich is not 
large enough compared to the diameter of the globe (6 inches). The addition of a neck 
lowers the note, and then the theory becomes more certainly applicable. 
It may perhaps be thought that the observations on resonance in Tables I. and II. do 
not extend over a sufficient range of pitch to give a satisfactory verification of a general 
formula. It is true that they are for the most part confined Avithin the limits of an 
octave, but it must be remembered that if the theory is true for any resonant air-space, 
it may be extended to include all similar air-spaces in virtue of Savaet’s law alone — a 
laAv which has its foundations so deep that it hardly requires experimental confirmation. 
If this be admitted, the range of comparison Avill be seen to be really very wide, including 
all proportions of L and E. When the pitch is much higher or much lower than in the 
Tables, the experimental difficulties are increased. For much lower tones the ear is not 
sufficiently sensitive, while in the case of the higher tones some of the indications relied 
on to fix the pitch are no longer available. 
* Gutta percha softened in hot water is very useful for temporary fittings of this sort. 
