DETERMINATION OF THE RATE OF VIBRATION OF TUNING-FORKS. 
11 
Consequently, this difference of amplitude does not appreciably affect the vibration 
number. 
3. Effect of the mode of fixing the fork. 
To determine whether any difference was perceptible when the fork was attached to 
the sounding box, the latter was supported on a piece of wood and a heavy leaden 
weight placed within it, the top being left without any pressure upon it. The experi¬ 
ment was not easy, as the pressure of the bow slightly moved the fork in the field of 
view, and the amplitude was small, which made the waves somewhat difficult to see. 
Three five-minute measurements were made, giving— 
512-489 at 16-2 
512-482 16-25 
512-477 16-35 
Mean 512-483 16-26 
The results previously given of the effect of bowing were made with the same fork 
at the same temperature ; a comparison with these would seem to indicate that fixing 
in a vice slightly diminishes the vibration number, to an extent of about '005 per cent. 
This might have been expected, as the fork communicates a slight motion to the body 
to which it is attached, and the heavier vice retards the fork. 
Effect of temperature on the vibration number of forks. 
In the previous paper some experiments were described by which the effect of a rise 
of temperature on a large fork, giving 60 vibrations per second, was found to be a 
diminution of the rate of vibration amounting to 'Oil per cent, for each degree centi¬ 
grade. It will be better to express this by the coefficient "00011 for 1° C. This 
number has been confirmed by some determinations of a 256 fork at various tempera¬ 
tures. Since it is not easy to devise a thoroughly satisfactory means for altering the 
temperature of the fork whilst in the apparatus, the determinations were made when 
The following numbers 
were thus obtained :— 
surrounding 
air were 
\ very different. 
1 . 
256-310 
at 15-01 C. 
2. 
256-273 
16-31 
3. 
256-260 
16-69 
4. 
256-175 
19-75 
5. 
256-137 
21-16 
6. 
256-052 
24-29 
7. 
256-008 
25-69 
Calculating the coefficient for each degree centigrade from the determination made 
at the lowest temperature as the starting point, the following values were found :— 
c 2 
