1879 -] 
Proceedings of Societies . 
259 
As frequent bowing might affecft the rate, two sets of measure- 
ments were made, in one of which the fork was bowed every 
20 seconds, and in the other every 5 seconds. 
Duration of 
Bowed every 
Bowed every 
Experiment. 
20 seconds. 
5 seconds. 
5 min 
... 512-470 
512*460 
3 » 
... 512:460 
5I2-452 
3 » 
... 512-460 
512-456 
Means 
... 512-463 
512-456 
No change of phase has ever been observed on the application 
of the bow. The same result was obtained by Lissajous, although 
Poske has since found that bowing produces an alteration. The 
authors have never seen any sudden jump of the wave during 
bowing. To test this in another manner two forks were arranged, 
one horizontally and the other vertically, so that both could be seen 
simultaneously in the microscope (the horizontal one being beyond 
the sub-stage). The Lissajous figure is seen at the angle made 
by the two forks. When bowed no change of the form of the 
figure took place ; its amplitude merely was increased. This 
arrangement of the forks is suggested as a method for comparing 
two forks of nearly the same pitch, or of a fork with its ocftave. 
A difference of amplitude produced no appreciable change in the 
rate of the fork. 
Large Amplitude. Small Amplitude. 
037 m.m. 0T5 m.m. 
256*277 256-275 
256*273 256-274 
Means ... 256-275 256-2745 
The mode of fixing the fork in a vice might have changed the 
rate : to test this two sets of measurements were made, in one 
of which the fork was fixed in the vice, and in the other on a 
sounding-box. 
On Sounding-Box. 
512-489 
512-482 
512-477 
Mean ... 512-483 
This result may be compared with that above given in which the 
fork was bowed every 20 seconds. It will be seen that the rate 
is rather less when the fork is held in the vice. In the previous 
paper the coefficient of change of rate for temperature is given 
as o-oooii for each degree centigrade: this number has been 
fully confirmed by numerous measurements. 
