268 A. M. Mayer—Acoustical Experiments. 
remove the fork from its case after it was placed on it. The 
ball remained at rest until the moment I suddenly stopped 
walking ; at that instant, the ball flew from the fork, while an 
assistant, whose ear was close to the case of fork 1, while his 
eye was directed to the screen, found that at the instant I 
stopped walking, the fork 1 sounded, while the ball jumped 
from its prong. 
Exps. 4 and 5. These experiments were exactly like Exps. 
2 and 3, except that I walked away from fork 1 instead of, ' 
approaching it. The results were the same as in Exps. 2 and 3. 
Exp. 6. Fork No. 3, giving 254 vibrations per second, was 
sounded as in Exp. 1. It had no effect in moving the ball. 
now screwed the fork off its case, and standing about 30 feet . 
from fork 1, with my arm, I swung the case toward fork 1, 
and while it was approaching it, I placed fork No. 3 on the case; 
the proper velocity (from eight to nine feet per second) having 
been obtained, the ball was suddenly projected from fork 1. 
On greatly increasing or decreasing the above velocity of the 
penne ease, the vibrations of fork 3 produced no effect on 
ork 1. : 
. 7. Fork No. 4, which gives two vibrations per second 
more than No. 1, was substituted in Exp. 6, but was placed on 
its swinging case, when this was receding from fork 1. The 
pare of this motion and of varying velocities was the same as 
in Exp. 6. 
Exp. 8. I placed fork 3 before the lantern, and swung fork L 
as in Exp. 7. The effects were the same as described in Exp. 7. 
Exp. 9. I now placed fork 4 before the lantern, and moved 
fork 1 as in Exp. 6. The effect on the ball was the same as 
in Exp. 6. ; 
im unison. Two forks, sounded together, may give no percep- 
tible beats, for they may constrain each other into a ee 
forced oscillation, and deus both will give the same number 0 
vibrations, yet m3 be removed from equality when sep 
The process I have adopted is as follows: 
¥ 
