254 A, M. Mayer—Researches in Acoustics. 
read: “ Does this theory accord with the facts that have been 
adduced? Let us, in the first place, examine our four tuning- 
forks, to ascertain whether their deportment harmonizes with 
this theory. And here let me remark that we have only to do 
with the fundamental tones of the forks. Care has been taken 
that their overtones should not come into play, and they have 
been sounded so feebly that no resultant tones mingled in an 
tones, 
512—256 ; difference=256. 
“Tt is plain that in this case we can have no beats, the differ- 
ence being too high to admit of them.” 
But if Prof. Tyndall had taken, in place of the above forks, 
two forks giving 40 and 80 vibrations per second, he would, ac- 
cording to his premises, have made this octave a most disso- 
nant interval; for would he not have had (80—40=40) forty 
ts per second entering his ear? Similarly, if we assume that 
33 beats per second always produce the maximum dissonance, 
then even the interval C &. which gives a difference of 64, 
is far removed from consonance, 
Prof. Tyndall then proceeds: “Let us now take the Jifth. 
Here the rates of vibration are 
384—256 ; difference—128. 
“This difference is barely under the number 132, at which the 
beats vanish: consequently the roughness must be very slight. 
“Taking the fourth, the numbers are 
384—312; difference=72. 
‘Here we are clearly within the limit, when the beats vanish, 
e 
1? 
the consequent roughness being quite sensible. 
“Taking the mayor third, the numbers are 
320—256; difference—64, 
“Here we are still further within the limits, and, accordingly, 
the roughness is more perceptible. 
_  Lhus we see that the deportment of our four tuning-forks 
_ 4s entirely in accordance with the explanation which assigns 
dissonance to beats,” 
of beats fall “ within 
anish,” and “the consequent rough- 
