336 
POPULAR SCIENCE REVIEW. 
motions distinctly visible to a large audience, as I intend pre- 
sently to show. What, now, is the exact distinction between a 
mere noise and a musical note — between harmony and discord ? 
A noise consists of the recurrence of sounding vibrations at 
irregular intervals ; whilst every musical note is produced by its 
own particular number of vibrations, which recur at perfectly 
equal intervals. Several contrivances exist, by means of which 
the number of these vibrations, which occur in a second of time, 
can be counted. It has been thus ascertained that the higher 
or shriller the note, the more frequent are the motions by which 
it is produced. A simple expedient will enable us to show the 
number of vibrations of a note — say the treble C of the piano, 
and to prove that this note is due to twice as many vibrations in 
a second as are necessary to form the middle C, or the octave 
immediately below it. 
Here are two tuning-forks, one of which, when caused to 
vibrate, emits a note which is an octave higher than the other. 
Attached to one of the prongs of each fork is a needle which 
partakes of the motions of the prong. If a piece of smoked 
glass be drawn across the points of the needles when the forks 
are not sounding, the soot will be scratched off the surface of 
the glass in the form of two straight lines, the image of which 
may be thrown upon the screen by means of a strong light. 
But if the tuning-forks be made to sound by drawing a violin 
bow across them, a second piece of smoked glass will then show 
not two straight, but two zigzag lines ; and the line produced 
by the shriller note will exhibit just twice as many notches as 
that caused by the other fork. In a similar manner, it might 
be shown that the intermediate notes are produced by vibra- 
tions of intermediate frequency, a definite number being 
required for each note, as may be seen in the table, which 
exhibits an octave of the musical scale. 
Batio of tue Sounds of the Musical Scale. 
c 
1 
1 ) E E 
G A B C 
0 
H 
0 n 4 
3 
3 5 15 9 
2 3 8J 
Vibrations por Second. 
Intervals. 
I) 
]•: 
y 
o 
A 
i3 
c 
2.5(5 
288 
320 
3411 
384 
420| . 
480 
512 
