3. When two currents of air are directed on the same radius against two
circles of similar holes arranged alternately, these circles sounded
simultaneously will produce the octave of the note which one of them
would give alone.
This experiment is performed by sounding circles 6 and 7 and pulling out
buttons 6 and 7.
4. If we direct three currents of air on the same radius against three
similar circles having holes alternating by a third of the distance
between two holes of the same circle, the three circles together produce
the fifth of the octave (Note 3) of a single circle.
Circles 3, 4, and 5 sounded together emit the note of circle 2.
(By sounding only two circles, 3 and 4, or 4 and 5, we make the same
experiment with two circles as disk No. 2 enabled us to make with
circle 8 alone; also, by sounding circle 3 alone, we obtain the note
corresponding to 12 holes; then pulling out button 4, the notes
corresponding to 12 and 36 holes are heard suddenly and very strongly;
but as soon as circle 5 is sounded also, the note of 12 disappears
completely, and we have left only that corresponding to 36 holes.
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