cular note was sung. The flame manometer of Koenig (_vide_ fig. 14)
shows that if the same note be sung with different vowels the serrated
flame image in the mirror is different for each vowel, and if a more
complicated form of this instrument be used (such as I show you in a
picture on the screen) the overtones of the vowel sounds can be analysed.
You will observe that this instrument consists of a number of resonators
placed in front of a series of membranes which cover capsules, each capsule
being connected with a jet of gas.

[Illustration: FIG. 14

Four-sided revolving mirror

Images of gas jets

Resonators, with capsules connected with gas jets]

[Description: FIG. 14.--Koenig's flame manometer. The fundamental note C is
sung on a vowel sound in front of the instrument; the lowest resonator is
proper to that note and the air in it is thrown into corresponding periodic
rhythmical vibrations, which are communicated through an intervening
membrane to the gas in the capsule at the back of the resonator; but the
gas is connected with the lighted jet, the flame of which is reflected in
the mirror, the result being that the flame vibrates. When the mirror is
made to revolve by turning the handle the reflected image shows a number of
teeth corresponding to the number of vibrations produced by the note which
was sung. The remaining resonators of the harmonic series with their
capsules and gas-jets respond in the same manner to the overtones proper to
each vowel sound when the fundamental note is sung.]

Each resonator corresponds from below upwards to the harmonics of the
fundamental note c. In order to know if the sound of the voice contains
harmonics and what they are, it is necessary to sing the fundamental note c
on some particular vowel sound; the resonators corresponding to the
particular harmonics of the vowel sound are thus set in action, and a
glance at the revolving mirror shows which particular gas jets vibrate.
Experiments conducted with this instrument show that the vowel _U=oo_ is
composed of the fundamental note very strong and the third harmonic (viz.
g) is fairly pronounced.

_O_ (_on_) contains the fundamental note, the second harmonic (the octave
c') very strong, and the third and fourth harmonics but weak.

The vowel _A_ (_ah_) contains besides the fundamental note, the second
harmonic, weak; the third, strong; and the fourth, weak.

The vowel _E_ (_a_) has relatively a feeble fundamental note,