resonance_.

An English writer records that he was once in the garden at the back
of a house while a gentleman was singing in the drawing-room. The
tone-quality was good, and the pitch so unusually high he hastened to
learn who sang tenor high C so beautifully. On entering the room,
instead of the tenor he had supposed, he found the singer was a
baritone, and the note sung was only middle C. The fundamental tone
had not reached him in the garden but the first overtone, an octave
above it, had. Concrete illustrations will make the subject still
clearer.

Experiment II

If an ordinary tuning-fork when vibrating is held in the hand its
intrinsic tone is too weak to carry far. Rest the handle of the
vibrating fork on a bare table or the panel of the door, and the sound
is greatly augmented. _The vibrations of the fork have by contact
induced similar vibrations in the wooden table or panel which
reinforce the primary tone._

Experiment III

Place the handle of the vibrating tuning-fork on a small upturned
empty box, or, better still, in contact with the body of a violin, and
the sound will be stronger than in the previous experiment, because to
the vibrations of the wood are added the vibrations of the air
enclosed in the box or the violin. _To the resonance of the wood has
been added the sympathetic resonance of the confined air._

Experiment IV

Hold the vibrating fork over the mouth of an empty fruit-jar and there
will probably be little or no reinforcement; but gently pour in water,
thereby shortening the air column within the jar, and the sound of the
fork will be gradually intensified until at a certain point it becomes
quite loud. If you pour in still more water the sound will gradually
become feebler. This shows that _for every tone an air column of a
certain size most powerfully reinforces that tone_.

Experiment V

As a sequence to the last experiment, take two fruit-jars of the same
size, and, having learned to what point to fill them for the greatest
resonance, fill one jar (after warming it) to the required point with
hot water, the other with cold water, and you will find that the
resonance of the heated, therefore expanded, air is much less than the
denser air of the cold jar. This shows that _the degree of density of
the air affects its resonance_.

Experiment VI

To demonstrate the resonance of the oral cavity, apart from the voice,
hold a vibrating tuning-fork before the open mout