e development of
these two senses by which the mental ideas of spoken words are memorised
and recalled. Had man been limited to articulate speech he could not have
made the immense progress he has made in the development of complex mental
processes, for language, by using written verbal symbols, has allowed, not
merely the transmission of thought from one individual to another, but the
thoughts of the world, past and present, are in a certain measure at the
disposal of every individual. With this introduction to the subject I will
pass on to give a detailed description of the instrument of the voice.

[Footnote A: Sense of movement.]

THE VOCAL INSTRUMENT

A distinction is generally made in physics between sound and noise. Noise
affects our tympanic membrane as an irregular succession of shocks and we
are conscious of a jarring of the auditory apparatus; whereas a musical
sound is smooth and pleasant because the tympanic membrane is thrown into
successive periodic vibrations to which the auditory receptor (sense organ
of hearing) has been attuned. To produce musical sounds, a body must
vibrate with the regularity of a pendulum, but it must be capable of
imparting sharper or quicker shocks to the air than the pendulum. All
musical sounds, however they are produced and by whatever means they are
propagated, may be distinguished by three different qualities:

(1) Loudness, (2) Pitch, (3) Quality, timbre or klang, as the Germans call
it.

Loudness depends upon the amount of energy expended in producing the sound.
If I rub a tuning-fork with a well-rosined bow, I set it in vibration by
the resistance offered to the rosined hair; and if while it is vibrating I
again apply the bow, thus expending more energy, the note produced is
louder. Repeating the action several times, the width of excursion of the
prongs of the tuning-fork is increased. This I can demonstrate, not merely
by the loudness of the sound which can be heard, but by sight; for if a
small mirror be fixed on one of the prongs and a beam of light be cast upon
the mirror, the light being again reflected on to the screen, you will see
the spot of light dance up and down, and the more energetically the
tuning-fork is bowed the greater is the amplitude of the oscillation of the
spot of light. The duration of the time occupied is the same in traversing
a longer as in traversing a shorter space, as is the case of the swinging
pendulum. The vibrating prongs of