to the place from
whence they proceeded. Sound in like manner expands in every
direction, and the extent of its progress is in proportion to the
impulse on the vibrating chord or bell.

Such is the yielding nature of fluids, that when other waves are
generated near the first waves, and others again near these, they
will perform their vibrations among each other without interruption;
those that are coming back will pass by those that are going
forwards, or even through them, without interruption: for instance,
if we throw a stone into a pond, and immediately after that, another,
and then a third, we shall perceive that their respective circles
will proceed without interruption, and strike the banks in regular
succession.

The atmosphere in the same manner possesses the faculty of conveying
sounds in the most rapid succession or combination, as distinctly as
they were produced. It possesses the power not only of receiving and
propagating simple and compound vibrations in direct lines from the
voice, or an instrument, but of retaining and repeating sounds with
equal fidelity after repeated reflection and reverberation, as is
evident from the sound of a French horn among hills.

Newton was the first who attempted to demonstrate that the waves or
pulses of the air are propagated in all directions round a sounding
body, and that during their progress and regress they are twice
accelerated and twice retarded, according to the law of a pendulum
vibrating in a cycloid. These propositions are the foundation of
almost all our reasoning concerning sound. When sonorous bodies are
struck, they, by their vibration, excite waves in the air, similar to
those caused by a stone thrown into water; some parts of these waves
entering the ear, produce in us that sensation which we call sound.
How these pulsations act upon the auditory nerve, to produce sound,
we know not, as we see no necessary connexion between the pulses and
the sensation, nor the least resemblance between them; but we can
trace their progress to a certain extent, which I shall now endeavour
to do.

The external part of the ear is called the auricle, or outward ear,
which is a cartilaginous funnel, connected to the bones of the
temple, by means of cellular substance, and likewise by its own
proper ligaments and muscles. This cartilage is of a very compound
figure, being a kind of oval, marked with spirals standing up, and
hollows interposed, to which other hollows and