we shall term
narisonance.

Thus the clear sounds, except those above mentioned, are formed in the
larynx along with the musical height or lowness of note; but receive
afterward a variation of tone from the various passages of the mouth:
add to these that as the sibilant sounds consist of vibrations slower
than those formed by the larynx, so a whistling through the lips
consists of vibrations quicker than those formed by the larynx.

As all sound consists in the vibrations of the air, it may not be
disagreeable to the reader to attend to the immediate causes of those
vibrations. When any sudden impulse is given to an elastic fluid like
the air, it acquires a progressive motion of the whole, and a
condensation of the constituent particles, which first receive the
impulse; on this account the currents of the atmosphere in stormy
seasons are never regular, but blow and cease to blow by intervals; as
a part of the moving stream is condensed by the projectile force; and
the succeeding part, being consequently rarefied, requires some time
to recover its density, and to follow the former part: this elasticity
of the air is likewise the cause of innumerable eddies in it; which
are much more frequent than in streams of water; as when it is
impelled against any oblique plane, it results with its elastic force
added to its progressive one.

Hence when a vacuum is formed in the atmosphere, the sides of the
cavity forcibly rush together both by the general pressure of the
superincumbent air, and by the expansion of the elastic particles of
it; and thus produce a vibration of the atmosphere to a considerable
distance: this occurs, whether this vacuity of air be occasioned by
the discharge of cannon, in which the air is displaced by the sudden
evolution of heat, which as suddenly vanishes; or whether the vacuity
be left by a vibrating string, as it returns from each side of the
arc, in which it vibrates; or whether it be left under the lid of the
valve in the trumpet stop of an organ, or of a child's play trumpet,
which continues perpetually to open and close, when air is blown
through it; which is caused by the elasticity of the currents, as it
occasions the pausing gusts of wind mentioned above.

Hence when a quick current of air is suddenly broken by any
intervening body, a vacuum is produced by the momentum of the
proceeding current, between it and the intervening body; as beneath
the valve of the trumpet-stop above mentioned