y, Into
semivocal sounds, which consist of a mixture of the two former; and,
lastly, Into interrupted sounds, represented by the letters properly
termed consonants.

The clear continued sounds are produced by the streams of air passing
from the lungs in respiration through the larynx; which is furnished
with many small muscles, which by their action give a proper tension
to the extremity of this tube; and the sounds, I suppose, are produced
by the opening and closing of its aperture; something like the trumpet
stop of an organ, as may be observed by blowing through the wind-pipe
of a dead goose.

These sounds would all be nearly similar except in their being an
octave or two higher or lower; but they are modulated again, or
acquire various tones, in their passage through the mouth; which thus
converts them into eight vowels, as will be explained below.

The hissing sounds are produced by air forcibly pushed through certain
passages of the mouth without being previously rendered sonorous by
the larynx; and obtain their sibilancy from their slower vibrations,
occasioned by the mucous membrane, which lines those apertures or
passages, being less tense than that of the larynx. I suppose the
stream of air is in both cases frequently interrupted by the closing
of the sides or mouth of the passages or aperture; but that this is
performed much slower in the production of sibilant sounds, than in
the production of clear ones.

The semivocal sounds are produced by the stream of air having received
quick vibrations, or clear sound, in passing through the larynx, or in
the cavity of the mouth; but apart of it, as the outsides of this
sonorous current of air, afterwards receives slower vibrations, or
hissing sound, from some other passages of the lips or mouth, through
which it then flows. Lastly the stops, or consonants, impede the
current of air, whether sonorous or sibilant, for a perceptible time;
and probably produce some change of tone in the act of opening and
closing their apertures.

There are other clear sounds besides those formed by the larynx; some
of them are formed in the mouth, as may be heard previous to the
enunciation of the letters b, and d, and ga; or during the
pronunciation of the semivocal letters, v. z. j. and others in
sounding the liquid letters r and l; these sounds we shall term
orisonance. The other clear sounds are formed in the nostrils, as in
pronouncing the liquid letters m, n, and ng, these