a space 85 feet long
and 26 feet deep.

HUMAN REEDS.

The most wonderful of all musical reeds is found in the human throat, in
the anatomical part called the _larynx_, situated at the top of the
_trachea_, or windpipe.

Slip a piece of rubber tubing over the end of a pipe, allowing an inch
or so to project. Take the free part of the tube by two opposite points
between the first fingers and thumbs and pull it until the edges are
stretched tight. Now blow through it. The wind, forcing its way between
the two rubber edges, causes them and the air inside the tube to
vibrate, and a musical note results. The more you strain the rubber the
higher is the note.

The larynx works on this principle. The windpipe takes the place of the
glass pipe; the two vocal cords represent the rubber edges; and the
_arytenoid muscles_ stand instead of the hands. When contracted, these
muscles bring the edges of the cords nearer to one another, stretch the
cords, and shorten the cords. A person gifted with a "very good ear"
can, it has been calculated, adjust the length of the vocal cords to
1/17000th of an inch!

Simultaneously with the adjustment of the cords is effected the
adjustment of the length of the windpipe, so that the column of air in
it may be of the right length to vibrate in unison. Here again is seen a
wonderful provision of nature.

The resonance of the mouth cavity is also of great importance. By
altering the shape of the mouth the various harmonics of any fundamental
note produced by the larynx are rendered prominent, and so we get the
different vocal sounds. Helmholtz has shown that the fundamental tone of
any note is represented by the sound _oo_. If the mouth is adjusted to
bring out the octave of the fundamental, _o_ results. _a_ is produced by
accentuating the second harmonic, the twelfth; _ee_ by developing the
second and fourth harmonics; while for _ah_ the fifth and seventh must
be prominent.

When we whistle we transform the lips into a reed and the mouth into a
pipe. The tension of the lips and the shape of the mouth cavity decide
the note. The lips are also used as a reed for blowing the flute,
piccolo, and all the brass band instruments of the cornet order. In
blowing a coach-horn the various harmonics of the fundamental note are
brought out by altering the lip tension and the wind pressure. A cornet
is practically a coach-horn rolled up into a convenient shape and
furnished with three keys, the depress