You must not imagine we have explained here the many
intricacies which occur in the ear; I can only hope
to give you a rough idea of it, so that you may picture
to yourselves the air-waves moving backwards and forward
in the canal of your ear, then the tympanum vibrating
to and fro, the hammer hitting the anvil, the stirrup
knocking at the little window, the fluid waving the
fine hairs and rolling the tiny stones, the ends of
the nerve quivering, and then (how we know not) the
brain hearing the message.
Is not this wonderful, going on as it does at every
sound you hear? And yet his is not all, for
inside that curled part of the labyrinth, which looks
like a snail-shell and is called the cochlea, there
is a most wonderful apparatus of more than three thousand
fine stretched filaments or threads, and these act
like the strings of a harp, and make you hear different
tones. If you go near to a harp or a piano,
and sing any particular note very loudly, you will
hear this note sounding in the instrument, because
you will set just that particular string quivering,
which gives the note you sang. The air-waves
set going by your voice touch that string, because
it can quiver in time with them, while none of the
other strings can do so. Now, just in the same
way the tiny instrument of three thousand strings
in your ear, which is called Corti’s organ,
vibrates to the air-waves, one thread to one set of
waves, and another to another, and according to the
fibre that quivers, will be the sound you hear.
Here then at last, we see how nature speaks to us.
All the movements going on outside, however violent
and varied they may be, cannot of themselves make
sound. But here, in the little space behind the
drum of our ear, the air-waves are sorted and sent
on to our brain, where they speak to us as sound.
Week 18
But why then do we not hear all sounds as music?
Why are some mere noise, and others clear musical
notes? This depends entirely upon whether the
sound-waves come quickly and regularly, or by an irregular
succession of shocks. For example, when a load
of stones is being shot out of a cart, you hear only
a long, continuous noise, because the stones fall
irregularly, some quicker, some slower, here a number
together, and there two or three stragglers by themselves;
each of these different shocks comes to your ear and
makes a confused, noisy sound. But if you run
a stick very quickly along a paling, you will hear
a sound very like a musical not. This is because
the rods of the paling are all at equal distances
one from another, and so the shocks fall quickly one
after another at regular intervals upon your ear.
Any quick and regular succession of sounds makes a
note, even though it may be an ugly one. The
squeak of a slate pencil along a slate, and the shriek
of a railway whistle are not pleasant, but they are
real notes which you could copy on a violin.
