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.