THE VOICES OF NATURE. 127 
and the mighty noise of the falling avalanche ; such 
sounds as these tell us how great arid terrible nature 
can be. 
Now, has it 1 ever occurred to you to think what 
sound is, and how it is that we hear all these things ? 
Strange as it may seem, if there were no creature that 
could hear upon the earth, there would be no such 
thing as sound, though all these movements in nature 
were going on just as they are now. 
Try and grasp this thoroughly, for it is difficult at 
first to make people believe it. Suppose you were 
stone-deaf, there would be no such thing as sound to 
you. A heavy hammer falling on an anvil would 
indeed shake the air violently, but since this air when 
it reached your ear would find a useless instrument, 
it could not play upon it. And it is this play on the 
drum of your ear and the nerves within it speaking 
to your brain which makes sound. Therefore, if all 
creatures on or around the earth were without ears or 
nerves of hearing, there would be no instruments on 
which to play, and consequently there would be no 
such thing as sound. This proves that two things 
are needed in order that we may hear. First, the 
outside movement which plays on our hearing instru- 
ment ; and, secondly, the hearing instrument itself. 
First, then, let us try to understand what happens 
outside our ears. Take a poker and tie a piece of 
string to it, and holding the ends of the string to your 
ears, strike the poker against the fender. You will 
hear a very loud sound, for the blow will set all the 
particles of the poker quivering, and this movement 
