This is because the
air at this height is so thin. On the top of Mont Blanc a pistol-shot can
scarcely be heard even though it is fired quite close; but if the same
pistol were to be fired off in the next field you would hear it, and put
your hand to your ears because the report was so loud.
But what makes the report? The pistol was fired into the air, and hit
nothing.
It was the air which was struck, and which sent back the sound. You
remember learning how light is turned back or reflected. Just as the
light-waves come back again, so do the sound-waves; very quickly if the
reflecting surface is near; after some time if it is far off. You know what
an echo is. There is a lovely place where some children I know used often
to go for a picnic. What they cared for most in Coombe Dingle was a wood
which they called the "Echo wood." They would stand beside a gate, and call
across the fields, and then listen. Very soon their own words, and even
their own tones, were sent back to them. The waves of air carried the
sounds along until they reached a pine wood which shut in the field. They
struck the tall trees, and were reflected, or sent back again, almost as
clearly as when first spoken.
Just in this way echoes of sound are, like birds, ever on the wing: the
whole air is alive with them. The walls of our rooms give back the tones
of our voices, but we hear no echo, because they are so near that the
repeating of the sound comes almost at the same moment as the sound itself.
Pages:
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84