36 THE FAIRY-LAND OF SCIENCE. 
ing travel to us, just as the quivering of the boards 
would from me to you ? Take a basin of water to rep- 
resent the ether, and take a piece of potassium like 
that which we used in our last lecture, and hold it 
with a pair of nippers in the middle of the water. You 
will see that as the potassium hisses and the flame 
burns round it, they will make waves which will 
travel all over the water to the edge of the basin, and 
you can imagine how in the same way waves travel 
over the ether from the sun to us. 
Straight away from the sun on all sides, never 
stopping, never resting, but chasing after each other 
with marvellous quickness, these tiny waves travel 
out into space by night and by day. When the spot 
of the earth where America lies is turned away from 
them and they cannot touch you, then it is night for 
you, but directly America is turned so as to face the 
sun, then they strike on the land, and the water, and 
warm it; or upon your eyes, making the nerves quiver 
so that you see light. Look up at the sun and picture 
to yourself that instead of one great blow from a fist 
causing you to see stars for a moment, millions of tiny 
blows from these sun-waves are striking every instant 
on your eye; then you will easily understand that this 
would cause you to see a constant blaze of light. 
But when the sun is away, if the night is clear we 
have light from the stars. Do these then too make 
waves all across the enormous distance between them 
and us ? Certainly they do, for they too are suns like 
our own, only they are so far off that the waves they 
send are more feeble, and so we only notice them 
when the sun's stronger waves are away. 
