THE FAIRY-LAND OF SCIENCE. 9 
rain. Pause for a moment and think. You have 
surely heard of gravitation, by which the sun holds 
the earth and the planets, and keeps them moving 
round him in regular order ? Well, it is this same 
gravitation which is at work also whenever a shower 
of rain falls to the earth. Who can say that he is not 
a great invisible giant, always silently and invisibly 
toiling in great things and small whether we wake or 
sleep ? 
Now the shower is over, the sun comes out, and the 
ground is soon as dry as though no rain had fallen. 
Tell me, what has become of the rain-drops ? Part no 
doubt have sunk into the ground, and as for the rest, 
why you will say the sun has dried them up. Yes, 
but how ? The sun is more than ninety-one millions 
of miles away ; how has he touched the rain-drops ? 
Have you ever heard that invisible waves are travelling 
every instant over the space between the sun and us ? 
We shall see in the next lecture how these waves are 
the sun's messengers to the earth, and how they tear 
asunder the rain-drops on the ground, scattering them 
in tiny particles too small for us to see, and bearing 
them away to the clouds. Here are more invisible 
fairies working every moment around you, and you 
cannot even look out of the window without seeing 
the work they are doing. 
If, however, the day is cold and frosty, the water 
does not fall in a shower of rain ; it comes down in the 
shape of noiseless snow. Go out after such a snow- 
shower, on a calm day, and look at some of the flakes 
which have fallen ; you will see, if you choose good 
specimens, that they are not mere masses of frozen 
