g6 THE FAIRY-LAND OF SCIENCE. 
dew, hoarfrost, snow, and ice, and we have only time 
shortly to see it on its travels, not merely up and down, 
as hitherto, but round the world. 
We must first go to the sea as the distillery, or the 
place from which water is drawn up invisibly, in its 
purest state, into the air; and we must go chiefly to 
the seas of the tropics, because here the sun shines 
most directly all the year round, sending heat-waves to 
shake the water-particles asunder. It has been found 
by experiment that, in order to turn I Ib. of water into 
vapour, as much heat must be used as is required to 
melt 5 Ibs. of iron; and if you consider for a moment 
how difficult iron is to melt, and how we can keep an 
iron poker in a hot fire and yet it remains solid, this 
will help you to realize how much heat the sun must 
pour down in order to carry off such a constant supply 
of vapour from the tropical seas. 
Now, when all this vapour is drawn up into the air, 
we know that some of it will form into clouds as it 
gets chilled high up in the sky, and then it will pour 
down again in those tremendous floods of rain which 
occur in the tropics. 
But the sun and air will not let it all fall down at 
once, and the winds which are blowing from the equa- 
tor to the poles carry large masses of it away with 
them. Then, as you know, it will depend on many 
things how far this vapour is carried. Some of it, 
chilled by cold blasts, or by striking on cold moun- 
tain tops, as it travels northward, will fall in rain in 
Europe and Asia, while that which travels southward 
may fall in South America, Australia, or New Zealand, 
or be carried over the sea to the South Pole. Wher- 
