II. Water
The other thing this round world is made of is water. In going around the earth you crossed oceans, lakes and rivers. You saw ice or frozen water. You saw water broken up into rain drops, frozen into hailstones or snow. But there was a great deal of water everywhere that you did not see at all, or if you saw it you didn't know it was water.
The story of water is just as interesting and wonderful as the story of land. Where shall we begin to find out about it? Let us begin with one day when you were a small boy playing out of doors. Mama called you.
"Run in, Johnny, it's going to rain!"
"Why is it going to rain?" you asked. Bright little boys and girls are big question marks, running around on two stout legs. They want to know the "why" of everything. Nearly all of their "whys" are very sensible, too, and ought to be answered.
See that dark cloud rolling up the sky. That cloud is as wet as a soaked sponge. The wind is blowing it up. The wind is colder than the air was a few moments ago. Now the little drops come pattering down. They are as round as shot from whirling so far down from the sky. The sun is out again. The rain has stopped. The dark cloud is gone. Where did it go? It fell to the earth in rain drops. But how did the rain cloud get up in the sky? What is a cloud?
You can make a very small cloud if it is a cold day. Go to the door and breathe into the frosty air. You can see your breath, can't you? Not all of it, just the water in your breath. The water is broken up into very fine mist, or vapor. Vapor is a kind of water dust. The air soaks up vapor as a sponge soaks up water. There is a beautiful little vapor cloud coming from the teakettle. The air soaks that up too. A wash boiler full of boiling clothes makes a big cloud that fills the kitchen. If you open a window or door it will all go out and be soaked up by the air.
If a cloud of vapor is made in a house and cannot get out, let as see what happens. The vapor from boiling water is very warm. The glass window is colder. The vapor gathers on the glass in a mist of tiny drops. The little drops roil together into big drops.
