That is right, Edna. If there were no vapor, there would be no clouds.

The air cools the vapor as soon as it leaves the engine. The cool air turns vapor to water-dust. This water-dust floats away in the air and looks like a cloud.

Watch the cloud. It floats in the air. It is gone. You do not see it now. Where is it?

I will tell you.

Water-dust scatters as

it floats in the air. It becomes very

light, and the air is warm enough to change it back to vapor.

Now you know that-

Heat changes water to vapor.

Cold air changes vapor to water-dust.
Warm air changes water-dust to vapor.
Vapor makes the air moist.

There is moisture in the air.
The moisture in the air is vapor.

What change does heat make in water?
Into what does cold air change vapor?

What makes water-dust?

What is the moisture in the air?

My little friends, would you like to know more about vapor? where the vapor comes from that makes the clouds? how it gets into the air?

You have seen the clouds form from the steam which came from the kettle and the engine. You know that heat is necessary to make steam.

You know that vapor is necessary to form clouds.

By heating water we change it to steam, and then by chilling steam we change it into clouds.

Is there any outdoor heat that makes

the vapor from which the clouds are formed?

Without heat there can be no vapor. Without vapor, no clouds. Can my little friends tell me where the heat comes from?

From the sun, Miss Stone! The sunbeams give us heat.

I thought you could tell if you tried. You are right. When the sunbeams fall upon the ground they heat it. Then the air near the ground is heated.

This heated air spreads out; or, as we say, expands. When air expands it becomes lighter and rises.

You have felt the hot air as it rises from a stove, have you not, Edna? The hot air floats away, and cold air takes its place to get warm.

Now when the sunbeams fall on the water they warm it. The warmed water spreads out expands.

That is, the top part of the water becomes very fine water-dust, and soon

changes to vapor. The warm air near the water mixes with the vapor and

floats away.

Then cold air takes its place. As soon as this cold air becomes warm and is mixed with vapor it floats away.

In this way vapor is sent into the air from the water in the ponds, the brooks, the rivers, the lakes, and the seas.

Indeed, from every wet surface the sunbeams send vapor into the air. Wet clothes hung on the line soon become dry.

Put a piece of ice where the sunbeams can fall upon it. Now notice that the piece of ice becomes smaller and smaller, even if it does not melt into water.

The sunbeams have changed the ice to vapor though it can not be seen.

This vapor of water floats away so quietly that we cannot tell when it goes.

Now you know where the vapor comes from with which the air is filled and of which the clouds are formed.