Look, Jessie, the water in the kettle is boiling.

How do you know it is, Ray?

Steam comes from the spout. This shows that the water is boiling.

The fire heats the water. When the water becomes hot it changes to steam.

Will all the water in the kettle turn to steam?

Yes, indeed, Jessie! It will change in a very short time if the water is kept boiling. You see, steam comes from the kettle all the time.

What does the steam look like?

O Edna! I think it looks like clouds. See! it floats in the air just as clouds do.

Look close to the mouth of the spout. Frank, do you see any steam there?

No, Miss Stone; I see no steam close to the mouth of the spout.

Let us put this plate in the cloud. Now, what do you see?

The plate is covered with drops of water. Some of the drops are large, and some are very small.

Now, Frank, we will dry this plate and put it between the mouth of the spout and What has happened?

the cloud.

The plate is covered with drops of water, just as it was when it was put into the cloud. From what did these drops of water come, Miss Stone?

These water-drops came from real steam. That is real steam between the mouth of the spout and the cloud. Real steam is vapor. You cannot see vapor. This cloudwhich you see is fine water-dust.

The plate was so cold that the waterdust changed to drops of water. The cold plate changed the vapor close to the spout to drops of water.

Now you know that vapor comes from boiling water. As soon as it leaves the spout, the air cools it.

The air cools the vapor just enough to change it to water-dust.

Where does the water-dust go, Ray?
It floats away in the air.

Let us see what heat does to waterdust.

Frank may hold this lighted lamp

under the cloud. See! the cloud is goHeat is changing it to vapor.

ing away.

Where is this vapor? Is it in the air? Yes; the air is full of vapor. Vapor makes the air moist. If there were no vapor in the air, we could not breathe.

What comes from boiling water?
What changes water to vapor?

What changes vapor to water-dust?
What changes water-dust to vapor?
What makes the air moist?

Oh, Miss Stone, see the white clouds floating in the air! Do those clouds come from the engine?

Yes, Jessie; every puff of the engine sends a cloud into the air.

Watch the cloud. Where does it form? See, Ray, it forms. just a little way from the top of the funnel. Look closely. Do you see that clear space between the cloud and the funnel? There must be something there, something that makes the cloud.

I know what it is. It is steam. It is vapor. Vapor makes clouds.