These get so heavy that they roll down the glass. They roll down the walls, too, and drop from the ceiling. If vapor is not turned out of doors it makes a room damp. That is just what happens when it rains. The vapor in the air goes up into the sky. When it finds a cold layer of air it rolls into large drops and falls.

Vapor is always going up. Most of it goes up from the ocean, the lakes and rivers. Three fourths of our big world is covered with water, you know. The sun warms the top layer of water and turns it into vapor. Every leaf and blade of grass on the land has water in it. The sun steals this water, too. Sometimes it takes so much and gives so little back again that the grass turns brown, and the leaves wilt. Every animal and plant drinks water and breathes it out again from the lungs, or gives it to the air through little holes in the skin called pores. You know how you perspire on a hot day? Little beads of water ooze out, all over you. You can find your pores with a mag-ni-fy-ing glass. You can find pores in green leaves, too.

Plants and animals perspire more on a hot day than on a cold one. The land and water give off more vapor in the summer than in the winter. Wring a handkerchief out of hot water, hang it in the sun and see how quickly it dries. Set a shallow pan of water in the sun and see how soon the water disappears. The air is always thirsty. It drinks like a greedy fish.

But then, it is not stingy. It gives back every bit of water it gets. But it does not always give it back where it got it. Sometimes it rises in vapor from the ocean, goes up in the sky to a layer of cold air, and falls back into the ocean almost as quick as you can say Jack Robinson. But it's a very good thing for little boys and girls and trees and bees, that all the vapor doesn't do that. The ocean doesn't need the water rightaway, and the land does. A great deal of vapor goes on long journeys. It uses the wind for horses. Haven't you seen fleecy clouds floating across the sky? They were riding on the wind. The winds find it no trouble at all to carry these vapor clouds along with them. The vapor clouds travel until they strike a cold layer of air. Then they roll into rain drops and fall.

As oceans are the great vapor tanks, so mountains are the chief rain makers. The tops of mountains are very cold, and they are so high up in the air that the vapor clouds bump right into them and turn to rain. In the winter the air is so cold that the rain, in falling, freezes into snow. Wide river valleys, islands and sea coasts, get a great deal of rain and snow, too, if the winds blow over them from the ocean. If the wind blows away from the land, so that it gets no rain, that land becomes a desert.

Just as the ocean is a great tank for making vapor, so the mountains and woods and cold countries are big storage houses for snow ; much of the summer rain is lost. It runs off at once into streams, or is soon taken up again by the sun, in vapor. But snow lies for months, in cold, high, or shaded places. In the spring it melts slowly and soaks into the fields. It takes snow a long time to get into rivers. It gives plants and seeds water just when they need it, to help them grow. A farmer can get along in a dry summer, if there has been a wet winter.

In the story about land you saw what a big part water plays in this world of ours. Every drop of rain that falls takes up just as much dust as it can carry on its tiny round back, and hurries away with it. It washes the dust and smoke and bad smells out of the air, and leaves it pure and clean. It washes the dust from all plants and makes them bright. It would give you a merry shower bath if you stood in it. It washes the houses and the streets. You can see muddy water running down the gutters. How clean everything is, even the pebbles in the road, after a bright, hard rain. Mother Earth has had her face washed, and she looks as if she liked it !

Sometimes vapor clouds cannot get above the earth. You know the steam from the boiling clothes "could not get out of the kitchen until you opened a window at the top. If the air lies very heavy above it and does not open a place for vapor to go up, it lies on the earth. Such low clouds are called fogs. You remember the kitchen walls dripped with vapor, making the room damp? Thick fogs make people and plants almost as wet as rain. Fogs are oftenest seen over the ocean, lakes, river valleys and swamp land. Sometimes they cover miles of sea, and shut in ships with milky white curtains of vapor. Then the ships must blow fog horns to keep other ships from running into them. The morning sun pulls a fog up into the sky, or a brisk wind scatters it through the air.

There is always some vapor in the air near the earth, even if there isn't enough for you to see it. If a pitcher of cold water stands in a room a little while, beads of vapor form on the outside, just as they did on the cold window pane. Sometimes the earth is cold enough to collect vapor beads from the air. When a cool night follows a hot day, the earth becomes colder than the air above it. So the warm vapor collects on cold plants, and spangles them with dew drops. If the night is very cold when dew forms, the little dew-drops are frozen on the plants. Then we have Jack Frost.

Beautiful High Altitude Crystal.

Jewelled Center.

A Beautifully Etched Crystal.

Feathery Local Storm Type.

Low Altitude Type.

High And Low Altitude Combined.

A Rare Beautifully Etched Crystal.

Beautiful Star-Shaped Design.

Cold High Altitude.

Elaborately Etched Design.

Prism-Like Crystal From High Altitude.

Solid High Altitude Crystal.