THE WIND.
What is the wind? We can feel the wind blow ing upon our faces. We can see what the wind does, but we cannot see the wind itself.
Sometimes the wind blows against us so strongly we can hardly stand up. The wind carries our hats down the street. It tips over houses and great trees.
All about us there is something which we can not see. We call this the air. The air keeps us alive. At every breath our lungs are filled with it.
When the air moves we feel it pushing against us. Wind is then only the air in motion. The air surrounds the whole earth. It is never quiet, but is always doing work. It makes the windmills go around, and sends the ships across the sea.
On a summer day the wind cools our cheeks and rustles gently in the trees. In the winter it is fierce and strong. When it blows very hard we say there is a storm. Then the air rushes swiftly along and sometimes does a great deal of harm.
Now what is it that makes the wind blow? You have all sat by the fireplace and watched the flames roar up the chimney. The fire makes the air near it very hot. Hot air is lighter than cold air, and is pushed upward by the cold air which rushes in and takes its place. As soon as the cold air be
comes warm, it, in turn, rises, and this makes a wind up the chimney. We say the fire draws well when the air moves fast. You cannot see the air moving, but hold a little paper windmill in front of the fire place and it will turn around as it does in the wind out of doors.
Winds blow over the earth for the same reason that air draws up the chimney.
The sun shines upon the earth and makes it hotter in some places than in others. Where the air becomes hotter it rises faster, and the cool air rushes along to the place where the hot air was. When this happens we feel the wind blowing.
The wind may blow from any direction. The north wind is usually cold. It makes us shiver and put on our coats.
The south wind is warm. It brings the rain and the spring flowers. The south wind wakens all Nature from its winter sleep.
When clouds cover the sky and the south wind blows, people say it will rain.
After the rain the wind changes and blows from the north. It soon chases all the clouds away. Now we have fair weather.