Terry Hargrove, age 10, of Montgomery, Ala., for his question:

WHERE DO CLOUDS COME FROM?

The clouds live a free and easy life, sailing where they wish over the sky and changing shape as they go. They even appear and disappear when they choose. Or so it seems. Actually the clouds are not free to do just as they wish. Everything they do is governed by rules and regulations. They are made of tiny droplets of water mixed with the air. And they can form only when things are just right.

The story begins when the sun dries up moisture from the land and seas. This moisture turns into gaseous vapor, which mingles with the other invisible gases in the air. The air can hold only so much water vapor and no more. Warm air can hold more vapor than cool air. So when warm, moist air chills, it must give up some of its vapor. This surplus vapor changes into droplets of water  and forms the misty clouds.