Carol Sue Van Dyke, age 14, of Peoria, for her question:

By what process does rain form?

Rain is formed by the stuff which makes clouds. As a rule, we only see this fluffy material floating overhead. We get a closer look at it on a misty dayi For mist, or fog, is really no more than a cloud resting on the ground. We also get a close look at the clouds from an airplane. Up there, we can get a good look at the shapes of the clouds. They seem to be vary solid, floating in the air.

This cloud stuff really is made of fide water droplets. It takes a vast number of these droplets to form one raindrop. If you could scale yourself down to see the size of these droplets, you would wonder how the job could be done. Imagine yourself to be less than a quarter of an inch tall. The cloud drops remain the same size but, compared to you, they will seem much bigger.

You might think that you had landed in the middle of a tennis practice game. The cloud droplets are the tennis balls. Maybe two or throe are being volleyed around the court and there seems little chance of two balls crashing in mid air. How then can maybe a thousand of these droplets team up to form a raindrop? That is the mystery of tho rainmaking process.

Remember that these droplets are made of water. They are liquid and tend to cling like liquid. Now imagine a solid object charging through a host of droplets. Maybe it will strike a few of them. And, being small droplets of waters they will cling to it. In time, this small object may gather up the moisture from a thousand droplets. They will gel into one big raindrop. The droplets are small and light enough to float aloft. The raindrop is too heavy and down it falls.

Of course these solid objects flying around in a misty cloud are very small. To act as the core, or nucleus, of a raindrop, an object might be no larger than a cloud droplet. And such fine, solid particles do fly around in the air. Dust, soot, grains of pollen and even fine spores are always being tossed and blown by the winds high above the ground.

Particles of salt also take to the air over the; surf and pounding ocean waves. There also may be fine fragments of ice present in a cloud. One part of a cloud may be much colder than another ‑ cold enough to freeze some of the droplets into tiny crystals of ice.

Any one of these small solid objects will serve to get the raindrops started. Most weather experts agree that such nuclei are necessary to get the droplets into raindrops large enough to fall. Too, monster raindrops may form in a cloud. These monsters, however, never reach the ground. They break into smaller raindrops, no bigger than one fifth of an inch, on their way down,