Roger Fox Jr., age 7, of Bald Creek, N.C., for his question:

WHAT IS OZONE?

Ozone is a form of oxygen. You can smell it sometimes right after a thunderstorm or near an electric switch. It was discovered by a German chemist named Christian Friedrich Schonbein in 1840.

High energy radiation from the sun strikes oxygen in the earth's atmosphere and converts some of it to ozone. Air at ground level contains less than one part of ozone per million parts of air. At 15 miles above the ground there is a more concentrated layer of ozone. It contains about six parts of ozone per million parts of air, but even this small amount helps to shield the earth from much of the sun's ultraviolet light. Ultraviolat rays harm living tissues and, without the protective ozone layer, plants and animals probably could not live on the earth.