Roger Barbour, age 11, of Colorado Springs, Colo., for his question:

WHAT IS CLOUD SEEDING?

General Electric Company in Schnectady, N.Y.) started  some experiments to modify rainfall in 1946. Commercialweather control operations then began in 1950 in a number of different areas. The object: to increase rainfall.

Weather experts say  not more than 5 percent of all water in storm clouds ever falls to earth as rain. If the fallout could be increased by only 2.5 percent, then the rainfall would be half again as great. To accomplish this, storm clouds are now often seeded with tiny particles of dry ice or silver iodide dropped from airplanes. The particles attract moisture in the clouds to form waterdrops, and the drops fall to earth as rain.