Cindy Byal, Age 13, Of Mingo, Ia., For her question:

How much is an inch of rain water on an acre?

An inch of rain water collected in the bottom of a teacup weighs no more than a few pennies. But over large land areas the weight of this amount of rainfall totes up to amazing proportions. One inch of rainfall on the entire state of Ohio, for example, weighs somewhat more than two billion tons.

The weight of an inch of rain water on one square mile is 72,300 tons. The weight of one inch of rainfall per acre is 113 tons. This is a tremendous weight to drop upon our heads, and if the rain fell down in one liquid lump the earth would be smashed out of shape with every shower. But it falls in small drops, widely separated from each other, and the tremendous weight is no more than the patter of tiny feet.