Elaine McKinney, age 13, of Victoria, British Columbia, Canada, for her question:

What makes a seashell roar?

A seashell sits silently on the seashore and utters not a sound when you take it home and place it on a shelf. However, if you hold it close to your ear, you may hear a roaring that sounds somewhat like the rushing waves on a tidal beach. Not every kind of shell has one of these mysterious orchestras. The right shell must have a curved dome of snail like coils and a wide mouth. One of the best is a graceful conch shell but the flat clam shell is no use at all.

Actually, the shell itself does not provide the roaring orchestra. The original sound is produced by your own beating heart and the pulsing of the blood coursing through your body. Under normal conditions, these personal sounds are too soft tor~you to hear. But the shell is a natural echo chamber with lots of small chambers and curved walls. As the soft sound of your pulse bounces back and forth inside the shell, it is amplified to a roar like the swoosh of distant surf.