Mike Purseil, age 9, of Great Falls, Mont., for his question:

WHEN WAS THE HARMONICA INVENTED?

Two musical instruments sate the name of "harmonica." One is the mouth organ that was invented independently in both England and Germany in the 1820s and the other is the glass harmonica that was invented in the 1760s by the colonial genius Benjamin Franklin.

Franklin's instrument was a mechanized version of the much simpler musical glasses that were popular in the 18th Century. These were a set of glass containers, graduated in size to give a full scale of musical notes.

Franklin's glass harmonica had a set of glasses fixed on a horizontal spindle that revolved by a treadle. The spindle was arranged in a trough to keep the glasses wet and produce shimmering, bell like tones when touched by the fingers to the wet edges. Mozart and Beethoven even wrote some special pieces for the glass harmonica.

The mouth organ is an oblong box fitted with a row of air channels, each ending in a small metal free reed. Sounds are made by blowing or suction. It is a child's toy and is also used in country and Western music.