James L. Smith, Jr., age 12, of Winston Salem,North Carolina, for his question:

What do they call the end of a river?

Actually a river has two ends, a start and a finish line. The starting point is called its source, or beginning. The source of even the greatest river is very small, perhaps a spring gushing from the ground or a small stream. The source of the great Mississippi is a little creek, small enough to jump across. The source of the great Amazon starts where several trickles of melting ice merge together, high in the lofty Andes.

As it flows along, the young river is joined by other streams and tributaries. They add their waters to the main stream and the river grows. Its path is decided by the slope of the land, for water must flow downhill. At last it winds its way to the level of the ocean and empties its fresh river waters into the salty sea. This finish

line is called the mouth of the river. Here a sizeable river dumps layers of mud. It forms a wide fan shaped delta and split's apart into sluggish channels.