Tom Phelps, age 7, of Dunlap, I11., for his question:

WHY DON'T RIVERS RUN OUT OF WATER?

Sometimes rivers do run out of water. Then their beds become dry ditches. But sooner or later, more water comes running in and fills them up again. Actually the river water comes from the clouds when they shed their rain  often on the far distant hills. The water runs down, down the slopes in little streams that join to make bigger streams. The bigger streams add their water to the rivers  and the rivers carry it all to the sea. All this flowing water comes from the clouds, as the falling rain runs down the slopes to fill the rivers.