Tracy Albright, age 10, of Lancaster, Pennsylvania, for her question:

Where is the Nile River widest?

All great rivers open their mouths wide and still wider when they reach the sea. The mighty Nile is more than 4,100 miles long, which makes it the longest river in the world. The streams and lakes that feed the young river are in Central Africa. There, in some places it is more than a mile wide. But as it flows northward through the desert it grows narrower. When it reaches Cairo, its stream is only about 100 yards wide.

Then it begins to open its mouth. During its last 100 miles it spreads into a fan shaped delta. When at last it reaches the Mediterranean, the width of the great river is 155 miles. The Nile is a flood river that rises and spreads wider after the rainy season. Sometimes the floods swell 12 miles or more across the valley. But even in the heaviest flood seasons, the widest part of the river is the delta, where it joins the sea.