Anthony Johnson, age 10, of Butte, Mont., for his question:

WHAT IS THE WORLD'S LONGEST RIVER?

The Nile River of Africa is the world's longest river. It starts at Lake Victoria in east central Africa and generally flows north through Uganda, Sudan and Egypt to the Mediterranean Sea, for a distance of 3,470 miles.

From its remotest headstream, the Luvironza River in Burundi, the river is actually 4,145 miles long. The river basin has an area of more than 1 million square miles.

The source of the Nile is one of the upper branches of the Kagera River in Tanzania. The Kagera follows the boundary of Rwanda northward, turns along the boundary of Uganda and drains into lake Victoria. On leaving Lake Victoria at the site of the now submerged Ripon Fails, the Nile rushes for 300 miles between high, rocky wails and over rapids and cataracts, at first north west and then west, until it enters Lake Albert. The section of the river between the two lakes is called the Victoria Nile.

The river leaves the north end of Lake Albert as the Albert Nile, flows through north Uganda, and at the Sudan border it becomes the Bahr &I Jabel. At its junction with the Bahr al Chazel, the river becomes the White Nile. At Khartoum, the White Nile is joined by the Blue Nile or Bahr al Azraq