Gordon Stone, age 12, of Cumberland, Md., for his question:

WHERE IS THE OB RIVER?

The Ob river is one of the chief rivers of Russia in Asia. The Ob rises in the Alati Mountains of western Siberia and flows northwestward for 2,287 miles before it empties into the Arctic Ocean through the Gulf of Ob. A total of 1,125,200 square miles of land, an area about four times the size of Texas, is drained by the Ob River.

The navigable waterways of the Ob and its tributaries total about 19,000 miles. The lower part of the river is two to four miles wide while the estuary averages 50 miles in width.

The Ob is blocked with ice from October to June. In summer, the river is an important water route for shipping grain, dairy products, livestock, wool and meat. Most of this moves to the railways for shipment to western Russia, but some is exported by way of the Arctic Ocean.