Rebecca Melton, age 11, of Gastonia, North Carolina, for her question:

Are there really rivers in the oceans?

This seems ridiculous, because a proper river is expected to flow between two banks of solid earth. Naturally there is no solid ground to make river banks out in the wide, watery oceans. But did you ever hear someone speak of the current in a river? This is the streaming water, flowing who knows where. When we refer to a river as a current, we can ignore its earthy banks. This sort of current can stream through the ocean like a flowing river.

The notion of rivers in the oceans is rather fanciful. Scientists and other practical people prefer to be more precise    which is why they refer to these streams of water as ocean currents. And yes, indeed, they do exist. The most noticeable ones flow around and around the major oceans in enormous, swirling eddies. Behind the scenes, down in the deep oceans, there are other huge currents of sweeping water, often flowing in the opposite direction from those at the surface.

The Gulf Stream is the most famous of ocean currents, perhaps because it was the first one to be discovered. Back in the 1600s, sailors noticed a powerful current, sweeping westward across the Atlantic just north of the equator. They took advantage of its pushing power when they sailed from the Old World to the New. Others noticed a similar current sweeping back to Europe from off Labrador. Benjamin Franklin gathered more details and helped to chart the complete current, as it swirls in circles around the North Atlantic Ocean.

A matching surface current swirls in the opposite direction around the South Atlantic. Two huge Pacific currents swirl north and south of the equator, in opposite directions. Another wheels around the Indian Ocean. All of them seem to get their starting power from the trade winds that blow toward the equator. Their paths are governed by the continents, the spinning earth and the prevailing winds.

For example, the easterly trades sweep the mighty Gulf Stream westward, just north of the equator. The American land mass turns most of its current northward as far as Labrador, where a cold current comes down from the Arctic. Near this barrier, the warm Gulf Stream veers right and crosses the North Atlantic with the prevailing

1972 westerlies. Off the shores of Europe and Africa, it veers south to rejoin itself near the equator. These mighty surface currents seem to go nowhere. But they help to keep the global ocean healthy by mingling its mixture of waters.

In the 1950s, oceanographers found a deep ocean current in the Pacific, flowing eastward below a surface current flowing westward. Its path has been traced more than 3,500 miles and other submarine currents still are being found and charted. One of them eddies around the North Atlantic, almost two miles below the famous Gulf Stream    and swirling in the opposite direction.