Rare films of exploration in progress

The Explorers: A Century of Discovery PBS, tomorrow, 8-9:30 p.m., check local listings. Narrator: E.G. Marshall. Writer/ producer: Nicolas Noxon. Executive producers for the National Geographic Society: Dennis B. Kane and Thomas Skinner. Columbus Day is the ideal time for this National Geographic Society special about exploration: The society is celebrating its own 100th anniversary on the 496th anniversary of Columbus's discovery of America.

Surprisingly, the most effective segments of this potpourri of discovery pictures are film segments. The superb still photography from the magazine must take a back seat. Rather than attempt an all-out history of exploration, the 90-minute special wisely concentrates on the events, for which there is exciting material.

Some highlights: the Antarctic adventures of Adm. Richard E. Byrd; the expedition of Robert Peary; the 1931 French expedition that crossed the Himalayas; the William Beebe bathysphere dives; the digs of Louis, Mary, and Richard Leakey in Africa; the chimpanzee and gorilla research of Jane Goodall and Dian Fossey; the Titanic dives of Robert Ballard; the expeditions to retrieve treasure ships off the coast of Turkey and to save an isolated people in New Guinea.

There is astounding footage of each of these explorations, underwritten by the National Geographic Society. Sometimes, however, the trumpeting of the great projects begins to sound a bit like self-praise, as the nepotistic structure of the society and its magazine are revealed.

But why quibble?

``The Explorers'' is an unforgettable adventure. If you yourself can't climb Everest, dive down to the Titanic, or dig for early man in Africa, this National Geographic special is the perfect designated pinch-hitter.