A BRIDGE TO AFAR

They're not just for nature lovers anymore. Over the years, the National Geographic Society has been responsible for some of the most fascinating documentaries on any topic, and four programs just released on tape, THE EXPLORERS: A CENTURY OF DISCOVERY, RETURN TO EVEREST, FOR ALL MANKIND, and CAMERAMEN WHO DARED (1984-89, Columbia TriStar, $19.95 each, $59.95 per set), are among the most compelling. Even the weakest of these four, The Explorers, offers such bracing footage of so many sublime moments that viewers can excuse it for being one long commercial for its sponsor. The other three tapes prove that the society's self-congratulation is largely justified. Return to Everest accompanies Sir Edmund Hillary to Nepal more than 30 years after his historic conquest of Mount Everest, while For All Mankind follows Apollo explorers to the moon (and yes, they do appear to be drinking n their spaceship). Cameramen Who Dared focuses on the brave (or foolhardy) souls who scale mountains, dive under seas, dodge artillery, and climb trees 150 feet high as baboons relieve themselves from above, all so that armchair adventurers can experience the world. Most memorable is an Australian photographer's chilling documentation of his own accidental death. All tapes: A-