The pure joy of cave exploration had its zenith in the establishment of the seven-mile link between Kentucky's huge Flint Ridge and Mammoth cave systems. You don't have to be a spelunker to shiver with back-chills and scalp-thrills as the authors face dangerous holes and hidden rivers during their 20-year assault on this underground Everest of tunnels. Tight spots?--""The crack narrowed progressively until it confined the explorers tightly on all sides. They moved forward by wiggling kneecaps, elbows, and toes. Then the floor of the gunbarrel passage dropped away into black nothingness below."" And that's the easy part! It's when you're hanging onto a slick pit wall and your lamp goes out that things really get hairy. Cavers Brucker and Watson load each rift with high spirits and vigorous fellowship in their thrill-a-minute 24-hour odysseys into the gloomy earth with its blazing wonderland pockets and halls. A wisecracking Kon-Tiki of superman speleology, with a superb payoff chapter and clever asides on the edge of doom.