"To dowse," says the author of this definitive study of the divining art, "is to search with the aid of a handheld instrument such as a forked stick or a pendular bob on the end of a string - for anything: subterranean water flowing in a narrow underground fissure, a pool of oil or a vein of mineral ore, a buried sewer pipe or electrical cable, an airplane downed in a mountain wilderness, a disabled ship helplessly adrift in a gale, a lost wallet...