LOCK AND KEY

History, metaphor, and mechanics, of both the words ``lock'' and ``key'' and the little machines themselves. Tchudi traces how we've kept things safe (whether money, people, or secrets) with devices from rocks rolled into cave entrances to voice-pattern, palm, and retina recognition. But however ingenious the lockmaker, lockpicks have always kept pace. In the glory days of mechanical locks and thieves, a manufacturer once offered ú200 to anyone who could pick his lock—an offer that stood for 50 years before being paid. Safes have been test-blasted by atomic bombs (some survived, some didn't). At his best with anecdotes and wordplay, Tchudi does little to explain locks' mechanics, while the few detailed drawings (reproduced from other books) don't really show what moves and what stays still. One drawing, of an electrical lock, merely shows what looks like a common padlock with a cord attached—not very informative. The author can be literal-minded to a fault: he passes along Jonathan Swift's advice—keep a cat in the cupboard to keep mice from breaking the china—with the comment that the real problem is that the cat would run away. Still, an intriguing survey. Bibliography; index. (Nonfiction. 10+)