A mechanism has ceased its functioning. In all probability, the device at first needed only slight modification, then would no longer respond even to these promptings. Tarnished by time, the thing became a historical artifact, a representation, bearing an intriguing inscription and a date: "John Brown, 1839." Shut away in a chest among other objects of a bygone era, the timepiece is an heirloom of a family from Gouldtown, New Jersey, whose roots in...