Contents: Discovery of the Antikythera shipwreck; Discovery of and research on the mechanism fragments, 1902-73; The casing, general construction, and dial work; The arrangement of the plates and components of the mechanism; The door plates and orientation and use of the mechanism; The accuracy of gear teeth numbers; Description of individual gears and gear trains; The inscriptions; The Antikythera mechanism as an historical document; The early history of gearing and clockwork; and The invention of complicated clockwork and the differential gear. App.: Composition of the metal fragments (contrib. by Earle Caley and Cyril Smith); and Tech. note on radiography of fragments. Illus.