From childhood Alexander Calder enjoyed inventing mechanical toys and gadgets. In Paris during the 1920s and 1930s he encountered a new type of sculpture, pioneered by Picasso and the Russian Constructivists: assemblages of wood, metal, plastic, and cardboard, with space incorporated as part of the design. Calder began building similar abstract pieces in 1930 but gave them a new dimension--motion. Fellow artist Marcel Duchamp christened the moving sculptures "mobiles."One of Calder's largest mobiles, Ahab is composed of three arcs made of steel rods and irregularly shaped disks that suggest natural forms. The title refers to the maniacal sea captain who pursued the white whale in Herman Melville's novel Moby Dick (1851).