Boudreaux-Verdet engine. Historical illustration of the complex 'Quadruplex' version of the Boudreaux-Verdet internal combustion engine, by French engineers Louis Boudreaux and Louis Verdet. The initial Boudreaux-Verdet engine was produced in 1905 (the 'Duplex'). This is a more complicated later version. These engines were distinguished by a feature called a differential piston. They were most commonly used in boats. Artwork from 'Moteurs' (1911) by French civil engineer Max de Nansouty (1854-1913), part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.