Hercule-Progres turbine. 19th-century illustration of the US-French Hercule-Progres water turbine, mounted in a masonry chamber. Water turbines harness the power of moving water as it rotates the blades (lower centre). A variety of designs were developed in the 19th century. This one had a guaranteed efficiency of between 80 and 85 percent. The label ('brevetee sgdg') indicates that it has been patented 'sans garantie du gouvernement' (without government guarantee). 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.