Sir Francis Pettit Smith, English inventor of the screw propeller, c 1856.
© Science Museum / Science & Society Picture Library
Oil painting of Sir Francis Pettit Smith (1808-1874), an English farmer, and inventor of the screw propeller. The screw propeller had curved blades which pushed the water backwards, and propelled the boat forward. In contrast to the paddle wheel commonly in use, the propeller stayed under water and was thus les easily damaged.