Francis Petit Smith and Thomas Pilgrim, mid 19th century.
© Science Museum / Science & Society Picture Library
Sir Francis Pettit Smith (1808-1874), the English inventor of the screw propeller is seen here on the left, shaking hands with Thomas Pilgrim (1800-1871). 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.