Ericsson, er'ik-son, John (1803-1889), a noted inventor. He was a native of Sweden. After reaching young manhood and serving a term in the army, he left the service and established himself as an inventor. Among other useful appliances was a contrivance for regulating the aim of a cannon on a pitching ship. Another was a successful hot air engine, and still a third invention was the screw propeller, now used almost universally on steam-ships. It consists essentially of a series of slanting blades attached to one end of a shaft. The propeller rests in the water behind the ship. The shaft runs through the hold of the ship to the machinery, where it is driven by steam power. As the shaft revolves, the screw propeller turns with it, thrusting the ship forward with a powerful stroke. Most ships are provided with a pair of twin propellers. In 1839 Ericsson came to the United States. His fame rests on the construction of the iron-clad, Monitor. It was built for the United States just in time to meet the Confederate iron-clad, Merrimac, in Hampton Roads, March 9, 1862. At his death the United States government sent an armed cruiser to convey his remains to Sweden. See MONITOR; BATTLESHIP.