John Ericsson (1803-1889), Swedish-born American engineer and inventor, perfected the screw propeller and constructed radically designed warships, notably the ironclad "Monitor."

John Ericsson was born in Långbanshyttan, Värmland Province, on July 31, 1803. He began as an iron miner but showed an aptitude for machinery construction, drafting, and engraving. After work as a surveyor on the Göta Ship Canal, he became an army topographic officer in 1820.

In 1826 Ericsson went to London, where he worked mainly on engines and on locomotives and screw propulsion for boats, receiving 14 patents. English railroad builders kept him profitably at work.

To devise a means of using heat more efficiently than did steam engines, Ericsson applied flame directly in a "caloric" engine. His most lucrative invention was a steam fire engine. To improve marine engines and keep propulsion apparatus underwater, he designed a screw propeller (patented 1836) which was more efficient...