Alexander Mitchell (engineer)
Alexander Mitchell was an Irish engineer who from 1802 was blind. He is known as the inventor of the screw-pile lighthouse.
Early life
Born in Dublin, his family moved to Belfast while he was a child, and he received his formal education at Belfast Royal Academy, where he excelled in mathematics.Career
Originally working in brickmaking in Belfast, he invented machines used in that trade, before patenting the screw-pile in 1833, for which he would later gain some fame. The screw-pile was used for the erection of lighthouses and other structures on mudbanks and shifting sands, including bridges and piers. Mitchell's designs and methods were employed all over the world from Portland breakwater to Bombay bridges. Initially it was used for the construction of lighthouses on Maplin Sands in the Thames Estuary, the Wyre Light at Fleetwood in Lancashire, and at Belfast Lough where his lighthouse was finished in July 1844.In May 1851 he moved to Cobh to lay the foundation for a lighthouse on the Spit Bank; the success of these undertakings led to the use of his invention on the breakwater at Portland, the viaduct and bridges on the Bombay, Baroda and Central India Railway and a broad system of Indian telegraphs.
While in Cork, Mitchell became friendly with astronomer John Thomas Romney Robinson, and mathematician George Boole.