Alexander Mitchell (engineer)

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Alexander Mitchell, (April 13, 1780 – June 25, 1868) was an Irish engineer who from 1802 was blind. He is known as the inventor of the screw-pile lighthouse. He was a native of Dublin, and received his formal education at Belfast Academy where he excelled in mathematics.

Mitchell was a brickmaker in Belfast, who invented machines used in that trade, and "the screw pile" for which he gained some fame. The screw pile was used for the erection of lighthouses and other structures on mudbanks and shifting sands, and employed with great success all over the world from Portland breakwater to Bombay bridges. His screwpile was used for the construction of lighthouses on Maplin Sands, the Thames Estuary, at Morecambe Bay, and at Belfast Lough where his lighthouse was finished in July 1844.

In 1848 he was elected member of the Institution of Civil Engineers and received the Telford medal for a paper on his invention.

In May 1851 he moved to Cobh to lay the foundation for that lighthouse; the success of these undertakings led to the use of his invention on the breakwater at Portland, the viaduct and bridges on the Baroda and Bombay railway and the whole system of Indian telegraphs.

He was friendly with astronomer John Thomas Romney Robinson, and mathematician George Boole.

He died at Glen Devis near Belfast on 25 June 1868.