Profession: electrical engineer

Siemens revolutionised electricity generation, invented the moving-coil loudspeaker, did much to advance international telegraphy, and helped found the electrical engineering industry. His gold and silver electro-plating technology was sold by his brother Wilhelm (later William) to a Birmingham industrialist. Helmholtz, a lifelong friend, was met initially in the circle around Siemens’ teacher Magnus (who, impressed by Siemens’ dynamo, offered to make a public presentation about it). Siemens, together with Helmholtz, Clausius, Kirchhoff and Wiedemann, was active in the Physical Society of Berlin, founded by du Bois-Reymond (who became a good friend).

Siemens corresponded with Wheatstone about electromagnetic issues, and together they invented a self-excited generator. He spent two days showing Faraday around his revolutionary gas furnace in Birmingham, but when Faraday gave his lecture about it he accidentally burned his notes (Siemens later named a cable-laying ship after Faraday). Werner von Siemens was his brother and fellow engineer.