Filing coherer used by Sir Oliver Lodge, 1894.
© Science Museum / Science & Society Picture Library
Invented in 1890 by the Frenchman Edouard Branly (1844-1940), the coherer is one of the most important of early radio wave detectors. Its potential for wireles communication was realised by the English physicist Sir Oliver Lodge (1836-1920) who gave the first public demonstration of wireles transmision and reception at the Royal Institution, London in June 1894. This coherer, used by Lodge at Oxford in 1894, was a glas tube filled with metallic filings loosely packed between two metal plugs attached to the wires of an electric circuit. These filings remained a poor conductor until subjected to radio waves.