An early coherer, 1894. A coherer is an ear

An early coherer, 1894. A coherer is an early form of radio detector, usually consisting of a glas tube loosely filled with metal filings whose bulk electrical resistance decreases in the presence of radio waves. Sir Joseph Oliver Lodge (1851-1940) realised the potential of the coherer for wireles communication, and gave the first demonstration of a wireles transmision and reception at the Royal Institution in London in 1894.