coherer

 Any device in which an imperfectly conducting contact between pieces of metal or other conductors loosely resting against each other is materially improved in conductivity by the influence of Hertzian waves; -- so called by Sir O. J. Lodge in 1894 on the assumption that the impact of the electic waves caused the loosely connected parts to cohere, or weld together, a condition easily destroyed by tapping. A common form of coherer as used in wireless telegraphy consists of a tube containing filings (usually a pinch of nickel and silver filings in equal parts) between terminal wires or plugs (called conductor plugs).  [Webster 1913 Suppl.]