After the patent for the telephone was granted to Alexander Graham Bell in 1876, further development was fast. In 1882 the Englishman Cromwell Fleetwood Varley (1828–1883) devised a better version of the microphone, of which this is an example. The sound of a voice sets a membrane, to which a small carbon-rod is attached, into vibration. In a coil the vibrating rod generates an induced current, which is led through a wire to a receiver. In the receiver a reverse process sets a membrane into vibration, which reproduces the recorded sound. Varley’s design of this electromagnetic microphone was then applied by Bell in all his telephones. Varley was also known for his spiritistic research about the existence of ghosts, which he hoped to detect with electric appliances.
