Iron borings coherer (Branly type), 1894

Made:
1894 in England
maker:
Edouard Branly
and
Oliver Joseph Lodge
Group photograph of (from top left, clockwise) 1924-36, Spark gap or knob coherer, unknown maker, England, 1889.  Used

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Science Museum Group Collection
© The Board of Trustees of the Science Museum

Science Museum Group Collection
© The Board of Trustees of the Science Museum

Science Museum Group Collection
© The Board of Trustees of the Science Museum

Science Museum Group Collection
© The Board of Trustees of the Science Museum

Group photograph of (from top left, clockwise) 1924-36, Spark gap or knob coherer, unknown maker, England, 1889. Used
Science Museum Group Collection
© The Board of Trustees of the Science Museum

Iron borings coherer (Branly type), probably made by Oliver Lodge, England, 1894. Mounted on wooden baseboard with electric bell components mounted alongside as vibrator for restoring the coherer.

Iron borings coherer (Branly type), probably made by Oliver Lodge, England, 1894. Mounted on wooden baseboard with electric bell components mounted alongside as vibrator for restoring the coherer.

The coherer was the first practical device for detecting Hertzian waves. It was devised by French physicist Edouard Branly in about 1890. He did not, however, investigate its use for detecting Hertzian waves. Its most familiar form was a tube containing metal filings or turnings loosely packed between metal plugs. This presented a high resistance to current but changed to low resistance in the presence of electric waves because the filings 'cohered' or stuck together. In order to restore the high-resistance state the tube needed to be given a mechanical tap or jolt. This particular coherer was used as a receiver during Lodge’s British Association lecture on 14 August 1894, but contrary to some later accounts the signals sent did not form an intelligible message. The electric bell mechanism was used as the vibrator to restore the borings to the high-resistance state.

Details

Category:
Radio Communication
Object Number:
1924-37/2
Materials:
iron, metal (unknown) and wood (unidentified)
type:
coherer
taxonomy:
  • components
  • components
  • component - object
  • radio receiver
credit:
Donated by Mr. Oliver Lodge [Grandson of Sir Oliver Lodge]