Lane-Fox Carbon Filament Lamp

The British inventor St. George Lane-Fox was one of the pioneers in the development of the incandescent lamp. He was narrowly beaten by Swan and Edison, but continued to develop his own design which was made for several years. This and many other examples bear a label of the Eastern Electric Light & Power Co., as well as L. Clarke, Muirhead & Co. The former is believed to have been a subsidiary of the Anglo-American Brush company who bought the Lane-Fox patents to manufacture his lamp, and the latter was possibly responsible for the measurement and labelling.

A key feature of many Lane-Fox lamps is the unusual glass-to-metal seals, as well as the method of filament connection. His patent tries to explain their virtues, however they are suspected to have been of more value as a potential method of circumventing the powerful Edison and Swan patents.

The filament is made from carbonised roots of the Italian grass Chrysopogum Gryllus, commonly found in French brooms. This was boiled in caustic soda and potash to loosen the skin, the remaining fibre then being stretched and wound onto formers for carbonisation. To bring the resistance down to the desired value, these were heated electrically in hydrocarbon vapour to increase the thickness as necessary. The connection between the filament and the platinum leading-in wires is effected with a paste of fine plumbago powder in indian ink. The joint is reinforced by a surrounding tube of drilled graphite. Curiously there is no continuous wire from the lamp terminals to the filament. The copper leads and platinum sealing wires are connected by small cups of mercury, the latter being held in place by tightly packed cotton wool, sealed under plaster of paris.
Manufacturer: Anglo-American Brush Electric Light Co. Ltd.
Lamp Power: 97 Watts
Lamp Voltage: 43 Volts
Lamp Current: 2.3 Amperes
Cap Type: Hooks Copper wires
Bulb Type: E-60 E-19 in eighths/inch
Bulb Finish: Clear Lead-alkali silicate glass
Filament Type: U-shape Carbonised vegetable fibre
Atmosphere: Vacuum
Luminous Flux: 251 lm 20 Candle Power
Luminous Efficacy: 2.6 lm/W 5 Watts per Candle
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: Approx. 2000K CRI: Ra 100
Chromaticity Co-ordinates: CCx: CCy:
Rated Lifetime: Unknown
Burning Position: Vertical only
Overall Length: 125 mm (excl. wires) 5 inches
Light Centre Length: 83 mm (excl. wires) 3ΒΌ inches
Factory: Hammersmith England
Date of Manufacture: 10th January 1882
Original / Present Value: Unknown