Lamp Inventors 1880-1940:

Carbon Filament Incandescent From Tyne & Wear County Council Museums "Joseph Swan in his 50's." "I had the mortification one fine morning of finding you on my track and in several particulars ahead of me -- but now I think I have shot ahead of you and yet I feel there is almost an infinity of detail to be wrought out in the large application now awaiting development and that your inventive genius as well as my own will find very ample room for exercise in carrying out this gigantic work that awaits execution."

-- Joseph Swan in a letter to Thomas Edison, 24 September 1880. Cited in Brian Bowers, Lengthening the Day New York: Oxford University Press, 1998. Edison was not the only inventor trying to make a light bulb. One of his major competitors was England's Joseph W. Swan. A chemist, Swan experimented in the 1850s and 60s with carbon filaments. His early efforts failed however, because the vacuum pumps of those years could not remove enough air from the lamps. By the mid-1870s better pumps became available, and Swan returned to his experiments. By late 1878, Swan reported success to the Newcastle Chemical Society and in February 1879 demonstrated a working lamp in a lecture in Newcastle. His lamps contained the major elements seen in Edison's lamps that October: an enclosed glass bulb from which all air had been removed, platinum lead wires, and a light-emitting element made from carbon. Why then is Edison generally credited (outside Britain) with inventing the light bulb? Like other early inventors, Swan used a carbon rod with low electrical resistance in his lamp. Due to the relationship between resistance and current, a low resistance element required lots of current in order to become hot and glow. This meant that the conductors bringing electricity to the lamp would have to be relatively short (or impossibly thick), acceptable for an experiment or demonstration, but not for a commercial electrical system. Made from an arc-lamp element, Swan's carbon rod gave off light but did not last very long. Gasses trapped in the rod were released when the lamp was activated, and a dark deposit of soot quickly built up on the inner surface of the glass. So while Swan's lamp worked well enough for him in a demonstration, it was impractical in actual use. Edison realized that a very thin "filament" with high electrical resistance would make a lamp practical. High resistance meant only a little current would be required to make the filament glow and allow much longer copper lines of modest size to be used. Edison's Bristol-board lamps of December 1879 lasted about 150 hours, and his bamboo lamps of early 1880 lasted 600 hours. It is for this realization about high resistance, and for his conception of the lamp as only one part of an integrated system, that Edison is generally credited with inventing the first practical incandescent lamp. Swan did not lose out entirely however. While it appears that he never sent the letter that he wrote to Edison (cited above), his patents were strong enough to win in British courts. After another lamp maker lost a patent suit to Swan, the Edison interests decided to negotiate rather than risk losing a suit of their own. In 1883 the Edison & Swan United Electric Light Company was established. Known commonly as "Ediswan" the company sold lamps made with a cellulose filament that Swan had invented in 1881. Variations of the cellulose filament became an industry standard, except with the Edison Company. Edison continued using bamboo filaments until the 1892 merger that created General Electric -- and that company then shifted to cellulose.

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