Editing Fluorescent lamp (section)

===Early discharge lamps===
[[Image:Early Cooper Hewitt mercury vapor lamp.jpg|thumb|upright|One of the first [[mercury vapor lamp]]s invented by [[Peter Cooper Hewitt]], 1903. It was similar to a fluorescent lamp without the fluorescent coating on the tube and produced greenish light. The round device under the lamp is the [[ballast (electrical)|ballast]]. ]]

[[Thomas Edison]] briefly pursued fluorescent lighting for its commercial potential. He invented a fluorescent lamp in 1896 that used a coating of [[Scheelite|calcium tungstate]] as the fluorescing substance, excited by [[X-rays]]. Although it received a patent in 1907,<ref>{{patent|US|865367}} ''Fluorescent Electric Lamp''</ref> it was not put into production. As with a few other attempts to use Geissler tubes for illumination, it had a short operating life, and given the success of the incandescent light, Edison had little reason to pursue an alternative means of electrical illumination. [[Nikola Tesla]] made similar experiments in the 1890s, devising high-frequency powered fluorescent bulbs that gave a bright greenish light, but as with Edison's devices, no commercial success was achieved.

One of Edison's former employees created a gas-discharge lamp that achieved a measure of commercial success. In 1895 [[Daniel McFarlan Moore]] demonstrated lamps {{convert|2|to|3|m|ft|sp=us}} in length that used [[carbon dioxide]] or [[nitrogen]] to emit white or pink light, respectively. They were considerably more complicated than an incandescent bulb, requiring both a high-voltage power supply and a pressure-regulating system for the fill gas.<ref name=etheric>{{cite news |title=Mr. Moore's Etheric Light. The Young Newark Electrician's New And Successful Device. |url=https://www.nytimes.com/1896/10/02/archives/mr-moores-etheric-light-the-young-newark-electricians-new-and.html |newspaper=New York Times |date=October 2, 1896 |access-date=2008-05-26 |archive-date=2018-07-25  |archive-url=https://web.archive.org/web/20180725215030/https://www.nytimes.com/1896/10/02/archives/mr-moores-etheric-light-the-young-newark-electricians-new-and.html |url-status=live }} Paid access.</ref>

[[File:Peter Cooper Hewitt.jpg|thumb|upright|[[Peter Cooper Hewitt]]]]
Moore invented an electromagnetically controlled valve that maintained a constant gas pressure within the tube, to extend the working life.<ref>{{cite book |title=Modern illuminants and illuminating engineering |last1=Gaster |first1=Leon |last2=Dow |first2=John Stewart |date=1915 |publisher=Whittaker & Co. |url=https://archive.org/details/modernilluminan01dowgoog |pages=[https://archive.org/details/modernilluminan01dowgoog/page/n127 107]–111}}</ref> Although Moore's lamp was complicated, expensive, and required very high voltages, it was considerably more efficient than incandescent lamps, and it produced a closer approximation to natural daylight than contemporary incandescent lamps. From 1904 onwards Moore's lighting system was installed in a number of stores and offices.{{sfn|Bright|1949|pp=221–223}} Its success contributed to [[General Electric]]'s motivation to improve the incandescent lamp, especially its filament. GE's efforts came to fruition with the invention of a [[tungsten]]-based filament. The extended lifespan and improved efficacy of incandescent bulbs negated one of the key advantages of Moore's lamp, but GE purchased the relevant patents in 1912. These patents and the inventive efforts that supported them were of considerable value when the firm took up fluorescent lighting more than two decades later.

At about the same time that Moore was developing his lighting system, [[Peter Cooper Hewitt]] invented the [[mercury-vapor lamp]], patented in 1901 ({{patent|US|682692}}). Hewitt's lamp glowed when an electric current was passed through mercury vapor at a low pressure. Unlike Moore's lamps, Hewitt's were manufactured in standardized sizes and operated at low voltages. The mercury-vapor lamp was superior to the incandescent lamps of the time in terms of [[Efficient energy use|energy efficiency]], but the blue-green light it produced limited its applications. It was, however, used for photography and some industrial processes.

Mercury vapor lamps continued to be developed at a slow pace, especially in Europe. By the early 1930s they received limited use for large-scale illumination. Some of them employed fluorescent coatings, but these were used primarily for color correction and not for enhanced light output. Mercury vapor lamps also anticipated the fluorescent lamp in their incorporation of a ballast to maintain a constant current.

Cooper-Hewitt had not been the first to use mercury vapor for illumination, as earlier efforts had been mounted by Way, Rapieff, Arons, and Bastian and Salisbury. Of particular importance was the mercury-vapor lamp invented by Küch and Retschinsky in [[Germany]]. The lamp used a smaller bore bulb and higher current operating at higher pressures. As a consequence of the current, the bulb operated at a higher temperature which necessitated the use of a quartz bulb. Although its light output relative to electrical consumption was better than that of other sources of light, the light it produced was similar to that of the Cooper-Hewitt lamp in that it lacked the red portion of the spectrum, making it unsuitable for ordinary lighting. Due to difficulties in sealing the electrodes to the quartz, the lamp had a short life.<ref>{{Cite web |url=http://lamptech.co.uk/Documents/M7%20Kuch%20%26%20Retschinsky.htm |title=Article about Küch and Retschinsky lamp |access-date=2020-06-23  |archive-date=2020-06-11  |archive-url=https://web.archive.org/web/20200611162322/http://lamptech.co.uk/Documents/M7%20Kuch%20%26%20Retschinsky.htm |url-status=live }}</ref>