Editing Incandescent light bulb (section)

===Incandescent arc lamps===
A variation of the incandescent lamp did not use a hot wire filament, but instead used an arc struck on a spherical bead electrode to produce heat. The electrode then became incandescent, with the arc contributing little to the light produced. Such lamps were used for projection or illumination for scientific instruments such as [[microscope]]s. These arc lamps ran on relatively low voltages and incorporated tungsten filaments to start [[ionization]] within the envelope. They provided the intense concentrated light of an [[arc lamp]] but were easier to operate. Developed around 1915, these lamps were displaced by mercury and [[xenon arc lamp]]s.<ref>{{cite web|title=Incandescent Arc Lamps|url=http://www.lamptech.co.uk/Miscellaneous.htm|publisher=Museum of Electric Lamp Technology|year=2004|url-status=live|archive-url=https://web.archive.org/web/20130801233142/http://lamptech.co.uk/Miscellaneous.htm|archive-date=1 August 2013}}</ref><ref>G. Arncliffe Percival, ''The Electric Lamp Industry'', Sir Isaac Pitman and Sons, Ltd. London, 1920 pp. 73–74, available from the [[Internet Archive]]</ref><ref>S. G. Starling, ''An Introduction to Technical Electricity'', McMillan and Co., Ltd., London 1920, pp. 97–98, available at the [[Internet Archive]], good schematic diagram of the Pointolite lamp</ref>