Editing Telegraphy (section)

=== Heliograph ===

[[File:Australian Heliograph in Egyptian Desert 1940.png|thumb|right|upright=0.7|Australian troops using a Mance mk.V heliograph in the [[Western Desert (Egypt)|Western Desert]] in November 1940]]
{{main|Heliograph}}
[[File:11903A LO with Heliograph CA 1912 (22762702845).jpg|thumb|left|upright=1.2|[[US Forest Service]] lookout using a Colomb shutter type heliograph in 1912 at the end of a telephone line]]

A [[heliograph]] is a telegraph that transmits messages by flashing sunlight with a mirror, usually using Morse code. The idea for a telegraph of this type was first proposed as a modification of surveying equipment ([[Carl Friedrich Gauss|Gauss]], 1821). Various uses of mirrors were made for communication in the following years, mostly for military purposes, but the first device to become widely used was a heliograph with a moveable mirror ([[Henry Christopher Mance|Mance]], 1869). The system was used by the French during the [[Siege of Paris (1870–71)|1870–71 siege of Paris]], with night-time signalling using [[kerosene lamp]]s as the source of light. An improved version (Begbie, 1870) was used by British military in many colonial wars, including the [[Anglo-Zulu War]] (1879). At some point, a morse key was added to the apparatus to give the operator the same degree of control as in the electric telegraph.<ref name=Woods2>David L. Woods, "Heliograph and mirrors", pp. 208–211 in, Christopher H. Sterling (ed), ''Military Communications: From Ancient Times to the 21st Century'', ABC-CLIO, 2008 {{ISBN|1851097325}}.</ref>

Another type of heliograph was the [[heliostat]] or [[heliotrope (instrument)|heliotrope]] fitted with a Colomb shutter. The heliostat was essentially a surveying instrument with a fixed mirror and so could not transmit a code by itself. The term ''heliostat'' is sometimes used as a synonym for ''heliograph'' because of this origin. The Colomb shutter ([[Francis Bolton|Bolton]] and [[Philip Howard Colomb|Colomb]], 1862) was originally invented to enable the transmission of morse code by [[signal lamp]] between [[Royal Navy]] ships at sea.<ref name=Woods2/>

The heliograph was heavily used by [[Nelson A. Miles]] in [[Arizona]] and [[New Mexico]] after he took over command (1886) of the fight against [[Geronimo]] and other [[Apache]] bands in the [[Apache Wars]]. Miles had previously set up the first heliograph line in the US between [[Fort Keogh]] and [[Fort Custer (Montana)|Fort Custer]] in [[Montana]]. He used the heliograph to fill in vast, thinly populated areas that were not covered by the electric telegraph. Twenty-six stations covered an area {{convert|200 by 300|mi|km|order=flip|abbr=on}}. In a test of the system, a message was relayed {{convert|400|mi|km|order=flip|abbr=on}} in four hours. Miles' enemies used [[smoke signal]]s and flashes of sunlight from metal, but lacked a sophisticated telegraph code.<ref>Nelson A. Miles, ''Personal Recollections and Observations of General Nelson A. Miles'', vol. 2, pp. 481–484, University of Nebraska Press, 1992 {{ISBN|0803281811}}.</ref> The heliograph was ideal for use in the American Southwest due to its clear air and mountainous terrain on which stations could be located. It was found necessary to lengthen the morse dash (which is much shorter in American Morse code than in the modern International Morse code) to aid differentiating from the morse dot.<ref name=Woods2/>

Use of the heliograph declined from 1915 onwards, but remained in service in Britain and [[British Commonwealth]] countries for some time. Australian forces used the heliograph as late as 1942 in the [[Western Desert Campaign]] of [[World War II]]. Some form of heliograph was used by the [[mujahideen]] in the [[Soviet–Afghan War]] (1979–1989).<ref name=Woods2/>
{{clear|left}}