Editing Optical telegraph (section)

==Early designs==
[[File:Rees's Cyclopaedia - Hooke's optical telegraph.png|thumb|Illustration showing Robert Hooke's proposed system. At top are various symbols that might be used; ABCE indicates the frame, and D the screen behind which each of the symbols are hidden when not in use.]]
Optical telegraphy dates from ancient times, in the form of [[hydraulic telegraph]]s, torches (as used by ancient cultures since the discovery of fire) and [[smoke signals]]. Modern designs of semaphores developed via several paths, often simultaneously.

Possibly the earliest was by the British [[polymath]] [[Robert Hooke]], who gave a vivid and comprehensive outline of visual telegraphy to the [[Royal Society]] in a 1684 submission in which he outlined many practical details. The system (which was motivated by military concerns, following the [[Battle of Vienna]] in 1683) was never put into practice.<ref>{{cite web|url=http://mysite.du.edu/~jcalvert/railway/semaphor/semhist.htm |title=The Origin of the Railway Semaphore |publisher=Mysite.du.edu |access-date=2013-06-17}}</ref><ref>{{cite web |url=http://www.ilt.columbia.edu/projects/bluetelephone/html/part2.html |title=History of the Telephone part2 |publisher=Ilt.columbia.edu |access-date=2013-06-17 |archive-url=https://web.archive.org/web/20121128120005/http://www.ilt.columbia.edu/projects/bluetelephone/html/part2.html |archive-date=2012-11-28 |url-status=dead }}</ref>

[[File:Rees's Cyclopaedia - Richard Lovell Edgeworth's optical telegraph.png|thumb|Sir [[Richard Lovell Edgeworth]]'s proposed optical telegraph for use in Ireland. The rotational position of each one of the four indicators represented a number 1-7 (0 being "rest"), forming a four-digit number. The number stood for a particular word in a codebook.]]
One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor, Sir [[Richard Lovell Edgeworth]] in 1767.<ref>{{cite encyclopedia|editor-first=Abraham|editor-last=Rees|editor-link=Abraham Rees|encyclopedia=Cyclopædia|title=Telegraph|url=https://archive.org/details/cyclopaediaorun35rees|year=1802–1820|publisher=Longman, Hurst, Rees, Orme & Brown
|volume=35|location=London|at=Unpaginated work: pages 9-11 of the article entry}}</ref> He placed a bet with his friend, the [[horse racing]] gambler [[William Douglas, 4th Duke of Queensberry|Lord March]], that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on high ground, the signal would be observed from one station to the next by means of a [[telescope]].{{sfn|Burns|2004}} The signal itself consisted of a large pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512. He returned to his idea in 1795, after hearing of Chappe's system.

While Edgeworth was developing his design, [[William Playfair]], a Scottish political economist traveling in Europe in 1794, surreptitiously obtained the design and alphabet of the French system from a fleeing royalist. Playfair, who had numerous connections to British officials, provided a model of the system to the Duke of York, commander of British forces, then based in Flanders, and, according to the ''Encyclopædia Britannica'', "hence the alphabet and plan of the machine came to England."<ref>''Encyclopædia Britannica'', Vol. 18 (Edinburgh: Bell and Macfarquhar, 1797) p. 336 https://ia601900.us.archive.org/32/items/1797EncyclopediaBritannicaNLS/Third%20edition%20-%20Encyclopaedia%20Britannica%20Volume%2018%2C%20STR-ZYM.pdf</ref><ref>{{Cite book |url=https://books.google.com/books?id=vkdOAAAAcAAJ&dq=%22william+playfair%22+telegraph&pg=PA458 |title=The Annual Biography and Obituary (etc.) |date=1824 |publisher=Longman, Hurst, Rees |language=en}}</ref>