Editing Optical telegraph (section)

===United Kingdom===
[[File:Murray Shutter Telegraph 1795.png|thumb|right|Diagram of UK Murray six-shutter system, with shutter 6 in the horizontal position, and shutters 1–5 vertical]]
In Ireland, [[Richard Lovell Edgeworth]] returned to his earlier work in 1794, and proposed a telegraph there to warn against an anticipated French invasion; however, the proposal was not implemented. [[Lord George Murray (bishop)|Lord George Murray]], stimulated by reports of the Chappe semaphore, proposed a system of visual telegraphy to the [[British Admiralty]] in 1795.<ref name="EdEnc1832"/> He employed rectangular framework towers with six five-foot-high octagonal shutters on horizontal axes that flipped between horizontal and vertical positions to signal.<ref name="Mech1828">[https://books.google.com/books?id=rNZQAAAAYAAJ&pg=PA298 Lieutenant Watson's Telegraph] Mechanics' magazine, Volume 8 No. 222, Knight and Lacey, 1828, pages 294-299</ref> The Rev. Mr Gamble also proposed two distinct five-element systems in 1795: one using five shutters, and one using five ten-foot poles.<ref name="EdEnc1832"/> The British Admiralty accepted Murray's system in September 1795, and the first system was the 15 site chain from London to [[Deal, Kent|Deal]].<ref name="Wrixon2005">F.B. Wrixon (2005), {{ISBN|978-1-57912-485-4}} Codes, Ciphers, Secrets and Cryptic Communication pp. 444-445 cover Murray's shutter telegraph in the U.K., with codes.</ref> Messages passed from London to Deal in about sixty seconds, and sixty-five sites were in use by 1808.<ref name="Wrixon2005"/>

[[File:Stalbanshighstreet1807 cropped640.jpg|thumb|[[St. Albans]] High Street in 1807, showing the shutter telegraph on top of the city's Clock Tower. It was on the London to Great Yarmouth line.<ref name=OT>{{Cite web|url=http://www.vauxhallandkennington.org.uk/telegraph.shtml|title = Optical Telegraph}}</ref>]]

Chains of Murray's shutter telegraph stations were built along the following routes: [[London]]–[[Deal, Kent|Deal]] and [[Sheerness]], London–[[Great Yarmouth]], and London–[[Portsmouth]] and [[Plymouth]].<ref name=OT/> The line to Plymouth was not completed until 4 July 1806, and so could not be used to relay the news of Trafalgar.{{sfn|Burns|2004|p=49}} The shutter stations were temporary wooden huts, and at the conclusion of the Napoleonic wars they were no longer necessary, and were closed down by the Admiralty in March 1816.<ref name="MSSC">Military Signals from the South Coast, John Goodwin, 2000</ref>

Following the Battle of Trafalgar, the news was transmitted to London by frigate to Falmouth, from where the captain took the dispatches to London by coach along what became known as the [[Trafalgar Way]]; the journey took 38 hours. This delay prompted the Admiralty to investigate further.

A replacement telegraph system was sought, and of the many ideas and devices put forward the Admiralty chose the simpler semaphore system invented by [[Sir Home Popham]].<ref name="EncyBrit1824"/><ref name="EdEnc1832"/> A Popham semaphore was a single fixed vertical 30 foot pole, with two movable 8 foot arms attached to the pole by horizontal pivots at their ends, one arm at the top of the pole, and the other arm at the middle of the pole.<ref name="Burns2004"/><ref name="EncyBrit1824"/> The signals of the Popham semaphore were found to be much more visible than those of the Murray shutter telegraph.<ref name="Burns2004"/> Popham's 2-arm semaphore was modelled after the 3-arm Depillon French semaphore.<ref name="Burns2004"/> An experimental semaphore line between the Admiralty and Chatham was installed in July 1816, and its success helped to confirm the choice.<ref name="MSSC"/>

Subsequently, the Admiralty decided to establish a permanent link to Portsmouth and built a chain of semaphore stations. Work started in December 1820<ref name="MSSC"/> with Popham's equipment replaced with another two-arm system invented by [[Charles Pasley]]. Each of the arms of Pasley's system could take on one of eight positions and it thus had more [[codepoint]]s than Popham's.<ref>Holzmann & Pehrson, p. 196</ref> In good conditions messages were sent from London to Portsmouth in less than eight minutes.<ref>C. I. Hamilton, ''The Making of the Modern Admiralty: British Naval Policy-Making, 1805–1927'', p. 92, Cambridge University Press, 2011 {{ISBN|9781139496544}}.</ref> The line was operational from 1822 until 1847, when the railway and electric telegraph provided a better means of communication. The semaphore line did not use the same locations as the shutter chain, but followed almost the same route with 15 stations: Admiralty (London), [[Chelsea Royal Hospital]], [[Putney Heath]], [[Coombe, Kingston upon Thames|Coombe Warren]], [[Claygate|Coopers Hill]], [[Chatley Heath]], [[Pewley Hill]], [[Witley|Bannicle Hill]], [[Haste Hill]] ([[Haslemere]]), [[Woolbeding|Holder Hill, (Midhurst)]], [[Harting|Beacon Hill]], [[Compton Down, Compton|Compton Down]], [[Camp Down, Portsdown Hill|Camp Down]], [[Lumps Fort]] (Southsea), and [[HMNB Portsmouth|Portsmouth Dockyard]]. The semaphore tower at [[Chatley Heath]], which replaced the Netley Heath station of the shutter telegraph, is currently being restored by the [[Landmark Trust]] as self-catering holiday accommodation.<ref>{{cite web |title=Our plans for Semaphore Tower |url=https://www.landmarktrust.org.uk/news-and-events/Current-Restoration-Projects/semaphore-tower-appeal/our-plans/ |website=Landmark Trust |access-date=21 March 2020}}</ref> There will be public access on certain days when the restoration is complete.<ref>{{cite web |last1=Curley |first1=Rebecca |title=Chatley Tower restoration to make landmark rentable |url=https://www.yourlocalguardian.co.uk/news/18249227.chatley-tower-restoration-make-landmark-rentable/ |website=Sutton & Croydon Guardian |date=20 February 2020 |publisher=Newsquest Media Group Ltd |access-date=21 March 2020}}</ref>

The Board of the [[Port of Liverpool]] obtained a [[local act of Parliament]], the [[Liverpool Improvement Act 1825]] ([[6 Geo. 4]]. c. clxxxvii), to construct a chain of Popham optical semaphore stations from [[Liverpool]] to [[Holyhead]] in 1825.<ref>''Faster Than The Wind, The Liverpool to Holyhead Telegraph'', Frank Large, an avid publication {{ISBN|0-9521020-9-9}}</ref> The system was designed and part-owned by Barnard L. Watson, a reserve marine officer, and came into service in 1827. The line is possibly the only example of an optical telegraph built entirely for commercial purposes. It was used so that observers at [[Holyhead]] could report incoming ships to the [[Port of Liverpool]] and trading could begin in the cargo being carried before the ship docked. The line was kept in operation until 1860 when a railway line and associated electrical telegraph made it redundant.<ref>Holzmann & Pehrson, p. 197</ref><ref>Seija-Riitta Laakso, ''Across the Oceans: Development of Overseas Business Information Transmission 1815-1875'', BoD - Books on Demand, 2018 {{isbn|9517469047}}</ref>{{rp|181–183}} Many of the prominences on which the towers were built ('[[telegraph hill]]s') are known as [[Telegraph Hill (disambiguation)|Telegraph Hill]]<!--intentional link to DAB page--> to this day.

====British empire====
=====Ireland=====
In Ireland R.L. Edgeworth was to develop an optical telegraph based on a triangle pointer, measuring up to 16 feet in height. Following several years promoting his system, he was to get admiralty approval and engaged in its construction during 1803–1804. The completed system ran from Dublin to Galway and was to act as a rapid warning system in case of French invasion of the west coast of Ireland. Despite its success in operation, the receding threat of French invasion was to see the system disestablished in 1804.<ref>Adrian James Kirwan, 'R.L. Edgeworth and Optical Telegraphy in Ireland, c. 1790-1805' in Proceedings of the Royal Irish Academy (2017). https://www.jstor.org/stable/10.3318/priac.2017.117.02?seq=1#page_scan_tab_contents</ref>

=====Canada=====
In Canada, [[Prince Edward, Duke of Kent and Strathearn|Prince Edward, Duke of Kent]] established the first semaphore line in North America. In operation by 1800, it ran between the city of [[City of Halifax|Halifax]] and the town of [[Annapolis Royal|Annapolis]] in [[Nova Scotia]], and across the [[Bay of Fundy]] to [[Saint John, New Brunswick|Saint John]] and [[Fredericton]] in [[New Brunswick]]. In addition to providing information on approaching ships, the Duke used the system to relay military commands, especially as they related to troop discipline. The Duke had envisioned the line reaching as far as the British garrison at [[Quebec City]], but the many hills and coastal fog meant the towers needed to be placed relatively close together to ensure visibility. The labour needed to build and continually man so many stations taxed the already stretched-thin British military and there is doubt the New Brunswick line was ever in operation. With the exception of the towers around Halifax harbour, the system was abandoned shortly after the Duke's departure in August 1800.<ref>{{Citation|last=Raddall|first=Thomas H.|title=Warden of the North|publisher=McClelland and Stewart Limited|place=Toronto, Canada|year=1971|url=http://www.ourroots.ca/toc.aspx?id=6183&amp;qryID=8cbb8294-7361-4fdc-ac50-78627a229b5f}}</ref><ref>{{Citation|last=Rens|first=Jean-Guy|title=The invisible empire: A history of the telecommunications industry in Canada|publisher=McGill-Queen's University Press|place=Montreal, Canada|year=2001|isbn=9780773520523|url=https://books.google.com/books?id=8kUmt-Q7ySMC&pg=PA7 }}</ref>

=====Malta=====
[[File:Sudika Nadur Ta' Kenuna.jpg|thumb|left|[[Ta' Kenuna Tower]], a semaphore tower in [[Nadur]], [[Gozo]], Malta, built by the British in 1848]]
The British military authorities began to consider installing a semaphore line in [[Malta]] in the early 1840s. Initially, it was planned that semaphore stations be established on the bell towers and domes of the island's churches, but the religious authorities rejected the proposal. Due to this, in 1848 new semaphore towers were constructed at [[Għargħur Semaphore Tower|Għargħur]] and [[Għaxaq Semaphore Tower|Għaxaq]] on the main island, and another was built at [[Ta' Kenuna Tower|Ta' Kenuna]] on Gozo. Further stations were established at the [[Grandmaster's Palace (Valletta)|Governor's Palace]], [[Selmun Palace]] and the [[Giordan Lighthouse]]. Each station was staffed by the [[Royal Engineers]].<ref>{{cite web|title=Semaphore Tower|url=http://gharghur.gov.mt/semaphore-tower/|website=Għargħur Local Council|archive-url=https://web.archive.org/web/20160304094408/http://gharghur.gov.mt/semaphore-tower/|archive-date=4 March 2016}}</ref>

=====India=====
[[File:Semaphore Tower at Khatirbazar, Andul.jpg|thumb|upright|The Semaphore Tower at Khatirbazar, Andul in Howrah district of West Bengal]]

In India, semaphore towers were introduced in 1810. A series of towers were built between [[Fort William, India|Fort William]], [[Kolkata]] to [[Chunar Fort]] near [[Varanasi]].The towers in the plains were {{cvt|75 – 80|ft}} tall and those in the hills were {{cvt|40 – 50|ft}} tall, and were built at an interval of about {{cvt|13|km}}.<ref>{{cite news |last1=Singh |first1=Gurvinder |title=Towering messengers of a bygone era |url=https://www.thehindubusinessline.com/blink/know/towering-messengers-of-a-bygone-era/article23923909.ece |access-date=31 March 2019 |issue=Business Line |date=18 May 2018}}</ref>

=====Van Diemen's Land=====
In southern [[Van Diemen's Land|Van Diemens Land]] ([[Tasmania]]) a signalling system to announce the arrival of ships was suggested by Governor-In-Chief [[Lachlan Macquarie]] when he made his first visit in 1811 <ref>{{cite web |title=Maquarie's Journals - Saturday 30th. Novr. 1811.| url=https://www.mq.edu.au/macquarie-archive/journeys/1811/1811a/nov30.html|website=Journeys In Time }}</ref> Initially a simple flag system in 1818 between Mt. Nelson and [[Hobart]], it developed into a system with two revolving arms by 1829, the system was quite crude and the arms were difficult to operate. In 1833 [[Charles O'Hara Booth]] took over command of the [[Port Arthur, Tasmania|Port Arthur]] penal settlement, as an "enthusiast in the art of signalling" <ref>{{cite book |last1=Masters |first1=W.E. |title=The Semaphore Telegraph System of Van Diemen's Land |date=1973 |publisher=Cat & Fiddle Press |isbn=0-85853-009-0 |page=8}}</ref> he saw the value of better communications with the headquarters in Hobart. During his command the semaphore system was extended to include 19 stations on the various mountains and islands between Port Arthur and Hobart. Until 1837 three single rotating arm semaphores were used. Subsequently the network was upgraded to use signal posts with six arms - a pair top, middle and bottom. This enabled the semaphore to send 999 signal codes. Captain George King of the Port Office and Booth together contributed to the code book for the system.<ref>{{cite book |last1=Masters |first1=W.E. |title=The Semaphore Telegraph System of Van Diemen's Land |date=1973 |publisher=Cat & Fiddle Press |isbn=0-85853-009-0 |page=14}}</ref> 
King drew up shipping related codes and Booth added Government, Military and penal station matters. In 1877 Port Arthur was closed and the semaphore was operated for shipping signals only, it was finally replaced with a simple flagstaff after the introduction of the telephone in 1880.

[[File:LowHeadSemaphore.jpg|thumb|left|alt=A restored two-arm semaphore post at Low Head in Tasmania|A restored two-arm semaphore post at Low Head in Tasmania]]

In the north of the state there was a requirement to report on shipping arrivals as they entered the Tamar Estuary, some 55 kilometers from the main port at this time in [[Launceston, Tasmania|Launceston]]. The [[Tamar Valley, Tasmania|Tamar Valley]] Semaphore System was based on a design by Peter Archer Mulgrave.<ref>{{cite book|title=Peter Archer Mulgrave|chapter=Mulgrave, Peter Archer (1778–1847)|chapter-url=https://adb.anu.edu.au/biography/mulgrave-peter-archer-2489|website=Australian Dictionary of Biography|publisher=National Centre of Biography, Australian National University}}</ref> This design used two arms, one with a cross piece at the end. The arms were rotated by ropes, and later chains. The barred arm positions indicated numbers 1 to 6 clockwise from the bottom left and the unbarred arm 7,8,9, STOP and REPEAT.[[File:FanPositions2.png|thumb|right|alt=Fan positions for the Mulgrave design used in the Tamar Valley Semaphore System|The vane positions indicate code numbers.]] A message was sent by sending numbers sequentially to make up a code. As with other systems the code was decoded via a code book. On 1 October 1835 it was announced in the Launceston Advertiser - "...that the signal stations are now complete from Launceston to George Town, and communication may he made, as well as received, from the Windmill Hill to George Town, in a very few minutes, on a clear day".<ref>{{cite web|title=Launceston Advertiser - 1 Oct 1835|url=https://trove.nla.gov.au/newspaper/article/84775296?searchTerm=semaphore# |newspaper=Launceston Advertiser|date = October 1835}}</ref> The system comprised six stations - Launceston Port Office, Windmill Hill, Mt. Direction, Mt.George, George Town Port Office, Low Head lighthouse. The Tamar Valley semaphore telegraph operated for twenty-two and a half years closing on 31 March 1858 after the introduction of the electric telegraph.<ref>{{cite book |last1=Shipp |first1=Wayne |title=The Tamar Valley Semaphore Telegraph |date=2014 |publisher=Low Head Pilot Station Museum |isbn=978-0-646-93206-4 |page=37}}</ref>
In the 1990s the Tamar Valley Signal Station Committee Inc. was formed to restore the system. The works were carried out over several years and the semaphore telegraph was declared complete once more on Sunday 30 September 2001.<ref>{{cite book |last1=Shipp |first1=Wayne |title=The Tamar Valley Semaphore Telegraph |date=2014 |publisher=Low Head Pilot Station Museum |isbn=978-0-646-93206-4 |page=ix}}</ref>