Fig. 1: Signaling with a Mance heliograph, 1910.

A heliograph (Greek: Ἥλιος helios, meaning "sun", and γραφειν graphein, meaning "write") is a wireless solar telegraph that signals by flashes of sunlight (generally using Morse code) reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. The heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. Its main uses were military, survey and forest protection work. Heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975.^[1]

[edit] Description

Fig. 2: German Heliograph made by R. Fuess in Berlin (on display at the Museum of Communication in Frankfurt).

There were many heliograph types. Most heliographs were variants of the British army Mance Mark V version (Fig.1). It used a mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the reflected target in the mirror and moving his head until the target was hidden by the unsilvered spot. Keeping his head still, he then adjusted the aiming rod so its cross wires bisected the target.^[2] He then turned up the sighting vane, which covered the cross wires with a diagram of a cross, and aligned the mirror with the tangent and elevation screws so the small shadow that was the reflection of the unsilvered spot hole was on the cross target.^[2] This indicated that the sunbeam was pointing at the target.

The flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. If the sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. If the sun was behind the sender, the sighting rod was replaced by a second mirror, to capture the sunlight from the main mirror and reflect it to the receiving station.^[3][4] The U. S. Signal Corps heliograph mirror did not tilt. This type produced flashes by a shutter mounted on a second tripod (Fig 4).^[3]

The heliograph had some great advantages. It allowed long distance communication without a fixed infrastructure, though it could also be linked to make a fixed network extending for hundreds of miles, as in the fort-to-fort network used for the Geronimo campaign. It was very portable, did not require any power source, and was relatively secure since it was invisible to those not near the axis of operation, and the beam was very narrow, spreading only 50 feet per mile of range. However, anyone in the beam with the correct knowledge could intercept signals without being detected.^[1][5] For the Boer war, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam.^[1] Conversely, the narrow beam made it very difficult to stay aligned with a moving target, as when communicating from shore to a moving ship, and the British issued a dispersing lens to broaden the heliograph beam from its natural diameter of 0.5 degrees to 15 degrees for that purpose^[6]

The distance that heliograph signals could be seen depended on the clarity of the sky and the size of the mirrors used. A clear line of sight was required, and since the Earth's surface is curved, the highest convenient points were used. For ordinary conditions, a flash could be seen 30 miles (48 km) with the naked eye, and much farther with a telescope. The maximum range was considered to be 10 miles for each inch of mirror diameter. Mirrors ranged from 1.5 inches to 12 inches or more. The record distance was established by a detachment of U.S. signal sergeants by the inter-operation of stations on Mount Ellen, Utah, and Mount Uncompahgre, Colorado, 183 miles (295 km) apart on September 17, 1894, with Signal Corps heliographs carrying mirrors only 8 inches square.^[7]

[edit] History

Fig. 3 Ottoman heliograph crew at Huj during World War I, 1917.

The German professor Carl Friedrich Gauss, of Georg-August University of Göttingen, developed and used a predecessor of the heliograph (called heliotrope) in 1821^[8] . His device directed a controlled beam of sunlight to a distant station to be used as a marker for geodetic survey work.

Sir Henry Christopher Mance (1840–1926), of British Army Signal Corps, developed the first apparatus about 1869^[9] while stationed at Karachi, in the Bombay Presidency in British India. Mance was familiar with heliotropes by their use for the Great India Survey.^[7] The Mance Heliograph was operated easily by one man, and since it weighed about seven pounds, the operator could readily carry the device and its tripod. During the Jowaki Afridi expedition sent by the British-Indian government during 1877, the heliograph was first tested in war.^[10][11]

Fig. 4: US Signal Service Heliograph, 1898.

The simple and effective instrument that Mance invented was to be an important part of military communications for more than 60 years. The usefulness of heliographs was limited to daytimes with strong sunlight, but they were the most powerful type of visual signaling device known. During pre-radio times heliography was often the only means of communication that could span ranges of as much as 100 miles with a lightweight portable instrument.^[7]

In the United States military, by January 1880, Colonel Nelson A. Miles had established a line of heliographs connecting Fort Keogh and Fort Custer, Montana, a distance of 140 miles.^[12] Major W. J. Volkman of the US Army, demonstrated in Arizona and New Mexico the possibility of performing communication by heliograph over a range of 200 miles. The network of communication begun by General Miles during 1886, and continued by Lieutenant W. A. Glassford, was perfected during 1889 at ranges of 85, 88, 95, and 125 miles over a rugged and broken country, which was the stronghold of the Apache and other hostile Indian tribes.^[7]

By 1887, heliographs in use included not only the British Mance and Begbie heliographs, but also the American Grugan, Garner and Pursell heliographs. The Grugan and Pursell heliographs used shutters, and the others used movable mirrors operated by a finger key. The Mance, Grugam and Pursell heliographs used two tripods, and the others one. The signals could either be momentary flashes, or momentary obscurations.^[13] During 1889, the US Signal Service reviewed all of these devices, as well as the Finley Helio-Telegraph,^[13] and finding none completely suitable, developed the US Signal Service heliograph, a two-tripod, shutter-based machine of 13 7/8 lb. total weight, and ordered 100 for a total cost of $4,205.^[14] In 1893, the number of heliographs manufactured for the US Signal Service was 133.^[15]

The heyday of the heliograph was probably the Second Boer War in South Africa, where it was much used by both the British and the Boers.^[1] The terrain and climate, as well as the nature of the campaign, made heliography a logical choice. For night communications, the British used some large Aldis lamps, brought inland on railroad cars, and equipped with leaf-type shutters for keying a beam of light into dots and dashes. During the early stages of the war, the British garrisons were besieged in Kimberley, Ladysmith, and Mafeking. With land telegraph lines cut, the only contact with the outside world was via light-beam communication, helio by day, and Aldis lamps at night.^[7]

During 1909, the use of heliography for forestry protection was introduced in the United States. By 1920 such use was widespread in the US and beginning in Canada, and the heliograph was regarded as "next to the telephone, the most useful communication device that is at present available for forest-protection services".^[3] D.P. Godwin of the US Forestry Service invented a very portable (4.5 lb) heliograph of the single-tripod, shutter plus mirror type for forestry use.^[3]

The Red Army during the Russian Civil War made use of series of heliograph stations to disseminate intelligence efficiently about basmachi rebel movements in Turkestan during 1926.^[16]

The heliograph remained standard equipment for military signallers in the Australian and British armies until the 1960s, where it was considered a "low probability of intercept" type of communication. Canada had the last major army to have the heliograph as an issue item. By the time the mirror instruments were retired they were seldom used for signalling.^[7] As recently as the 1980s, heliographs were used by Afghan forces during the Soviet invasion of Afghanistan. Signal mirrors are still included in survival kits for emergency signaling to search and rescue aircraft.

[edit] Heliographs in fiction

• Rudyard Kipling's humorous poem "A Code of Morals" describes a fictional interception of a heliograph signal in 19th century Afghanistan.^[5]
• In the book The War of the Worlds by H.G. Wells (1898), heliographs are used to convey information about the invading Martians.^[17]
• The short story "The Attack on the Mountain" by Glendon Swarthout, in the Saturday Evening Post Magazine, July 4, 1959, described the use of the heliograph in the American West.^[18]
• The 2004 Western novel The Sergeant's Lady by Miles Hood Swarthout is set against the background of the heliograph network used in the U.S. Army campaign against the Apache Indians.^[18]
• In the 2010 science fiction novel "Terminal World" by Alastair Reynolds, the faction of people known as 'Swarm' use heliographs as communication between airships.
• In Robert Penn Warren's "All the King's Men", a heliograph serves as an important image and appears early—- on the second page of the novel.
• In Agatha Christie's 1947 novel The Labours of Hercules from the short story "The Erymanthian Boar" detective Hercule Poirot uses a heliograph to communicate from the top of Rochers Neiges where he is trapped to the police at the mountain's base.
• In Larry Niven's Ringworld series, revealed in The Ringworld Throne, the Ghoul species use heliographs for their vast communication network across the Ringworld. The Spill Mountain People are the only species outside of the Ghouls to know of this means of communication until Louis Wu spoke to the protector Tunesmith.
• In the role-playing game Space: 1889, the Great Powers communicate with their colonial possessions on the inner planets of the Solar System by means of "orbiting heliograph stations".
• In the Tintin book The Red Sea Sharks (orig. "Coke en stock"), US Navy communicates by heliograph to bad man Rastapopoulos.
• In the television series Lost, Benjamin Linus signals his people using a heliograph in the episode "There's No Place Like Home (Part 1)".
• In the Agatha Christie novel And Then There Were None Lombard suggests creating a heliograph to contact the mainland.
• The books "Matter" and "Feersum Endjinn" by Iain M Banks both feature several instances of heliographic communication.

[edit] See also

• Heliotrope (instrument)
• Semaphore line
• Signal lamp
• Telegraph hill
• Heliography, an early photographic process invented by Joseph Nicéphore Niépce around 1822

Wikimedia Commons has media related to: Heliographs

[edit] References

"Great Days of the Heliograph" by Lewis Coe

[edit] External links

• Heliography Photographs of British, American and Portuguese heliographs.
• The Heliograph A description of the British Mance, Begbie and French LeSeurre heliographs with illustrations (1899)
• Eliografo Detailed color photographs of a World War 2 British Mance heliograph (Italian).
• Australian War Memorial: 70+ historical heliograph photographs
• Royal Signals Datasheet No. 2. The Heliograph (revised April 2003)
• CHAPTER IV THE HELIOGRAPH (PAGE 48 OF THE 1905 SIGNALLING HANDBOOK)
• Mance Mark V Heliograph Detailed photos of a British Mark V Heliograph and kit, links to patents. Clicking on visible photos reveals high resolution photos.
• The Heliograph in the Apache Wars
• Signals communication in the South African War 1899-1902
• Superaldis, an Heliograph / Aldis lamp simulator