Foghorn

A foghorn or fog signal is a device that uses sound to warn vehicles of

Audible fog signals have been used in one form or another for hundreds of years, initially simply fog bells or gongs struck manually.

At some lighthouses, a small cannon was let off periodically to warn away ships, but this was labor-intensive and dangerous.^[2] In the United States, whistles were also used where a source of steam power was available, though Trinity House, the British lighthouse authority, did not employ them, preferring an explosive signal.

Throughout the 19th century efforts were made to automate the signalling process. Trinity House eventually developed a system (the "Signal, Fog, Mk I") for firing a gun-cotton charge electrically. However, the charge had to be manually replaced after each signal. At Portland Bill, for example, which had a five-minute interval between fog-signals, this meant the horns had to be lowered, the two new charges inserted, and the horns raised again every five minutes during foggy periods.^{[This paragraph needs citation(s)]}

Clockwork systems were also developed for striking bells.^[3] Stricken bells were developed throughout the 1800s with the use of a governor, including the use of a giant triangle of 4 ft long sides in Maine in 1837. Ships were required to carry bells, with an exemption for Turkish ships because Islam forbade the use of bells.^[4]

Captain James William Newton claimed to have been the inventor of the fog signalling technique using loud and low notes.^[5]

Mechanization

The first

The development of fog signal technology continued apace at the end of the 19th century.[7] During the same period an inventor, Celadon Leeds Daboll, developed a coal-powered foghorn called the Daboll trumpet for the American lighthouse service, though it was not universally adopted.^[8] A few Daboll trumpets remained in use until the mid-20th century.

In the

One of the first automated fog bells was the Stevens Automatic Bell Striker.[10]

Some later fog bells were placed under water, particularly in especially dangerous areas, so that their sound (which would be a predictable code, such as the number "23") would be carried further and reverberate through the ship's hull. For example, this technique was used at

Diaphone

From the early 20th century an improved device called the diaphone, originally invented as an organ stop by Robert Hope-Jones,^[9] and developed as a fog signal by John Northey of Toronto, became the standard foghorn apparatus for new installations.^[where?] Diaphones were powered by compressed air and could emit extremely powerful low-frequency notes.

In 1982, the Dutch broadcaster VPRO aired a live foghorn concert on national radio composed by Marnie Bjornson, relaying the sound of the foghorns in Emden, Calais, Nieuwpoort, Scheveningen, Den Helder, Lelystad, Urk, Marken and Kornwerderzand, mixed with studio music by sound artist Alvin Curran.^[13]

Obsolescence

Since automation of lighthouses became common in the 1960s and 1970s, most older foghorn installations have been removed to avoid the need to run the complex machinery associated with them, and have been replaced with electrically powered diaphragm or

Fog signals have also been used on railway lines since the middle of the 19th century to indicate to warn of disabled trains, work parties, or other hazards on the line ahead. Small explosive detonators or torpedoes are placed on the track, and detonated by the pressure of the wheels of the oncoming train.

Study of foghorns

British writer Jennifer Lucy Allan was awarded a PhD by the University of the Arts London in 2019 for her thesis on Fog tropes : a social and cultural history of the foghorn^[15] and subsequently published a book: The Foghorn's Lament: the Disappearing Music of the Coast.^[16]

See also

• Siren (alarm)
• Air horn

References

Further reading

• Allan, Jennifer Lucy (2021). The Foghorn's Lament : the Disappearing Music of the Coast. London: White Rabbit.
  ISBN 9781474615037
  .

External links

Wikimedia Commons has media related to Foghorns.

"The Atmosphere in Relation to Fog-Signaling I" .

ISSN 0161-7370 – via Wikisource

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• Listen to Golden Gate Bridge foghorn
• a list of foghorn clips from San Pedro, CA.- Foghorn 1 is a good example of a diaphone.
• Terry Pepper, Seeing the Light, "Fog Signal Technology."
• Location of foghorns that can still be heard in UK Archived 2010-01-22 at the Wayback Machine
• BBC Radio 4 - The Foghorn: A Celebration
• Association of Lighthouse Keepers: archive clips of a variety of fog signal sounds from around the UK