Foghorn

All foghorns use a vibrating column of air to create an audible tone, but the method of setting up this vibration differs. Some horns, such as the Daboll trumpet, used vibrating plates or metal reeds, a similar principle to a modern electric car horn. Others used air forced through holes in a rotating cylinder or disk, in the same manner as a siren. Semi-automatic operation of foghorns was achieved by using a clockwork mechanism (or "coder") to sequentially open the valves admitting air to the horns; each horn was given its own timing characteristics to help mariners identify them.^[1]

Early fog signals

An early form of fog signal. The fog bell at Fort Point Light Station, Maine.

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 had the obvious disadvantage of having to be fired manually throughout the whole period the fog persisted (which could be for several days). Lighthouse windows and lighting apparatus were susceptible to damage depending on the proximity of the explosion.^[2] One incident of lax handling of explosives nearby resulted in a concussion that propelled the lighthouse keeper at Fort Amherst, who was seated, to the other end of the room.^[3] 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.

Clockwork systems were also developed for striking bells.^[4] 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.^[5]

Captain James William Newton claimed to have been the inventor of the fog signalling technique using loud and low notes.^[6]

Mechanization

Foghorns near Lizard Point, Cornwall. This installation uses a siren to produce sound.

Another Trinity House fog siren installation on Flat Holm, now restored by the Flat Holm Project

Bearing mechanism of Sumburgh lighthouse Foghorn (Shetland)

Trinity House warning notice

The first automated steam-powered foghorn was invented by Robert Foulis, a Scotsman who emigrated to Saint John, New Brunswick, Canada. Foulis is said to have heard his daughter playing the piano in the distance on a foggy night, and noticed the low notes were more audible than the higher notes: he then designed a device to produce a low-frequency sound, as well as a code system for use with it. Foulis repeatedly presented his concept to the Commissioners of Light Houses for the Bay of Fundy for installation on Partridge Island. While the Commissioners initially rejected Foulis's plan, one commissioner eventually encouraged Foulis to submit detailed plans to the Commission. For reasons unknown, the plans were given to another Canadian engineer, T. T. Vernon Smith, who officially submitted them to the Commissioners as his own. The foghorn was constructed at Partridge Island in 1859 as the Vernon-Smith horn. After protest by Foulis and a legislative inquiry, Foulis was credited as the true inventor, but he never patented or profited from his invention.^[7]

The development of fog signal technology continued apace at the end of the 19th century.^[8] 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.^[9] A few Daboll trumpets remained in use until the mid-20th century.

In the United Kingdom, experiments to develop more effective foghorns were carried out by John Tyndall and Lord Rayleigh, amongst others. The latter's ongoing research for Trinity House culminated in a design for a siren with a large trumpet designed to achieve maximum sound propagation (see reference for details of the Trials of Fog Signals^[10]), installed in Trevose Head Lighthouse, Cornwall in 1913. One reporter, after hearing a Brown steam-powered siren for the first time, described it as having "a screech like an army of panthers, weird and prolonged, gradually lowering in note until after half a minute it becomes the roar of a thousand mad bulls, with intermediate voices suggestive of the wail of a lost soul, the moan of a bottomless pit and the groan of a disabled elevator."^[5]

One of the first automated fog bells was the Stevens Automatic Bell Striker.^[11]

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 White Shoal Light (Michigan).^[12][13] This was an earlier precursor to RACON.

Diaphone

From the early 20th century an improved device called the diaphone, originally invented as an organ stop by Robert Hope-Jones,^[10] and developed as a fog signal by John Northey of Toronto, became the standard foghorn apparatus for new installations. 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.^[14]

Obsolescence

Foghorn on Ailsa Craig, where the fog signal was discontinued in 1966.

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 compressed air horns. Activation is completely automated: a laser or photo beam is shot out to sea, and if the beam reflects back to the source (i.e. the laser beam is visible due to the fog), the sensor sends a signal to activate the foghorn. In many cases, modern navigational aids, including GPS, have rendered large, long-range foghorns completely unnecessary, according to the International Association of Lighthouse Authorities.^[15]

Discover more about History related topics

Fog bell

Fog bell

A fog bell is a navigation mark used as an audible aid to navigation in seafaring, especially in fog and poor visibility. Floating navigation signs with bells are called bell buoys. On ships, the ship's bell is used for sound signals. Due to more suitable sound generators, but also the development and spread of radar, satellite navigation and electronic charting systems, fog bells have lost their importance for maritime navigation.

Maine

Maine

Maine is the easternmost state in the New England region of the Northeastern United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and northwest, respectively. The largest state by total area in New England, Maine is the 12th-smallest by area, the 9th-least populous, the 13th-least densely populated, and the most rural of the 50 U.S. states. It is also the northeasternmost among the contiguous United States, the northernmost state east of the Great Lakes, the only state whose name consists of a single syllable, and the only state to border exactly one other U.S. state. Approximately half the area of Maine lies on each side of the 45th parallel north in latitude. The most populous city in Maine is Portland, while its capital is Augusta.

Gong

Gong

A gong is a percussion instrument originating in East Asia and Southeast Asia. Gongs are a flat, circular metal disc that is typically struck with a mallet. They can be small or large in size, and tuned or can require tuning.

Lighthouse

Lighthouse

A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways.

Cannon

Cannon

A cannon is a large-caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder was the primary propellant before the invention of smokeless powder during the late 19th century. Cannons vary in gauge, effective range, mobility, rate of fire, angle of fire and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. A cannon is a type of heavy artillery weapon.

General lighthouse authority

General lighthouse authority

A general lighthouse authority (GLA) is one of three agencies primarily responsible for aids to navigation in the United Kingdom and the Republic of Ireland. They are divided into regions as follows:Trinity House: England & Wales, Channel Islands and Gibraltar Northern Lighthouse Board: Scotland and the Isle of Man Commissioners of Irish Lights : the whole of Ireland

Nitrocellulose

Nitrocellulose

Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and sulfuric acid. One of its first major uses was as guncotton, a replacement for gunpowder as propellant in firearms. It was also used to replace gunpowder as a low-order explosive in mining and other applications. In the form of collodion it was also a critical component in an early photographic emulsion, the use of which revolutionized photography in the 1860s.

Portland Bill

Portland Bill

Portland Bill is a narrow promontory at the southern end of the Isle of Portland, and the southernmost point of Dorset, England. One of Portland's most popular destinations is Portland Bill Lighthouse. Portland's coast has been notorious for the number of shipwrecked vessels over the centuries. The dangerous coastline features shallow reefs and the Shambles sandbank, made more hazardous due to the strong Portland tidal race.

Lizard Point, Cornwall

Lizard Point, Cornwall

Lizard Point in Cornwall is at the southern tip of the Lizard Peninsula. It is situated half-a-mile (800 m) south of Lizard village in the civil parish of Landewednack and about 11 miles (18 km) southeast of Helston.

Cornwall

Cornwall

Cornwall is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic Ocean, to the south by the English Channel, and to the east by the county of Devon, with the River Tamar forming the border between them. Cornwall forms the westernmost part of the South West Peninsula of the island of Great Britain. The southwesternmost point is Land's End and the southernmost Lizard Point. Cornwall has a population of 568,210 and an area of 3,563 km2 (1,376 sq mi). The county has been administered since 2009 by the unitary authority, Cornwall Council. The ceremonial county of Cornwall also includes the Isles of Scilly, which are administered separately. The administrative centre of Cornwall is Truro, its only city.

Flat Holm

Flat Holm

Flat Holm is a Welsh island lying in the Bristol Channel approximately 6 km (4 mi) from Lavernock Point in the Vale of Glamorgan. It includes the most southerly point of Wales.

Shetland

Shetland

Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands, and Norway. It is the northernmost region of the United Kingdom.

Fog signals have also been used on railway lines since the middle of the 19th century to indicate to the driver of a moving train that a broken down train, a work party, or some other unforeseen hazard is 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. The loud report of the explosion provides the indication to the driver, which, in most cases, requires the train to be stopped immediately. During World War II, these devices were modified to detonate demolition charges during railroad sabotage operations.

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Detonator (railway)

Detonator (railway)

A railway detonator is a coin-sized device that is used as a loud warning signal to train drivers. It is placed on the top of the rail, usually secured with two lead straps, one on each side. When the wheel of the train passes over, it explodes, emitting a loud bang. It was invented in 1841 by English inventor Edward Alfred Cowper.

Explosive

Explosive

An explosive is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An explosive charge is a measured quantity of explosive material, which may either be composed solely of one ingredient or be a mixture containing at least two substances.

Detonator

Detonator

A detonator, frequently a blasting cap, is a small sensitive device used to detonate a larger, more powerful but relatively insensitive secondary explosive of an explosive device used in commercial mining, excavation, demolition etc.

World War II

World War II

World War II or the Second World War, often abbreviated as WWII or WW2, was a global conflict that lasted from 1939 to 1945. The vast majority of the world's countries, including all of the great powers, fought as part of two opposing military alliances: the Allies and the Axis. Many participants threw their economic, industrial, and scientific capabilities behind this total war, blurring the distinction between civilian and military resources. Aircraft played a major role, enabling the strategic bombing of population centres and the delivery of the only two nuclear weapons ever used in war.

Sabotage

Sabotage

Sabotage is a deliberate action aimed at weakening a polity, effort, or organization through subversion, obstruction, disruption, or destruction. One who engages in sabotage is a saboteur. Saboteurs typically try to conceal their identities because of the consequences of their actions and to avoid invoking legal and organizational requirements for addressing sabotage.

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^[16] and subsequently published a book: The Foghorn's Lament: the Disappearing Music of the Coast.^[17]