A boom or a chain (also boom defence, harbour chain, river chain, chain boom, boom chain or variants) is an obstacle strung across a navigable stretch of water to control or block navigation.
![](http://178.128.105.246/cars-http-upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Siege_of_Londonderry_boom_detail.jpg/220px-Siege_of_Londonderry_boom_detail.jpg)
In modern times they usually have civil uses, such as to prevent access to a dangerous river channel. But, especially historically, they have been used militarily, with the goal of denying access to an enemy's ships: a modern example is the anti-submarine net.
Booms have also been used to force passing vessels to pay a toll.[1][2]
Description
editA boom generally floats on the surface, while a chain can be on the surface or below the water. A chain could be made to float with rafts, logs, ships or other wood, making the chain a boom as well.
Historical uses
editEspecially in medieval times, the end of a chain could be attached to a chain tower or boom tower. This allowed safe raising or lowering of the chain, as they were often heavily fortified.[1] By raising or lowering a chain or boom, access could be selectively granted rather than simply rendering the stretch of water completely inaccessible. The raising and lowering could be accomplished by a windlass mechanism or a capstan.[3]
Booms or chains could be broken by a sufficiently large or heavy ship, and this occurred on many occasions, including the siege of Damietta, the raid on the Medway and the Battle of Vigo Bay.[4][5][6][7]A Frequently, however, attackers instead seized the defences and cut the chain or boom by more conventional methods. The boom at the siege of Derry, for example, was cut by sailors in a longboat.
As a key portion of defences, booms were usually heavily defended. This involved shore-based chain towers, artillery batteries, or forts. In the Age of Sail, a boom protecting a harbour could have several ships defending it with their broadsides, discouraging assaults on the boom. On some occasions, multiple booms spanned a single stretch of water.
Gallery
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Crusaders break a chain protecting the harbour (at left) in the siege of Damietta.
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Boom towers in Norwich
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Remains of the great chain that protected the Golden Horn
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A preserved section of the Hudson River Chain
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Remains of the Shoeburyness Boom, built to protect the Thames Estuary from Soviet submarines during the Cold War
Examples
editHistorical
edit- The entrance to the Cothon at Carthage was protected by a chain.
- The chain at Fort Blockhouse, protecting Portsmouth Harbour from 1431 to 1539.
- The Leonine Wall included a chain blocking the Tiber
- A chain spanned the Golden Horn
- A chain and boom blocked the River Medway during the Raid on the Medway
- Hudson River Chain
- The chain blocking the Parana River during the Battle of Vuelta de Obligado
- A chain was placed from Columbus, Kentucky across the Mississippi River to Missouri in order to block Union ships during the American Civil War[8]
- Between the A Palma Castle in Mugardos and Saint Philip Castle , in ria of Ferrol, to defend the city and naval base.
See also
edit- Anti-submarine net
- Boom defence vessel - a vessel charged with laying anti-submarine nets
- Log boom - a boom for collecting logs
- Boom (containment) - a boom for containing oil spills
Notes
edit- A.^ Some sources have the chain being dismantled instead of broken by a ship in the siege of Damietta and in the raid on the Medway.
References
edit- ^ a b Philip Davis (May 7, 2012). "Site types in the Gatehouse listings — Chain Tower". Gatehouse. Retrieved October 17, 2013.
- ^ Boom Towers, Norwich
- ^ Bob Hind (January 27, 2013). "Filling in the missing links on history of harbour chain". The News. Archived from the original on October 21, 2013. Retrieved October 17, 2013.
- ^ Gibbon, Edward. The History of the Decline and Fall of the Roman Empire, Volume 6. p. 510.
- ^ "THE DUTCH IN THE MEDWAY - 1667". M.A. de Ruyter Foundation. Archived from the original on October 21, 2013. Retrieved October 21, 2013.
- ^ Hervey, Frederic (1779). The Naval History of Great Britain: From the Earliest Times to the Rising of the Parliament in 1779. W Adlard. pp. 77.
- ^ Long, WH (2010). Medals of the British Navy and How They Were Won. Great Britain: Lancer Publishers. p. 24. ISBN 9781935501275.
- ^ "The Mississippi River in the Civil War Historical Marker".