Clock towers are a specific type of structure that house aturret clock and have one or moreclock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another building. Some other buildings also have clock faces on their exterior but these structures serve other main functions.
Clock towers are a common sight in many parts of the world with some being iconic buildings. One example is theElizabeth Tower in London (usually called "Big Ben", although strictly this name belongs only to the bell inside the tower).
There are manystructures that may have clocks or clock faces attached to them and some structures have had clocks added to an existing structure. According to theCouncil on Tall Buildings and Urban Habitat, a structure is defined as a building if at least fifty percent of its height is made up of floor plates containing habitable floor area. Structures that do not meet this criterion are defined astowers. A clock tower historically fits this definition of a tower and therefore can be defined as any tower specifically built with one or more (often four)clockfaces and that can be either freestanding or part of achurch or municipal building such as atown hall. Not all clocks on buildings therefore make the building into a clock tower.
The mechanism inside the tower is known as aturret clock. It often marks the hour (and sometimes segments of an hour) by sounding largebells orchimes, sometimes playing simple musical phrases or tunes. Some clock towers were previously built asBell towers and then had clocks added to them. As these structures fulfil the definition of a tower they can be considered to be clock towers.
Although clock towers are today mostly admired for their aesthetics, they once served an important purpose. Before the middle of the twentieth century, most people did not have watches,[citation needed] and prior to the 18th century even home clocks were rare. The firstclocks did not have faces, but were solelystriking clocks, which sounded bells to call the surrounding community to work or to prayer. They were therefore placed in towers so the bells would be audible for a long distance. Clock towers were placed near the centres of towns and were often the tallest structures there. As clock towers became more common, the designers realized that adial on the outside of the tower would allow the townspeople to read the time whenever they wanted.
The use of clock towers dates back toantiquity. The earliest clock tower was theTower of the Winds inAthens, which featured eightsundials and was created in the 1st century BC during the period ofRoman Greece. In its interior, there was also awater clock (or clepsydra), driven by water coming down from theAcropolis.[1]
InSong dynastyChina, anastronomical clock tower was designed bySu Song and erected atKaifeng in 1088, featuring a liquidescapement mechanism.[2] In England, a clock was put up in a clock tower, the medieval precursor toBig Ben, atWestminster, in 1288;[3][4] and in 1292 a clock was put up inCanterbury Cathedral.[3] The oldest surviving turret clock formerly part of a clock tower in Europe is theSalisbury Cathedral clock, completed around 1390. A clock put up atSt. Albans, in 1326, 'showed various astronomical phenomena'.[3]
Al-Jazari of theArtuqid dynasty inUpper Mesopotamia constructed an elaborate clock called the "castle clock" and described it in hisBook of Knowledge of Ingenious Mechanical Devices in 1206. It was about 3.3 metres (11 feet) high, and had multiple functions alongsidetimekeeping. It included a display of thezodiac and the solar and lunar paths, and a pointer in the shape of thecrescent moon that travelled across the top of agateway, moved by a hiddencart and causing automatic doors to open, each revealing amannequin, every hour.[5][6] It was possible to re-program the length ofday andnight daily in order to account for the changing lengths of day and night throughout the year, and it also featured fiverobotic musicians who automatically play music when moved bylevers operated by a hiddencamshaft attached to awater wheel.
Line (mains) synchronous tower clocks were introduced in the United States in the 1920s.
Some clock towers have become famous landmarks. Prominent examples includeElizabeth Tower built in 1859, which houses theGreat Bell (generally known asBig Ben) inLondon,[7] the tower ofPhiladelphia City Hall, theRajabai Tower inMumbai, theSpasskaya Tower of theMoscow Kremlin, theTorre dell'Orologio in thePiazza San Marco inVenice,Italy, thePeace Tower of theParliament of Canada inOttawa, and theZytglogge clock tower in theOld City ofBern,Switzerland.
The tallest freestanding clock tower in the world is theJoseph Chamberlain Memorial Clock Tower (Old Joe) at theUniversity of Birmingham inBirmingham, United Kingdom.[8] The tower stands at 100 metres (330 feet) tall and was completed in 1908. The clock tower ofPhiladelphia City Hall was part of the tallest building in the world from 1894,[9] when the tower wastopped out and the building partially occupied,[10][11] until 1908.
Taller buildings have had clock faces added to their existing structure such as thePalace of Culture and Science inWarsaw, with a clock added in 2000. The building has a roof height of 187.68 m (615.7 ft), and an antenna height of 237 m (778 ft). TheNTT Docomo Yoyogi Building inTokyo, with a clock added in 2002, has a roof height of 240 m (790 ft), and an antenna height of 272 m (892 ft).
TheAbraj Al Bait, a hotel complex inMecca constructed in 2012, has the largest and highest clock face on a building in the world, with its Makkah Royal Clock Tower having an occupied height of 494.4 m (1,622 ft), and a tip height of 601 m (1,972 ft).[12] The tower has four clock faces, two of which are 43 m (141 ft) in diameter, at about 400 m (1,300 ft) high.[13]
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