Clock Tower, Palace of Westminster



The Clock Tower is the world's largest four-faced, chiming clock. The structure is situated at the north-eastern end of the Houses of Parliament in Westminster, London. It is often colloquially referred to as Big Ben, which is actually the nickname of the main bell housed within the tower (formally known as the Great Bell). The Clock Tower has also been referred to as The Tower of Big Ben and, incorrectly, St Stephen's Tower, which is actually the spired tower towards the middle of the Palace and is also the main point of entry for attendees of debates and committees.

Structure of the clock


The tower was raised as a part of Charles Barry's design for a new palace, after the old Palace of Westminster was destroyed by fire on the night of 22 October 1834. However, although Barry was the chief architect of the palace, he turned to Augustus Pugin for the design of the clock tower, which resembles earlier Pugin designs, including one for Scarisbrick Hall. The design for the Clock Tower was Pugin's last design before his final descent into madness and death, and Pugin himself wrote, at the time of Barry's last visit to him to collect the drawings: "I never worked so hard in my life for Mr Barry for tomorrow I render all the designs for finishing his bell tower & it is beautiful." The tower is designed in Pugin's celebrated Gothic Revival style, and is 96.3m high.

The first 61m of the structure is the Clock Tower, consisting of brickwork with stone cladding; the remainder of the tower's height is a framed spire of cast iron. The tower is founded on a 15m square raft, made of 3m thick concrete, at a depth of 4m below ground level. The four clock faces are 55m above ground. The interior volume of the tower is 4,650 cubic metres (164,200 cubic feet).

Due to ground conditions present since construction, the tower leans slightly to the north-west, by roughly 220 millimetres (8.66 in) at the clock face, giving an inclination of approximately 1/250. Due to thermal effects it oscillates annually by a few millimetres east and west.

Clock faces
The clock faces are large enough to have once allowed the Clock Tower to be the largest four-faced clock in the world, but have since been outdone by the Allen-Bradley Clock Tower in Milwaukee, Wisconsin. The builders of the Allen-Bradley Clock Tower did not add chimes to the clock, so the Great Clock of Westminster still holds the title of the "world's largest four-faced chiming clock". The clock mechanism itself was completed by 1854, but the tower was not fully constructed until four years later, in 1858.



The clock and dials were designed by Augustus Pugin. The clock faces are set in an iron frame 7m in diameter, supporting 312 pieces of opal glass, rather like a stained-glass window. Some of the glass pieces may be removed for inspection of the hands. The surround of the dials is heavily gilded. At the base of each clock face in gilt letters is the Latin inscription DOMINE SALVAM FAC REGINAM NOSTRAM VICTORIAM PRIMAM, which means O Lord, keep safe our Queen Victoria the First.

The clock became operational on 7 September 1859.

Mechanism


The clock is famous for its reliability.. This is due to the skill of its designer, the lawyer and amateur horologist Edmund Beckett Denison, later Lord Grimthorpe. As the clock mechanism, created to Denison's specification by clockmaker Edward John Dent, was completed before the tower itself was finished, Denison had time to experiment. Instead of using the deadbeat escapement and remontoire as originally designed, Denison invented the double three-legged gravity escapement. This escapement provides the best separation between pendulum and clock mechanism. Together with an enclosed, wind-proof box sunk beneath the clockroom, the Great Clock's pendulum is well isolated from external factors like snow, ice and pigeons on the clock hands, and keeps remarkably accurate time.

The idiom of putting a penny on, with the meaning of slowing down, sprang from the method of fine-tuning the clock's pendulum. The pendulum carries a small stack of old penny coins; adding or subtracting coins has the effect of minutely altering the position of the bob's centre of mass, the effective length of the pendulum rod and hence the rate at which the pendulum swings. Adding or removing a penny will change the clock's speed by 2/5th of one second per day.

Despite heavy bombing the clock ran accurately throughout the Blitz. It slowed down on New Year's Eve 1962 due to heavy snow, causing it to chime in the new year 10 minutes late.

The clock had its first and only major breakdown in 1986. The chiming mechanism broke due to metal fatigue on 5 August 1986, and was reactivated again on 9 May 1987. During this time BBC Radio 4 had to make do with the pips.

It stopped on 30 April 1997, the day before the general election, and again three weeks later.

On Friday, 27 May 2005 the clock stopped ticking at 10:07 pm local time, possibly due to hot weather (temperatures in London had reached an unseasonal 31.8 °C (90 °F). It resumed keeping time, but stalled again at 10:20 pm local time and remained still for about 90 minutes before starting up again.

On 29 October 2005, the mechanism was stopped for approximately 33 hours so that the clock and its chimes could be worked on. It was the lengthiest maintenance shutdown in 22 years.



The clock tower's "Quarter Bells" were taken out of commission for four weeks starting at 7:00 am local time on 5 June 2006, as a bearing holding one of the quarter bells was damaged from years of wear and needed to be removed for repairs. During this period, BBC Radio 4 broadcast recordings of British bird song followed by the pips in place of the usual chimes.

On 11 August 2007, Big Ben went silent and the clock temporarily also stopped keeping time for maintenance that lasted one month. The bearings that help sound the chime on each hour were replaced, for the first time since installation. During the maintenance works, the clock was not driven by the original mechanism, but by an electric motor. Once again, BBC Radio 4 had to make do with the pips during this time.

Great Bell
The main bell, officially known as the Great Bell, is the largest bell in the tower and part of the Great Clock of Westminster. The bell is better known by the nickname Big Ben, which is often mistakenly applied to the Clock Tower.

The original bell was a 14.5-tonne (16 ton) hour bell, cast on 6 August 1856 in Stockton-on-Tees by John Warner & Sons. The bell was never officially named, but the legend on it records that the commissioner of works, Sir Benjamin Hall was responsible for the order. Another theory for the origin of the name is that the bell may have been named after a contemporary heavyweight boxer Benjamin Caunt. It is thought that the bell was originally to be called Victoria or Royal Victoria in honour of Queen Victoria, but that an MP suggested the nickname during a Parliamentary debate; the comment is not recorded in Hansard.

Since the tower was not yet finished, the bell was mounted in New Palace Yard. The bell cracked under the striking hammer, and its metal was recast at the Whitechapel Bell Foundry as the 13.76-tonne (13.54 ton (long), 15.17 ton (short)) bell, which stands at a height of 2.2 metres with a diameter of 2.9 metres, and it is still in use today. The new bell chimes the A, and was cast on 10 April 1858 and mounted in the tower alongside four quarter-hour bells, the ring of bells that ring the familiar changes. The bell was first heard across London on 31 May 1859. This bell also cracked, just two months after coming into use. For three years, Big Ben was taken out of commission and the hours were struck on the lowest of the quarter bells until it was simply fitted with a smaller hammer and rotated so the hammer would not strike the crack. Holes were also drilled on each side of the crack to prevent it from spreading, resulting in a distinctive, slightly off-key tone. At the time of its casting, Big Ben was the largest bell in the British Isles until "Great Paul", a 16 ton bell currently hung in St. Paul's Cathedral, was cast in 1881.

Other Bells
Along with the main bell, the belfry houses four quarter bells which play the Westminster Quarters on the quarter hours. The four quarter bells are G sharp, F sharp, E, and B. They play a 20-chime sequence, 1–4 at quarter past, 5–12 at half past, 13–20 and 1–4 at quarter to, and 5–20 on the hour. Because the low bell (B) is struck twice in quick succession, there is not enough time to pull a hammer back, and it is supplied with two wrench hammers on opposite sides of the bell. The tune is that of the Cambridge Chimes, first used for the chimes of Great St Mary's church, Cambridge, and supposedly a variation, attributed to William Crotch, on a phrase from Handel's Messiah. The notional words of the chime, again derived from Great St Mary's and in turn an allusion to Psalm 37, are: "All through this hour/Lord be my guide/And by Thy power/No foot shall slide". They are written on a plaque on the wall of the clock room.

Similar turret clocks
Turret clocks around the world are inspired by the look of the Great Clock.

Britain
A six-metre (20 ft) metal replica of the Clock Tower, known as Little Ben and complete with a working clock, stands on a traffic island close to Victoria Station.

There are two similar clock towers in Birmingham. The taller is the Joseph Chamberlain Memorial Clock Tower ("Old Joe"), located at the University of Birmingham. At 100 metres (328 ft) it is the tallest free-standing clock tower in the world. The University clock is a replica, however, of the Torre del Mangia in Italy rather than the Big Ben Clock Tower. Another tower, Big Brum, is located in Chamberlain Square in Birmingham City Centre.

Baby Big Ben is the Welsh version of the Clock Tower at the pierhead in Cardiff. Its mechanism is almost identical to the one which powers the Big Ben clock in London.

Other countries
There are other replicas, one of the finest of which is a two-third exact replica of the movement made by Dent located in the Queen's Royal College, Trinidad. There is another in Zimbabwe.

The clock tower of the Gare de Lyon in Paris and the Peace Tower of the Canadian Parliament Buildings in Ottawa draw inspiration from the clock tower.

The 47m tower of the City Hall in Pietermaritzburg, South Africa, contains a quarter-chime Westminster tower clock and carillon manufactured by Gillett & Johnston of Croydon. Its four faces are each three metres in diameter.

Significance in popular culture
The clock has become a symbol of the United Kingdom and London, particularly in the visual media. When a television or film-maker wishes to quickly convey to a non-UK audience a generic location in Britain, a popular way to do so is to show an image of the Clock Tower, often with a Routemaster bus or Hackney carriage in the foreground. This gambit is less often used in the United Kingdom itself, as it would suggest to most British people a specific location in London, which may not be the intention. Big Ben is often polled as the Most Iconic London Film Location.

The sound of the clock chiming has also been used this way in audio media, but as the Westminster Quarters are heard from other clocks and other devices, the unique nature of this particular sound has been considerably diluted.

The Clock Tower is a focus of New Year celebrations in the United Kingdom, with radio and TV stations tuning to its chimes to welcome the start of the year. Similarly, on Remembrance Day, the chimes of Big Ben are broadcast to mark the 11th hour of the 11th day of the 11th month and the start of two minutes' silence.

ITN's "News at Ten" opening sequence features an image of the Clock Tower with the sound of Big Ben's chimes punctuating the announcement of the news headlines, and has done so on and off for the last 41 years. The Big Ben chimes continue to be used during the headlines and all ITV News bulletins use a graphic based on the Westminster clock face. Big Ben can also be heard striking the hour before some news bulletins on BBC Radio 4 (6 pm and midnight, plus 10 pm on Sundays) and the BBC World Service, a practice that began on 31 December 1923. The sound of the chimes are sent in real time from a microphone permanently installed in the tower and connected by line to Broadcasting House.

Londoners who live an appropriate distance from the Clock Tower and Big Ben can, by means of listening to the chimes both live and on the radio or television, hear the bell strike thirteen times on New Year's Eve. This is possible due to what amounts to a one-strike offset between live and electronically transmitted chimes by virtue of a combination of digital coding and decoding and satellite transit delay. Guests are invited to count the chimes aloud as the radio is gradually turned down.

Big Ben was also used in the filming of Shanghai Knights starring Jackie Chan and Owen Wilson, and was partially destroyed in the Doctor Who episode Aliens of London. An animated version of the clock and it's inner workings were also used as the setting for the climactic final battle between Basil of Baker Street and his nemesis Ratigan in the Walt Disney animated film The Great Mouse Detective.

Awards
It was announced on 9 April, 2008 that a survey of 2,000 people found that the tower was the most popular landmark in the United Kingdom.