The Elizabeth Tower (previously called the Clock Tower or St. Stephen's Tower). Known popularly as Big Ben, being part of Charles Barry's design for a new palace, after the old Palace of Westminster was largely destroyed by fire on the night of 16 October 1834.
The new parliament being built in a neo-gothic style. 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 tower was Pugin's last design before his final descent into madness and death. 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 315 feet (96.0 m) high.
The bottom 200 feet (61.0 m) of the tower's structure consists of brickwork with sand coloured Anston limestone cladding. The remainder of the tower's height is a framed spire of cast iron. The tower is founded on a 50 feet (15.2 m) square raft, made of 10 feet (3.0 m) thick concrete, at a depth of 13 feet (4.0 m) below ground level. The four clock dials are 180 feet (54.9 m) above ground. The interior volume of the tower is 164,200 cubic feet (4,650 cubic metres).
Despite being one of the world's most famous tourist attractions, the interior of the tower is not open to overseas visitors, though United Kingdom residents can arrange tours (well in advance) through their Member of Parliament. However, the tower currently has no lift, though one is planned, so those escorted must climb the 334 limestone stairs to the top.
Due to changes in ground conditions since construction, the tower leans slightly to the north-west, by roughly 230 millimetres (9.1 in) over 55 m height, giving an inclination of approximately 1/240. This includes a planned maximum of 22 mm increased tilt due to tunnelling for the Jubilee line extension. Due to thermal effects, it oscillates annually by a few millimetres east and west.
The clock and dials designed by Augustus Pugin. The clock dials are set in an iron frame 23 feet (7.0 m) 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 gilded. At the base of each clock dial 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.
Unlike most other Roman numeral clock dials, which show the '4' position as 'IIII', the Great Clock faces depict '4' as 'IV'.
The clock's movement is famous for its reliability. The designers were the lawyer and amateur horologist Edmund Beckett Denison, and George Airy, the Astronomer Royal. Construction entrusted to clockmaker Edward John Dent; after his death in 1853 his stepson Frederick Dent completed the work, in 1854. As the tower was not complete until 1859, 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. The pendulum is installed within an enclosed windproof box beneath the clockroom. It is 13 feet (4.0 m) long, weighs 660 pounds (300 kg), suspended on a strip of spring steel 1/64 inch in thickness, and beats every 2 seconds. The clockwork mechanism in a room below weighs 5 tons. On top of the pendulum is a small stack of old penny coins; these are to adjust the time of the clock. Adding a coin has the effect of minutely lifting the position of the pendulum's centre of mass, reducing the effective length of the pendulum rod and hence increasing the rate at which the pendulum swings. Adding or removing a penny will change the clock's speed by 0.4 seconds per day.
On 10 May 1941, a German bombing raid damaged two of the clock's dials and sections of the tower's stepped roof and destroyed the House of Commons chamber. Architect Sir Giles Gilbert Scott designed a new five-floor block. Two floors are occupied by the current chamber, which was used for the first time on 26 October 1950. Despite the heavy bombing the clock ran accurately and chimed throughout the Blitz.
The main bell, officially known as the Great Bell but better known as Big Ben, is the largest bell in the tower and part of the Great Clock of Westminster.
The original bell was a 16 ton (16.3-tonne) hour bell, cast on 6 August 1856 in Stockton-on-Tees by John Warner & Sons. The Bell was possibly named in honour of Sir Benjamin Hall, and his name is inscribed on it.However, 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 first bell was transported to the tower on a trolley drawn by sixteen horses, with crowds cheering its progress. During the bell's testing, it cracked beyond repair and a replacement had to be made. The bell was recast on 10 April 1858 at the Whitechapel Bell Foundry as a 13½ ton (13.76-tonne) bell. This was pulled 200 ft (61.0 m) up to the Clock Tower’s belfry, a feat that took 18 hours. It is 7 feet 6 inches (2.29 m) tall and 9 feet (2.74 m) diameter. This new bell first chimed in July 1859; in September it too cracked under the hammer. According to the foundry's manager, George Mears, the horologist Denison had used a hammer more than twice the maximum weight specified. 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 repaired. To make the repair, a square piece of metal was chipped out from the rim around the crack, and the bell given an eighth of a turn so the new hammer struck in a different place. Big Ben has chimed with a slightly different tone ever since and is still in use today with the crack unrepaired. Big Ben was the largest bell in the British Isles until "Great Paul", a 16¾ ton (17 tonne) Bell currently hung in St Paul's Cathedral, was cast in 1881.
Along with the Great Bell, the belfry houses four quarter bells which play the Westminster Quarters on the quarter hours. The four quarter bells sound G♯, F♯, E, and B. They were cast by John Warner & Sons at their Crescent Foundry in 1857 (G♯, F♯ and B) and 1858 (E). The Foundry was in Jewin Crescent, in what is now known as The Barbican, in the City of London.
The quarter bells play a once-repeating, 20-note sequence of rounds and four changes in the key of E major: 1–4 at quarter past, 5–12 at half past, 13–20 and 1–4 at quarter to, and 5–20 on the hour (which sounds 25 seconds before the main bell tolls 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, based on violin phrases from the air "I know that my Redeemer liveth" in Handel's Messiah. The Notional words of the chime, again derived from Great St Mary's and in turn, an allusion to Psalm 37:23–24, 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.
One of the requirements for the clock was that the first stroke of the hour bell should be correct to within one second per day. Currently, the tolerance is with reference to Greenwich Mean Time (BST in summer).So, at twelve o'clock, for example, it is the first of the twelve hour-bell strikes that signifies the hour (the New Year on New Year's Day at midnight). The time signalled by the last of the "six pips" (UTC) may be fractionally different.
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