Astonishing Science. Spectacular museum.
The clock was installed at Wells Cathedral in Somerset towards the end of the 14th century. The Cathedral's accounts from 1327, 1343 and 1392 still survive but only the last of these mentions the clock. Mentions of the clock in later accounts show that it has been in continuous use since 1392. It appears slightly more advanced than the Salisbury Cathedral clock and was therefore probably built after 1386.
It is unlikely that the public would have been able to see the clock originally. The transept containing the face was not open to the public in the early 14th century and the Cathedral does not seem to have received many visitors in the 14th and 15th centuries. The clock was probably installed to enable the Cathedral's staff to start services on time.
The clock originally had a foliot balance and a verge escapement. Signs of these still remain. In the 17th century, it was given a pendulum and an anchor escapement to improve its timekeeping. In its original form, the clock could gain or lose up to fifteen minutes in a day. The first public clock to be built with a pendulum and an anchor escapement could have been the one installed at King's College, Cambridge in 1671. At about that time, almost all older public clocks were adapted and given pendulums. The only surviving exceptions are the clocks from Cassiobury Park and Dover Castle.
In this picture of the Wells clock, the anchor engages the small wheel roughly half-way along the top of the clock. The pendulum hangs down from just to the left of this wheel and its bob is the circular object just above the wooden base.
In 1742, the mechanism was modified again so that it would only need to be wound up once every day. In 1837, it was removed to the Cathedral's undercroft and replaced with a new mechanism. This did not work very well and was replaced again in 1880. This third mechanism has had to be repaired several times.
The original mechanism was moved to the Patent Office Museum in London in 1871, where a few wheels were replaced and new bells added, and came to the Science Museum in 1884. The 19th century bells are interesting because they are made of steel rather than the usual bell metal.
Despite being a very early example, the operation of the original clock was quite complicated. It had three trains of wheels, each driven by a separate weight but controlled by the same escapement. One of these kept the clock's two faces running smoothly, another controlled the actions which happen every hour and the third controlled those which happen every fifteen minutes. These actions happen in various places around the Cathedral and are operated by an arrangement of wires and pulleys.
The face inside the cathedral is the oldest surviving original clock-face in the world. As well as telling the time on a 24-hour dial, it shows the motion of the Sun and Moon in the sky, the phase of the Moon and the number of days since the last new Moon.
Above the inside face are figures of four horsemen. Every hour, they were made to charge round a tower in opposite directions several times. One of them carries a lance which would knock one of the others onto his back every time they passed. By 1968, the number of tourists crowding the area in front of the clock every hour had become so large that the tournament was shortened and made to happen every fifteen minutes, with help from an electric motor.
In the fifteenth century, the clock was given a second face, on the outside of the Cathedral. It was originally divided into 24 hours and had only one hand but was changed to a conventional 12-hour face in the 19th century. Above this face are two knights in armour. Every fifteen minutes, they each rotate to ring the bells hanging above them.
The figure shown above is known as Jack Blandifer. He rings the hours on the bell in front of him, turning his head slightly as if listening to the tone of each ring. He also uses his heels to strike bells every fifteen minutes. The mechanism for operating him clearly formed part of the original clock although the current figure and his sentry-box appear to have been replaced in the 17th century. In an engraving made in 1823, he is shown in a different place in the Cathedral. His current position means that he and the horsemen can be seen at the same time.
The clock also operates a bell which strikes the hours in the Cathedral's tower and can be heard over a wide area of the city.
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