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The Wells Cathedral clock is an astronomical clock in the north transept of Wells Cathedral, England. The surviving mechanism, dated to between 1386 and 1392, was replaced in the 19th century, and was eventually moved to the Science Museum in London, where it continues to operate. The dial represents the geocentric view of the universe, with sun and moon revolving round a central fixed earth. It may be unique in showing a philosophical model of the pre-Copernican universe.

Another dial is mounted on the outside wall, driven from the same mechanism. This was first installed in the 14th or 15th centuries, but has been restored a number of times.

Contents 1 Description 2 History 3 References 4 See also 5 External links

The dial proposes a model of the universe. Against a background of stars, the sun (the large gilded star on the outer ring) moves in a circle, and indicates the time using the 24 hour analog dial, which is marked in Roman numerals from I to XII, then from I to XII again. Noon is probably at the top of the dial.

In the corners, four angels hold the four cardinal winds. These may be generating the power that makes the universe operate.

The minutes are indicated by a smaller star on the ring inside. This was probably added in the 16th century.

The inner circle shows the moon. A pointer indicates the age of the moon, between 1 and 30 days. The black and white disk above the centre shows the moon's phase. The white disk rotates once in a synodic month. The inscription around the moon phase indicator says sphericus archetypum globus hic monstrat microcosmum, which translates as This spherical globe here demonstrates the archetype - the macrocosm. Howgrave-Graham suggests that the scribe erroneously put microcosmum, when macrocosmum is the more obvious word. Opposite the moon circle is a weighted pivoted disc, containing a small painting of Phoebe, representing the moon. The inscription reads: Sic peragrat Phobe, or So progresses Phoebe.

At the centre of the dial, the ball represents the earth, and the clouds suggest the same.

Above the clock is a set of figures, known as Jack Blandifers) which hit the bells, and a set of jousting knights who chase each other every 15 minutes.

There are mentions of a clock at Wells during the first half of the 14th century.

In 1388, Bishop Ralph Erghum moved from Salisbury to Wells. He had previously been Bishop of Salisbury, from 1375 to 1388, and had installed a clock there in 1386. He may have brought his clockmakers with him to Wells. The two clocks are almost identical in construction, although the Wells clock shows some improvements and additions, which suggests that some valuable lessons had been learned. The Wells striking system uses a double lever, for example, which is more reliable than the system used in Salisbury.

The clock was converted to pendulum and anchor escapement in the 17th century. It was installed in the Science Museum in 1884.

• R P Howgrave-Graham, New light on ancient turret clocks Antiquarian Horology, 1954

• Salisbury cathedral clock

• Science Museum