The Canterbury Portable Sundial

Anglo-Saxon Portable Sundial
Anglo-Saxon Portable Sundial, Canterbury Cathedral 01513 (1-2)

The Canterbury Portable Sundial, often referred to as St Dunstan’s watch, was found in 1938 by workmen clearing the cloister garth at Canterbury. There were various devices for keeping the time in Anglo-Saxon England, from sundials to Alfred’s candle clock. However, this portable sundial is a unique find. 

It is dated roughly to the 10th century and consists of a silver tablet, 61mm x 16mm, on a chain and a small peg.

The two faces of the sundial have three columns inscribed with pairs of the months in abbreviated Latin. They are equidistant from the marker for the summer solstice. Each column has a hole at the top into which the peg is inserted. The peg is made of gold and terminates in an animal’s head. It acted as a gnomon to cast the sun’s shadow.

If the tablet was held facing the sun with the peg inserted in the correct hole, the position of the peg’s shadow gave a rough idea of the time. Around its sides runs the inscription ‘[SA]LVS FACTORI [PA]X POSSESSOR[I]’: ‘Health to my maker, peace to my owner.’

The portable sundial is a unique find and probably belonged to someone associated with the Cathedral. It would have helped its owner to keep track of the time in accordance with the Benedictine Rule. The copy of the Rule at Canterbury was also prefaced with a table to show how long someone’s shadow would be at different times throughout the year.

In the 10th century Byrhtferth of Ramsey wrote in his Enchiridion that with the gnomon in place:

“you can consider in how orderly a fashion the sun advances on the sundial, as if some learned man sat down and wrote a verse with his pen.”

Much earlier Bede, writing in the early 8th century, also mentioned sundials, indicting their use in monastic circles. In his Ecclesiastical History of the English People, Book V.21 he says:

“Now the equinox, according to the opinion of all eastern nations, and especially of the Egyptians who took the palm from all other learned men in calculations, usually falls on the twenty first of March, as we can also prove by inspecting a sundial.”