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Inventory no. 54054 - Epact entry

Epact number: 43055

Polyhedral Dial

Attributed to Nicolaus Kratzer
circa 1525; London
Gilt brass; 100 mm in height

Main text

The challenge in designing a polyhedral sundial such as this one is to set a separate dial on each face of the chosen solid, so that as many as are receiving the sun tell the time. In this case the shape is based on an octagon and accommodates nine sundials.

Although the instrument is unsigned, it was probably made by the German mathematician Nicolaus Kratzer, who came to England in about 1518 and was astronomer to Henry VIII. Kratzer became a member of Corpus Christi College, Oxford, and he read the mathematical lecture founded by Cardinal Wolsey, Archbishop of York. This instrument was made for Wolsey; the four-sided base has Wolsey's arms, the arms of York Minster, and (on two sides) a cardinal's hat.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 54,054

Detailed text

There are dials on nine faces - the two large octagonal sides, and seven of the connecting rectangles (the bottom rectangle is supported by the base).

On the top face is a horizontal dial for hours 6 to12 to 6 and a circular hole with a pin support for a compass (the magnetic needle and glazed cover are absent). The gnomon is for latitude 52 degrees.

On the adjacent face to the south, set at right angled to the equatorial plane, is an upper polar dial, with hour lines 9 to 12 to 3. On the face opposite to this is an inferior polar dial, with lines marked 4, 6 and 8.

On the adjacent face to the north of the horizontal dial, set parallel to the equatorial plane, is an upper equinoctial dial, with hour lines 3 to 12 to 9. On the face opposite to this is an inferior equinoctial dial, with hour lines 4 to 12 to 5.

Vertical north and south dials are on the two vertical rectangles. Each octagonal face has a projection of the celestial sphere with the horizon, pole, equator, tropics, arctic and antarctic circles marked. Between the tropics are the hour lines for east and west vertical dials with hour lines 3 to 11 and 1 to 9 respectively; the remainder of the projections are dotted with stars.

Each dial is arranged for 52 degrees north

See L. Evans, 'On a Portable Sundial of Gilt Brass made for Cardinal Wolsey', Archaeologia, 57 (1901).

Jim Bennett

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