Epact Scientific Instruments of Medieval and Renaissance Europe

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Diptych Dial
Attributed to a Thomas Tucher
circa 1590; Nuremberg
Ivory; 58 x 117 x 15 mm

The outer side of the upper leaf has a wind rose with compass viewing hole, with 32 directions numbered from east. The cardinal points are named 'OR', 'M', 'OC' (the space for north is occupied by the compass viewing hole) in the central part, and outside the numbered directions they are engraved in two concentric circles. The innermost one has 'nort', 'ost', 'suid', 'west', with [star] at the intermediate directions. The outer circle has 'S', 'nortost', 'OR', 'suidost', 'M', 'suidwest', 'OC', 'westnort' alternating red and black colour. Fixed to the centre is a conuterchanged arm. Below the wind rose is a brass volvelle with index. On the volvelle is inscribed ' ? DAS ? IST DIE ? GROSS ? VR' and is engraved on the border with hour from 8 to 24 with dots at the half hour. The aperture on the volvelle shows the inscription on the ivory plate below, named 'TAG LENG' in red, and numbered in black from 8 to 16. The brass index rotates on a scale of hours engraved on the ivory leaf, 4 to 12 to 8 with dots at the half hour , and inscribed 'VERGLEIGVNG GROS VN KLAN VR' (the last two words engraved next to the length of the day on the inner circle). The remaining space is filled with foliage decoration.

The inner side of the upper leaf has a pin gnomon dial for the length of the day, numbered from 8 to 16 in red, and for Italian hours numbered from 14 to 24 in black. On the sides are the symbols of the zodiac signs. Below is the inscription 'QVANTIDAS TIEI' alternating red and black ink. Below is a vertical string gnomon dial, with a sun's effigy at the centre of the string attachment, and foliage below. The dial, in a circle, marks common hours from VII to XII to V, with stars and dots for the half and quarter hour respectively, alternating red and black ink. The rest of the leaf is filled with foliage decoration in brown and green ink.

The inside of the lower leaf has a compass, marked 'S', 'OR', 'M', 'OC', with a fleur-de-lis for the north and the maker's mark (a snake) punched twice. Glass and needle are missing. Surrounding the compass is a string gnomon dial for common hours numbered from 4 to 12 to 8, similar to the upper leaf, with stars and dots for the half and quarter hour, alternating red and black ink. Below is a gilt brass plate with a pin gnomon dial, engraved for 'P<OLVS> 45 G<RADUUM>' and 'DEITZS VNT WEIS ? VHR ?', with Italian hours from 9 to 23 and Babylonian hours from 1 to 15 juxtaposed. The rest of the space in the leaf is filled with foliage decoration in brown and green ink.

The outside of the lower leaf has a table of Epacts, named 'EPAGTA GREGORI' and 'EPAGTA IVLLIANA', starting at 17 / 7 and with the terms 'Julian' and 'Gregorian' reversed, as in many Tucher instruments. At the centre was a lunar volvelle, now missing, and surrounding it the ivory leaf is engraved with hours from 1 to 12 twice and lunar days from 1 to 291/2. The rest of the leaf is decorated with fruits and flowers and there are four bun feet.

Two catches keep the dial closed when not in use and one catch is used to keep the dial vertical when used.

The instrument was bequeathed by Octavius Morgan and is described in F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum (London, 1981), p. 39, no. 88.

Ilaria Meliconi

British Museum, London
Registration no. MLA 1888, 12-1.288

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