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Inventory no. 52632 - Epact entry

Epact number: 38263

Nocturnal and Sundial

circa 1600 ?; French
Gilt brass; 52 mm in diameter

Main text

This instrument is very similar to Epact 68501, which is also French and has the same combination of nocturnal and vertical disc dial. The example considered here is more complete, and shows that a small compass is missing from the other one. One additional feature here is a volvelle on the vertical sundial side which advises the owner which days in the year are favourable - 'les jours hereux' - and which unfavourable - 'les jours perileux'.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 52,632

Detailed text

The nocturnal face has an outer zodiac scale with the names of the constellations (sometimes abbreviated) and each sign has a scale 0 to 30, divided to 10, subdivided to |1/6|, numbered by 10. A moveable ring is supported by two diametric bars and is divided into hours by 24 points, the two representing 12 o'clock being extended to the zodiac scale. Beneath the ring, or pierced disc, is a date scale with the letters of the months, the days numbered by 10 but not accurately divided to single days. This can be used instead of the zodiac sign; the first point of Aires corresponds to 20 March.

This face also incorporates a lunar volvelle, and the ring has a scale 1 to 29 for the age of the moon. Above the ring is a disc with a small horizontal sundial with a folding gnomon, and beyond this, obscuring part of the ring and lunar scale is a small circular compass box with a pivoted lid. The needle is missing, but the cardinal points are marked 'O', 'M', 'O', 'S'. The disc is pierced to show the phase of the moon, and has an extended index arm for the nocturnal, marked 'LIGNE· DE· FOY'.

There is a delicately shaped and decorated handle, with a suspension shackle and ring.

The sundial face has a vertical disc dial, with a pivoted index arm carrying a folding gnomon. There is a calendar scales with abbreviated names of the months in French, divided to quarter months, for setting the position of the gnomon for the date, and on the opposite side of the disc a scale for ordinary hours, marked with Roman numerals, divided to quarter hours.

The gnomon and index arm are attached to a disc, with three circular scales and at the centre is a rotating disc with an index arm for reading across them. The central scale has abbreviated months in French, while the outer has corresponding sections marked 'LE' (once 'LEP') followed by a number, the inner 'L' (once 'LP') followed by a number. An inscription on the central disc explains: '·LE·GRAN·O ·SON·LES·IOVRS·HER|EVbar|' and '·LE·PETY·SON·LES·IOVRS·PERIL|EVbar|'.

A cartouche has the numbers 15917, so that it is unclear how to read this as a date.

With the original shaped and lined leather case with brass fittings.

Jim Bennett

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