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Inventory no. 36545 - Epact entry

Epact number: 57991

Nocturnal and Sundial

Signed 'G K·B'
Dated 1587; German
Gilt brass; 160 mm in length

Main text

Although there are a number of functions here, this is a single plate belonging to a more complicated instrument. Evidence for a hinge and catch, and for the former existence of a folding extension to the index arm of the nocturnal, show that this was once part of an astronomical compendium.

Even in its present reduced state, this instrument tells the time at night, the time by day in four latitudes, and for a single location gives the times of sunrise and sunset and the lengths of day and night throughout the year.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 36,545

Detailed text

Circular base plate with a shaped, pierced and decorated handle. On the nocturnal side that base plate has a blank circular edge and within this a series of concentric scales. The first two form a zodiacal calendar (the first point of Aires is at 11 January), with the months named in Latin and divided to 2 days, numbered by 10 (adapted to each month), and the zodiac with signs, constellation devices and planetary symbols, each sign with a scale of 30 degrees, divided to 10, subdivided to 1, numbered by 10. There are four concentric scales of numbered dots within the zodiac scale: two (for length of day and night) with numbers 8 to 16 to 8, two (for sunrise and sunset) with numbers 4 to 8 to 4 and dots for the half-hours. The final scale is divided into the four seasons: 'VER', 'ÆSTAS', 'AVTVMNVS', 'HYEMS'.

Above the plate, secured by a central pierced screw and nut, is an hour ring covering the blank outer portion of the base plate, connected to a central disc by 7 curved bands. The hour ring is divided 1 to 12 twice, subdivided to |1/4| hour, numbered by 1 and with a stud at each hour. Mounted on each band is a hand with part of a sleeve and a finger pointing to one of the seven scales. The bands are marked (respective to the scales listed above): 'DIES MENSIVM', GRADVS ZODIACI', 'LONGITVDO DIEI', 'LONGITVDO NOCTIS', 'ORTVS SOLIS', 'OCCASVS SOLIS', 'QVATVOR ANNI PARTES'. Several of the arms have been repaired with solder. Above the hour ring is a shaped and decorated index arm, incomplete, for the nocturnal.

There is a small inscription on the blank portion of the base plate, usually obscured by the hour ring: '15[?] AVG'. The '5' is not entirely clear, but there is a dot close to the inscription and a straight line from the centre through this dot crosses the calendar scale at 15 August or 0 Scorpio.

The reverse side has a horizontal sundial. A folding gnomon, with a spring plate, is adjustable for latitudes 45, 48, 51 and 54, and there are four corresponding hour scales, marked with their latitudes, alternate scales being marked with hours 4 to 12 to 8 in Roman and Arabic numerals. An outer band is decorated with foliage and snakes. A circle and central point for a magnetic needle (missing) lacks a cover, to secure which there are two holes in the base-plate; cardinal points marked 'MERIDIES', 'OCCIDENS', SEPTENTRIO', 'ORIENS'; target line offset for magnetic variation.

On this face, next to the handle is a catch, and opposite this holes for a hinge fitting. The handle is decorated with figures, grotesque faces, plants and animals.

Jim Bennett

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