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Astronomical Compendium
Late 16th century; German
Gilt and silvered brass; 95 x 95 x 17 mm

The compendium consists of two outer leaves and a central section whose sides are decorated with engraved foliage.

The upper cover is closed with a hook clasp and its outer face carries a lunar volvelle within a fixed scale of hours I to XII, I to XII, each hour subdivided to quarters. The volvelle has an outer scale of hours 1 to 12, 1 to 12 and is cut away to reveal a scale of the lunar month 1 to 28 [291/2], labelled 'DIES AETATIS LVNAE'. The inner portion of the volvelle has a circular aperture to reveal the phases of the moon and carries a central sun figure.

Around the volvelle is a wind rose with the eight principal directions and corresponding winds named in German. The corners of the face have foliate decoration.

The inner face carries a simplified astrolabe with an outer circle of equal hours, I to XII, I to XII, with the hours subdivided to quarters. The plate gives unequal hour lines 1 to 12, 1 to 12 for day and night and also shows the horizon as 'ORIENS' and 'OCCIDENS'. The rete includes only the ecliptic circle, with each zodiac sign represented by its symbol and divided to 10 and 2 and numbered by 10. Above the rete revolves a decorated index rule. The corners of the face are decorated with foliage engraving.

Folding into the central body of the instrument is an equinoctial ring dial with a string gnomon. The dial has an outer circle supported on a hinging base decorated with sea serpents. This circle, which carries a short scale representing latitudes of 42, 45, 48, 51 and 55?, would have been elevated to the vertical in use and aligned in the meridian. There is no visible means of support for keeping the circle vertical. On the inner circumference of the circle is a thin brass ring which carries the string gnomon and can be slid within the outer circle in order to adjust for latitude. The hour circle pivots within the ring and is placed perpendicular to the gnomon in use; again, there is no obvious means of fixing its position. On one side the hours run 1 to 12, 1 to 12, divided to half hours; on the other I to XII, I to XII in Gothic, divided to quarters.

The central body of the compendium carries a compass whose bowl is 43 mm in diameter. The base of the bowl, whose needle and glass are missing, is labelled in Latin with the four cardinal directions and is marked for variation. Around the compass is a scale of hours I to XII, I to XII, divided to quarters. There are the remains of red enamel between compass and hour scale and the corners of the face have foliage decoration.

The silvered base of the compass bowl carries an engraved classical female figure and is surrounded by 'table' of the latitudes of 68 places arranged as simply a string of characters.

The lower cover leaf is latched by a button-operated sprung clasp and its inner face carries an astrological table of the planetary rulers of the hours of day and night for a week. The 'DAGSTVNDEN' are tabulated separately from the 'NACHSTVNDEN' and the days of the week are given in German.

The outer face carries a horary quadrant and a shadow square, whose plumb line and bob are missing, though two small sights survive. The zodiac scales of the quadrant are labelled in German. Beyond the arc of the quadrant (divided to 10, 5 and 1 and numbered by 5) is a nude female figure within foliate decoration. The sides of the shadow square run 0 to 12, divided to 4 and 1 and numbered by 4. Within the shadow square there is foliate and line engraving.

The form of the lunar volvelle and horary quadrant, the German labelling of the wind rose, and the types of clasp are the same as Epact 30417; the two instruments are presumably by the same maker.

Stephen Johnston

Museum of the History of Science, Oxford
Inventory number 47446

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