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Inventory no. 35777 - Epact entry

Epact number: 30417

Astronomical Compendium

Unsigned
Late 16th century; German
Gilt and silvered brass; 88 x 87 x 15 mm

Main text

This unsigned instrument bears some resemblance to the compendia of Christoph Schissler but it is constructed and decorated in a cruder form. It has many similarities to another unsigned German instrument (Epact 72560).

The compendium has a compass and horizontal string gnomon sundial, adjustable for latitude, as well as lunar and horary volvelles and a table for the latitude of places.

On the base is a horary quadrant illustrated with engraved images of instruments in use for astronomical observation and display, and for surveying.



Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 35,777



Detailed text

This square form compendium with two outer leaves and a central portion carries a suspension ring in one corner. Its sides are decorated with a rather crudely formed repeating square pattern and applied wire wave.

The upper cover is closed with a hook clasp and its outer face carries a volvelle for converting equal hours to Italian or Babylonian hours. The fixed outer scale of equal hours runs I to XII, I to XII with each hour divided to quarters. The Roman numeration from I to V is normal but afterwards runs IV, IIV, IIIV, XI, X, IX, IIX. The volvelle's hours run 1 to 24 and in use the 24 mark is set to the time of either sunrise or sunset. The former provides Italian hours and an opening in the volvelle plate reveals the number of hours of the night; the latter provides Babylonian hours and the number of hours of the day.

The centre of the volvelle carries an engraved image of a classical male and female figure representing Peace disarming War. The corner spaces are decorated with foliage engraving surrounding a square pattern and fleur-de-lis.

The inner face of this cover carries a silvered lunar volvelle within a fixed scale of hours 1 to 12, 1 to 12, 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 29[|1/2|], 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 similar decoration to the outer face.

The central portion of the instrument has a string gnomon horizontal sundial of a type frequently found in compendia by Christoph Schissler. The dial is adjustable for latitudes 42, 45, 48, 51 and 54°, each hour scale running 4 to 12 to 8 and subdivided to halves. The sprung gnomon support is in the form of an arc and is inscribed 'ELEVATIO POLI', with notches for the each of the five latitudes. The gnomon is catgut and held taut by a barrel spring under the dial plate. Around the central compass are the four principal directions named in Latin (including 'SEPTENDRIONE'). The compass bowl is 21 mm in diameter and a short travel lever on its underside allows it to be adjusted for variation.

The bottom of the compass bowl carries an engraving of the head of a classical male figure; the reverse of the dial plate has foliage engraving.

The lower cover leaf is latched by a button-operated sprung clasp and its inner face carries a circular table of the latitudes of 49 places. Around and in the centre of the table is foliage and line engraved decoration.

The outer face carries a horary quadrant and a shadow square, whose plumb line and bob are missing. 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 an engraved vignette showing a quadrant being used for astronomical and surveying measurement, as well as a sphere in use. The sides of the shadow square run 0 to 12, divided to 4 and 1 and numbered by 4. Within the shadow square is an engraved figure apparently reaching up to the heavens.

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 72560; the two instruments are presumably by the same maker.

Stephen Johnston

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