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Diptych Dial
Signed by Hans Troschel
Dated 1618; Nuremberg
Ivory and brass; 102 x 166 x 16 mm

The outer side of the upper leaf has a wind rose with 32 directions, numbered and named in German. There is also a brass index arm and a compass viewing hole. Around the wind rose is a circle with the main winds named in Latin, and the inscription 'MONSTRO VIAM PERGE SECVRVS'. In the spandrel spaces is a decoration of fruits and foliage. On the top of the leaf is the inscription '[star] TEMPVS SVMPTVS EST PRECIOSISSIMVS [star]'. On the bottom part of the leaf is a polar pin gnomon dial (pin missing) with hours numbered from 7 to 12 to 5 and the declination of the sun indicated by means of the symbols of the zodiacal signs.

The inner part of the upper leaf has two pin gnomon dials, one on the right and one on the left. The left one indicates 'QVANTITAS DIEI' from 8 to 16 twice, and common hours numbered from VII to XII to V in red. The declination of the sun is also indicated with the symbols of the zodiacal signs. Below this dial is another pin gnomon dial indicating 'HORAE AB ORTV' from 1 to 11, and the inscription 'TEMPORE OMNIA MVTANTVR' (' time changes everything'). On the left side the pin gnomon dial indicates '[star] PLANETARVM HORAS [star]' from 1 to 12 with a small sun effigy, and below it another pin gnomon dial indicates 'HORAE AB OCCASV' from 13 to 24 with the symbols of Libra and Cancer, and the inscription 'NIHIL EST FVGACIVS TEMPORE' ('nothing is more fugitive than time'). Between the dials are the holes for adjusting the latitude to 57, 54, 51, 48, 45, 42 and 39 degrees with the indication 'DIE POLVS GRADTEN'. On the lower part of the leaf is a table with 72 cities and latitudes.

The inner part of the lower leaf has a compass (glass and ring missing) with the names of the cardinal points and the indication of magnetic deviation. Around it is the string gnomon dial for the aforementioned latitudes, all indicated twice on their circles, which have the hours numbered from 4 to 12 to 8, but only the larger circle for latitude 57 has lines and dots for the half and quarter hour. On the top of the circles is the indication 'HORAE AB MERIDIE' and in the spandrels, as below the circles, a foliate decoration. Below the decoration is a pin gnomon polar dial, indicating Italian hours from 9 to 24 and Babylonian hours from 1 to 15. The declination of the sun is indicated with the symbols of the zodiacal signs and the solstices are indicated 'SOLSTICIVM ESTIVVM [star]' and 'SOLSTICVM HIEMALE [star]'. On the borders of the leaf is a dial with common hours numbered from 6 to 12 and from 1 to 6, which was supposed to be used with the upper leaf as a gnomon.

The outer part of the lower leaf has a pierced lunar volvelle and aspectarium, with a table of epacts engraved '[star] EPACTA GREGORII [star]' and 'EPACTA IVLIANII [star]'. The maker's mark is punched twice in the circle for hours. Below it is a planetary table, indicated 'PLANETEN TAFEL' and showing the ruling planet for each day of the week. On its sides are two figures, perhaps allegorical, and the remaining space is filled with decoration of angels and foliage. There are four bun feet, and the maker's mark (a six-pointed star) is punched twice next to the hinge. On the left edge are two compartments, for stowing the pin and for the wind vane (missing).

Ilaria Meliconi

Museum of the History of Science, Oxford
Inventory number 71930

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