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Inventory no. 52020 - Epact entry

Epact number: 25257


circa 1300; French ?
Brass; 158 mm in radius

Main text

This instrument is an example of the very rare quadrans vetus, or old quadrant. The presence of the sliding, curved plate moving in a slot above the degree arc makes the instrument adjustable for use in any latitude.

The volvelle on the back had become separated from the quadrant itself, which was preserved in the Lewis Evans collection in the Museum of the History of Science in Oxford. The two pieces were only recently reunited.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 52,020

Detailed text

The instrument is an example of the quadrans vetus or old quadrant. On one side of the instrument is a shadow square marked [0] to 12, divided to 1 and numbered by 4. Superimposed on the shadow square are unequal hour lines marked 1 to 6 and (with a mirror script) 7 to 12. A sliding curved plate, only half of which remains, is engraved with the names and days of the months and the names of the zodiacal signs. The limb of the plate is engraved with a scale of degrees from [0] to 90° divided to 1°, numbered by 5°. On this side of the quadrant is also a plumb bob with a little pearl as a bead.

The other side of the quadrant has a lunar volvelle, part of which is missing. On the volvelle are engraved the days of the lunar month, 1 to [29.5] numbered 1 to 29. On the quadrant are engraved in two circles a calendar scale with the months divided in 30 or 31 days as appropriate, with the 10th, 20th and last day numbered, then a zodiac scale with signs divided in the same way numbered from 10 to 30 by 10. All the inscriptions are in Gothic lettering. The lunar volvelle has a decoration of an eight-leaf flower in the centre.

The quadrant has a ring for suspension.

Ilaria Meliconi

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