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Inventory no. 38947 - Epact entry

Epact number: 50307

Quadrant

Signed by Christian Heiden
Dated 1553; German
Brass; 102 mm in radius

Main text

This unusual quadrant is in the form of a square instead of a quarter of a circle, as was more common. Besides scales for unequal hours and the shadow square, features commonly found on quadrants, this example has a grid for finding the latitude or the declination of the sun by means of the observation of the sun's altitude at noon.

On the back is a Regiomontanus-type dial and a table of latitudes, and finely engraved foliage decoration.



Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 38,947



Detailed text

The quadrant has the form of a square instead of a quarter of a circle. It has sights on one straight edge and a movable rule pivoted at the apex. The rule has only one sight, which can be covered, and bears the inscriptions 'DIOPTRA' and '{L}INEA FIDUCIAE'.
On one side of the quadrant, where the rule is, is engraved next to the apex a shadow square from [0] to 12 to [0] by 3 to 1, with the indications 'VMBRA RECTA', 'VMBRA VERSA', 'VMBRA MEDIA'. The unequal hour lines are superimposed on the shadow square and are indicated 'Horae inaequales'. On a circle centred in the apex are engraved the symbols of the zodiacal signs indicating the declination of the sun and the indications 'Hyemis et veris' ('Winter and spring') and 'AEestatis et Autumni' ('Summer and Autumn').

Further away from the apex is a diagram with the declination of the sun, indicated by the symbols of the zodiacal signs and each divided into 3 parts, and latitudes marked from 25 to 67 divided to 5 and to 1, numbered by 5. They are indicated also with the inscriptions '· SCALA LATITVDINIVM ·' and '· ZODIACI LATITVDINVM ·'.

A circle centred in the apex indicated 'QVADRANS GENERALIS' is graduated [0] to 90 divided to 5 and to 1, numbered by 5. On the borders of the square is another shadow square from [0] to 60 on each side, divided to 5 and to 1, numbered by one. It is inscribed 'QVADRATVM GEOMETRICVM'. Another inscription next to the latitude lines reads '· QVADRANS GENERALIS · ACCOMMODATVS AD PERCIPIENDAS DE: CLINATIONES SIG: NORVM · IN DIVEr SIS locis · et latitu:dine variantibus' and next to the opposite edge to the apex is the signature 'CHRISTIANVS HEIDEN MATHEMATVM studiosus faciebat ANNO CHRISTI · M · D · LIII ·'.

On the other side of the square is a Regiomontanus-type dial with the indications 'ZODIACI LATITVDINVM' and 'SCALA LATITVDINVM', with latitudes from 30 to 60 divided to one, numbered by two. On its sides is foliate decoration, and below it is a table with the zodiac signs, indicated 'SIGNA ZODIACI Generalis', and common hours, indicated 'HORAE POST MEDIVM NOCTIS ET ANTE MERIDIEM', numbered from 3 to 12, and 'HORAE POST MERIDIEM' numbered from 1 to 9. There is the indication for 'Latus septentrionale' and 'Latus meridionale'.

On the right-hand side and at the bottom of the quadrant is a list of latitudes for 37 German towns, indicated 'CATALOGVS LATITVDINES CELEBERRIMARVM VRBIVM SVPERIORIS Germaniae'. On one of the edges are two sights which can be both closed and every edge has engraved a direction, '· MEDIVM COELI ·', '· LATVS BOREVM ·', '· MEDIVM NOCTIS ·', '· LATVS AVSTRALE ·'.

Ilaria Meliconi

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