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Signed by Gillis Coignet
circa 1575; Antwerp
Gilt brass; 182 mm in diameter

The rim of the mater bears a 24 unequal hour scale and a 360? altitude scale. The hour scale is numbered I to XII twice starting at the throne, divided to 4 minutes. The altitude scale is numbered by 10? clockwise starting at the east point, divided to 5? and subdivided to single degrees. The rim is riveted to the back plate and has a recess at 12 o'clock underneath the throne to accommodate the tongues of the plates.

The inside of the mater is blank.

The throne is of unusual shape, consisting of two trefoils connected by a strap and two stylized leaves pointing upwards. It is riveted to the back plate.

The rete, with a heart shaped design inside the ecliptic, gives the names of 24 stars. It has been heavily repaired and some of the engravings are lost due to the soldering.

The ecliptic is marked with the usual Latin names of the zodiac. Each sign is divided to 30?, numbered by 10?, divided to 5? and subdivided to single degrees.

The four plates are marked on both sides (except 4b) with the circles for the equator ('Aequinoctialis' on 3b) and the tropics ('Tropicus cancri' and 'Tropicus capricorni' on 3b), the azimuths for every 10? (numbered by 10?), almucantars for every 2? (numbered by 10?), lines for the unequal hours (numbered twice on the inside and on the outside 1 to 12) and the markings for the astrological houses ('domus' on 3b) in the manner of Regiomontanus (marked 1 to 12). The twilight curve is indicated ('Linea crepusculina vel aurore' on 3b). The 'HORIZON', 'Oriens' and 'Occidens' are marked on 3b. The plates are marked and laid out for the following latitudes ('Elevat{io}' and 'Ad elevatio polar{is} on 3b respectively): 1a) 36?; 1b) 39?; 2a) 42?; 2b) 45?; 3a) 48?; 3b) 51?; 4a) 54?; 4b) markings for a 'HORIZONTALE CATHOLICUM' with horizons for every 2? numbered by 10?. The 'Horizon rectus', the equator ('Aequinoctialis'), the meridian line ('Linea meridiana') and the tropic of Capricorn ('Tropicus capricorni') are marked.

The back bears several circular scales as follows (from the outside):

1) A 360? altitude scale, numbered by 10? (with divisions to 5? and subdivisions to single degrees) four times 0? to 90? starting at the east west line.

2) A scale with the usual Latin names of the zodiac with their symbols, each sign divided to 30?, numbered by 10?, divided to 5? and subdivided to single degrees.

3) A Julian calendar scale with the usual Latin names of the months, divided to the corresponding number of days, numbered by 10, divided to 5 and subdivided to single days. The equinoxes correspond with March 11 and September 13 1/2.

The bottom half of the empty space inside these circles is taken up by a double shadow scale ('SCALA ALTIMETRA') marked 'Vmbra recta' and 'Vmbra versa' to the base of 12, numbered by 3 and divided to single digits. The shadow scale is surrounded by a foliate scroll design with the signature 'AEgidius quiniet antverp faciebat' in a cartouche at the bottom.

The top half is taken up by a double horary quadrant for unequal hours, marked 1 to 6 to 12. In the centre is an escutcheon surrounded by mounted trefoils.

The rule and the alidade (with sighting vanes with both holes and sights) are both counterchanged and decorated with the same foliate scroll design as the back. The reverse of the rule has some old markings with a scale numbered 20 to 70 numbered by 10 still visible.

The instrument was purchased in 1895 and is described in F. A. B. Ward, A Catalogue of European Scientific Instruments in the Department of Medieval and Later Antiquities of the British Museum (London, 1981), pp. 117 ff., no. 339.

Silke Ackermann

British Museum, London
Registration no. MLA 1895,7-23.61

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