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Dated 1399; English
Gilt brass; 90 mm in radius

The lower half of the back of the instrument contains a list of the sun's noon altitudes during the year for the latitude 52( with the names of the months given as 'Ian' 'Feb' 'Mar' 'Apr' 'May' 'Iun' 'Iul' 'Aug' 'Sept' 'Octo' 'Nou' 'Dece'. The upper part contains a circle of 28 dominical letters beginning with 'e' for 1399. This circle is labelled 'Tabula bisexti' ('table of leap-years') on a horizontal scroll in the centre. Inside the circle there is a hare or rabbit in front of a tree.

The front bears markings for an horary quadrant with nine equal hour curves, punched '.4./.8. .5./.7. .6./.6. .7./.5. .8./.4. .9./.3. .10 /.2. .11./.1:. .12:'. The hour curves are intersected by a circular arc representing the equinoxes. The rim is marked for an altitude scale 0? to 90?, numbered by 10? and divided to single degrees.

The vacant space is taken up by a circle with a stag with chain and crown, known to be the badge of Richard II, surrounded by an unexplained legend ': Pri .3. di .3. pascha fi :.' There are two sighting vanes mounted on one edge. The post from which the plumb line is suspended is a later replacement; the plumb bob itself is missing.

A date scale edge marked with zodiac signs along the left and a set of hour numerals near the equinoctial line are later additions, supposedly from the Elizabethan period.

The instrument was acquired from the Reverend Greville J. Chester in 1860 and is described and illustrated 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. 55 f. no. 146 (with plates XVII, XVIII); G. L'E. Turner, "Charles Whitwell's addition, c. 1595, to a 14th-century quadrant", The Antiquaries Journal, 65 (1985), pp. 444-5 (with plates XXIXb, C and CI); S. Ackermann and J. Cherry, "Richard II, John Holland and Three Medieval Quadrants", Annals of Science (in preparation).

Silke Ackermann

British Museum, London
Registration no. MLA 1860,5-19.1

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