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Dated to 1400; English
Gilt brass; 89 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? N with the names of the months given as 'Ian Feb Mar Apl Mai Jun Jul Au Sep Oct No Dec'. The upper part contains a circular Easter table labelled 'Tabula paschal{is}' on a horizontal scroll in the centre. This circle contains 4 rings with the following punched markings (from the outside): 1) '+ Mar ti us: + A pri pri lis:'; 2) dates from 22nd [March] to 25th [April] i.e. the limits of the Easter dates (the space for the 21st March, the earliest Easter limit, is left blank); 3) a list of day letters starting with d; 4) Golden Numbers.

Along the left hand edge is a list of dominical letters for a complete 28-year solar cycle (from the top to the bottom): 'c/d b A g e/f d c b g/A f e d b/c A g f d/e c b A f/g e d e A/b g f e'. The first two entries have been obliterated by a hole drilled in the tip of the quadrant at a later date.

The front is marked as an horary quadrant with nine hour curves for equal hours, 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 as an altitude scale 0? to 90?, numbered by 10? and divided to single degrees. A shadow scale is superimposed on the hour lines, both sides divided into 12 digits, every second digit labelled.

There are two sighting vanes mounted on one edge. The pin from which the plumb line is suspended may be a later replacement; the plumb bob itself is missing.

The instrument was purchased in 1856 in the Whincopp sale 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), p. 56, no. 147; 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 1856,6-27.155

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