A rare and early brass astrolabe quadrant from the House of Agnes, Canterbury, probably English,  14
Lot 124
A highly important brass astrolabe quadrant or quadrans novus, English, 14th century,
Sold for £138,000 (US$ 233,872) inc. premium
Auction Details
A rare and early brass astrolabe quadrant from the House of Agnes, Canterbury, probably English,  14
Lot Details
A highly important brass astrolabe quadrant or quadrans novus, English, 14th century,
the copper based alloy instrument with two sight vanes and hole for for silken cord and weight (both now missing), engraved on one face with shadow square with scales marked 3, 6, 9 and 12, together with unequal hour lines, two semi-circles for finding the corda recta and corda versa, the remaining curves and scales are part of the folded astrolabe, at the carved border are scales to measure angles and right ascensions, inside this scale is a graduated zodiacal scale for twelve zodiacal signs,this scale is related to the folded ecliptic, the most characteristic feature of the quadrans novus, consisting of a northern branch extending from the equator (Aries) to the Tropic of Cancer (Cancer) and back again (Virgo) and a southern branch extending from the equator (Libra) to the Tropic of Capricorn (Capricorn) and back again (Pisces). The names of the zodiacal signs engraved on the northern branch are ARIES TAVR(VS) GEMIN(I) [CANC(ER] [LEO][VIRGO], the southern branch signs are LIBRA SCORPIVS SAGI [CAPRICORN] [AQVARI(VS)] [PISC(ES)], also engraved is a folded horizon, on the reverse of the quadrant is a representation of an eagles that moves over two two concentric circles with calendar information (now not moving due to oxidisation), the inner ring is engraved with the ordinal number of a 19-lear lunar circle, the outer ring is engraved with the corresponding date of the Easter Moon (the first full moon after the 21st March), each date is marked with a number, a letter followed by the first letter of the month radius 70mm, sides 68cc, thickness 1.5 to 2mm, weight 40 gms

Footnotes

  • Footnote
    Only seven astrolabe quadrants had been recorded to date. The present example, the eighth, is quite small, having a radius of only 70mm. Of those already known, the average size is 280mm radius and the smallest is 80mm radius.
    For a comprehensive study of the hitherto known astrolabe quadrants, see: Elly Dekker, "An Unrecorded Medieval Astrolabe Quadrant from c.1300", Annals of Science, 52(1995), 1-47

    Provenance
    The astrolabe quadrant was found in July 2005 by Andrew Linklater of the Canterbury Archaeological Trust during an archaeological watching brief at the House of St Agnes, St Dunstan's Street, Canterbury, Kent

    The Inventor
    It has been accepted that the astrolabe quadrant was invented by Jacob ben Machir ibn Tibbon of Montpellier (c.1236-1305) who was a member of a family that originated in Granada, his forebears noted for their translations from Arabic into Hebrew. Among the scientific, or astronomical works that he translated are: Euclid's Optics, the Sphere of Menelaus, and texts of the globe among other subjects. Those books of his own devising included the Quadrant of Israel written in Hebrew between 1288 and 1293, which was translated into Latin in 1299. here was the description of a new instrument that became known as the quadrans novus, in distinction to the quadrans vetus devised by Robertus Anglius in about 1276, when in Montpellier.

    Scientific Examination
    Thanks are due to Dr Brian Gilmour of the Oxford University Research Laboratory for Archaeology and the History of Art, for removing corrosion products, revealing a well preserved dense, dark green patinated surface. A metallurgical analysis was kindly undertaken by Dr Peter Northover using electron-probe micro-analysis, at the Oxford University Materials Characterisation Service.
    A full metallurgical report with table of the percentages of the elements present is available on request.

    Bonhams wish to thank both Elly Dekker and Professor Gerard L'E Turner. DSc. D.Litt., for their assistance with research for the preparation of these cataloguing notes and description.
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