‘With his sharp lok perseth the sonne’: A new quadrant from Canterbury

Summary

This paper describes a medieval instrument, a quadrans novus, which turned up during archaeological works in England. The invention of the instrument by Profacius in 1288 is discussed in terms of two other medieval instruments, the quadrans vetus and the common astrolabe. The characteristics of the present instrument are compared with those of the seven other known medieval quadrants. It is shown that the new quadrant was made in England for explicit use with the Sun.

Acknowledgements

It is a pleasure to thank John Willson, director of the Canterbury Archeological Society, for inviting me to study this instrument.

Notes

¹J. Vernet, ‘Jacob ben Machir Ibn Tibbon’, Dictionary of Scientific Biography, edited by C.C. Gillispie, XIII (1976), 400. See also Encyclopaedia Judaica, Vol. 15 (Jerusalem, 1971), 1129–30. Most of the Hebrew translations by Profacius are of astronomical texts such as: On the Moving Sphere, an Arabic translation of the Greek treatise by Autolycus (c.330 bc), On the Use of the Celestial Globe, a treatise by the Arabic astronomer Qus[tdot]ā ibn Lūqā who died in c. 912, On the Use of the Astrolabe, a work from al-Andalus by Ibn al-Saffār (d.1035) and also from al-Andalus a treatise On the Use of the Saphea by al-Zarquāli (died 1100), an astronomer and maker of scientific instruments known in Spain as Azarquiel. For the manuscripts, see Moritz Steinschneider, Die hebräischen Übersetzungen des Mittelalters (Berlin, 1893; repr. Graz 1956), and José María Millás Vallicrosa, Tractat de l'assafea d'Azarquiel (Barcelona, 1933).

²E. Poulle, ‘Le quadrant nouveau médiéval’, Journal des Savants (1964), 148–67; 182–214, esp. 183. This paper reviews the medieval development of the instrument. A translation by Armengaud Blasius was made in 1290 under the supervision of Profacius, whereas a second edition dates from 1301. After 1301, the descriptions of the construction of the instrument have hardly changed.

³Poulle 1964 (footnote 2), esp. 203–5 and 212.

⁴For examples of early western Islamic astrolabes, see L.A. Mayer, Islamic Astrolabists and their works (Genève, 1956), plates II and III, and Paul Kunitzsch, ‘Traces of a tenth-century Spanish-Arabic Astrolabe’, Zeitschrift für Geschichte der Arabisch-Islamischen Wissenschaften, 12 (1998), 113–20.

⁵See, for instance, the hour lines on the back of the astrolabe made by A[hdot]mad ben [Hdot]usain ben Ba[sdot]o, in Sharon Gibbs with George Saliba, Planispheric Astrolabes from the National Museum of American History (Washington, 1984), 137–39, especially 40, figure 25.

⁶S.K. Victor, Practical Geometry in the High Middle Ages, Memoirs of the American Philosophical Society, 134 (1979); N.L. Hahn, Medieval Mensuration: Quadrans Vetus and Geometrie Die Sunt Partes Principales, Transactions of the American Philosophical Society 72, no. 8 (1984).

⁷David A. King, A vetustissimus Arabic treatise on the QUADRANS VETUS’, Journal for the History of Astronomy, xxxiii (2002), 237–55.

⁸A picture of the quadrans vetus from the Libros del saber de astronomia del Rey D. Alfonso X de Castilla, compiled, annotated and with commentary by Rico y Sinobas (Madrid 1863–67, reprinted in Madrid 1999), was published in King 2002 (footnote 7), 241.

⁹R. Knorr, ‘Sacrobosco's quadrans: Date and sources’, Journal for the History of Astronomy, xxviii (1997), 187–222. See also M. Archinard, ‘The diagram of unequal hours’, Annals of Science xlvii (1990), 173–90.

¹⁰W.R. Knorr, ‘The Latin sources of quadrans vetus’, in Texts and contexts in ancient and medieval science: Studies on the occasion of John E. Murdoch's seventieth birthday, edited by E. Sylla and M.Mc Vaugh (Leiden, 1997) 23–67.

¹¹Knorr 1997, ‘The Latin sources of quadrans vetus’ (footnote 10), 23–67, and the plates I–IV following on 64.

¹²See the copy in the Museum of the History of Science, Oxford, SPHAERA, 1 (1995), 2 and www.mhs.ox.ac.uk/sphaera/

¹³There is an enormous literature on the early days of the astrolabe in the Latin West; see, for instance, the recent discussion by Charles Burnett, ‘King Ptolemy and Alchandreus the Philosopher: The earliest Texts on the Astrolabe and Arabic Astrology at Fleury, Micy and Chartres’, Annals of Science 55 (1998), 329–68. A convenient summary of Greek, Arabic and early Western developments is found in Richard Lorch, ‘The literature of the astrolabe to 1450’, in Koenraad van Cleempoel, Astrolabes at Greenwich. A Catalogue of the Astrolabes in the National Maritime Museum, Greenwich (Oxford, 2005), 23–30.

¹⁴Kunitzsch 1998 (footnote 4).

¹⁵David A. King, Islamic Astronomical Instruments (London, 1987), chapter I, 8–10.

¹⁶King 1987 (footnote 15), chapter XIV, 373–76.

¹⁷A very clear summary of the historical development of the sine and cosine is presented by Menso Folkerts, ‘Die Beitrage von Johannes von Gmunden zur Trigonometrie’, in Rudolf Simek and Kathrin Chlench (eds.), Johannes von Gmunden (c.1384–1442) Astronom und Mathematiker (Wien, 2006), 71–89.

¹⁸Treatises on the quadrans vetus and the quadrans novus included texts parallel to those on the common astrolabe and to each other. A detailed comparison between these texts is needed before the relation between the various instruments can be established with some certainty, as is emphasized by Knorr 1997, ‘The Latin sources of quadrans vetus’ (footnote 10), 27 and note 20.

¹⁹This information was kindly provided by John Willson, director of the Canterbury Archeological Society.

²⁰These seven instruments have been described by Elly Dekker, ‘An Unrecorded Medieval Astrolabe Quadrant from c.1300’, Annals of Science, 52 (1995), 1–47. At the time of writing, one of these instruments (labelled PCII in this study) was not available for a detailed investigation. It was later described in the Sales Catalogue Christie's South Kensington, Thursday 2 March 1995, lot 198, 35. This copy is now in the British Museum. It is here referred to as the London instrument. In this study, these quadrants are denoted according to their present location, except the one in a private collection, which is labelled PCI.

²¹The metallic contents of the instrument has been analysed by Peter Northover of Oxford Materials. Details are presented in his report ‘Analysis and metallography of a copper alloy quadrant’.

²²This comparison with the properties of the other known copies is based on the data in Dekker 1995 (footnote 20), 24, table 3.

²³Photos of the other instruments are in Dekker 1995 (footnote 20).

²⁴The mediation of a star is the distance along the ecliptic from the vernal equinox to the point of intersection of the hour circle through the star and the ecliptic. For the Sun, or a star in the ecliptic, the mediation equals the ecliptic longitude.

²⁵The * stands for an unclear abbreviation mark.

²⁶In treatises on the quadrans novus, the zenith is only mentioned in connection with circles of constant azimuth which pass through the zenith but are perpendicular to the horizon.

²⁷There are a number of medieval astrolabes where one finds the letter B on the back to indicate leap years. See, for example, the back of the astrolabes no. 293 and no. 295 in R.T. Gunther, The Astrolabes of the World (London, 1976), 469 and 472. Another example can be seen on the back of AST0570 in the collection of the National Maritime Museum, Van Cleempoel (footnote 13), 117.

²⁸For the leap of the Moon, see Bede, The Reckoning of Time, translated with introduction, notes and commentary by Faith Wallis, Liverpool, 1999, esp. 326–28.

²⁹For the perpetual calendar see O. Pedersen, ‘The ecclesiastical calendar and the life of the church’, in G.V. Coyne, M.A. Hoskin and O. Pedersen (editors), Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary, 1582–1982, Città di Vaticano (Vaticano,1983), 17–74; W.E. van Wijk, Le Nombre d'Or, Etude de chronologie technique suivie du texte de la Massa Compoti d'Alexandre de Villedieu avec traduction et commentaire (The Hague, 1936), 143–55.

³⁰Details are presented in the report by Peter Northover (footnote 21).

³¹Here it is presumed that a calendar or almanac was available to find the sign and degree of the Sun in the zodiac for a certain day of the year.

³²As an example of tabular data, one can mention the calendar by John Somer, who added precise data on the place of the Sun in the zodiac. He added also the values of the meridian altitude: ‘Afterwards is written the Sun's altitude at midday, with which you will thus easily be able to find the artificial time on a quadrant’; see The Kalendarium of John Somer, edited by Linne R. Mooney, The Chaucer Library (Athens, 1998), 101. The quadrant referred to here is not necessarily a quadrans novus. It could be a horary quadrant of the type made for Richard II and John Holland around 1400 for finding the (exact) time in equal hours where knowledge of the meridian altitude is likewise an important requirement; see Silke Ackermann and John Cherry, ‘Richard II, John Holland and three Medieval Quadrants’, Annals of Science 56 (1999), 3–23.

³⁴The Etymologies of Isidore of Seville, edited by Stephen A. Barney, W.J. Lewis, J.A. Beach, Oliver Berghof, with the collaboration of Muriel hall (Cambridge 2006), Book XII.vii.10–11, 264.

³³This is not the only association of the eagle in antiquity. In early Carolingian manuscripts on Germanicus’ Aratea, the eagle was also depicted carrying Jupiter, see Mechthild Haffner, Ein antiker Sternbilderzyklus und seine Tradierung in Handschriften vom Frühen Mittelalter bis zum Humanismus. Untersuchungen zu den Ilustrationen der ,,Aratea” des Germanicus (Hildesheim, Zurich, 1997), 34–35.

³⁵Geoffrey Chaucer, The Parliament of Fowls, line 331.

³⁶Dekker 1995 (footnote 20)