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London, John oflocked

(fl. c. 1260)
  • Wilbur R. Knorr

London, John of (fl. c. 1260), mathematician, was praised by Roger Bacon (d. 1292/1294) in his Opus tertium as one of two 'perfect' mathematicians (the other being Peter of Maricourt, called Peregrinus, author of a noted tract on the magnet), and judged superior to two other 'good' mathematicians, namely, Campanus of Novara, the prolific editor and writer on geometry and astronomy, and Master Nicolas, tutor of Amaury de Montfort (d. c.1300), third son of Simon de Montfort, earl of Leicester (d. 1265). Thus ranked with Peter and Campanus, John must have been a mathematician of distinction, known to Bacon at Paris in the 1260s.

Further data are conjectural. John of London may perhaps be the John Bandoun whom Bacon cites at about the same time, in conjunction with Robert Grosseteste (d. 1253) and Adam Marsh (d. 1259), as having flourished in the mathematical sciences. He may also be the Paris master, John of London, author of a short letter on astronomical questions posed to him by his own master, 'R. de Guedingue', and the accompanying table of stellar co-ordinates, established by observation at Paris in 1246 (Paris, Bibliothèque Nationale, MS Lat. 7413/2, fols. 19v–21, 36). In an edition of the same star catalogue, dated four years later, its compiler, Roger of Lincoln, cites Master John of London as (astronomus famosus), designer of a form of astrolabe used for verifying the star table (Erfurt, Stadtbibliothek MS Amplon. 4° 369, fol. 217). Kunitzsch, noting John's wide learning in astronomy and his unusual effort to establish the co-ordinates through observation, shows that John's table significantly influenced the tabulation and nomenclature of the stars in later catalogues. John may also be the Master John of London, owner and corrector of a copy of the De aspectibus of Alhazen (Ibn al-Haitham; d. 1038) that was consulted by Guido de Grana in his correction of another copy in 1269 (Edinburgh, Royal Observatory, MS Cr.3.3, fol. 189).

Other proposals made concerning Bacon's Master John of London doubtless are false. In particular, he cannot have been the gifted Franciscan friar John (not denominated ‘of London’, whose mathematical training was sponsored by Bacon; for the friar was barely twenty years old when Bacon wrote the Opus tertium.

Another John London (fl. c. 1290–c. 1325), astronomer, is recorded as the donor of a substantial collection of books to the library of the Benedictine abbey of St Augustine in Canterbury. From the extant inventory of the library, made late in the fifteenth century, it may be inferred that John London contributed over eighty books, including twenty-three in mathematics and astronomy, another twenty-three in medicine, and the balance in history, philosophy, and theology. Apart from works long standard, the astronomical titles display a concentration on research undertaken at Paris from the 1290s to the mid-1320s, for example, tracts by Peter of Denmark (Dacia) and Gillaume de St Cloud early in this period and by Jean de Lignières toward its end. No titles of later currency are discernible. Most of the thirteen surviving books from this donation have ex libris markings that identify the owner as either magister or frater. In one of them, Bodl. Oxf., MS Digby 174, fol. 99, a heading gives the owner's name as 'Johannes de Lond. cum monoculo', and affixes a rough sketch of a head, wearing a sort of master's cap, with a conspicuous left eye, but missing the right eye.

It can be inferred that John London was active as an astronomical master at Paris over three decades, before retiring to St Augustine's, where for a while he seems to have shared his astronomical interests with Michael Northgate. He appears not to be associable with anyone else attested under the same name. Against the suggestion that he may have been Bacon's protégé, the Franciscan friar John, is the later date of the book donor's activity, his Benedictine association, and the wealth implied by his substantial library. And against suggestions that he may have been the 'Dom. Joh. de London.' to whom the monk Reginald Lambourne wrote concerning the eclipse of 1363 (Bodl. Oxf., MS Digby 176, fols. 50–53v), is the implied gap of four decades between this date and the latest title in the book owner's astronomical collection; it has also been argued that this correspondent might be the Oxford scholar John Ashenden (d. in or before 1368).


  • R. Bacon, ‘Opus tertium’, Fr. Rogeri Bacon opera quaedam hactenus inedita, ed. J. S. Brewer, Rolls Series, 15 (1859)
  • Communia mathematica fratris Rogeri, ed. R. Steele [1940], vol. 16 of Opera hactenus inedita Rogeri Baconi, ed. R. Steele and F. M. Delorme [1905–40]
  • P. Kunitzsch, Typen von Sternverzeichnissen (Wiesbaden, 1966)
  • N. R. Ker, ed., Medieval manuscripts in British libraries, 2 (1977)
  • Emden, Oxf., 2.1157
  • J. C. Russell, ‘Dictionary of writers of thirteenth century England’, BIHR, special suppl., 3 (1936) [whole issue]
  • M. R. James, The ancient libraries of Canterbury and Dover (1903)
  • A. B. Emden, Donors of books to St Augustine's Abbey, Canterbury (1968)
  • L. Thorndike, A history of magic and experimental science, 8 vols. (1923–58), vol. 3


  • Bibliothèque Nationale, Paris, MS Lat. 741 3/2, fols. 19v–21, 36
A. B. Emden, , 3 vols. (1957–9); also (1974)
Bulletin of the Institute of Historical Research
Oxford Historical Society