Roger of Hereford

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(fl. England, second half of the twelfth century)

astrononmy, astrology.

Very little is known with certainty about Roger of Hereford’s career. There has been considerable speculation seeking to identify him with several other contemporaneous Englishmen named Roger. At the beginning of his Compotus, which is dated 9 September 1176, Roger refers to himself as “young” but adds that he has devoted many years to learning. The period of his activity probably lies in the decade from 1170 to 1180.

Roger of Hereford wrote several astronomical works. The Compotus, which consists of five books of twenty-six chapters, is critical of other Latin computists. The work is dedicated to Gilbert Foliot, bishop of Hereford until 1163, and then bishop of London. Roger also composed a set of astronomical tables for the latitude of Hereford, dated 1178, based on the Toledan and Marseilles tables. His other astronomical treatises include De ortu et occasione signorum and Theorica planetarum. Taking into consideration the period during which the latter work was probably written and the dates of the availability of Ptolemy’s Almagest in the Latin West (1160, 1175), Roger’s Theorica is likely one of the earliest works in that genre in the post-Latin Ptolemy period. The Digby manuscript of the Theorica (Digby MS 168, fols. 69 f.) is entitled “Incipit theorica Rogeri Herefordensis”; a later hand has added “floruit a.d. 1170 sub Henrico 20.” In the Theorica, Roger describes the “Hindu” procedure for the determination of’planetary latitudes, a technique that entered the West in the Toledan Tables as well as from other Arabic Sources. He also provides the Ptolemaic method for latitudes, which he calls “more likely.”

In addition to these astronomical contributions, Roger of Hereford wrote several works on astrology. One of these, Liber de divisione astronomiae, in the Bibliothèque Nationale manuscript, begins, “In the name of God the pious and merciful…,” which has a decided Arabic flavor and would indicate that the work might be a translation. Other astrological treatises by Roger include De quatuor partibus iudicorum astronomie, De iudiciis astronomie, Iudicia Herefordensis, and De tribus generalibus iudiciis astronomie. Several of these treatises apparently are extracts from the four-part work on astrology. Roger also wrote De re metallicis.

Roger of Hereford can be placed in that group of twelfth-century Englishmen who were instrumental in bringing Arabic scientific materials to the Latin West, either through direct translation or in the form of adaptations of Arabic sources. The group includes Robert of Chester, Daniel of Morley, Alfred of Sarashel (Alfred Anglicus), and Adelard of Bath. Whether Roger knew Arabic or traveled to Spain is unknown. Alfred of Sarashel, who translated the Arabic version of the De vegetabilis or De plantis, a work attributed to Aristotle but written by Nicholas of Damascus, dedicated his translation to Roger.

Whether Roger’s activity continued into the 1180’s is unknown. He may have been the Roger, clerk of Hereford, who served as itinerant justice with Walter Map in 1185. It has also been suggested that he died as a monk at the abbey of Bury St. Edmunds.


See Pierre Duhem, Le système du monde, III (Paris, 1958), 222–223, 520–523; C. W. Haskins, Studies in the History of Mediaeval Science (Cambridge, Mass., 1927), 87, 123–128; Josiah C. Russell, “Hereford and Arabic Science in England,” in Isis, 18 (1932), 14–25; and Lynn Thorndike, A History of Magic and Experimental Science, II (New York, 1923), 181–187, 260.

Claudia Kren

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Roger of Hereford

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