Bernard of Verdun

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Bernard of Verdun

also known as Bernardusde Virduno

(France, fl. latter part of the thirteenth century)


Nothing is known with certainty about the life and career of Bernard of Verdun, except his place of origin (not necessarily the city on the Meuse), that he was a Franciscan, and that he was, professor in his order. It is possible that he is the Bernard who carried on a correspondance with the French scholar Nicolas of Lyra (ca. 1270–1349). Bernard’s contribution to medical astronomy is his Tractatus super totam astrologiam, most likely written in the late thirteenth century. It discusses a turquet similar to one described by Francon de Pologne in a manuscript dated 1284. If we assume that Bernard’s sketchy account of this instrument is derived from Francon’s more adequate description, we might consider 1284 as a possible terminus post quem for Bernard’s Tractatus. However, it is quite possible that Bernard’s work preceded that of Francon. The Tractatus, both a defense and a description of the Ptolemaic system, contains no astrological allusions. Bernard was familiar with the alternative system of al-Biṭrūjī, and he considered it unfavorably. He also rejected the theory of trepidation, which he associated with Thābit ibn Qurra.

In design, Bernard’s treatise is similar to the Almagest of Ptolemy. The first two sections are devoted to preliminary matters both descriptive and mathematical, such as the characteristics of the four elements and the celestial region, the spherical nature of the heaven and its circular motion, the uniqueness of the world, the insensible size of the earth relative to the heaven, the construction of a table of arcs and chords, and the determination of declinations and ascensions. The remaining sections (excluding the tenth) treat the motion of the sun and the moon, eclipses, and lunar parallax, as well as the motion of the five planets visible to the naked eye. The solar, lunar, and planetary models are all derived from Ptolemy.

Bernard followed the popular rationalization that combined solid spheres with epicycles and eccentrics. Since in this adaptation of Ptolemy the greatest distance of any celestial body is equal to the least distance of the body immediately above, Bernard provides tables for the relative sizes and distances of the sun, moon, and planets. The values given correspond to those in the Theorica planetarum of Campanus of Novara, and were undoubtedly canonical in the Middle Ages. The tenth section describes the turquet (turketum, torquetum), a complex instrument designed for a variety of uses, e.g., to find the positions of the fixed stars and the planets, the altitude of the sun, the hour of the day or night. This section also contains a brief account of another astronomical instrument, a kind of noctilabium or “star-clock” that could be used to determine the hour of night by observation of the pole star and two other bright stars, the date being known.

Bernard’s sources are few: Ptolemy, al-Battānī, and Aristotle are his most quoted authorities. His intent in his treatise is to present the Ptolemaic system in a clear and concise, although simplified, manner. It is possible that the work was originally intended to familiarize Bernard’s students with the main outlines of Ptolemaic astronomy while avoiding the complexities of the Almagest. Insofar as it is a technical treatise on astronomy, the Tractatus falls in the same medieval astronomical tradition as the “theory of the planets” literature. The only distinctive difference between Bernard’s treatise and others in this genreis his introductory defense of Ptolemy as having provided the only explanation that will account for astronomical phenomena.


1. Original Works. A modern edition of Bernard’s Tractatus super totam astrologiam is Polykarp Hartmann, ed., Vol. XV in the series Franziskanische Forschungen (Wed, 1961). This edition is based on two manuscripts in the Biblioothèque Nationale. Lynn Thorndike, however, mentions the following additional manuscripts: Erfurt, Wissenschaftliche Bibliothek. Amplonian Collection. F 393, f22-f43, and F 386, f1-f25 (where the work is entitled Speculum celeste): Vatican Palatine, 1380; Vatican (Bibliotheca Apostolica Vaticana) 3097, f51r-f71r. See also. Thorndike,“Vatican Latin Manuscripts in the History of Science and Medicine,” in Isis, 13 (1929–1930), 53–102; Thorndike and P. Kibre. lncipits of Mediaeval Scientific Writings in Latin, rev. and enl. ed. (Cambridge, Mass., 1963);

II. Secondary Literature. Works concerning Bernard are Pierre Duhem, Le système du monde, III (Paris, 1958), 442–460; E. Littré Histoire littéraire de la France, XXI (Paris, 1847), 317–320; and Emmanuel Poulle, “Bernardde Verdum et le turquet,” in Isis55 (1964), 200–208, esp.202, n.3.

Three works dealing with the turquet are R. T. Gunther, Early Science in Oxford, II (Oxford, 1923), 35–36, 370–375; L. Thorndike, “Franco de Polonia and the Turquet,” in Isis, 36 (1954–1946), 6–7; and Erans Zinner, Astronomische Instrument des 11–18. Jahrhunders (Munich, 1956), pp. 177–183, pate 11, no 2. See Zinner, p. 164, plate 57, for information on the noctilabium

Claudia Kren

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Bernard of Verdun

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