Tractatus de sphaera, Algorismus, Computus lunaris

Circa 1256-1270

This striking manuscript includes three historiated initials that have been linked to the style of the Bari workshop in Paris (1250-70), all showing Sacrobosco teaching astronomy to tonsured students (fols. 1r, 29r, 43v). In addition to the diagrams of eclipses and solar and lunar motion that it shares with LJS 26, as well as a richly colored diagram of the Earth’s climates (fol. 16v), it also contains a circular table of solar conjunctions (fol. 40r) and an ouroboros (fol. 36r). The third text in this volume describes the computation of civil and ecclesiastical calendars.

Little is known about Sacrobosco’s life apart from his tenure as a professor of mathematics at the University of Paris, beginning in the 1220’s. He may have been born in Holywood, Yorkshire, and he was known during his lifetime for criticizing the imprecise Julian calendar, which had developed a total error of about ten days by the late thirteenth century.

UPenn LJS 216

28v-29r

Johannes de Sacrobosco (c. 1195–c. 1256)

Paris, France (?)

Latin

Parchment

58

165 x 110 mm

Modern velvet

Robert B. Honeyman; John D. Stanitz; Lawrence J. Schoenberg

Crofton Black, ed., Transformation of Knowledge: Early Manuscripts from the Collection of Lawrence J. Schoenberg (London: Paul Holberton, 2006), 39-40.