Students all over Europe, in universities, monastery schools and other institutions of learning, learned astronomy from Sacrobosco’s Sphere. Many of them took notes on the text and the lectures on the text that they attended. In a precious few cases, these notes have survived into the 21st century.
In the mid-17th-century a student named Gilles Rigaulx attended a set of lectures on Aristotelian philosophy in Valkenberg, a town in the southern Dutch province of Limburg, close to Maastricht. His notebook is preserved in the Wellcome Library in London. It contains notes on the following works of Aristotle: Physics, Metaphysics, On the heavens, On generation and corruption, Meteorology, and On the soul. Sandwiched between his notes on the Metaphysics and On the heavens, is Rigaulx’s summary of the Sphere. Rigaulx’s notes demonstrate that Sacrobosco’s Sphere was still being taught well into the 17th century, as was Aristotelian natural philosophy.
Rigaulx begins by stating that the four mathematical subjects are “Arithmetic, Geometry, Astrology and Music.” His notes follow the organization of Sacrobosco’s Sphere closely. He begins with definitions of a sphere. He describes the major circles that divide the spherical cosmos – the ecliptic (or equinoctial), the zodiac, the colures – and the minor circles – the tropics of Cancer and Capricorn and the Arctic and Antarctic Circles. He doesn’t include any of the diagrams or pictures that were commonly included in editions of Sacrobosco’s Sphere, so I’ve added the following annotated illustration of these circles from Joannes Regiomontanus, Epitome of Ptolemy’s Almagest (1496), for those unfamiliar with the terms.
Rigaulx explains the climactic zones on earth – torrid, frigid and temperate – as well as the ways the lengths of day and night vary throughout the year and in different parts of the earth. He finishes with a description of epicycles and eccentrics.
My favorite part of Rigaulx’s notes is the sketch of a man with an exaggeratedly large nose and chin, standing with his hands on his hips. This charming figure is on the page immediately before the notes on the Sphere start. I haven’t been able to find out who Gilles Rigaulx was, or what he did after his education in Aristotelian philosophy. I have no idea who the man in the doodle is, or if it is even supposed to represent a real person. But I love the reminder that students always have interests and lives outside of their academic studies
Further reading
Heinrich Kuhn, Aristotelianism in the Renaissance The Stanford Encyclopedia of Philosophy (Spring 2018 Edition)
The Sphere of Sacrobosco 