France, c. 1630

ASTRONOMY – Manuscript, "Traicté de l’Air," [France, c. 1630].

In French and Latin. 279 pages, 186 x 138mm in a fine civilité hand, brown ink on paper, with 5 full-page and 115 half-page or smaller drawings in text and 10 tables, text ruled in blind, two unbound sheets with drawings loosely inserted. Cotemporary vellum (head piece missing from spine).

A fine treatise on cosmology and mathematics, written in an excellent hand in civilité and with drawings and diagrams of exceptional quality. It includes a detailed exposition on the use of a proportional compass for a variety of problems. The work is divided into sections, the first of which, comprising 88 pages, is headed "Traicté de l’air", and begins with 38 definitions, followed by propositions and theorems relating to the nature of the atmosphere and the winds. This is followed by "De la terre et de l’eau", comprising 25 pages presented in a similar format. It is largely concerned with refuting the heliocentric system of Copernicus, who is described however as one of the greatest astronomers who ever lived. The third section is "De coelo et syderibus", written in Latin. It is the largest section in the work and comprises 90 pages. It presents a Tychonic planetary system, and examines in detail planetary and lunar motion, theories of comets, and presents calculations for planetary distances. It is a highly technical discussion of celestial motion. The next section, comprising six pages, is titled "Praxes astronomicae", and is also in Latin. This is followed by the final section, which is on the proportional compass, comprising 79 pages. The first part is titled "Premiere partie de pratiques du compas de proportion en geometrie". It presents a series of problems and solutions for calculating areas and volumes of regular and irregular shapes and objects. This is followed by chapters on the use of the proportional compass in music, optics, perspective, art, architecture, fortification, and cosmography. Given the mixture of the theoretical and practical, and French and Latin text, along with the very detailed and technical exposition of the Tychonic system, this probably represents the curriculum of a mathematics and physics course at a Jesuit institution.