FERNEL Jean De Proportionibus Libri Duo. Prior, qui de simplici proportione est, & magnitudinum & numerorum tum simplicium tum fractorum rationes edocet: Posterior, ipsas proportiones comparat: earumque rationes colligit.

Renouard 117; Sherrington, Fernel, p. 189 (3.C); Smith, Rara Arithmetica, p. 157; Schreiber, Colines, 35.

First edition of this rare treatise on proportions. 

It is adorned with a fine title page in a bravé wood frame decorated with 8 medallions with portraits of Ptolemy, Euclid, and allegorical portraits depicting astronomy, geometry, music, arithmetic, etc. as well as the armies of France and those of the dauphin. The edition is dedicated to the famous printer, philologist and humanist Étienne Dolet (1509-1546).

“The famous French physician Jean Fernel published De proportionibus libri duo in Paris in 1528. This treatise belongs to the tradition of texts on proportion that stems from Thomas Bradwardine’s Tractatus de proportionibus seu de proportionibus velocitatum in motibus (1328). In the first book, Fernel presents a theory of ratios that is traditional but contains some distinctive features, on the naming of ratios, on fractions and on irrational ratios. The second book is devoted to the theory of ratios of ratios” (Sabine Rommevaux, in: Historia Mathematica, vol. XL, 2).

Fernel’s book “is one of the best of the sixteenth-century treatises on the medieval proportion. It follows the Boethian treatment, as seen also in the work of Bradwardin” (Smith). 

“Fernel (1497-1558), before making a name for himself in medicine, was first attracted by the mathematical sciences, as evidenced by his first three publications — of which this is the third, and all three of which were issued by Simon de Colines: De Proportionibus was preceded by Monalosphaerium, 1527, and Cosmotheoria, 1528. Fernel received his M.D. degree in 1530 and became a very influential physician through his numerous writings; he became physician to Catherine de Médicis, whose barrenness he cured, and eventually was appointed chief physician to King Henri II” (Schreiber).

Very good copy.