Edward Worth was a Fellow of the Royal Society, one of the pre-eminent scientific communities in early modern Europe. Although he was not a corresponding member, it is clear that he was an avid follower of the publications of the Royal Society and, in particular, collected the many Newtonian commentaries emanating from the Society at that time. But Worth did not limit his scientific interests to the activities of Newton and his English counterparts. His set of volumes of the *Acta Eruditorum*, the Leipzig equivalent of the *Philosophical Transactions of the Royal Society*, bears witness to his commitment to science in all its forms.

Christoph Clavius, *Opera mathematica V. tomis distributa* (Mainz, 1611-12), title page.

Equally, Worth’s scientific collection (and more specifically his mathematical books) includes many works by Jesuits. The importance of the Jesuit nexus of mathematicians in the early modern world cannot be over-estimated. Michael John Gorman(1998) has drawn attention to the role of mathematics, natural philosophy and experimentalism in Jesuit culture during the period 1580-1670 and, as Feingold (2003) reminds us, more generally ‘we are still far from being fully conscious of the enormous contribution of Jesuit teachers to the formation of Catholic secular culture during the early modern period’. The images on this page show the title pages of texts by two famous Jesuit mathematicians: Christopher Clavius and Claud François Milliet Dechales. They were by no means isolated items in Worth’s collection for his library included famous texts on the Moon by the Jesuit astronomers Giambattista Riccioli and Francisco Maria Grimaldi among a host of other Jesuit scientific texts.

Undoubtedly one of the most famous Jesuit mathematicians was Christopher Clavius (1538-1612). Known primarily for his astronomical textbooks and his work on the new Gregorian calendar he was the author of a number of works specifically devoted to mathematics, such as his 1574 commentary on Euclid. As we can see here, Worth’s owned the famous 5 volume 1612 Mainz edition of his mathematical works and to this Worth added the 1608 Genevan edition of Clavius’ seminal edition of the astronomical works of Johannes de Sacro Bosco (c.1195-c.1256).

Clavius’ textbooks were the result of years of experience teaching mathematics at the Academy of Mathematics at the Collegio Romano. However, as Baldini (2003) reminds us, his books reflected his many roles in the Academy and therefore included not only the normal elementary course of mathematics available in other Jesuit colleges but also the advanced research of the Academy. Both Clavius’ work and Dechales’ *Cursus* demonstrate that the Jesuit curriculum viewed mathematical education in its broadest sense – i.e. it did not limit itself to arithmetic and geometry but also incorporated related disciplines, such astronomy, statics and optics. However, as Baldini notes, Archimedean statics were excluded from the scheme, as were mechanics, since they were viewed by Jesuits as being part of natural philosophy.

Baldini (2003) provides us with the following summary of the ‘Ordo servandus in addiscendis disciplinis mathematicis’ (i.e. the mathematical course at the Academy, written c. 1580):

- Elementary plane geometry (books I-IV of Euclid’s
*Elements*and their later development). - Elementary arithmetic and its applications.
- The Sphere and ecclesiastical computation.
- Theory of proportions and its applications to magnitudes (books IV-VI of the
*Elements*and their later developments). - Theory of measuring instruments.
- Advanced arithmetic (books VII-X of the
*Elements*and their later developments) - Algebra.
- Elementary solid geometry (books XI-XIII of the
*Elements*, then the Pseudo-Euclidean books XIV and XV and their later developments). - Plane and solid trigonometry.
- Theory and use of the astrolabe.
- Gnomonics.
- Geography.
- Practical geometry.
- Optics.
- Particular problems of astronomy.
- Theory of the planets and of the eighth sphere, and the use of the tables.
- Musical theory.
- Advanced geometry (works of Archimedes)
- Statics and theory of simple machines
- Problems of the geometry of conics.

Claud François Milliet Dechales,* Cursus seu Mundus Mathematicus* (Lyon, 1690), title page.

Claud François Milliet Dechales (1621-1678) was a French Jesuit famous for his translation of Euclid and his phenomenal *Cursus*, first published in 1674 and bought by Worth in a 1690 Lyon edition. Just as Clavius’ texts arose out of his pedagogical experience, so too did those of Dechales. His translation of Euclid (which proved to be particularly popular in France) appeared in 1660, just at the end of a three-year teaching programme at Lyon. His *Cursus*, a course covering all areas of mathematics in the Jesuit sense, took considerably longer to produce due to Dechales’ many work commitments – for instance, he was sent on a mission to Turkey at one point. As Feingold notes (2003), it was only after he recommenced teaching (initially as the King’s professor of hydrography and then as a professor in Lyon and Paris), that he was able to return to writing his major work.

**Sources**

Baldini, Ugo, ‘The Academy of Mathematics of the Collegio Romano from 1553 to 1612’, in Mordechai Feingold (ed.) *Jesuit Science and the Republic of Letters* (Cambridge, Massachusetts: MIT Press, 2003), 47-98.

Feingold, Mordechai ‘Jesuits: Savants’ in Mordechai Feingold (ed.) *Jesuit Science and the Republic of Letters* (Cambridge, Massachusetts: MIT Press, 2003), 1-46.

Gorman, Michael John, ‘The Scientific Counter-Revolution: Mathematics, Natural Philosophy and Experimentalism in Jesuit Culture, 1580-c.1670’, Ph.D. thesis, European University Institute, Florence, 1998.

**Text:** Elizabethanne Boran.