**Jean-Louis Calandrini** was a mathematician working in Geneva, Switzerland in the first half of the 18th century. A great supporter of Newton's theories, he was a major contributor, along with Thomas Le Seur and François Jacquier, to an highly annotated edition of Newton's *Principia*.

- The Geneva Academy, at which Calandrini studied and later worked, had been founded in 1559 by Jean Calvin for training ministers.
- Even at this early stage in his career, Calandrini was an avid follower of Newton and he would continue to work to bring Newton's ideas to as wide an audience as possible.
- The competition for the chair was between three men; the eldest was Amédée de la Rive while the other two were both young men, Calandrini who was twenty-one years old and Gabriel Cramer who was one year younger.
- Clearly they were looking to the future and seeing in Cramer and Calandrini two men who would make important future contributions to the Academy.
- De la Rive was offered the philosophy chair, which after all was what he had applied for in the first place, while Cramer and Calandrini were offered the mathematics chair on the understanding that they shared the duties and shared the salary.
- The magistrates put another condition on the appointment too, namely that Cramer and Calandrini each spend two or three years travelling and while one was away the other would take on the full list of duties and the full salary.
- It was a good plan for not only did it successfully attract all three men to the Academy, but it also gave Calandrini the opportunity to travel and meet mathematicians around Europe and he was to take full advantage of this which both benefited him and the Academy.
- In 1724 Calandrini set out for his three years of travelling, first going to Basel in Switzerland where he studied with Johann Bernoulli, then to Leiden in the Netherlands where he studied with Willem 'sGravesande who was a strong supporter of Newton, next to Paris and finally to London.
- After these three years of travelling, Calandrini began his teaching at the Geneva Academy.
- Cramer and Calandrini divided up the mathematics courses each would teach.
- Cramer taught geometry and mechanics while Calandrini taught algebra and astronomy.
- Calandrini also presented Newton's theory in terms compatible with physico-theology: according to this viewpoint, the theory of gravitation reveals the visible effects of a continuous providential intervention of God in the natural phenomena.
- Calandrini and Cramer joined efforts at the Academy in promoting this pious view of Newtonian natural philosophy.
- Calandrini's views on religion meant that he taught his physics in terms of a world rationally designed by God and continually kept in order by Him.
- Two of the lecture series by Samuel Clarke, A Demonstration of the Being and Attributes of God (1704) and A Demonstration of the Being and Attributes of God (1705) particularly impressed Calandrini.
- Calandrini used these lectures in teaching his students.
- He was friendly with Calandrini and, in 1728, together with Calandrini and a few other friends he founded the review journal Bibliotheque italique which aimed at making Italian science known to a French speaking audience.
- This was an important venture for Calandrini since, as we will see below, it led to his connection with two friars of the Minim Order in Rome, Thomas Le Seur and François Jacquier.
- When Calandrini had visited Leiden he had become friendly with Willem 'sGravesande and, three years later, Cramer had also made a visit to 'sGravesande who persuaded the two Geneva professors to publish in the Journal Historique de la République des Lettres.
- The paper by Calandrini Dissertation "Sur la force des corps" Ⓣ(Essay on the strength of bodies) was published in the first of the two 1733 volumes.
- Actually the paper is anonymous but in a later paper by 'sGravesande in the same journal, he says that the earlier paper was by Calandrini.
- In 1734 Amédée de la Rive retired from the chair of philosophy at the Geneva Academy and Calandrini applied for the position.
- Again there was a competition for the chair but this time Calandrini was appointed.
- The arrangement to share the chair of mathematics between Cramer and Calandrini ended and Cramer became the only occupant of the chair of mathematics.
- This meant some changes in the courses that Calandrini taught for he now taught logic as well as theoretical physics.
- Calandrini is best known for his work as an editor and commentator on Newton's "Principia" Ⓣ(Mathematical Principles of Natural Philosophy).
- The project was suggested by Calandrini, and although he is not listed on the title page, he was a major contributor to the annotations.
- It may well be that Calandrini came to know about the two Minims via his cooperation with Bourguet and the 'Bibliothèque Italique', which promoted many exchanges with the literati active in the peninsula.
- The commentary by Calandrini, Le Seur and Jacquier attempts to explain the basic mathematics and physics that Newton assumes his readers will know.
- One typical example of this is the treatise by Calandrini on conic sections.
- Newton uses many properties of conic sections without giving proofs of them and Calandrini covers all this.
- In 1752 Calandrini became the treasurer of the city of Geneva, and five years later in 1757 he became a trustee of the city.
- The first clue that this is not the mathematician Jean-Louis Calandrini is the date 1764 of Watson's paper.
- The mathematician Calandrini died in 1758 so receiving a letter from him shortly before 1764 seems unlikely (even if the post was slower in those times!).
- The Calandrini who William Watson was corresponding with was a artillery general, which explains his concerns with lightning striking powder magazines.
- Let us end with the following comment about Calandrini.

Born 30 August 1703, Geneva, Switzerland. Died 29 December 1758, Geneva, Switzerland.

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Origin Switzerland

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive