1/2 17th century

An instrument-maker specialised in optics who was closely associated with the savants of Mersenne's circle. According to Baillet he was not an artisan working only with his hands, but was one who possessed the theory of his activities, was not unskilled in mathematics and was accepted on equal terms by the savants whom he frequented. He made instruments for Jacques Aleaume (d. 1627), some or all of which were purchased by Claude Mydorge who also seems to have continued working with Ferrier for a time. He also made instruments for Jean-Baptiste Morin. In 1626 or 1627, Ferrier was brought into contact with Descartes for whom, in collaboration with Mydorge, he ground a successful convex hyperbolic lens and in June 1629 Descartes tried to persuade Ferrier to join him the Netherlands there to try out a new idea that Descartes had for lens-grinding.1 Ferrier did not go, as he was trying to get a logement in the Louvre - a quest in which Descartes helped him. At this time Ferrier was making an astronomical quadrant fitted with telescopic sights (the earliest such instrument known) for Morin, but in October Descartes sent to him a description of a lens-grinding machine for which Ferrier suggested several improvements in his reply. In the spring of 1630 to Descartes' consternation, he decided to join him in Franeker. Probably as a result of Mersenne passing on the gist of Descartes' negative attitude, Ferrier never made the journey, but relations between the two men rapidly deteriorated, Descartes denigrating Ferrier in his letters who was much upset and asked others such as Gassendi and Fr. de Condren to intercede with Descartes on his behalf.2
Despite Descartes' negative view of Ferrier as a time-wasting self-aggrandiser who was less competent than he seemed, others recognised Ferrier's skills. François Niceron for example stated that Ferrier alone might be capable of realising Descartes' ideas about lens formation,3 and there are several references in the correspondence of Mersenne to tools devised by Ferrier in the process of his glass works.4 That he also made other instruments is attested by a inclination compass which he showed to Georges Fournier,5 and by a brass quadrant which he graduated in 1641 listed in the inventory of instruments of the Académie des Sciences.6 Morin attributed the invention of circular transversal scales to Ferrier in the early 1630s.7

1 For a detailed account of their relations see Shea which, although it adds relatively little to the account given by Daumas 98-9, offers a different perspective. It also corrects Ferrier_s name from Guillaume as given by Daumas to Jean.
2 The letter that Gassendi wrote to Renerus, Descartes’ disciple, on Ferrier’s behalf is translated in Taussig __
3 François Niceron,La Perspective curieuse…,Paris 1638, ii 376._
4 E.g. an instrument 'pour descrire la ligne necessaire à la convexité desdictes lunettes et miroirs convexes', Peiresc to Dupuy 8 January 1628 which Ferrier made for Alleaume.
5 George Fournier, Hydrographie contenant la théorie et la pratiqve de tovtes les parties de la navigation 2nd ed. Paris, 1667, 422-3
6 No 428 of the 1793 Inventory. Daumas 99.
7 Longitudinum cœlestium atque terrestrium scientia (1634) cited in Lalande,Astronomie, 2nd edition, ii, 759.

Paris

1635

ark:/18469/1rh9f