6S2 



DESCARTES. 



Wescartes. In this sequestered spot, lie 1111*0611 his attention to me- 

 *— ~v— ' taphysics, theology, meteorology, and dioptrics ; but as he 

 had left in France almost all his tools for grinding lenses, 

 he could not proceed so smoothly with his optical stu- 

 dies. An account of the parhelia which were seen at 

 Rome on the 20th of March 1629, had been sent to 

 liim, both by Mersenne and by Renier or Reneri ; and 

 he was thus led to compose his valuable treatise on me- 

 teors, which also contains his discoveries respecting the 

 rainbow. 



After he returned to Amsterdam, he spent the whole 

 of tlie winter of 1629 in chemical experiments, and in 

 the dissection of animal bodies ; and he informs us, that 

 he every day found something new in these sciences. 

 Havhi"- received a visit from his friend Mersenne, Des- 

 cartes went to England in 1631 ; and in the neighbour- 

 hood of London, he made a number of observations on 

 the variation of the needle. Henry Reneri, who was 

 the first person that embraced the opinions of Descar- 

 tes, was elected Professor of Philosophy at Deventer, a 

 circumstance which induced the latter to take up his 

 residence in that town in the spring of 1 633. Here he 

 completed several works which he had formerly begun, 

 but particularly his Dioptrics, and his " Treatise on 

 the World ;" and he applied himself principally to the 

 study of astronomy. His " Treatise on the World" 

 having been carefully revised, he was on the eve of 

 sending it to Mersenne to have it printed at Paris with 

 the royal privilege; but having heard of the persecution 

 of Galileo, he was obliged to abandon this design, as 

 his own work contained similar opinions. 



From Deventer, Descartes went to Amsterdam in 

 l63t, and he soon after performed a tour through 

 Denmark and the lower parts of Germany with his 

 fViend M. De Ville-Brissieux, a celebrated mechanic 

 and chemist of those times. From Amsterdam, to 

 which he returned, he again went to Deventer, whence 

 he set off to Leuwarden in Friesland, where he com- 

 posed his treatise on mechanics. In March 1636 he 

 returned to Amsterdam ; and, in passing over the Zuy- 

 der Sea, he made some curious observations on the 

 coloured rings with which candles are sometimes sur- 

 rounded. 



On the 4th May 1G37, he obtained, in tine most ho- 

 nourable manner, the royal privilege, not only to pub- 

 lish those treatises which he had prepared, but also 

 every thing that he had written, or might still write, du- 

 ring the rest of his life. These treatises were publish- 

 ed anonymously at Leyden, in 4to, and entitled, Dis- 

 cours de la Methode pour bien conduire sa raison, el 

 cherchcr la verite dans les sciences. Plus, la Dioptriqne, 

 les Melcores, et la Gcomelrie qui sunt des Essais de cette 

 methode. In presenting copies of this work to his 

 friends at Paris and Rome, Descartes omitted to send 

 one to Roberval, professor of mathematics at Paris ; and 

 it is said, that this neglect was the cause of that bitter 

 animosity which he ever afterwards felt and displayed 

 towards Descartes. 



Among the numerous combatants that were called 

 into the field by the publication of Descartes book, the 

 most distinguished was M. Fermat, counsellor to the 

 parliament of Thoulouse, and one of the finest mathema- 

 ticians of the age. Fermat stated several objections to 

 the dioptrics of Descartes, and, before he received his 

 reply, he sent him a copy of his book De maxhnis et 

 minimis, under the name of M- Carcavi, a friend of his 

 own. This present gave rise to a new dispute, which 

 was carried on at Paris through the medium of Mer- 

 senne and Mydorge on the part of Descartes, and M. Pas-. 



cal and Roberval on the part of Fermat. The dispute Desc 

 became at last personal, owing to the intemperate hos- '~*~ 

 tility of Roberval ; but Fermat had the good sense to 

 disapprove of this conduct, and it had the effect of pro- 

 ducing a complete reconciliation between the two con- 

 tending mathematicians. Descartes took a keen part 

 against Roberval, in the question which was now agi- 

 tated in France respecting the cycloid; and his time 

 was almost wholly occupied in unprofitable replies to 

 the objections which were every where urged against 

 his philosophy. 



The Cartesian doctrines were now making rapid 

 progress in Holland, in consequence of the zeal of 

 Reneri, who had been removed from the university 

 of Deventer to that of Utrecht. One of his disciples, 

 named Henry Regius, imbibed the same views with his 

 master, and was so eager to make himself acquaint- 

 ed with the new philosophy, that he went to receive 

 instructions from Descartes himself. The death of 

 Reneri, which happened about this time, removed the 

 restraint which his high reputation had laid upon the 

 enemies of Descartes at Utrecht, and called forth the 

 hostility of Voetius, who was professor of divinity in 

 that university. This theologian, who was also the 

 principal clergyman in the city, published theses in 

 June 1639, in which he branded the new philosophy 

 as atheistical, and as pernicious to the Protestant reli- 

 gion, and the repose of the United Provinces. These 

 insinuations were ably repelled by his colleague Regius. 

 The professor of divinity, irritated at the ability of this 

 reply, determined to ruin the reputation of Regius as 

 well as that of Descartes. In Regius's Lectures on Me- 

 dicine, he sought for the opportunity which he wished; 

 and he soon found, that this enlightened physician had 

 taught the heretical doctrine of the circulation of the 

 blood, which had been discovered by our countryman 

 Harvey. A complaint was, on this ground, laid before 

 the university, and Voetius had the address to interest 

 even the rector and the personal friends of Regius and 

 Descartes, against the new opinions ; and to induce the 

 university to publish an ordonnance, to prevent the dis- 

 semination of opinions contrary to its statutes. The 

 troubles which were excited by this dispute, attracted 

 the notice of the civil power ; and it was at last agreed, 

 at the suggestion of Descartes, in his answer to the or- 

 donnance, and with the approbation of the magistrates 

 of Utrecht, that Regius should be allowed to teach the 

 new philosophy, but that he should be admonished to 

 moderate his zeal, and to modify some of the boldest 

 of his opinions. 



The opinions of Descartes were received in England 

 with great avidity. Lord Charles Cavendish, the bro- 

 ther of the Duke of Newcastle, who was enamoured of 

 the Cartesian philosophy, invited Descartes, and his 

 friend Mydorge, to settle in England. Descartes seem- 

 ed disposed to accept of the invitation, particularly 

 when he was assured that the king was a Catholic in 

 his heart; but Mydorge, who had a family at Paris, 

 did not comply with the same readiness. Charles I. 

 promised to make a handsome provision for the two 

 mathematicians; but the commencement of the civil 

 war induced all parties to abandon the arrangement 



The tranquillity of Descartes was about this tune dis- 

 turbed by a dispute with the Jesuits, in which he was 

 embroiled by M. de Saumaise. M. Bourdin, professor of 

 mathematics in the Jesuits college of Clermont, attack- 

 ed the tenets of Descartes, but particularly his diop- 

 trics, in theses, which were supported on the 30th o£ 

 June 1640, and his friend Mersenne defended him. 



