11 



the Faculte des Sciences, which had been established in consequence 

 of the strong recommendation of Poinsot, and for twenty-five years 

 Chasles devoted himself assiduously to his duties at the Sorbonne. 

 The " Traite de Geometrie Superieure," an elaborate and masterly 

 treatise which embodied the substance of a course of lectures given to 

 the Faculte des Sciences, appeared in 1852. This book became scarce, 

 but about two months before his death, Chasles had the satisfaction of 

 seeing a second edition of it published, accompanied by his excellent 

 " Discours d' Inauguration." 



The " Traite de Geometrie Superieure " was followed in 1865 by the 

 first volume of his " Traite des Sections Coniques," being a sequel to 

 the former. No other volume of this work ever appeared, though 

 much desired by mathematicians. 



In 1863 Chasles published his book " Les Trois Livres de Porismes 

 d'Euclide, retablis pour la premiere fois, d'apres la Notice et les 

 Lemmes de Pappus, et conformement au sentiment de R. Simson, sur 

 la Forme des Enonces de ces Propositions." The publication of this 

 work led to a short controversy with M. P. Breton (" Question des 

 Porismes — notices sur les debats de priorite auxquels a donne lieu 

 l'ouvrage de M. Chasles sur les porismes d'Euclide," Paris, 1865 ; and 

 a second part, Paris, 1866). M. Chasles comments on these in his 

 " Rapport." 



In 1851 Chasles was elected a member of the French Academy, of 

 which he had been a corresponding member since 1839. In 1854 he 

 became a foreign member of the Royal Society, and in 1865 he 

 received the Copley medal, which was given to him in acknowledg- 

 ment of his historical and original Researches in Pure Geometry. 

 He was the first, and for some years the only, foreign member of the 

 London Mathematical Society. He was also a member of the Cam- 

 bridge Philosophical Society. 



Chasles continued his labours in the cause of science without inter- 

 ruption, from the time of his leaving the Lycee Imperiale until he was 

 eighty years of age. An interval of sixty-eight years separates the 

 first note of the pupil Chasles, which appeared in the " Correspondance 

 sur l'ficole Poly technique," from the last memoir he presented to the 

 Academy. In the " Catalogue of Scientific Papers" will be found the 

 titles of 177 of his papers, and it is computed that the number 

 published since 1873 would probably bring the total to nearly 270. 

 The subjects range over curves and surfaces of the second and of any 

 degree, geometry, mechanics (and attractions), history, and astronomy. 

 His " Rapport " perhaps furnishes the best key to his writings, and at 

 pages 72 — 126, 220 — 280 will be found an account of his own contri- 

 butions to geometry. 



Chasles' life was a happy and simple one. He lived quietly and 

 abstemiously, respected and loved by all the scientific friends whom he 



