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geometrice consideratd ; seu de Maximis et Minimis pars prior ele- 

 mentaris, and in which he treats geometrically, and with singular 

 elegance and vigour of demonstration, all the elementary problems 

 relating to isoperimetric figures and solids. About the same time 

 he presented to the Academy of Berlin a memoir, which was after- 

 wards published in its Transactions, on the minima relating to the 

 figure of the cells of bees, a subject which he appears, in that paper, 

 to have exhausted. 



The prize proposed by the same Academy in 1786, was adjudi- 

 cated to him for a memoir, which was since published under the 

 title of Exposition elementaire des principes des calculs superieurs. 

 In this masterly essay the differential calculus is derived from a prin- 

 ciple which D'Alembert had, in the first edition of the Encyclo- 

 pedie, so happily illustrated, and which is now so generally recog- 

 nised as the basis of that calculus ; namely, the doctrine of limits. 



On his return to Geneva in 1789, I'Huillier published an opus- 

 cle, M^hich acquired great celebrity, entitled La Polygonometrie ; 

 ou de la mesure des figures rectilignes, et abrege dHsoperimetrie ele- 

 mentaire, ou de la dependance 7nutuelle des grandeurs et des limites 

 des figures ; at the conclusion of which he gives a masterly sum- 

 mary of his former researches on elementary isoperimetry. In this 

 work are given several formulee of great genei-ality, and which, at 

 that time, were entirely new, and were calculated to facilitate the 

 study of numerous relations arising from the perimeters and areas of 

 polygons. About the same period, indeed, Mascheroni published 

 formulae very analogous to those of I'Huillier ; but the latter after- 

 wards succeeded in showing that he had arrived at the same results 

 by original processes. 



During the tempestuous years of the revolution, I'Huillier sought 

 in Germany the retirement so necessary to his pursuits ; and chose 

 Tubingen as his residence. The fruit of his labours during this 

 seclusion was a work almost wholly new, which appeared at Tubin- 

 gen, in 1795, under the title Principiorum calculi differentialis et 

 integralis expositio elementaris. 



He was invited, about this time, to the chair of the Higher Ma- 

 thematics in the University of Leyden ; but his attachment to his 

 native country was too deeply rooted to admit of his accepting this 

 flattering offer: and eventually, in June of the same year (1795), 

 he attained the object of his highest ambition, by receiving, after 

 a successful public competition, the appointment of Professor of 

 Mathematics in the Academy of Geneva. 



At a subsequent period he was associated with his friend and col- 

 league Professor Prevost in the composition of several memoirs on 

 the calculation of probabilities, which appeared under their joint 

 names in the memoirs of the Berlin Academy. The questions 

 treated of in these memoirs, although they do not reach the higher 

 problems belonging to this department of mathematics, are yet re- 

 solved by methods remarkable for their perspicuity and elegance. 

 L'Huillier published, in 1804, his Elemens raisonnes d'Algebi-e, pu- 

 blics a Vusage des etudians ; in 2 vols. 8vo, a work of considerable 



