152 



SCIENCE. 



[N. S. Vol. I. No. 6. 



cabbage leaves with a lancet. How he got 

 on at surgeiy, Poisson himself relates best: 

 " One day my uncle sent me," he saj^s, " to 

 put a blister on the arm of a sick child; 

 the next day when I presented mj'self to 

 remove the apparatus, I found the child 

 dead. This event, very common, they saj', 

 made a profound impression upon me; and 

 I declared at once that I would never be- 

 come a physician." 



He returned to his home, where, soon 

 afterwards, an accidental circumstance re- 

 vealed the true bent of his mind. His 

 father, being still a government officer, re- 

 ceived a copy of the Journal de I'Ecole Poly- 

 technique. The son read it, and was able, 

 unaided, to understand some of its contents. 

 He was encouraged to study and soon went 

 to the school of Fontainebleau. Here he 

 was fortunate in finding a good and sympa- 

 thetic teacher in one M. Billy, who took 

 a warm interest in, and formed a life-long 

 attachment for, his pupil. 



At the age of seventeen Poisson went to 

 Paris to enter the JEcole Poly technique. His 

 genius soon disclosed itself, and at the end of 

 his first year he was excused from the re- 

 quirements of the set curriculum and al- 

 lowed fi-eedom of choice in his studies. Be- 

 fore he had been at the school two years, or 

 before he was twenty years of age, he pub- 

 lished two memoirs which attracted the 

 attention of mathematicians, and led to his 

 speedy entrance into Parisian scientific 

 society, whose leaders at that time were La- 

 grange and Laplace. They were quick to 

 recognize and appreciate Poisson's ability, 

 and it was doubtless through their good 

 offices that Poisson was appointed to a pro- 

 fessorship at the JEcole Poly technique, where he 

 succeeded the distinguished Fourier in 1806. 

 From this time to the end of his life in 1840, 

 Poisson was connected with the educational 

 system of France. As a scientific investiga- 

 tor his untiring patience, industry, and suc- 

 cess have been equalled only by those of 



Euler, Lagrange, and Laplace. " Life," he 

 was wont to saj^, " is good for two purposes 

 only: to invent mathematics and to expound 

 them." 



One of the best estimates of the character 

 and scope of Poisson's work may be inferred 

 fi'om the esteem in which he was held by 

 Lagrange and Laplace. They treated him 

 with the greatest consideration ; and that 

 Lagrange considered him a worthy succes- 

 sor in the footsteps of the most eminent of 

 mechanicians is shown by the following in- 

 cident related by Arago: "I am old," said 

 Lagrange to Poisson one day ; " during my 

 long intervals of sleeplessness I divert my- 

 self by making numerical calculations. 

 Keep this one ; it may interest you. Huy- 

 ghens was 13 years older than l^ewton ; I 

 am 13 years older than Laplace ; d'Alem- 

 bert was 32 years older than Laplace ; La- 

 place is 32 years older than you." Ai'ago 

 remarks that no more delicate way could 

 be conceived of intimating to Poisson liis ad- 

 mission to the inner circle of the fraternity 

 of mathematical genius. 



The dazzling spendor of the achieve- 

 ments in djaiamical asti-onomy during the 

 epoch of Laplace not onljr diverted atten- 

 tion from other applications of mechanical 

 science, but it would seem also to have led 

 to an underestimate of the importance of 

 such applications. Thus the work of Fou- 

 rier and Poisson in the theory of heat, and 

 that of Fresnel and Gi-een in the theorj^ of 

 light', were not duly appreciated by contem- 

 porary philosophers. All eyes were turned 

 towards the heavens. The permanence of 

 the solar system and the dangers of en- 

 counters with comets were more important 

 questions than those presented by pheno- 

 mena close at hand. For nearly a quarter 

 of a century after the epoch of Laplace, 

 comparativelj^ little pi-ogress was made in 

 the fundamental ideas of our science, though 

 its machinery received many important ac- 

 cessions, especially from Green and Gauss. 



