280 P I S S N he broke into the cottage, and there saw, with painful astonishment, the object of all his hopes suspended by a small cord to a nail fixed in the wall. This was a precau tion on the part of the peasant nurse to prevent her charge from perishing under the teeth of the carnivorous and unclean animals that circulated in the house. Poisson, in telling the story, added " A gymnastic effort carried me incessantly from one side of the vertical to the other ; and it was thus, in my tenderest infancy, that I made my pre lude to those studies on the pendulum that were to occupy so much of my maturer age." Having survived the perils of infancy, and received the elements of his education (reading and writing) from his father, the question arose what calling he was to follow. It was at first suggested that he should be made a notary ; but the family council, with amusing irony, decided that this profession made too great demands upon the intellect, and surgery was preferred. He was sent to an uncle who exercised this art at Fontainebleau, and forthwith began to take lessons in bleeding and blistering, then the leading branches of a surgeon s practice. To train him in the former, he was set to prick the veins of cabbage leaves with a lancet, but made little progress ; how he sped in the latter he himself relates as follows : " Once my uncle sent me, with one of my comrades, M. Vanneau, now established in the colonies, to put a blister on the arm of a child ; the next day, when I presented myself to remove the apparatus, I found the child dead ; this event, very common they say, made the most profound impression upon me ; and I declared at once that I would never be either physician or surgeon. Nothing could shake my reso lution, and they sent me back to Pithiviers." Here accident and the bent of nature solved the problem that had passed the wisdom of the family council. The elder Poisson, being .a Government official, received a copy of the Journal de Vficole Polytechniqiie ; the son read it, and soon began unaided to solve the problems propounded there from time to time ; and thus his mathematical talent was discovered. He was sent to the 6cole Centrale of Fontainebleau, and was fortunate in having a kind and sympathetic teacher, M. Billy, who, when he speedily found that his pupil was becoming his master, devoted himself to the study of higher mathematics in order to follow and appreciate him, and predicted his future fame by the punning quotation from Lafontaine l " Petit Poisson dcviendra grand Pourvu que Dieu lui prete vie." At the age of seventeen the young provincial, less remarkable for the elegance of his attire than for the pro fundity of his scientific knowledge, came up to Paris to undergo the entrance examination for the Polytechnic School. He passed first in his year, and immediately began to attract the notice of the professors of the school, who, seeing his obvious genius, excused him from the ordinary drudgery of the curriculum, and left him free to follow the studies of his predilection. The wisdom of this course was soon proved; for, in 1800, less than two years after his entry, he published two memoirs, one on Bezout s method of elimination, the other on the number of integrals of an equation of finite differences. The latter of these memoirs was examined by Lacroix and Legendre, who recommended that it should be published in the Recueil des Savants Strangers, an unparalleled honour for a youth of eighteen. This success at once pro cured for Poison an entry into the Parisian scientific society of the day, the like of which for brilliancy has never elsewhere been seen. Its two kings both patronized him. Lagrange, whose lectures on the theory of functions 1 This prediction is sometimes attributed to Laplace. he attended at the Polytechnic School, early recognized his talent, and became his friend ; while Laplace, in whose footsteps Poisson followed, regarded him almost as his son. The rest of his career, till his death on the 25th of April 1840, was almost entirely occupied in the composition and publication of his many works, and in discharging the duties of the numerous educational offices to which he was successively appointed. Immediately after finishing his course at the Polytechnic School he was appointed repetiteur there, an office which he had discharged as an amateur while still a pupil in the school ; for it had been the custom of his comrades often to resort to his room after an unusually difficult lecture to hear him repeat and explain it. He was made professeur suppleant in 1S02, and full professor in succession to Fourier in 1806. In 1808 he became astronomer to the Bureau des Longitudes ; and, when the Faculte des Sciences was instituted in 1809, he was appointed Professeur de la Mdcanique Rationelle. He further became member of the Institute in 1812, exa miner at the military school at St Cyr in 1815, leaving examiner at the Polytechnic in 1816, councillor of the university in 1820, and geometer to the Board of Longitude in succession to Laplace in 1827. In 1817 he married Mademoiselle Nancy de Bardi, daughter of a French family which had emigrated to Eng land, and by her he had two sons and two daughters. Poisson was a simple-minded affectionate man. This is seen in the close relations which he kept up with his old teacher M. Billy, who ardently loved and admired his former pupil, and whose presence at the Institute was a well-known sign that Poisson was to read a paper there. Although he never returned to Pithiviers after his entry into the Polytechnic School, he corresponded constantly with his parents, more especially with his mother ; and he regularly sent copies of his memoirs to his father, who read and re-read with unwearied patience the parts of them within his comprehension. His tastes seem to have been of the simplest description ; he took little exercise, and he had more than a Frenchman s horror of travelling. Arago says that he only travelled once, and that by medical prescription, disguised under the form of some mission connected with the Polytechnic School, and that, after devoting his savings to the purchase of a beautiful farm in the department of Seine-et-Marne, he never so much as visited it. It is probable that his simplicity of character had much to do with his passing apparently quite undisturbed through the stormy time in which he lived, a period in which many men of mark lost their heads, and few such escaped without loss of office and fortune. His father, whose early experiences led him to hate aristocrats, bred him in the stern creed of the first republic. Throughout the empire Poisson faithfully adhered to the family prin ciples, and refused to worship Napoleon. Napoleon, how ever, never interfered with Poisson s promotion. He said once himself that he never did anything uselessly, cer tainly never committed a useless crime ; and he was wise enough to see that nothing was to be gained by persecut ing the harmless academician, whose fame he doubtless regarded like that of the other savants of France as an apanage of his own glory. When the Bourbons were restored, his hatred against Napoleon led him to become a Legitimist a conclusion which says more for the simplicity of his character than for the strength or logic of his political creed. He was faithful to the Bourbons during the Hundred Days, in fact was with difficulty dissuaded from volunteer ing to fight in their cause. After the second restoration his fidelity was recognized by his elevation to the dignity
of baron in 1825; but he never either took out his