Leonard Euler[7] was born at Basle, April 15, 1707. His father was the clergyman of Reichen, near Basle, and had himself been a pupil of James Bernouilli. He intended his son for his own profession, and after having been himself his first instructor in mathematics, sent him to the university of Basle. John Bernouilli was at this time Professor, and his sons, Nicolas and Daniel, two more of the _eight_ Bernouillis known to the history of science, were under him. With the sons Euler contracted an intimate friendship; and obtained such a degree of favour even with their father, that the latter gave him a private lesson weekly, upon points more advanced than those treated in the public course. This was a strong mark of favour from John Bernouilli, who was of an unamiable disposition, jealous of his brother, of his son, and finally of almost every one who displayed a superior talent for mathematics. Euler at first turned his attention to theology, in accordance with the wishes of his father, but this was not of long continuance. At the age of nineteen, besides obtaining a degree from his University, he had merited the notice of the Academy of Sciences for a memoir on some points of naval architecture. In the same year, he was an unsuccessful candidate for a Professorship at Basle, an unlucky event, M. Condorcet observes, for his country, inasmuch as a few days afterwards he left it for Russia, and never returned. His friends the Bernouillis (Nicolas and Daniel) had, two years before, accepted invitations from the Empress Catherine; and he followed them in hopes of obtaining employment and subsistence at St. Petersburgh. But by the time he arrived, both Nicolas Bernouilli and the Empress were dead, the Academy of St. Petersburgh was left without a patron, and Euler, a nameless stranger, could not for a long time obtain any settled avocation. How he maintained himself we are not told; but he was upon the point of entering the Russian service as a sailor, when his prospects brightened, and he obtained the place of Professor of Natural Philosophy. In 1733 he succeeded Daniel Bernouilli, who returned to his own country, as Professor of Mathematics. In the same year he married a young lady named Gsell, the daughter of an artist of Basle, who had emigrated to Russia in the reign of Peter the Great. Footnote 7: We have followed the _éloge_ of Condorcet as to facts and dates. We should have preferred that of M. Fuss, but have not had the opportunity of seeing it. The mere biographical details of Euler’s life are, however, of the simplest character.