**Leonhard Euler**, was born on April 15, 1707, and died on September 18, 1783. He was the most prolific mathematician in history. His 866 books and articles represent approximately one third of the entire body of research in mathematics, physical theories, and mechanical engineering published between 1726 and 1800. In pure mathematics, he integrated Leibniz's differential calculus and Newton's method into mathematical analysis; refined the notion of a FUNCTION; created many common mathematical notations, including the *and*, *i*, the symbol of *pi* and the symbol of *sigma*; and laid the foundation for the theory of special functions, introducing the beta and gamma transcendental functions.

**AND**Uler also worked on the origins of the CALCULATION OF VARIATIONS, but retained his work in deference to LAGRANGE. He was a pioneer in the field of TOPOLOGY and did NUMBER THEORY in a science, stating the prime number theorem and the law of bikadratic reciprocity. In physics he articulated Newtonian dynamics and laid the foundation of analytical mechanics, especially in his Theory of Rigid Body Movements (1765). Like his teacher Johann Bernoulli, he worked out continuous mechanics, but he also worked on the kinetic theory of gases with the molecular model. With Alexis CLAIRAUT he studied lunar theory. He also did fundamental research on elasticity, acoustics, light wave theory, and ship hydromechanics.

**AND**Uler was born in Basel, Switzerland. His father, a pastor, wanted his son to follow in his footsteps and sent him to the University of Basel to prepare him for ministry, but geometry soon became his favorite subject. By Bernoulli's intercession, Euler obtained his father's consent to switch to mathematics. After failing to obtain a physicist position at Basel in 1726, he joined St. Petersburg Academy of Science in 1727. When the academy's capitals were retained, he served as a lieutenant in the Russian Navy from 1727 to 1730. He became professor of physics at the academy in 1730 and professor of mathematics in 1733 when he married and left Bernoulli's house. His reputation grew after the publication of many articles and his book Mechanica (1736-37), which first extensively presented Newtonian dynamics in the form of mathematical analysis.

**AND**In 1741, Euler joined the Berlin Academy of Science, where he remained for 25 years. In 1744 he became the director of the math section of the academy. During his stay in Berlin, he wrote more than 200 articles, three books on mathematical analysis, and a scientific popularization, Letters to the Princess of Germany (3 vols., 1768-72). In 1755 he was elected a foreign member of the Paris Academy of Science; During his career he has received 12 of these prestigious biennial awards.

**AND**In 1766 Euler returned to Russia after Catherine the Great made a generous offer. At the time, Euler was having differences with Frederick the Great over academic freedom and other matters. Frederick was enraged at his departure and was invited Lagrange to replace him. In Russia, Euler became almost completely blind after a cataract operation, but was able to continue his research and writing. He had a prodigious memory and could dictate treatises on optics, algebra, and lunar motion. At his death in 1783, he left a vast reserve of articles. The St. Petersburg Academy has continued to publish them for the next 50 years.

Bell, Eric T., Men of Mathematics (1937; repr. 1986); Boyer, Carl, A History of Mathematics (1968); Spiess, Otto, Leonhard Euler (1929); Truesdell, C., "Leonhard Euler, Supreme Geometer (1707-1783)," in Irrationalism in the Eighteenth Century, ed. by Harold E. Pagliaro (1972).