Poncelet, Jean-Victor (1788-1867)

French mathematician and military engineer who advanced projective geometry. His book Traité des propriétés projectives des figures (1822) deals with the properties of plane figures that remain unchanged when projected.

Poncelet was born in Metz. He took part in Napoleon's campaign against Russia, and was captured. During his two years as a prisoner of war, he began his work on geometry. On his release in 1814, he returned to Metz and was engaged on projects in military engineering there until 1824, when he became professor of mechanics at a local military school. In 1830 he was elected a member of Metz Municipal Council and secretary of the Conseil-Général of the Moselle. He moved to the University of Paris 1838 and ended his career as commandant of the Ecole Polytechnique with the rank of general.

Poncelet had been a pupil of Gaspard Monge, the originator of modern synthetic geometry, but Poncelet also used analytical geometry and contributed greatly to the development of the relatively new synthetic (projective) geometry. He became the centre of controversy over the principle of continuity, and developed the circular points at infinity.

Poncelet developed a new model of a variable counterweight drawbridge, which he described and publicized in 1822. His most important technical contributions were concerned with hydraulic engines, such as Poncelet's water wheel, with regulations and with dynamometers, as well as in devising various improvements to his own fortification techniques.