Jean-Victor Poncelet (July 1, 1788 - December 22, 1867) was a French engineer and mathematician. As a mathematician, his most notable work was in projective geometry, in particular, his work on Feuerbach's theorem. He also made discoveries about projective harmonic conjugates; among these were the poles and polar lines associated with conic sections. These discoveries led to the principle of duality, and also aided in the development of complex numbers and projective geometry. As a military engineer, he served in Napoleon's campaign against the Russian Empire in 1812, in which he was captured and held prisoner until 1814. Later, he served as a professor of mechanics at the ?cole d'Application, and published Introduction ? la m矇canique industrielle, a work he is famous for, and improved the design of turbines and water wheels. He served as professor at the Facult矇 des Sciences at the University of Paris, and finally as the commandant general of his alma mater, the ?cole Polytechnique. He died in 1867 at the age of 79. His is one of the 72 names inscribed on the Eiffel tower.