Michel Chasles

Michel Floréal Chasles (1793 to 1880) was a French mathematician best remembered for his work in geometry. Born at Épernon, he studied at the École Polytechnique in Paris under Siméon Denis Poisson and was drafted to help defend Paris in 1814 before giving up thoughts of an engineering or stockbroking career to pursue mathematics. His 1837 book Aperçu historique sur l'origine et le développement des méthodes en géométrie, a study of the method of reciprocal polars in projective geometry, brought him wide respect, a professorship at the École Polytechnique in 1841 and a chair at the Sorbonne in 1846. He developed a theory of characteristics that gave the correct count of 3264 conics tangent to five given conics, correcting Jakob Steiner, and he established several results all called Chasles's theorem, including the description of a rigid motion as a screw displacement. He received the Copley Medal in 1865. He is also known as a collector who bought forged letters from Denis Vrain-Lucas, and his name is one of the 72 inscribed on the Eiffel Tower.