Émile Lemoine

Émile Lemoine was a French civil engineer, mathematician and geometer, born in Quimper in 1840 and died in Paris in 1912. He was educated at the military school of La Flèche and then at the École Polytechnique, graduating in 1866, but he did not take up a state career and instead made his own way, working as a science teacher, an assistant to the astronomer Pierre Jules César Janssen, and later as a civil engineer in Paris, where he rose to chief inspector in the gas inspection service. His contribution to mathematics was mainly in geometry. In 1873 he showed that the symmedians of a triangle are concurrent at a point now called the Lemoine point, and that parallels through it to the sides meet the sides in six points on the Lemoine circle. He also proposed a classification of geometric constructions by counting elementary operations, which he called geometrography. He helped found the Association Française pour l'Avancement des Sciences and was the first editor of the journal L'Intermédiaire des Mathématiciens, and he was a gifted amateur musician who founded the amateur group La Trompette.