Pierre Charles Francois Dupin (1784-1873), French mathematician. Dupin was born in Varzy, central France, and studied mathematics under Monge at the Ecole Polytechnique in Paris. While still an undergraduate he discovered Dupin cyclides, a type of torus. In 1803 he graduated and became a naval engineer although he continued his researches in topology. In 1813 he published Developments in Geometry, introducing the Dupin indicatrix that characterises the local shape of a surface. He invented the thematic, or chloropleth map when he published a map showing the distribution of illiteracy in France as shadings. In later life he was an active politician.