History of crime fiction (1839) and Maurits Christopher Hansen's ""Mordet paa Maskinbygger Roolfsen" - The Murder of Engineer Roolfsen" (1839). An example of an early crime/revenge story is the American poet and short story writer Edgar Allan Poe's (1809–1849) tale "The Cask of Amontillado", published in 1846. Poe created the first fictional detective (a word unknown at the time) in the character of C. Auguste Dupin, as the central character of some of his short stories (which he called "tales of ratiocination"). In the words of William L. De Andrea ("Encyclopedia Mysteriosa", 1994), he One of the early developments started by Poe was the
Dupin indicatrix Dupin indicatrix In differential geometry, the Dupin indicatrix is a method for characterising the local shape of a surface. Draw a plane parallel to the tangent plane and a small distance away from it. Consider the intersection of the surface with this plane. The shape of the intersection is related to the Gaussian curvature. The Dupin indicatrix is the result of the limiting process as the plane approaches the tangent plane. The indicatrix was invented by Charles Dupin. For elliptical points where the Gaussian curvature is positive the intersection will either be empty or form a closed curve. In the