Michael Harrison (writer) Michael Harrison (writer) Michael Harrison (25 April 1907 – 13 September 1991) was the pen name of English detective fiction and fantasy author Maurice Desmond Rohan. Michael Harrison was born in Milton, Kent, England, on 25 April 1907. He attended the University of London and served briefly in the British Military Intelligence during World War II. He married Marie-Yvonne Aubertin. Harrison published seventeen novels between 1934 and 1954 when he turned to writing detective fiction. He wrote pastiches of Conan Doyle's Sherlock Holmes and Poe's C. Auguste Dupin and was a noted Sherlock Holmes scholar. His most successful work, "In
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