Gentleman detective English country house. This archetype of British detective contrasts with the more "hardboiled" counterpart in American crime fiction. Gentlemen detectives appeared early in modern detective fiction, which began in the late 19th century. C. Auguste Dupin, created by Edgar Allan Poe, is widely considered to be the first fictional detective in English literature. He appeared in three short stories written in the 1840s: "The Murders in the Rue Morgue" (1841), "The Mystery of Marie Rogêt" (1842) and "The Purloined Letter" (1844). Poe created Dupin before the word "detective" had been coined, but began many common elements of detective fiction: Dupin
Dupin cyclide of Dupin cyclides is invariant under the larger group of all Lie sphere transformations; any two Dupin cyclides are Lie-equivalent. They form (in some sense) the simplest class of Lie-invariant surfaces after the spheres, and are therefore particularly significant in Lie sphere geometry. The definition also means that a Dupin cyclide is the envelope of the one-parameter family of spheres tangent to three given mutually tangent spheres. It follows that it is tangent to infinitely many Soddy's hexlet configurations of spheres. A further special property of a cyclide is: An elliptic cyclide can be represented parametrically by the following formulas