Crime fiction by the Danish author Steen Steensen Blicher, published in 1829. Better known are the earlier dark works of Edgar Allan Poe. His brilliant and eccentric detective C. Auguste Dupin, a forerunner to Arthur Conan Doyle’s Sherlock Holmes, appeared in works such as "The Murders in the Rue Morgue" (1841), "The Mystery of Marie Roget" (1842), and "The Purloined Letter" (1844). With his Dupin stories, Poe provided the framework for the classic detective story. The detective’s unnamed companion is the narrator of the stories and a prototype for the character of Dr. Watson in later Sherlock Holmes stories. Wilkie Collins' epistolary
Dupin cyclide that the class of Dupin cyclides is invariant under Möbius (or conformal) transformations. In complex space formula_2 these three latter varieties can be mapped to one another by inversion, so Dupin cyclides can be defined as inversions of the torus (or the cylinder, or the double cone). Since a standard torus is the orbit of a point under a two dimensional abelian subgroup of the Möbius group, it follows that the cyclides also are, and this provides a second way to define them. A third property which characterizes Dupin cyclides is that their curvature lines are all circles (possibly through