History of modern literature born. Mikhail Lermontov published "A Hero of Our Time" In 1841 Phillipe-Ignace François Aubert de Gaspé died. Edgar Allan Poe published two short stories: "A Descent into the Maelström" and "The Murders in the Rue Morgue". The latter introduced the fictional detective C. Auguste Dupin. Mikhail Lermontov was killed in a duel. In 1842, Nikolai Gogol published "Dead Souls". In 1843 the transatlantic author Henry James was born. Edgar Allan Poe published a poem: "Lenore" and four short stories: "The Gold-Bug", "The Black Cat", "The Tell-Tale Heart" and a C. Auguste Dupin short story called "The Mystery of Marie Roget".
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