Gentleman detective He lives in Paris with his close friend, the anonymous narrator of the stories. Like the much later Lord Peter Wimsey (see below), Dupin is a bibliophile, and met his narrator friend while both were searching for "the same rare and very remarkable volume" in an obscure library. For hobbies, Dupin is "fond" of enigmas, conundrums, and hieroglyphics. Dupin also bears the French title "Chevalier", meaning that he is a knight in the Légion d'honneur. The classic British gentleman detective appears soon after Poe's Dupin. A gentleman amateur is the ultimate hero of "The Moonstone" (1868), a famous epistolary novel
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