Arthur Conan Doyle study of such a character [viz., Bell] I used and amplified his methods when in later life I tried to build up a scientific detective who solved cases on his own merits and not through the folly of the criminal." Robert Louis Stevenson was able, even in faraway Samoa, to recognise the strong similarity between Joseph Bell and Sherlock Holmes: "My compliments on your very ingenious and very interesting adventures of Sherlock Holmes. ... can this be my old friend Joe Bell?" Other authors sometimes suggest additional influences—for instance, the famous Edgar Allan Poe character C. Auguste Dupin. Dr. (John)
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