Natural speed please
In a 1927 Fox newsreel Conan Doyle explained: “In the old-fashioned detective stories, the detective always seems to get to his results either by some sort of lucky chance or without giving an explanation on how: it seemed to me that he is bound to give his reasons, why he came to this conclusions.” So he began to think of turning scientific methods onto the work of detection and took inspiration from the method of diagnosis used by one of his professors at university: Joseph Bell (1837-1911), who “wouldn’t do these things by chance; he would get the thing by building it up, scientifically”. Conan Doyle wrote to him, "It is most certainly to you that I owe Sherlock Holmes. ... Round the centre of deduction and inference and observation which I have heard you inculcate I have tried to build up a man.” Sherlock Holmes was also modeled after Sergeant Cuff, a character by Wilkie Collins, and Auguste Dupin by Edgar Allan Poe.
If you are curios about the newsreel you can watch it here: http://www.archive.org/details/SirArthurConanDoyleSpeaks_272