<P> Despite Holmes' remarkable reasoning abilities, Conan Doyle still paints him as fallible in this regard (this being a central theme of "The Adventure of the Yellow Face"). </P> <P> Though Holmes is famed for his reasoning capabilities, his investigative technique relies heavily on the acquisition of hard evidence . Many of the techniques he employs in the stories were at the time in their infancy (for example, Scotland Yard's fingerprint bureau opened in 1901). </P> <P> The detective is particularly skilled in the analysis of trace evidence and other physical evidence, including latent prints (such as footprints, hoof prints, and shoe and tire impressions) to identify actions at a crime scene (A Study in Scarlet, "The Adventure of Silver Blaze", "The Adventure of the Priory School", The Hound of the Baskervilles, "The Boscombe Valley Mystery"); using tobacco ashes and cigarette butts to identify criminals ("The Adventure of the Resident Patient", The Hound of the Baskervilles); handwriting analysis and graphology ("The Adventure of the Reigate Squire", "The Man with the Twisted Lip"); comparing typewritten letters to expose a fraud ("A Case of Identity"); using gunpowder residue to expose two murderers ("The Adventure of the Reigate Squire"); comparing bullets from two crime scenes ("The Adventure of the Empty House"); analyzing small pieces of human remains to expose two murders ("The Adventure of the Cardboard Box"), and an early use of fingerprints ("The Norwood Builder"). </P> <P> Because of the small scale of much of his evidence, the detective often uses a magnifying glass at the scene and an optical microscope at his Baker Street lodgings . He uses analytical chemistry for blood residue analysis and toxicology to detect poisons; Holmes's home chemistry laboratory is mentioned in "The Adventure of the Naval Treaty". Ballistics feature in "The Adventure of the Empty House" when spent bullets are recovered and matched with a suspected murder weapon . </P>

When did the first sherlock holmes come out