Sherlock Holmes: Other Sciences

Sherlock Holmes knew more chemistry than any other science. But in this chapter, we shall find that he was well informed in a number of other sciences as well. Since mathematics contributes to all sciences, we first examine the Canon for instances of mathematical knowledge. We find a number of references to and uses of math in nearly all the early stories. After Holmes and Moriarty supposedly went over the Reichenbach Falls in The Final Problem (FINA) and Holmes returned, he rarely used math again. In A Study in Scarlet (STUD), Watson scoff s at a magazine article that claims that the conclusions of a trained observer are as “infallible as so many propositions of Euclid.” He soon learns that his new roommate Holmes is the author of the article. So here, very early on, we have Holmes drawing a mathematical analogy to his deductive work. He invokes Euclid again in the second story, Sign of Four (SIGN). This time he chides Watson about his writing style. Holmes accuses Watson of allowing romanticism to creep into his narration of the previous case, STUD. According to Holmes, this awkward technique produces “much the same effect as if you worked a love-story or an elopement into the fifth proposition of Euclid.” The fifth proposition states that if two sides in a triangle are equal, then the angles opposite those two sides will also be equal. Note that Holmes makes no calculation using Euclid’s proposition, but he depends on Watson’s knowledge of math to make a point about the way the narrative of STUD was written. This is the first time, but not the last, that he criticizes Watson the chronicler. In SIGN, Holmes’s conversation again assumes that his listener is acquainted with mathematical terms. When he sees that Tonga has left a footprint in creosote, he claims that tracking him will be as easy as using the “rule of three,” which states that if three of the four terms in a proportion are known, then the fourth may be calculated.