Holmes being near perfect in most of the stories while Watson gradually devolves into a complete buffoon makes sense when you think about who's supposedly writing these stories, Dr. Watson himself after the fact and thus through Nostalgia Goggles. Reading the stories it becomes quite clear that these stories are being written from the perspective of someone who damned near worships Holmes from the beginning. It's highly likely that when writing these stories Watson props up Holmes intelligence and competence while simply ignoring, skipping over, or forgetting most of the bad or incompetent moments of Holmes or his own moments of intelligence and competence to make his friend look good while fixating on his own faults at the same time. This only becomes more and more pronounced as the years and the stories go by and thus book Holmes looks more competent while book Watson looks more like an idiot.
Alternatively, given that many clients learned of Holmes through Watson's stories, Watson may have intentionally devalued himself so that criminals would underestimate him and dismiss him as Holmes' weakling lackey.
A lot has been made of the apparent disparity between Holmes's knowledge in A Study in Scarlet (where he had nil knowledge of Literature and didn't even know that the earth circled the sun) and the remainder of the stories (where he is able to quote Goethe and Flaubert in the original). But consider this; at the time of A Study in Scarlet Watson was, by his own account, an unemployed idler and Holmes was furiously attempting to start his detective business up. Of course he wouldn't particular care who Thomas Carlyle was, not at a time when he may have been trying to prove someone's innocence. He would, however, care very deeply about how to prove where someone had been from the type of mud on their clothes and might talk to Watson about this as a way of sorting his own thoughts out. It wasn't until later on when he had bonded with Watson that he became comfortable enough to talk about trivialities.
It's also not impossible that Holmes might've picked up a few things from living with Watson.
If you read A Study in Scarlett carefully you will see that he is willfully, deliberately ignorant of things not relevant to his work. He thinks that human memory is limited, comparing it to a room, and that one should be careful with what to furnish it with. He expressly states that he will try to forget what Watson just told him. Supposedly he abandoned this misconception about how memory works later in his life.
Either that, or after several cases where he solves the problem due to some odd bit of knowledge not directly related to criminology, Holmes comes to the conclusion that pretty much anything can be potentially relevant to his work at least once given that he specializes in taking cases outside of conventional criminology, so he'd better broaden his general knowledge base. It's instructive to note that in "The Valley of Fear" Holmes is able to prove that Moriarty is earning a substantial amount of unreported income because of his knowledge of the current market prices for classical art, something that the Holmes of 'A Study In Scarlet' would have dismissed as entirely irrelevant.
Exactly. There's clear evidence in "The Five Orange Pips" that his views on general knowledge had evolved."I say now, as I said then, that a man should keep his little brain-attic stocked with all the furniture that he is likely to use, and the rest he can put away in the lumber-room of his library, where he can get it if he wants it. Now, for such a case as the one which has been submitted to us to-night, we need certainly to muster all our resources."
The Hound of the Baskervilles:
Watson remarks on the death of the escaped convict Neil Selden, brother of Henry Baskerville's butler's wife, that "Evil indeed is the man who has not one woman to mourn him." After the hound set loose by Stapleton fails to kill Henry Baskerville, his abused wife gleefully leads Holmes and Watson to his hideout. Watson doesn't outright say it, but this gives a strong impression of just how evil Stapleton is. (althechi)
The novel opens with Holmes reading about Dr James Mortimer who has written papers on 'Is Disease a Reversion', 'Some Freaks of Atavism' and 'Do we regress?'. Atavism is defined as 'The tendency to revert to ancestral type'. Later on, we discover that the main villain, Stapleton is a relative of the Baskervilles. How? By the fact that he looks almost identical to the painting of the evil Sir Hugo Baskerville (who was responsible for the Baskerville curse). In other words, Stapleton is a reversion to the evil Baskerville type and we have an incredibly brilliant piece of foreshadowing. Culfy
Professor James Moriarty is nicknamed "The Napoleon of Crime". Napoleon was finally defeated in Waterloo. What better way to end him than with a lot of water?
"The Man with the Watches" (traditionally considered a non-canon Holmes story by Arthur Conan Doyle): James, in the penultimate paragraph of his letter, says that he told his mother Edward was faring well in London, but never specifies if he spoke to Joe Willson about Edward. But the latter must have noticed the long absence of his sales agent in England - even moreso one he knew in person and a member of his longtime friends' family - and thus at least attempted to inquire further. And any one of the countless articles in English newspapers mentioning a dead man with six richly decorated American watches, complete with the man's description, would have revealed the truth.
Minor example combined with Values Dissonance: In "The Sign of Four", the kennel-keeper from whom Watson acquires the tracking dog Toby keeps a badger in his home. Most modern readers will dismiss his remarking on this as a (weak) injection of comedy. However, readers in Victorian times and those familiar with the era's customs will catch on that the badger is probably there as live bait for the dogs: possibly to train them what badgers smell like, but more likely so they can practice killing badgers. Not very horrific when written, but an ugly notion reminiscent of blood sports today.
The whole concept of Moriarty being a university professor is pretty horrifying in the fridge sense. Imagine, for those who go or have been to university, that one of your own lecturers was secretly a murderous evil criminal mastermind. Amusing at first but if you dwell on it, its kind of disturbing. Someone so abhorrent such as Moriarty having such a strong influence on the young and their education. And nobody has reason to suspect a damn thing. It's not just your professors. It could be your friends, your parents, your siblings, your school teachers, even just a person you walked past on the street. Who knows what kind of double lives people lead?
There's no indication that she died *soon* after the events of the story. As she was much younger than Watson, the fact that she did not outlive him might have been enough for him to call the death untimely.
It's Helen's hearing the strange noises that wakes her up the morning she decides to see Sherlock Holmes. Later on, Holmes theorizes that it's possible for the victim to not be bitten by the snake for up to a week and both the light and Holmes' striking the bellcord with his cane anger the snake into crawling back, biting the murderer...if that's the case, Helen might've prevented her own murder due to her insomnia!
The sheer number of times when Holmes manages to find the real culprit and exonerate an innocent party can become Fridge Horror if you consider that each and every one of those wrongfully-accused parties would likely have been imprisoned or executed without him. Holmes only begins practicing his trade in the 1870s. Just how many innocent people were being convicted of crimes they had nothing to do with, before he or his methods became established?