Watson is a cheap, efficient little sod of a literary device. Holmes doesn't need him to solve crimes any more than he needs a ten-stone ankle weight. The audience, Arthur. The audience needs Watson as an intermediary, so that Holmes's thoughts might be forever kept just out of reach. If you told stories from Holmes's perspective, everyone would know what the bleeding genius was thinking the whole time. They'd have the culprit fingered on page one.
In the darkest corner of a darkened room, all Sherlock Homes stories begin. In the pregnant dim of gaslight and smoke, Holmes would sit, digesting the day's papers, puffing on his long pipe, injecting himself with cocaine. He would pop smoke rings into the gloom, waiting for something, anything, to pierce into the belly of his study and release the promise of adventure; of clues to interpret; of, at last he would plead, a puzzle he could not solve. And after each story he would return here, into the dark room, and die day by day of boredom. The darkness of his study was his cage, but also the womb of his genius.
On Westminster Bridge, Arthur was struck by the brightness of the streetlamps running across like a formation of stars. They shone white against the black coats of the marching gentlefold and fuller than the moon against the fractal spires of Westminster. They were, Arthur quickly realized, the new electric lights, which the city government was installing, avenue by avenue, square by square, in place of the dirty gas lamps that had lit London's public spaces for a century. These new electric ones were brighter. They were cheaper. They required less maintenance. And they shone farther into the dime evening, exposing every crack in the pavement, every plump turtle sheel of stone underfoot. So long to the faint chiaroscuro of London, to the ladies and gentlemen in black-on-black relief. So long to the era of mist and carbonized Newcastle coal, to the stench of the Blackfriars foundry. Welcome to the cleasing glare of the twentieth century.
Harold had become, over the past week, a connoisseur of silences. He was an expert at differentiating the particulars; was this a Tranquil Silence, marked by slow sighs and peaceful smiles? Or was it a Tired Silence, marked by ornery chair shifting? Or a Tense Silence, full of tight breaths and cautious glances?
Why, of course, if the reader were smart enough, he could figure the whole thing through after just the first few pages! But in his heart Arthur knew that his readers didn't really want to win. They wanted to test their wits against the author at full pitch, and they wanted to lose. To be dazzled.