As The Hound of the Baskervilles opens, Dr. Watson picks up a walking stick left behind by a visitor the night before. Watson examines the stick and notes that it has a silver band inscribed with the words “To James Mortimer, M.R.C.S., from his friends of the C.C.H.” and the year “1884.” Watson thinks that the stick’s owner is likely an “old-fashioned family practitioner.”
Sherlock Holmes is sitting at the breakfast table with his back toward Watson, so Watson is startled when Holmes asks him, “Well, Watson, what do you make of it?” Watson does not think that he has given Holmes any clues about his actions, and he replies with a question of his own, namely, “How did you know what I was doing?” Sometimes Watson thinks that Holmes must have eyes in the back of his head.
Holmes responds with a humorous quip: “I have, at least, a well-polished, silver-plated coffee-pot in front of me.” This, of course, is exactly how Holmes knows what Watson is doing; he can see Watson’s reflection in the coffee pot.
Holmes invites Watson to make some observations about the walking stick, and he praises his friend as he does so. Then, however, Holmes takes the stick in his own hands, looks closely, and announces that most of Watson’s conclusions are “erroneous.” Holmes proceeds to put together a detailed portrait of the stick’s owner that turns out to be accurate right down to the man’s dog.