During a particularly slow afternoon in our chambers, Holmes and I had rejoined for a hot beverage when he chose to spring another of his unexpected riddles on me.
“Here’s a little puzzle to keep your brain sharp on this dullest of days, Watson,” he said, with something of a twinkle in his eye. “The riddle is this: It enters dry, and yet comes out wet. The longer it’s in, the stronger it gets. What is it?”