"The deeper one ventures, the wider yawns the cave. In the beginning we only see the crusty rim of rock about the entrance—we may pass by, or step in, but once in, Watson—ah, once we are inside—we are drawn deeper, and deeper still."
I paused to draw on my cigarette. He was watching me intently. "You look at a button and see a button. I look at a button and see when it was made, who made it, why they made it, where they made it, if they were a cripple and how their wife pulls weeds on Saturday afternoon."
He leaned forward. "It is a great burden, Holmes, I admit."
"That's only the beginning! When I look at the button hole, I observe how it was cut. Is it too large? A nervous hand, perhaps? The colour of the thread, the type of stitching. Is that type the normal one for the cut of coat? Quality of material? And anything I don't know, I must look up at once—"
"Holmes."
"Do you understand what I'm saying, Watson? The depth to which my mind can go is inexorable; whenever I think I've mastered something, the floor opens beneath me, and there's another level, more information, more connections to be made—"
He grasped my shoulders. "Holmes: breathe."