'One night -- it was on the twentieth of March, 1888 -- I was returning from a journey to a patient (for I had now returned to civil practice), when my way led me through Baker Street. As I passed the well-remembered door, which must always be associated in my mind with wooing, and with the dark incidents of the Study in Scarlet, I was seized with a keen desire to seek Holmes again, and to know how he was employing his extraordinary powers. His rooms were brilliantly lit, and, even as I looked up, I saw his tall, spare figure pass twice in a dark silhouette against the blind. He was pacing across the room swiftly, eagerly, with his head sunk upon his chest and his hands clasped behind him. To me, who knew his every mood and habit, his attitude and manner tole their own story. He was at work again. He had risen out of his drug-created dreams and was hot upon the scent of some new problem. I rang the bell and was shown up to the chamber which had formerly been in part my own.
His manner was not effusive. It seldom was; but he was glad, I think, to see me. With hardly a word spoken, but with a kindly eye, he waved me to an armchair, threw across his case of cigars, and indicated a spirit case and a gasogene in the corner. Then he stood before the fire and looked me over in his singular introspective fashion.
"Wedlock suits you," he remarked. "I think, Watson, that you have put on seven and a half pounds since I saw you."
"Seven!" I answered.
"Indeed, I should have thought a little more. Just a trifle more, I fancy, Watson. And in practice again, I observe. You did not tell me that you intended to go into harness."
"Then, how do you know?"
"I see it, I deduce it. How do I know that you have been getting yourself very wet lately, and that you have a most clumsy and careless servant girl?"
"My dear Holmes," said I, "this is too much. You would certainly have been burned, had you live a few centuries ago. It is true that I had a country walk on Thursday and came home in a dreadful mess, but as I have changed my clothes I can't imagine how you deduce it. As to Mary Jane, she is incorrigible, and my wife has given her notice; but there, again, I fail to see how you work it out."
He chuckled to himself and rubbed his long, nervous hands together.
"It is simplicity itself," said he; "my eyes tell mt that on the inside of your left shoe, just above where the firelight strikes it, the leather is scored by six almost parallel cuts. Obviously they have been caused by someone who has very carelessly scraped round the edges of the sold in order to remove crusted mud from it. Hence, you see, my double deduction that you had been out in vile weather, and that you had a particularly malignant boot-slitting specimen of the London slavey. As to your practice, if a gentleman walks into my rooms smelling of iodoform, with a black mark of nitrate of silver on his right forefinger, and a bulge on the right side of his top-hat to show where he has secreted his stethoscope, I might be dull, indeed, if I do not pronounce him to be an active member of the medical profession."
I could not help laughing at the ease with which he explained his process of deduction. "When I hear you give your reasons," I remarked, "the thing always appears to me to be so ridiculously simple that I could easily do it myself, though at each successive instance of your reasoning I am baffled until you explain your process. And yet I believe that my eyes are as good as yours."
"Quite so," he answered, lighting a cigarette, and throwing himself down into an armchair. "You see, but you do not observe." '
-- Sir Arthur Conan Doyle, A Scandal in Bohemia