"How, then, did you deduce the telegram?"
"Why, of course I knew that you had not written a letter, since I sat opposite to you all morning. I see also in your open desk there that you have a sheet of stamps and a thick bundle of postcards. What could you go into the post-office for, then, but to send a wire? Eliminate all other factors, and the one which remains must be the truth."
"In this case it certainly is so," I replied after a little thought. "The thing, however, is, as you say, of the simplest. Would you think me impertinent if I were to put your theories to a more severe test?"
"On the contrary," he answered, "it would prevent me from taking a second dose of cocaine. I should be delighted to look into any problem which you might submit to me."
"I have heard you say it is difficult for a man to have any object in daily use without leaving the impress of his individual– ity upon it in such a way that a trained observer might read it. Now, I have here a watch which has recently come into my possession. Would you have the kindness to let me have an opinion upon the character or habits of the late owner?"
I handed him over the watch with some slight feeling of amusement in my heart, for the test was, as I thought, an impossible one, and I intended it as a lesson against the some– what dogmatic tone which he occasionally assumed. He balanced the watch in his hand, gazed hard at the dial, opened the back, and examined the works, first with his naked eyes and then with a powerful convex lens. I could hardly keep from smiling at his crestfallen face when he finally snapped the case to and handed it back.