there that you have a sheet of stamps and a thick bundle of post-
cards. 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 that it is difficult for a man to have any
object in daily use without leaving the impress of his
individuality 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 somewhat 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.