“Something on the surface of the mirror interposed between my eye and the reflection, slightly blurring the image.  I focussed on it with some difficulty and then saw that it was a group of finger-marks; the prints made by the greasy fingers of my dandy customer when he had leaned on the glass to inspect his teeth.  As they grew distinct to my vision, I was aware of a curious sense of familiarity; at first merely subconscious and not strongly attracting my attention.  But this state lasted only for a few brief moments.  Then the vague feeling burst into full recognition.  I snatched out my lens and brought it to bear on those astounding impressions.  My heart thumped furiously.  A feeling of awe, of triumph, of fierce joy and fiercer rage surged through me, and mingled with profound self-contempt.

“There could be no mistake.  I had looked at those finger-prints too often.  Every ridge-mark, every loop and whorl of the varying patterns was engraved on my memory.  For twenty years I had carried the slightly enlarged photographs in my pocket-book, and hardly a day had passed without my taking them out to con them afresh.  I had them in my pocket now to justify rather than aid my memory.

“I held the open book before the glass and compared the photographs with the clearly-printed impressions.  There were seven finger-prints on the mirror; four on the right hand and three on the left, and all were identical with the corresponding prints in the photographs.  No doubt was possible.  But if it had been—­

“I darted across to the chair.  The floor was still littered with the cuttings from that villain’s head.  In my idiotic preoccupation with the other man I had let that wretch depart without a glance at his hair.  I grabbed up a tuft from the floor and gazed at it.  Even to the unaided eye it had an unusual quality when looked at closely; a soft, shimmering appearance like that of some delicate textile.  But I gave it only a single glance.  Then rushing through to the parlor, I spread a few hairs on a glass slip and placed it on the stage of the microscope.

“A single glance clenched the matter.  As I put my eye to the instrument, there, straying across the circular field, were the broad gray stripes, each with its dark line of medulla obscured at intervals by rings of tiny bubbles.  The demonstration was conclusive.  This was the very man.  Humanly speaking, no error or fallacy was possible.

“I stood up and laughed grimly.  So much for instinct!  For what fools call intuition and wise men recognize for mere slipshod reasoning!  I could understand my precious intuition now; could analyze it into its trumpery constituents.  It was the old story.  Unconsciously I had built up the image of a particular kind of man, and when such a man appeared I had recognized him at a glance.  The villainous Tartar face:  I had looked for it.  The fierce, furtive, hunted manner; the restless suspicion; the mop of grayish-brown hair.  I had expected them all, and there they were.  My man would have those peculiarities, and here was a man who had them.  He, therefore, was the man I sought.