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 upon his right forefinger, and a bulge on the right side of

his top-hat to show where he has secreted his stethoscope, I must 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. The distinction

is clear. For example, you have frequently seen the steps which lead up from

the hall to this room.”


“Frequently.”


“How often?”


“Well, some hundreds of times.”


“Then how many are there?”


“How many? I don’t know.”


“Quite so! You have not observed. And yet you have seen. That is just my

point. Now, I know that there are seventeen steps, because I have both seen and

observed. By the way, since you are interested in these little problems, and

since you are good enough to chronicle one or two of my trifling experiences,

you may be interested in this.” He threw over a sheet of thick,

pink-tinted notepaper which had been lying open upon the table. “It came

by the last post,” said he. “Read it aloud.”


The note was undated, and without either signature or address.


“There will call upon you to-night, at a quarter to eight

o’clock,” it said, “a gentleman who desires to consult you

upon a matter of the very deepest moment. Your recent services to one of the