eard of
one or the other. So all life is a great chain, the nature of which is
known whenever we are shown a single link of it. Like all other arts,
the Science of Deduction and Analysis is one which can only be acquired
by long and patient study nor is life long enough to allow any mortal
to attain the highest possible perfection in it. Before turning to
those moral and mental aspects of the matter which present the greatest
difficulties, let the enquirer begin by mastering more elementary
problems. Let him, on meeting a fellow-mortal, learn at a glance to
distinguish the history of the man, and the trade or profession to
which he belongs. Puerile as such an exercise may seem, it sharpens the
faculties of observation, and teaches one where to look and what to look
for. By a man's finger nails, by his coat-sleeve, by his boot, by his
trouser knees, by the callosities of his forefinger and thumb, by his
expression, by his shirt cuffs--by each of these things a man's calling
is plainly revealed. That all united should fail to enlighten the
competent enquirer in any case is almost inconceivable."

"What ineffable twaddle!" I cried, slapping the magazine down on the
table, "I never read such rubbish in my life."

"What is it?" asked Sherlock Holmes.

"Why, this article," I said, pointing at it with my egg spoon as I sat
down to my breakfast. "I see that you have read it since you have marked
it. I don't deny that it is smartly written. It irritates me though. It
is evidently the theory of some arm-chair lounger who evolves all these
neat little paradoxes in the seclusion of his own study. It is not
practical. I should like to see him clapped down in a third class
carriage on the Underground, and asked to give the trades of all his
fellow-travellers. I would lay a thousand to one against him."

"You would lose your money," Sherlock Holmes remarked calmly. "As for
the article I wrote it myself."

"You!"

"Yes, I have a turn both for observation and for deduction. The
theories which I have expressed there, and which appear to you to be so
chimerical are really extremely practical--so practical that I depend
upon them for my bread and cheese."

"And how?" I asked involuntarily.

"Well, I have a trade of my own. I suppose I am the only one in the
world. I'm a consulting detective, if you can understand what that is.
Here in London we have lots of Government detectives and lots of private
ones. When these fellows are at