e thieves and recover the stolen property.

"Shadowing," too, is a matter of experience. Let anyone who doubts its
difficulties try the experiment of keeping sight of a person in a
frequented thoroughfare. When a suspect knows or guesses he is being
followed--as he inevitably does, if it is continued for a day or two--it
becomes ten times more difficult. Unless incessant watchfulness is
maintained, a shadowed person will be lost sight of in five minutes.
Shadowing is, when possible, always done by detectives in pairs,
sometimes in threes. Detective No. 1 shadows the suspect, detective No.
2 shadows his colleague. Then if the suspect stops or turns suddenly No.
1 walks innocently on and No. 2 takes up the chase. It is a wearisome
task when a person has to be watched incessantly, for it may not be
possible to assign a spot with any certainty for reliefs to continue the
trail.

When the young detective begins his career he will carry a virgin
drab-coloured diary in his breast pocket, wherein he will be expected to
record every moment spent on duty, every penny he spends. If any
illusion remains in his mind that he will be turned loose on the streets
to catch thieves or murderers, it is quickly destroyed. Hard labour is
his portion. Small enquiries at pawnbrokers', searching directories to
verify addresses, running errands for his superiors, and doing all the
small odd jobs are his immediate concern.

Only now and again is he called upon to play a minor part in an arrest.
But all the while he will be learning and improving his acquaintance
with the thieves in his district. All his painfully acquired knowledge
goes for little unless he can cultivate a certain friendship with the
rogues in the vicinity of his sphere of duty.

The "informant" plays a big part in the workings of Scotland Yard. If
the old phrase, "Honour among thieves," had any truth in it, London
would be a poor place for honest men to live in. But gossip of the
underworld is easily attainable to ears that wish to catch it.

One of the problems which beset the architect of New Scotland Yard was
this same problem of the informant. An inconspicuous entrance had to be
arranged by which access could be unobtrusively gained by a person too
shy to be seen walking publicly up the main entrance of the headquarters
of police.

A great detective once told the writer how, in his early days, he set to
work to learn the world, and gained valuable acquaintance with the