The sanctified tradition that a detective was an agile person with a variety of side-whiskers no longer obtains even in light literature, and the most imaginative of us is frankly aware of the fact that a detective is just a common man earning (or pretending to earn) a common living by common and obvious means.  Yet in spite of ourselves we are accustomed to attribute superhuman acuteness and a lightning-like rapidity of intellect to this vague and romantic class of fellow-citizens.  The ordinary work of a detective, however, requires neither of these qualities.  Honesty and obedience are his chief requirements, and if he have intelligence as well, so much the better, provided it be of the variety known as “horse” sense.  A genuine candidate for the job of Sherlock Holmes would find little competition.  In the first place, the usual work of a detective does not demand any extraordinary powers of deduction at all.

Leaving out of consideration those who are merely private policemen (often in uniform), and principally engaged in patrolling residential streets, preserving order at fairs, race-tracks, and political meetings, or in breaking strikes and preventing riots, the largest part of the work for which detectives are employed is not in the detection of crime and criminals, but in simply watching people, following them, and reporting as accurately as possible their movements.  These functions are known in the vernacular as spotting, locating, and trailing.  It requires patience, some powers of observation, and occasionally a little ingenuity.  The real detective under such circumstances is the man to whom they hand in their reports.  Yet much of the most dramatic and valuable work that is done involves no acuteness at all, but simply a willingness to act as a spy and to brave the dangers of being found out.

There is nothing more thrilling in the pages of modern history than the story of the man (James McPartland) who uncovered the conspiracies of the Molly McGuires.  But the work of this man was that of a spy pure and simple.

Another highly specialized class of detectives is that engaged in police and banking work, who by experience (or even origin) have a wide and intimate acquaintance with criminals of various sorts, and by their familiarity with the latters’ whereabouts, associates, work, and methods are able to recognize and run down the perpetrators of particular crimes.

Thus, for example, there are men in the detective bureau of New York City who know by name, and perhaps have a speaking acquaintance with, a large number of the pick-pockets and burglars of the East Side.  They know their haunts and their ties of friendship or marriage.  When any particular job is pulled off they have a pretty shrewd idea of who is responsible for it and lay their plans accordingly.  If necessary, they run in the whole gang and put each of them through a course of interrogation, accusation, and browbeating until some one breaks down or makes a slip that involves him in a tangle.  These men are special policemen whose knowledge makes them detectives by courtesy.  But their work does not involve any particular superiority or quickness of intellect —­the quality which we are wont to associate with the detection of crime.