of the detective force is constantly employed at this routine business, while fifteen per cent., or even less, is engaged on work that is not in a large measure mechanical.
As for Chief Manning, his genius for directing his subordinates is inconspicuously employed all the time.

But occasionally a more exacting demand will be made on it.

It may be in a homicide case in which a wife has poisoned her husband.
Of course, in a case of this sort, "stool pigeon" men are useless, for no professional crooks are involved.

So Manning assigns six or seven of his best men to the case.

They do not roam about promiscuously, treading on one another's toes.