There are a great many private detective organizations in New York City, some of which are located in elegant and commodious quarters, with a net-work of agencies covering the whole country and extending even to Europe. Between these reliable firms and the guttersnipe operator there are among detectives, as among other professions, every grade of reliability and respectability, some making a handsome living and some earning a bare existence. There are some thousands of them, and they all occasionally find something to do which pays. It may be watching some money-broker's exchange down-town, for the dishonest boy of some establishment clandestinely selling the postage stamps of his firm. It may be shadowing a confidential clerk, whose blood-shot eyes and generally "used-up" air have attracted the notice of his employers, who thereupon desire to learn where and how his evenings are spent. It may be some bank clerk, hitherto enjoying the confidence of the directors, but who now, in consequence of certain rumors, desire to have him watched. Or it may be any of a thousand instances in which an employee ceases to retain the full confidence of his employer, and the convenient private detective's services are at once put in requisition. Undoubtedly it would greatly surprise the army of clerks, cashiers and assistants of this and every great city to learn how many of them are thus under detective espionage. The young fellow may have fallen into the web of the siren. He may be down at Coney Island or at the races enjoying himself; utterly unconscious that a pair of watchful eyes is observing every motion and chronicling every act. Some fatal morning the reckoning comes. He may be a bank teller, and he is requested by the board of directors to show his books and give an account of the situation and prospects of the bank. Despite his proficiency in bookkeeping, he will be unable to figure up and cover the money he has squandered in gambling houses, on the street, or at the race-course. _"Crimine ab uno disce omnes,"_ says Virgil. From a single offense you may gather the nature of the whole.