In the early history of the Department in our own country persons were occasionally employed, in cases of emergency, to act as its representatives, and to exercise temporary supervision over some of the various branches of the mail service; but the Special Agent system, as it now exists, was first organized in the year 1840, while the Hon. Amos Kendall was at the head of the Department. The number of Special Agents in the United States has been gradually increased since their first establishment, and is now eighteen, suitably distributed throughout the country, each one having a district assigned him as the particular field of his operations, but to act elsewhere if so ordered. It is not the intention to enter into an argument for the purpose of proving the usefulness of this branch of the Department. If this has not been shown by the facts recorded in the former part of this volume, as well as by the many prominent and familiar cases all over the country, which have been so successfully conducted by other members of the corps, it would be in vain to attempt it now. I would only say a few words respecting the power of this system, to _prevent_ crime. There are some persons in the world of firm principles and unbending rectitude, who need not the aid of outward circumstances for the maintenance of an upright character. But perhaps the majority of mankind require some external helps in the way of restraints, from public opinion, and even the threatenings of the law. On such the fear of detection frequently acts in a most salutary manner, deterring from the commission of crime, and sometimes leading to a higher motive for right conduct than apprehension of punishment. In more than one instance, after the conclusion of some important case of depredation, I have been informed that money-letters, passing upon other routes than the ones under suspicion, and even at a considerable distance, have been regarded with a reverence never felt for them before. A portly envelope was considered a sort of Trojan horse, filled with the elements of destruction, ready to overwhelm the explorer of its treacherous recesses. This extraordinary caution was owing, of course, to the knowledge (which often gets out in spite of the utmost endeavors to prevent it) that the Special Agent was abroad; and when once a person has been thoroughly impressed with the danger of tampering with the forbidden thing, he does not soon nor easily yield to the whisperings of the tempter.