Special agents, apart from those qualities alluded to by Mr. Blair, should be men of intelligence and character, and possess an intuitive knowledge of physiognomy, phrenology, philosophy, or the ancient Moshical, or, rather, the Mosaical, so as to be able at a glance to read men and become acquainted with their “inward dispositions and with the faculties of their souls,” and be enabled to say, with Mr. Evelyn, who studied the science, “that man is all dissimulation.” But we contend that there are men who, having made the subject of detection a study, not by examining the features or watching the actions of others, but by analytical observations, are alone capable of fulfilling these positions. The system of ferreting out losses, or, rather, its process, is a science, and one that to succeed must be closely studied. Science is knowledge, art, power, and skill in the use of such knowledge: if it be directed to one particular object, exercising caution in such connection, the result will inevitably be favorable. The duties of a special agent are such that these qualifications are essential to success. And we may say that in the selection of men—men who now hold these positions—the postal department has not been governed by petty political influence, but on the principle involved in our popular maxim, “_The right man in the right place_.” The duties of a special agent are, in a measure, “secrets of the office,” and his movements are generally so quiet that few persons in and out of the office have the least idea what those duties are: hence the mystery in which all his operations seem involved. Perhaps it would not be proper, or, at least, so far as the interest of the department is concerned, for us to explain the exact position these special agents hold. They have a wide range of duties, which, however, it is not necessary to particularize and, as stated, explain, except so far as either of them may have a bearing upon the object of this work. All losses of valuable letters or depredations on the mails are submitted to them for investigation. The particular means to be used in discovering the exact locality of a theft from the mails or in ferreting out and arresting the perpetrators, are left entirely to their intelligence, vigilance, and ingenuity. It is natural that a special agent should become reserved, unobtrusive, quiet in all his actions, no hurry or bustle, ever cautious, so that he may be enabled to make discoveries without leading to suspicion and alarming the guilty. Indeed, such an effect on a man’s natural temperament would be the consequence of his peculiar business. His means, however, depend upon his observation: he first learns the amount of loss, the nature of the theft, the character of the money, and the line of postal communications between the sender and the expectant recipient. These are his ground-works, upon which he erects his superstructure, theoretical and practical, for the detection of the criminal.