This is the designation of a very useful and indispensable class of officials, who were hardly known to the service in this country previous to the year 1839. Their introduction appears to have been contemporaneous with the employment of railroads for the transportation of the U. S. mails, and a necessary consequence of the adoption of this mode of conveyance. The number of these Agents has been progressively increased in proportion with the extension of railroads, and they are now employed upon nearly all these roads in this country, as well as upon many of the steamboats which carry the mails. Since 1847, they have increased as follows:-- In 1848 there were 47 1849 " " 61 1850 " " 100 1851 " " 127 1862 " " 209 1864 " " 260 1856 " " 295 By the terms of contract with each railroad company, it is required to furnish a suitable car for the use of the mail or Route Agent when so requested by the Department. The Agent occupies this traveling post-office, or mail car, receives and delivers mails along the route; assorts, and gives the proper direction to all mail matter passing through his hands; mails such letters, pre-paid _by stamps_, as are handed him, and accompanies the mails in their transit between the post-office and the railroad station or steamboat, at the terminus of the route. It is too often the case that persons of influence, in proposing a candidate for this responsible post, greatly undervalue the nature and importance of the duties to be performed, supposing that they involve merely the mechanical labor of delivering mail bags at the different post-office stations upon the route. The fact is, that the successful working of our postal machinery depends in no small degree upon the active, faithful, and intelligent discharge of the Route Agents' duties. In New England especially, and perhaps in some other sections of the country, a very large proportion of the correspondence passes through the hands of these officials, at some stage in its progress. Much care, and a thorough knowledge of the topography of the sections of the country through which the route lies, as well as that of more distant portions, are therefore required for giving letter and other packages a direction by which they will reach their destination in the shortest possible time. And that essential preliminary, the ascertaining where a given package is to go, is a matter not always easy of accomplishment. For the most skilful interpreters of the species of chirography known as "quail tracks," are often taxed to their utmost capacity of learning and experience, in the endeavor to decipher the outside addresses of packages which they are required to "distribute" without loss of time.