About the year 1850, it was noticed that stamps of different colors and design were received in the mails from various parts of the world. Then the idea of collecting stamps came into vogue. After a time children and young people generally began to collect and to study stamps. Every minute variation of paper, with style of printing, gum, water mark, and other differences was considered as making a different issue, and in some cases as many as fifty distinct styles of a single stamp have been collected. An extra fee of ten cents secures the immediate special delivery by messenger of any letter thus sent. Merchandise parcels can be sent as well as letters and papers. There is a money order system and at the present time a great deal of thought is put upon the question of post-office savings banks, which have already been successfully established in Great Britain and other countries of Europe. By the Constitution of the United States, Congress has power "to establish post-offices and post-roads." Before roads were common between one State and another, the mail was carried on horseback. Later, mail wagons were used to convey the mails from one office to another. As stagecoaches multiplied they were used as mail wagons, the Government paying the stage company a sum of money for carrying the mail pouches. [Illustration: ASSORTING MAIL ON THE TRAIN.] The general introduction of railroads modified this system of mail carriage. Almost every railroad has become a postal road, the mail being carried upon its trains. Most of the trains upon the main lines of railroads have each a postal car fitted up with the proper conveniences for receiving and delivering the mail at the various stations and sorting it while the train is moving. Suppose a mail pouch to be received at New Haven; before reaching Bridgeport its contents are sorted; all that is to go to Bridgeport is put into a separate pouch and dropped off at that place; that which is to go to Greenwich is put into another pouch and left there, and so on. The mail of New York City is put into various pouches according to its destination. The mail matter for the sub-offices, like Station A and Station B, is put into separate pouches and sent from the railroad station on 42d Street directly to these offices, while that for the central office is so sorted that there is no delay in sending it out after its arrival at the office. The letters for lock boxes are placed together by sections, while those for carriers are put up in divisions so as to be delivered at once to the several carriers. Meantime mail matter which is to go beyond New York is put into proper pouches so that one can be dropped off at Trenton, another at Philadelphia, and so on.