The lay observer will scarcely appreciate, in the absence of the actual analysis, that there exists so many branches of this subject, each branch of which, by itself, may be considered the object of a separate professional science and a distinct human industry. EARLY RAILROAD HISTORY. Railways had their origin in tramways laid over 200 years ago in the mineral districts of England, which conveyed coal to the sea. Animal motive power was used. By the discovery, in 1814, of the adhesion of a smooth wheel to a smooth rail, it became possible to consider the employment of the tractive power of a rolling locomotive, and for some time subsequent to this, to the trial trip of the "Rocket," in 1829, which may be described as the first successful steam locomotive, the experiments were along these lines. While industrial railroads similar in character to the English existed in this country, the Baltimore & Ohio was the pioneer American railroad built for public use. On July 4, 1828, the first rail was laid by Charles Carroll, the only surviving signer of the Declaration of Independence, and thirteen miles were opened for traffic in 1830. In the same year the West Point Foundry began building locomotives, producing the "De Witt Clinton," in 1831. It weighed three and one-half tons, and was built for the Mohawk & Hudson Railroad, the pioneer company of the present New York Central Lines, which had been chartered in 1826, four years before actual construction was begun. The line was opened from Albany to Schenectady in 1831; to Utica in 1836, and to Buffalo in 1842. Connections to New York and Boston were built in rapid succession. About this time, in Pennsylvania, the Columbia Railroad was built from Philadelphia to Columbia, on the Susquehanna River, forming the pioneer division of the present Pennsylvania System. Several companies were chartered about the same time in Massachusetts.