The only purpose originally intended to be served by the Stockton and Darlington Railway was the finding of a better outlet for coal from the South Durham coalfield. A company, with Edward Pease as the moving spirit, was formed in 1816, but two years later the projectors were still undecided whether to make a canal or "a rail or tramway." George Overton, who preceded George Stephenson as a distinguished railway engineer, wrote to them, however, advising the latter course. "Railways," he said, "are now generally adopted, and the cutting of canals nearly discontinued"; and he told them, further, that within the last fifteen years the great improvements made in the construction of tram-roads had led to the application of the principle to a number of new roads. His advice was adopted, and the first Act, obtained after several unsuccessful efforts, authorised the making and maintaining of "a railway or tramroad" from the river Tees, at Stockton, to Witton Park Colliery, with various branches therefrom. The line would, the Act said, be "of great public utility by facilitating the conveyance of coal, iron, lime, corn and other commodities from the interior of the county of Durham to the town of Darlington and the town and port of Stockton," etc. It was first intended to use wooden rails, and to rely on horse-power, no authority for the employment of locomotives being obtained under the Act of 1821; but George {226}Stephenson, on being appointed engineer to the line, persuaded the company to adopt iron rails in preference to wooden ones, and to provide a locomotive such as he had already constructed and successfully employed at Killingworth Colliery. Two-thirds of the rails laid were of malleable iron and one-third of cast iron. It was not, however, until September, 1824, that the order was actually given for a locomotive, some of the promoters having still shown a strong preference for the use of stationary engines and ropes. The line was opened for traffic on September 27, 1825, and the locomotive which had been ordered--the "Locomotion" as it was called--was ready for the occasion. It weighed seven tons, and had perpendicular cylinders and a boiler provided with only a single flue, or tube, 10 inches in diameter and 10 feet in length, the heat being abstracted therefrom so imperfectly that when the locomotive was working the chimney soon became red-hot.[38] The usual speed was from four to six miles an hour, with a highest possible of eight miles an hour on the level.