In 1819, the owners of the Hetton Colliery, in the county of Durham, determined to have their wagon-way altered to a locomotive railroad. The result of the working of the Killingworth Railway had been so satisfactory that they resolved to adopt the same system. One reason why an experiment so long continued and so successful as that at Killingworth should have been so slow in producing results perhaps was, that to lay down a railway and furnish it with locomotives, or fixed engines where necessary, required a very large capital, beyond the means of ordinary coal-owners; while the small amount of interest felt in railways by the general public, and the supposed impracticability of working them to a profit, as yet prevented the ordinary capitalists from venturing their money in the promotion of such undertakings. The Hetton Coal Company were, however, possessed of adequate means, and the local reputation of the Killingworth engine-wright pointed him out as the man best calculated to lay out their line and superintend their works. They accordingly invited him to act as the engineer of the proposed railway. Being in the service of the Killingworth Company, Stephenson felt it necessary to obtain their permission to enter upon this new work. This was at once granted. The best feeling existed between him and his employers, and they regarded it as a compliment that their colliery engineer should be selected for a work so important as the laying down of the Hetton Railway, which was to be the longest locomotive line that had, up to that time, been constructed in the neighborhood. Stephenson accepted the appointment, his brother Robert acting as resident engineer and personally superintending the execution of the works. The Hetton Railway extended from the Hetton Colliery, situated about two miles south of Houghton-le-Spring, to the ship-places on the banks of the Wear, near Sunderland. Its length was about eight miles; and in its course it crossed Warden Law, one of the highest hills in the district. The character of the country forbade the construction of a flat line, or one of comparatively easy gradients, except by the expenditure of a much larger capital than was placed at Stephenson's command. Heavy works could not be executed; it was therefore necessary to form the line with but little deviation from the natural conformation of the district which it traversed, and also to adapt the mechanical methods employed for its working to the character of the gradients, which in some places were necessarily heavy.