These solid tram-plates were made of cast-iron, that metal being considered the most convenient for manufacture and the least liable to suffer loss from rust and oxidization. Another advantage of the cast-iron was that broken tram-plates could be melted down and recast at a moderate cost. Long lengths of these cast-iron plate tramways were laid down in this country and abroad, and short portions of some of them remain in existence even to the present day. They were of immense service for 185 the transportation of heavy materials, and without their adventitious aid many valuable collieries and quarries must long have remained idle and undeveloped. In thus providing a level, smooth, and comparatively durable wheel-track for the waggons, these tramways became the fitting pioneers of the great railway system which was to follow. Notwithstanding the great superiority of the cast-iron plates as compared with the former timber beams, much inconvenience was still caused by gravel and dirt falling on to the wheel-track and seriously impeding the haulage of the waggons. To overcome this difficulty the next step taken was to remove the guiding flange from the tram-plate and transfer it to the wheel, thus developing and introducing the original flanged wheel. This was a most important step, and paved the way for other improvements. The rails, or _edge rails_, as they were at first called, were made sufficiently high to allow ample space for the wheel-flanges to clear the ground, and were secured to cast-iron chairs placed on wooden cross-sleepers, or in some cases to stone blocks, as shown in Figs. 233, 234, and 235. The narrow top of rail, and its height above the horse-path, effectually prevented the lodgment of gravel or dirt, and the flanges on the wheels ensured a more even course. From the irregular and easily choked-up tram-plate, the system changed to the clean rail and properly defined track. Waggons could be hauled with greater freedom, and with less wear and tear to themselves and to the roadway. At this time the use of the steam-engine was becoming more general, and a fine field was opened out for its application as a motive-power on the tramways. Stationary engines, or _winding engines_, as they were called, were first employed to haul the trucks by means of long ropes passed round revolving drums, and supported at intervals by grooved pulleys placed between the rails at suitable distances. In this way fair loads could be conveyed, and at moderate cost; but the system was found to be only suitable for short distances, and it had the great drawback that horses or other motive-power were still necessary for sorting or distributing the trucks before and after their transit by rope haulage.