B. ENGINEERING AND GENERAL CONSTRUCTION Track or Permanent Way.—The desire to move heavy min erals such as stone and coal more easily than by road led to the employment of "wagon-ways" in Great Britain during the 17th century. These "wagon-ways" merely consisted of wooden planks laid on the ruts caused by the cart wheels, but they enabled much greater loads to be hauled by horses, at that time the source of motive power. It soon became necessary to hold these planks in their proper position by means of sleepers or cross-ties, a name still used in America. Owing to the rapid wear of the planks it became the custom to cover them with metal plates, or strips, usually of iron, while the sleepers were covered with earth to prevent damage from the horses' hoofs. The use of metal on the planks in its turn created undue wear on the wooden wheels of the wagons, mainly of the chaldron type still visible on Tyne side; consequently iron wheels were adopted. Growth of traffic caused the strips to work loose, with the result that attempts were made to cast iron rails in 1767 at Coalbrookdale Iron Works. These rails were of the L type, namely a flat plate with a vertical section on the inner side to prevent the wheels from running off the rails (fig. 1). They were usually spiked to the wooden cross ties, although in some cases they were mounted on stone blocks to reduce the wear on the cross-ties, which in that case were placed at much less frequent intervals. Plate rails of this type were used by Benjamin Outram on the Ticknall Tramway in 1799, and sim ilar rails were used on the Surrey Iron Railway of 18o1 and the Silkstone Railway of 1809. In order to hold the rail in position some of these plate rails were I-. shaped. In the north of Eng land the edge type of rail (fig. 2) was preferred and became the prototype of the present railway rail. With the edge-rail the wheel rested on the top, with a flange tohold it to the rail designed as part of the wheel, and not as part of the rail, and run ning inside the latter. Blenkinsop's rail way at Leeds in 1812 used rails of the edge type weighing 4olb. per yd., mounted upon pedestals. With the coming of steam trac tion the edge rail was almost universally adopted, except where the railway was of a tramway type designed to run along the highway. Cast iron rails of this date were
usually about 3ft. long and were not con nected at the ends. George Stephenson used the "half-lap" joint on his Killing worth Railway and, later, for the Stockton and Darlington line employed malleable iron rails weighing 281b, per yd. The wrought iron edge-rail, often of the "fish bellied" type, was mainly used during the 'thirties of last century. In the case of the Liverpool and Manchester line it weighed 351b. The pedestal of 1812 became the chair of the Liverpool and Manchester, which was spiked to the cross-ties and the rails wedged by compressed wooden keys into the chairs. On this line fish bellied rails gave place to parallel rails, namely, those of uni form cross section for all their length.
C. B. Vignoles (1793-1875) used the flat-bottomed rail (fig. 3) in England in 1836; it eliminated the chair since it could be spiked direct to the sleeper, while I. K. Brunel employed a bridge rail (fig. 4) on the Great Western Railway. Joseph Locke introduced the double-headed rail (fig. 5) in 1835, which theoretically enabled the rail to be reversed, but in practice damage caused to the base resting in the metal chair prevented this. The present design of "bull," or single-headed rail (fig. 6) was evolved from the double-headed rail and has been standard in Great Britain for many years ; the Great Western giving up its bridge-rail on the conversion of gauge in 1892. An important development was the adoption of the steel rail shortly after Bessemer invented his process of steel manufacture, though to-day many rails are manu factured by the open hearth process. During the 19th century the growth in length and weight of rails had been continuous and by 1894 the L.N.W.R. was using 6oft. rails, although in 1922 rails used by the other railways were mainly 4o or 45ft. long, and weighed between 90 and loolb. per yd. In 1924 the British Standard Section Steel Rail weighed 951b. per yd. with a lighter rail of 851b. per yd. for branch lines. The L.M.S.R. uses 6oft. rails for its main line and this length is becoming more popular. although some railways still use 45ft. rails.