it rested in the chairs, to an extent which rendered it unfit for a running surface. This section of rail is still in use on some of the railways in this country, but it is being rapidly superseded by the "bull-headed" section (Fig 4, No. 6), which is simply a refined and enlarged copy of George Stephenson's single-headed rail, and was used in very nearly its present form on the Shropshire Union Railway some forty years ago.
Up to the year 1847 the ends of the rails rested in joint chairs, but in that year Mr. Bridges Adams introduced the suspended joint with fish-plates (Fig. 5, No. 1), by which a much greater degree of elasticity was imparted to the permanent way. The innovation was not adopted upon the London and North-Western Railway until the year 1853, but although, since then, many other plans have received a trial, and some hundreds of patents have been taken out, this form of connecting the rails is found to be the most simple and effectual, and, with one improvement, which is shown by Fig. 5 No. 2, is still used universally on the London and North-Western Railway.
Rails have gradually increased in length, in depth, and in sectional area, but perhaps the greatest improvement which has been effected in them is in the change of material from malleable iron to Bessemer steel. Steel is not only found to be more homogeneous, generally wearing uniformly from end to end, but its strength is half as great again as that of iron, and the rail may thus be reduced in weight by abrasion and corrosion to an extent that would be unsafe in an iron rail. On the other hand, it is only fair to add that steel corrodes more rapidly than iron (in the proportion of about five to four), and in tunnels, and in manufacturing districts
