Some tramways added an iron wearing rail atop the wooden rail. However the thin wearing rail, while more durable, also wore out under heavy use or became detached from the wooden rail underneath . What was needed was to make the rails solely out of iron, a much stronger solution and with reduced friction compared to wood. Iron rails could also carry heavier wagons which might break wooden rails. The strongest rails were fish-bellied rails, a type patented by Willian Jessop, which had the thickest iron (the "fish belly") in between the sleepers . However cast iron rails were much more expensive than wood.
|Fish bellied rail, public domain image |
Among the earliest iron rails were at Coalbrookdale in 1767 , they may have also been used at the Middleton Railway as early as 1758 . The Caldon Low line in Derbyshire also had iron rails not long afterwards. Cast iron rails also appeared in South Wales in the early 1790s. The extra expense of iron rails meant that such a railway was a more long term investment often attracting interest from canal companies who saw railways as a cheaper way to extend their network especially in areas of hilly terrain where a canal would need to major expense of lock flights . A major line was the Cromford & High Peak Railway which linked to the Cromford Canal.
|Cromford & High Peak Railway|
The rails used on these tramways were known as "edge-rails". They were intended to work with flanged wheel, as railway tracks do today. However there was a competing type of track which gained popularity in the late 1700s, the flanged rail or plateway. These were L-shaped and intended for use with wagons which had flat (unflanged) wheels . They were first developed by John Curr in 1787 and were cheaper and easier to make than edge-rails . They would also allow normal road carts to use the plateway, though in the event this seldom occurred. Networks of plateways quickly expanded, especially in the Midlands and South Wales though the North East of England where the largest wooden wagonway networks had been built the edge-rail remained the rail of choice. Plateways lost their popularity as steam power began to be used.
A drawback with cast-iron rails was their brittleness under heavy load . Plateways helped alleviate the problem somewhat. The main breakthrough came with the wrought-iron rail. Wrought-iron was stronger and was patented by John Birkenshaw in 1820  as a T-rail with a flat top and a fish-belly to add strength between sleepers, a development of which is now standard on railways across the world. Birkenshaw's rails were supported by George Stephenson and used on the Stockton & Darlington main line in 1825 and the rest (as they say) is history...
|Wagon of the Stratford & Moreton Tramway, notice the rails|
 Andy Guy & Jim Rees, Early Railways 1569-1830 (Shire Publications, 2016) p. 18
 Bertram Baxter, Stone Blocks & Iron Rails (Tramroads) (David & Charles, 1966) p. 43
 John Elfreth Watkins, The development of the American rail and track (US Govt, 1891) p. 657
 Baxter p. 40
 Mark Jones, Discovering Britain's First Railways (History Press, 2012) p. 25
 Baxter p. 22
 Jones p. 26
 Guy & Rees p. 20
 Michael Bailey, "The history of tracks and trains: a lesson in joined-up thinking", Proceedings of ICE Civil Engineering 158 August 2005, p. 135
 Baxter p. 53