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Early rails were used on horse drawn wagon ways originally with wooden rails, but from the 1760s using strap-iron rails, which consisted of thin strips of cast iron fixed onto wooden rails.

An early proponent of this design was Benjamin Outram. His partner William Jessop preferred the use of "edge rails" in 1789 where the wheels were flanged and, over time, it was realised that this combination worked better.

These were superseded by cast iron rails that were flanged (i.e. 'L' shaped) and with the wagon wheels flat.

However, the long-term expense involved in frequent maintenance outweighed any savings.

The first steel rails were made in 1857 by Robert Forester Mushet, who laid them at Derby station in England. Steel is a much stronger material, which steadily replaced iron for use on railway rail and allowed much longer lengths of rails to be rolled.

These rails were too fragile to carry heavy loads, but because the initial construction cost was less, this method was sometimes used to quickly build an inexpensive rail line.

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Answer 

Early rails were used on horse drawn wagon ways originally with wooden rails, but from the 1760s using strap-iron rails, which consisted of thin strips of cast iron fixed onto wooden rails.
These rails were too fragile to carry heavy loads, but because the initial construction cost was less, this method was sometimes used to quickly build an inexpensive rail line.
However, the long-term expense involved in frequent maintenance outweighed any savings.
These were superseded by cast iron rails that were flanged (i.e. 'L' shaped) and with the wagon wheels flat.
An early proponent of this design was Benjamin Outram. His partner William Jessop preferred the use of "edge rails" in 1789 where the wheels were flanged and, over time, it was realised that this combination worked better.
The first steel rails were made in 1857 by Robert Forester Mushet, who laid them at Derby station in England. Steel is a much stronger material, which steadily replaced iron for use on railway rail and allowed much longer lengths of rails to be rolled.

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