The increase in steel production from the 1860s meant that railways could finally be made from steel at a competitive cost. Being a much more durable material, steel steadily replaced iron as the standard for railway rail, and due to its greater strength, longer lengths of rails could now be rolled. Wrought iron was soft and contained flaws caused by included dross. Iron rails could also not support heavy locomotives and was damaged by hammer blow. The first to make durable rails of steel rather than wrought iron was Robert Forester Mushet at the Darkhill Ironworks, Gloucestershire in 1857.