(p. 300) The other weight problem was the one that licked Trevithick at Penydarren: The tracks on which the locomotive ran were just not able to survive the tonnage traveling over them. Driving a five-ton steam locomotive over rails designed for horse-drawn carts was only slightly more sensible than driving a school bus over a bridge made of wet ice cubes. In both cases, it’s a close call whether the vehicle will skid before or after the surface collapses.
. . .
(p. 301) Two years later, Stephenson, in collaboration with the ironmonger William Losh of Newcastle, produced, and in September 1816 jointly patented, a series of’ improvements in wheels, suspension, and–most important–the method by which the rails and “chairs” connected one piece of track to another. Stephenson’s rails seem mundane next to better-known eureka moments, but as much as any other innovation of the day they underline the importance of such micro-inventions in the making of a revolution. For it was the rails that finally made the entire network of devices–engine, linkage, wheel, and track–work.
Rosen, William. The Most Powerful Idea in the World: A Story of Steam, Industry, and Invention. New York: Random House, 2010.
(Note: ellipsis added.)