What changes if you put the engine on wheels?

That time, that place

Watt's engine let factories stand anywhere. What they made still moved by horse and barge. British roads were mud, and a canal took years to dig.

Mines already ran coal wagons on rails — pulled by horses.

Why this question

What if you put the engine on the wagon? Weight was the problem: early engines were the size of a house, and no rail would carry one.

And there was doubt. Could a smooth iron wheel grip a smooth iron rail without slipping? Some argued for a toothed rack.

Stephenson had worked engines at the pit. He knew friction was enough.

What was found

In 1825 the Stockton and Darlington opened, forty kilometres of the world's first public steam railway. He drove the locomotive himself on opening day, with people clinging to the wagons.

When Liverpool to Manchester opened in 1830, the journey fell from days to hours.

Standard time followed. Until then each town lived by its own sundial, and London and Bristol clocks differed by about ten minutes. A timetable requires one time. That is why we now share a clock.