Puffing Billy

Look at the way it works. A single boiler drives two vertical cylinders, and the pistons push a pair of rocking beams overhead that turn the wheels through gears underneath. There are no rails inside the wheels; Puffing Billy proved that smooth iron wheels on smooth iron rails had enough grip to pull a heavy load, which was still doubted at the time. The chimney is tall because the fire needed a strong draught, and the wooden buffer beams and the tender behind carry the marks of decades of hard use. Nearly everything you see is original.

Puffing Billy was built before George Stephenson's Rocket and before any public railway existed. It belongs to the world of coal mines rather than passengers, yet everything that followed, from the Liverpool and Manchester line to today's high speed trains, descends from experiments like this one. It has been on display in South Kensington since the 1860s, one of the longest continuous exhibits of any museum object. A memorable detail is that the engine was so heavy for its early cast iron rails that it was rebuilt with eight wheels for a time, then changed back to four when stronger rails were laid.

Did You Know? Puffing Billy broke so many brittle cast iron rails that it was rebuilt on eight wheels, then returned to four once stronger rails arrived.