From The Principles and Practice and Explanation of the Machinery of Locomotive Engines in Operation, found on archive.org.
The book seems to be part of an 1850 re-printing of Thomas Tredgold’s 1827 masterwork… (deep breath)… The steam engine : comprising an account of its invention and progressive improvement; with an investigation of its principles, and the proportions of its parts for efficiency and strength: detailing also its application to navigation, mining, impelling machines, &c. And the results collected in numerous tables for practical use…. Whew.
This thing in the picture, though, was a thing that used steam to move a piston. I mean, that’s what the whole engine did, sure, but this thing represents, uh, some improvement that Robert Stephenson made to it in order to keep the boiler next to the cylinders on a thing what was rolling down a track. A choo-choo train, in other words.
Stephenson’s original locomotive looked something like this. From that came cars and superhighways and all the rest of it.