In the 1840's, steam locomotives were clumsy, inefficient, and slow. Also, they had a bad habit of exploding due to reasons. As such, alternative means of powering trains were actively studied.
The atmospheric railway presented itself as a solution by simply relocating the steam engine off the train and into a building, where it worked to create a vacuum in a long pipe, which in turn pulled a piston connected to a train.
Unfortunately, since the leather flap on the Samuda design which covered the cut-out where the arm connecting the piston to the train moved used bee-wax and tallow to make a seal, rats had a habit of wanting to gnaw on it. And when the engine was powered up, the vacuum created sucked them violently into the pipe.
The end result was that the train had a habit of arriving to its station following [b]a torrent of rat blood and viscera[/b].https://www.youtube.com/watch?v=JaRVy31lTlQ[Embed