Watching the latest Poldark episode last night....
No wonder Poldark's cousin drowned in the mine! The external shots of the pumping engine house clearly showed that no pump was attached to the end of the beam engine!
As I remember the early Cornish engines (of Poldark's time) were mainly atmospheric without Watt's parallel motion, hence the curved end of the beam to accommodate a chain linkage.
Poldark should have gone to evening classes!
Ian.