That's exactly what I noticed Peter!
Where were the Bob / beams?
Also as others have also pointed out
Where were the Boilers?
Where were the huge piles of Coal need to power it all?
Would "600 guineas" get a New Boulton / Watt engine?
I suppose you could argue they only worked to adit level and the smoke was from cooking whilst they await delivery of a new engine.
Poldark also mentioned using Iron Ladders - would they have lasted longer than pitch pine in that corrosive setting?
Is it safe to come out of the bunker yet?