In the 1700s deep undersea mining was mysterious and dangerous. An unknown science.  Carlisle Spedding, the mining engineer for Saltom pit, faced problems of sea water, Fire Damp (Methane) and roof falls.  He met these with innovative technology.

To fight explosive Fire Damp and suffocating Choke Damp, he invented a way to keep air moving in the mine.  His  'air coursing' mechanism was a series of doors in the tunnels. The doors forced air through all parts of the mine. 

He built stone dams where the fire damp was worst .Pipes behind the dams brought the gas to the surface.  It was burned to boil the water for the steam winding engine.  In 1733 'flintmills' were introduced to give illumination without naked flames.  This reduced the risk of explosions. 

The risk of sea water flooding the mine was always present. Speeding installed massive Newcomer Pumping engines to prevent the mine flooding. Roof collapses were common so the miners left pillars of coal to support tunnel rooves.  This plan of the mine looks like a city street map.  It reads “Pillars taken away 1837 – 1838”.  As each pillar was mined away, a bit more of the roof would collapse.