One of a number of mines found in Gunnerside Gill, just north of the village of Gunnerside, Sir Francis Level was first started in 1864 to reach lead deposits in the Fairfold Vein, a process which was speeded up with the introduction of compressed air drilling machinery. An adit, 1.4km (almost a mile) long leads to a shaft which was sunk to gain access to lower levels and contains lift cages and winding equipment which are in a good state of preservation. A collapse near the entrance means that access to the mine is via an airshaft part way along the tunnel.  The collapse also means that the water in the tunnel has backed up and can be up to 1.5m (5 feet) deep depending on the weather.
The mine takes it's name from the son of Sir George Denys who drove the level.