The Tan Hill coal has been extensively worked on the southern flanks of Great Shunner Fell, where its outcrop runs south on East Side, past Cotterdale Colliery, before turning northwards, near the head of Coal Gill, into Hearne Gill. On reaching the beck near West Pits Colliery, the outcrop runs southwards again for about 500 metres before turning north into Fossdale Gill and across the watershed onto Howgate Edge above the Butter Tubs. The seam has also been followed to the north of Lovely Seat, where it was worked at Willy Pit.
A report of 1673 states that the Cotterdale coalfield had been worked inefficiently for many years, but things were put into better order in the 1650s, when coal began to be won from a line of new pits. The latter were only expected to last another two years, however, when it would be necessary to drive a water level and sink a row of new pits around 25 fathoms deep. This would be more expensive to work, but the development would have an expected life of from 20 to 30 years.
In the mid 1760s an attempt was made to open a new pit in Long Gill, but the seam was found to be poor here and attention shifted to Hearne Gill, where a drainage level was driven in the rock under the coal. There was a coke oven at Hearne Pit. William Brown, the Northumbrian colliery viewer, realised that the coal ran under the hill, which he called Turney Fell, and that future workings would be much deeper. These pits would, however, be worked from levels, not shafts.
It seems likely that Cotterdale coal level was driven from Jinglemea Bog fairly soon after Brown’s visit, probably by the lessee, Winifred Pulleine, the widow of Thomas Pulleine. The years from 1785 to 1804 saw Cotterdale making an average annual profit of around £120. At the level, the seam dips west-north-west at 1 in 36 and is split into two leaves by a three inch (0.07m) dirt band, the top coal was 21 inches (0.5m) thick and the bottom coal six inches (0.15m). This level was last worked in 1926.
A pit on Hood Rigg, near the Butter Tubs, was working the Tan Hill coal in 1820 and 1821, when it made £1589.86 in profit.
Gill, M.C. “Great Dales Coalfield, Eastern Areas” British Mining No.86 (2008), pp.68-108
Spensley, I.M. Mines and Miners of Wensleydale, The author, 2014