The Grassington Grit seam, but here called the Thick Coal, was worked at the head of Dowber Gill. Here the seam, which was about two feet (0.6m) thick, was in the shale above the Bearing Grit. It was also worked at Hay Dike Colliery, on the slopes of Great Whernside, and outcropped in Thornpengill at Mossdale.
Gill, M.C. “Great Dales Coalfield, Eastern Areas” British Mining No.86 (2008), pp.68-108
Gill, M.C. The Wharfedale Mines (British Mining No.49, 1994)
Dickinson, J.M. “Old Providence Lead Mine” Memoirs, Vol.2 No.3 (1973), pp.101-103