Cwt y Bugail quarry is set in a remote, high altitude (500m+) location between Blaenau Ffestiniog and Cwm Penmachno. The quarry, partly underground, was an enlargement of the old Bugail working which opened in the 1820s and developed following its connection to the Rhiwbach tramway in the 1860s. Material was uphauled from two pit/underground workings to be reduced in a mill equipped with perhaps as many as 20 saw-tables and dressing machines. Finished product was then removed on a branch of the Rhiwbach tramway. The main inclines and mill were powered by steam, an oil engine replacing steam at the mill in latter years. The quarry was notable for containing not only the one in situ steam incline winder in the industry, in the shape of an 1860s Aveling and Porter traction engine taken off its wheels after 1909, but also parts of a Lister petrol locomotive and a barrage-balloon winch, which once raised blocks from an underground chamber. It also operated a blondin haulage system.
At its peak the quarry produced more than 3000 tons per annum employing more than 100 men, mostly living in barracks (which remained in use till as late as the 1950s). By 1898 it was employing 68 men, falling to 42 in 1937-8. The quarry operated at a reduced level until the 1960s.
Remains (in the early 1990s) include several buildings, in particulara large mill now much dilapidated, inclines, barracks and a steam incline winding engine.

Sources:
D.Gwyn, Welsh Slate: the Archaeology and History of an Industry (RCAHMW 2015), pp.144, 152 & 180.
A.J.Richards, A Gazeteer of the Welsh Slate Industry (1991), p.128.

David Leighton, RCAHMW, 29 January 2015