[3] In 1856, a prosperous mill owner from Ardwick, Sir Edmund Buckley purchased the Lordship of Dinas Mawddwy and with it a large estate covering 12,000 acres of the town and local area.

[4] In 1864, William Bullock, the mayor of Congleton formed the Merioneth Slate and Slab Company and leased the quarry.

The quarry operated until the First World War when its warehouse at Dinas Mawddwy station was requisitioned for timber cutting.

[5] In the late 1860s, the Merioneth Slate and Slab Company opened another quarry on the west side of Foel Dinas, called Cae Abaty.

This was separated from the main quarry by a large ridge, and a pair of linked 2 ft 2 in (660 mm) gauge inclines were laid to lift rock up from Cae Abaty and lower it to the upper mill at Minllyn.

[6] Cae Abaty is a relatively small quarry and the requirement to haul rock over Foel Dinas would have made it expensive to operate.

The original workings were a series of open pits known as Bron-yr-Wylfa at the bottom of the east flank of Foel Dinas.

In the 1803s, the Minllen Slate and Slab Company opened a new set of quarries about 800 feet (240 m) higher up the mountain where the Narrow Vein surfaced.

[2] The steam engine powering the upper mill was replaced at an unknown date by a Pelton wheel fed from a small reservoir above it.