Wrysgan was an underground slate quarry, which was located on a small inaccessible site, some 1,390 feet (420 m) above sea level, to the west of Cwmorthin.

The feature for which the quarry is best known, a spectacular incline which descended 600 feet (180 m) down to the Ffestiniog Railway, and which passed through a tunnel towards the top, was completed in 1872.

[1] Power to drive the mills was provided by waterwheels, supplied from a small reservoir, Llyn y Wrysgan, situated to the south of the main quarry buildings.

Steam engines proved to be costly to run, and the company tried to negotiate use of the unused Cross Mill at Cwmorthin quarry.

Whenever empty wagons needed to ascend the incline, the main motor from the mill was borrowed and connected to the haulage drum.

It was separated from Cwm Ystradau by a sharp ridge, through which the quarry bored an inclined tunnel in order to connect to the Festiniog Railway.

In the final days of operation, a rope haulage system was used to move the rock from the underground chambers to the foot of the incline.

[10] Wrysgan, like most of the slate quarries in the Blaenau Ffestiniog region, was excavated as a series of chambers, with pillars of rock left between them to support the mountain above them.

[11] The most obvious feature of the quarry is the main incline with its tunnel, which is clearly visible from locations near Tanygrisiau railway station.

[10] The construction of the incline to the south east in 1872, which connected directly to the Ffestiniog Railway, simplified the export of slates.

Most travelled to Minffordd, where the Ffestiniog had interchange sidings with the Cambrian Railways and its predecessors, but some slate continued on to Porthmadog Harbour, from which 762 tons were shipped in 1902.

[13] At the time of operation of Wrysgan, the Ffestiniog was a continuous downward gradient from Blaenau Festiniog[broken anchor] to Boston Lodge, and loaded slate trains were run by gravity, with brakesmen controlling the speed by applying the brakes when necessary.

Consequently, the locomotive assigned to be Top Shunter that day would follow the train down, and once the extra wagons were attached, would restart it by giving it a push.