Description

The monument consists of the relatively complete shaft winding engine house for a steam engine which formerly raised slate from a shaft connected to a slate quarry: the best-preserved of only two examples in the Gwynedd slate industry. Ty Mawr East Slate Quarry (also known as Nantlle Vale) is believed to have worked from c.1860 to c.1910. The engine house was probably built in the 1890s and was formerly situated at the north-east side of a quarry pit which has now been infilled. The winding shaft to the north-east of the engine house has also been filled.

The building is rectangular, constructed of sawn slate slabs and country rock. A spinal wall 4m high seems to have had a pitched roof on each side. The east side contained the boiler house and still has a fine chimney to full height. The west side contained the engine. A platform for the drum or drums is to the west. Shaft winding was uncommon in the slate industry, despite the widespread need for mechanical up-haulage, and the engine house contrasts with remains of other haulage systems elsewhere.

The monument is of national importance for its potential to enhance our knowledge of mining in Wales. It is both typical of many mining industries and a notable contrast to normal practice in slate quarrying. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structure itself may be expected to contain archaeological information concerning chronology and building techniques. An engine house may be part of a larger cluster of industrial monuments and their importance can further enhanced by their group value.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw