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Engine House, Boilerhouse, Bunker and remains of chimney to south

A Grade II* Listed Building in Talysarn, Gwynedd

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Latitude: 53.0542 / 53°3'15"N

Longitude: -4.2435 / 4°14'36"W

OS Eastings: 249732

OS Northings: 353122

OS Grid: SH497531

Mapcode National: GBR 5K.CMMX

Mapcode Global: WH43T.SHHG

Entry Name: Engine House, Boilerhouse, Bunker and remains of chimney to south

Listing Date: 10 December 1992

Last Amended: 21 July 2000

Grade: II*

Source: Cadw

Source ID: 22901

Building Class: Industrial

Location: On a ridge of bastard rock which divides the main Dorothea Quarry from the South Dorothea Quarry; located by the side of the road access to the quarry.

County: Gwynedd

Community: Llanllyfni

Community: Llanllyfni

Locality: Nantlle

Built-Up Area: Talysarn

Traditional County: Caernarfonshire

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The Dorothea Quarry in the centre of the Nantlle vale was opened in 1829 by William Turner and John Morgan. From 1853 the quarry was owned by the Williams family until its closure in 1970. In 1904 (date on foundation stone) a Cornish beam engine was installed, replacing water power, to provide power for lifting wagons in and out of the open pits and to pump out the workings through a shaft about 140m deep. The engine, manufactured by Holman Bros. of Camborne (Cornwall) remained in regular use until 1952 and occasionally until 1956.


Sawn squared slate blocks with gable-ended slate roof 3 storeys over basement. Rectangular plan, aligned roughly north-west to south-east. Small-paned sash windows with slate lintels and cills on each face. Entrance in south-east end wall under brick arch approached by sawn slab steps. Large ground-floor opening in north-west end wall, also with brick arch. Remains of clock high up between top-floor windows on north-east wall. Iron beam of engine supported high up on north-west wall and projecting through vertical timber boarding in gable; pair of doors flanking beam open out on to remains of wooded inspection balconies. At the north-west end the shaft head is surrounded by a wall of sawn slate blocks approximately 2m high and attached to the engine house; the shaft head is spanned by 2 steel joists. Against the south-west wall of the engine house are the remains of the boiler house, now roofless but with the principal timbers surviving; it houses the remains of 2 boilers. To the south is the square base of the remote chimney, constructed of sawn slate blocks, approximately 3m high; the former iron extension has been removed.


Access to interior not available at time of survey but noted as retaining its early C20 Cornish beam engine.

Reasons for Listing

Listed Grade II* as the only remaining example of an engine house with a Cornish beam engine remaining in situ within the area of the Gwynedd slate industry.

Scheduled Ancient Monument (No.165).

Other nearby listed buildings

  • II South-western aerial ropeway revetment, incline and associated buildings
    Located above the south side of the North Dorothea Slate Quarry, between the Cornish beam engine house to the west and the ruins of the former slate mill to the east.
  • II Causeway
    Located off the B 4418 to the north of Dorothea House, beginning beyond Pont Wythdir and running north-east for approximately 100m across marshy ground with a spoil heap to the north-west on the south
  • II Tunnel Portal and Tunnel
    Located in the hillside to the north of Talysarn Hall.
  • II North-eastern aerial ropeway revetment, incline and associated buildings
    Located above the east side of the North Dorothea Slate Quarry between Pen-y-Bryn to the north-east and the ruins of the former slate mill to the south-east.
  • II Strainer arches and retaining walls
    Located to the south of Pen-y-bryn, the strainer arches and walls retain the slate waste tips flanking the route of the Dorothea Quarry branch of the former Nantlle Railway.
  • II Capel Mawr, Sunday School and railed steps to chapel forecourt
    Located in a commanding position at the eastern end of Talysarn with its Sunday School directly to the east, the chapel is set high above the road at the top of its own steps.
  • II Pen-y-bryn
    Located on the north side of the old Talysarn to Nantlle Road within the former Cloddfa'r Lon Slate Quarry.
  • II Seion Congregational Church
    Situated in an elevated position amidst terraced housing approximately half way up Cavour Street; in front of the chapel is a small forecourt behind an irregularly coursed rubblestone wall, topped by

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