1.

The Welsh Slate Museum, a branch of the National Museums and Galleries of Wales, was opened in 1972 in the quadrangular workshops of the former Dinorwic Slate Quarry, which had closed the previous year. Dinorwic was the second largest slate quarry in the world, after its near neighbour Penrhyn Quarry, and formed part of the Assheton Smith family's Vaynol estate.

Quarrying was under way on the common land above the museum by 1700 and from 1787 Assheton-Smith leased out his own quarries to a group of English venturers, who carted the slates down the steep road down the hillside behind the museum to a quay on the site of the present Llanberis Lake Railway station. From here cargoes were boated to the head of the lake, from where they were carted to the sea. This cumbersome system was replaced by a succession of other transport routes. In 1843 a 4ft gauge railway was built along the lake-shore, operated by Crampton steam locomotives from 1848. This served the quarry until 1961.

The site of the present museum was the main engineering hub of the quarry. The massive quadrangular yard derives from agricultural, rather than industrial, practice, and was completed in 1870, replacing earlier facilities in the quarry itself. It is an unusual example for the Welsh slate industry of a building which is decorative as well as functional, and was clearly constructed to make an impression on the owners' house-guests when they visited the quarry. The iron suspension water-wheel which drives the machinery was built by the Caernarfon firm of DeWinton, and has recently been restored by National Museums and Galleries of Wales, working with Dorothea Restorations and the Gwynedd Archaeological Trust. The waterwheel is the second largest in Britain at 15.4m in diameter and once provided all the power for the Dinorwic Slate Quarry Workshops.

The area around the quarry has also been a focus for visitors since the late eighteenth century, reflected in the opening of the Royal Victoria Hotel (c. 1823), and of the Snowdon Mountain Railway, using Swiss locomotives and technology, in 1896. The Llanberis Lake Railway runs along the trackbed of the former quarry railway, and uses 2ft gauge locomotives from the internal quarry system.

B.A. Malaws, RCAHMW 6 September 2000.

2.

The National Slate Museum is housed in the former Dinorwic Quarry workshops, once the main engineering hub of the quarry. It is located in an area known as Gilfach Ddu, an area of made-up ground on the shores of Padarn lake, at the foot of Snowdon, near a series of inclined planes from the quarry, and adjacent to the Vivian quarry and inclines, and the Dinorwic Quarry hospital.

The massive quadrangular yard recalls the practice of a large landed estate rather than an industrial complex. It was completed in 1870, replacing earlier facilities in the quarry itself. It is an unusual example within the Welsh slate industry of a building which is decorative as well as functional, and was clearly constructed to make an impression on the owners' house-guests when they visited the quarry. The operational iron suspension water-wheel by the Caernarfon firm of De Winton is the largest in mainland Britain, at 15.4m in diameter and once provided all the power for the machinery here. It contrasts with the replacement pelton of 1925. Most of the quarry machinery and the foundry survive, and the site as a whole is a time-capsule of mid-Victorian practice.

Other features include a relocated and reconstructed winding engine house from the Hafod Owen department within the quarry, a manager’s house, locomotive sheds, the castellated mouth of a tunnel connecting with the quarry, and the Llanberis Lake Railway, which operates on the trackbed of part of the quarry railway system.

Statement of Significance:

The impressive quadrangular quarry workshops complex built in 1870 associated with the Dinorwic Slate Quarry (NPRN 40538) is now the National Slate Museum, presenting the history and heritage of the slate industry of Wales. Its scale, form and architectural ambition are remarkable, combining an almost fort-like appearance with some of the well-established conventions of the stable block of a great country house, with a gate-house, and a clock controlling workers’ movements and time-keeping. An aristocratic ambience is also evident in the order and unified building style of structures in its immediate environment, including the manager’s house, locomotive sheds and a tunnel-mouth. Conserved machinery, tools and other artefacts are interpreted within the museum, illustrating the extent of craft-skill and technical knowledge necessary to maintain the quarry and its transport systems as a going concern required. The working suspension water-wheel which once powered the workshops, the largest survivor in mainland Britain, illustrates the advantages of using tried and tested sources of renewable energy well into the Industrial Revolution period, just as its replacement turbine illustrates the development of this technology over a period of fifty-five years.

The Museum’s functional linkages with the Quarry, with the Vivian department (NPRN 40571) and with the railway systems (NPRN 546222) are immediately apparent. Its visual relationship with the spectacular natural environment of mountain and lake is compelling.

This site is part of the Slate Landscape of Northwest Wales World Heritage Site, Component Part 2: Dinorwig Slate Quarry Mountain Landscape. Inscribed July 2020.

Sources:

Louise Barker & Dr David Gwyn, March 2018. Slate Landscapes of North-West Wales World Heritage Bid Statements of Significance. (Unpublished Report: Project 401b for Gwynedd Archaeological Trust)
Tirwedd Llechi Gogledd Orllewin Cymru / The Slate Landscape of Northwest Wales. Nomination as a World heritage Site (Nomination Document, January 2020)
Wales Slate World Heritage Site https://www.llechi.cymru/

H. Genders Boyd, RCAHMW, January 2022

Site Record