Ancient Monuments

History on the Ground

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Dorothea Quarry, Pyramids, Inclines, Mill & Winding Houses, etc

A Scheduled Monument in Llanllyfni, Gwynedd

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Latitude: 53.0544 / 53°3'15"N

Longitude: -4.2397 / 4°14'22"W

OS Eastings: 249987

OS Northings: 353135

OS Grid: SH499531

Mapcode National: GBR 5K.CNKN

Mapcode Global: WH43T.VH99

Entry Name: Dorothea Quarry, Pyramids, Inclines, Mill & Winding Houses, etc

Scheduled Date: 29 July 1991

Source: Cadw

Source ID: 3322

Cadw Legacy ID: CN199

Schedule Class: Industrial

Category: Engine house

Period: Post Medieval/Modern

County: Gwynedd

Community: Llanllyfni

Traditional County: Caernarfonshire


[Condensation of ‘The Dorothea: a Quarry Park’ (unpub study) by G P and A Jones and Dorothea Restorations, 1988]: The first slate quarrying on an industrial scale began at Dorothea in 1829 when a quarry adventurer, William Turner, and his son-in-law John Morgan opened what is now Quarry A, then known as Cloddfa Turner. Turner came from Lancashire and had interests in several other quarries. In 1849 a consortium of local quarrymen, entrepreneurs and farmers formed the Dorothea Quarry Co and took over the workings. The name ‘Dorothea’ came from the wife of Richard Garnons who owned the Pant Du estate on which the quarry was sited. This was unusual since virtually all the large scale operations were under English management at that time. In 1860 the company became known as ‘John Williams and Co’ and the Williams family retained control until voluntary liquidation in March 1970.

The history of the quarry is well documented and many of the personalities are known. During the late 19th and early 20th centuries Dorothea was the principal quarry in the Nantlle valley, producing, at its peak in the 1870s, 13,000 tons of roofing slates per annum and employing around 500 men.

By the 1880s five pits had been sunk to about 300ft and these were ultimately to reach a maximum depth of over 500ft. It is this depth which marks Dorothea from other quarries and which forced important innovations, particularly in lifting material from the quarry floor. The hand-winches of the early working were followed by horse-powered ‘whimseys’ in the 1830s and, when tramways were introduced, water-powered inclines led down to the pit floor. In 1841 the first of a series of steam-powered chain inclines (later cable inclines) was installed and these remained the principal means of extraction until they were phased out in the 1950s. These were supplemented by Blondin cableways in 1900. The last Blondin operated until 1965 when a road was blasted to the lowest floor then being worked, and road transport took over.

[Mike Yates' text:] The quarry is now flooded, giving the false impression of a single pit and the surrounding buildings are ruinous. However the function of the structures can be identified and the layout of the workings is clear.

Three areas have been scheduled to include a representative selection of the most important features on the site. These are focused on the pyramids which appear unique to Dorothea, but also include adjacent associated structures and the large mill which was at the heart of the operations.

The numbers in brackets refer to those used by Mr G P Jones in his survey (see above).

WESTERN AREA Winding engine houses: a (11), b (10), d (12), e (13) and f (13a) Loco shed: c (18) Pyramid: g (Pyramid C) Transporter incline: h (Incline C) Contractors’ shelters: i

CENTRAL AREA Dorothea large mill: k

EASTERN AREA Winding engine houses: l (3), m (3a), n (4) and o (19) Pyramid: p (Pyramid B) Transporter incline: q (Incline A)

The monument is of national importance for its potential to enhance our knowledge of the slate industry. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structures themselves may be expected to contain archaeological information concerning chronology and building techniques.

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

Source: Cadw

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