The industrial complex known as y felin fawr (‘the big mill’) is situated to the north of Penrhyn quarry, at the first location where its railway crossed a stream strong enough to turn water-wheels. This was where slate slabs were sawn and shaped, and where the quarry’s engineering needs were met; though it lacks the architectural ambition and deliberate organisation of the Dinorwic quarry yard, it is solidly built and well organised. It operated until 1965 and is now managed by a community enterprise.
A mill to saw raw blocks into architectural slabs had been established here by 1802, when it was equipped with circular saws – the earliest known location in the world to have used circular saws to cut stone, also predating their use to saw lignum vitae in the Royal Navy dockyard at Portsmouth. The two present mills were built in 1865-6, to the design of William Francis, the quarry manager, a development of the design tried out experimentally at the Prince of Wales Slate Quarry in the Cwmstradllyn and Cwm Pennant component part of the proposed site. An 1867 extension of the western mill housed a renewable-tip ‘Hunter’ saw.
The foundry dates from 1866, replacing an earlier structure erected in 1834. It is typical of its period, built out of sawn slate slabs with quoins of igneous rock. The blast was provided by a suspension water-wheel which survives in a building to the eastern perimeter of the site, by Henry Sugden and Son of Bramley, near Leeds.
The houses Tai'r Stablau were built in 1875 on the site of stables for the horses that formerly pulled the slate wagons to Port Penrhyn; the slate slab-built shed added against the southern gable wall of the western mill was built in the same year for the first steam locomotive on the Penrhyn Quarry Railway, with a later siding for an internal combustion locomotive. Later structures include a two-bay locomotive repair shop, built out of sawn slate blocks; the more northerly range housed a range of machine tools, in the other an inspection pit and an overhead gantry crane survive. At the southern perimeter of the site, where the railway passed into the quarry, is a fine slate-slab road over-bridge dating from 1900. The river which powered the complex follows its original course and is apparent both upstream and downstream. The culvert through which it crosses under the site is accessible.
Two waterwheels survive on site, one of which is situated between the two slate-slab mills, which it formerly powered, the other on the eastern perimeter, which formerly provided the blast for the foundry. Both are in need of restoration.
Other buildings and structures on the site include slate-makers’ shelters (gwaliau) where broken slates were trimmed for commercial sale. The river which powered the complex follows its original course and is apparent both upstream and downstream. The culvert through which it crosses under the site is accessible. The mills were consolidated in 1999-2000 by Gwynedd Council for conversion to light industrial units.
This site is part of The Slate Landscape of Northwest Wales World Heritage Site, Component Part 1. Penrhyn Slate Quarry and Bethesda, and the Ogwen Valley to Port Penrhyn. Inscribed July 2020.
Hannah Genders Boyd, RCAHMW, January 2022
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/