CN415

Penrhyn Slate Quarry Railroad  

09/08/2021  

Designated  

Gwynedd  

Llandygai  

260230  

369640  

Transport  

Railway  

Industrial  

The monument comprises the relict remains of the Penrhyn Slate Quarry Railroad, developed to take slates from Penrhyn Quarry (CN416), Bethesda to Felin Fawr slate mills and onwards to Porth Penrhyn, Bangor for international export. The railroad ran for a distance of almost 8km utilising the relatively steady gradient adjacent to the river Ogwen to navigate the route between Bethesda and Bangor. Construction of the railroad was complete by 1801. Built as a horse-drawn system using wagons with double-flanged wheels on iron rails, it utilised technologies developed within the internal quarry system at Penrhyn that were to become a standard across the North Wales slate quarries, such as the 2’ gauge rail. It was the first railroad of its type in the industry, developed at a time when most quarries used packhorses to transport material to the nearest navigable watercourse, for export via river wharf. The railroad was designed by Thomas Dadford, an engineer from the West Midlands. The unusual use of three inclined planes – Marchogion, Dinas and Ty’n Y Clwt – is thought to be evidence of Dadford’s background in canal construction. The railroad remained in use until 1879 when it was replaced by the steam-locomotive powered Penrhyn Quarry Railway (CN417) that utilised a more circuitous route between Felin Fawr Slab Mills and Porth Penrhyn which required no inclined planes. The railroad today survives as five relict sections: Area A - Ty’n Y Clwt Incline to Bron Ogwen Cottages, Area B - Dinas Incline to Halfway House Bridge, Area C - Lôn Isaf to Tyddyn Iolyn, Area D - A55 to Llandygai Village and Area E - Home Farm to the Cegin Viaduct. Area A: Ty’n Y Clwt Incline to Bron Ogwen Cottages. The southern end of area A comprises a short, rock-cut section of railroad and the buried remains of the Ty’n Y Clwt inclined plane and winder house. Slate waste had been tipped over the incline prior to the publication of the Ordnance Survey 1st Edition map (1889) and today only the lowest few metres are now visible as a low rubble stone embankment bisected by the footpath that runs W from Tan Ysgafell. North of the footpath, the next 150m of railroad is a well-preserved marshalling yard that includes substantial, stone-built wharves. This area is illustrated on the 1875 survey by Spooner and is shown to include sidings and other buildings of uncertain function. Whilst these ancillary structures are not immediately visible today this area should be considered to retain significant archaeological potential. The formation continues NNW for a further 380m, partly forming the track to Tyn Y Clwt Isa and then forming a small footpath until it is subsumed within the gardens of Bron Ogwen Cottages. Area B: Dinas Incline to Halfway House Bridge. The southern extent of Area B adjoins the later Penrhyn Quarry Railway (CN417), the construction of which is thought to have destroyed the Dinas Incline winder house. Visible stratigraphy at the top of the incline illustrates the way in which some elements of the railroad were incorporated into the later railway. The ephemeral remains of the Dinas Incline survive as a low earthwork crossing the fields to the SE of Dinas Farm at an oblique angle to the natural hill slope. A bridge carries Ffordd Y Lord across the incline and it is again visible as a heavily overgrown cutting to the S of Pen Isa’r Allt (‘the lower end of the inclined plane’). The formation has been part-buried by the construction of the adjacent water treatment works but survives as a well-built stone bank on its E face until it becomes a clearly defined rock-cut shelf with substantial retaining walls supporting it 4m above the Ogwen River. The railroad extends circa 300m N where it turns W to cross the Tregarth Road at the junction with Halfway House Bridge but has been destroyed thereafter by later road improvements. Area C: Lôn Isaf to Tyddyn Iolyn. Area C comprises a sinuous 900m length of railroad which survives as an earthwork in pasture to the East of Lôn Isaf. The formation is clearly defined along its length and is generally well preserved. The central section survives as a substantial earthwork with stones eroding from the E face. Several field walls surmount the southern half of area B whilst the northern section is heavily wooded. At Tyddyn Iolyn the formation is subsumed within gardens and then survives only as a slight earthwork in the fields to the north, clearest when viewed using LiDAR (aerial laser scanning technology). Area D: A55 to Llandygai Village. To the north of the A55 the formation survives as a well preserved, low earthwork c.550m in length gradually becoming more substantial and well defined at the north end. In situ bank material is visible along stretches of the E face. The W face is visible on LiDAR despite erosion from historic ploughing. A public footpath and historic field boundary have helped to ensure the preservation of this length but N of Bryn the railroad survives only as a fossilised route. Area E: Home Farm to the Cegin Viaduct. Some of the best-preserved elements of the Penrhyn Quarry Railroad survive within Area E. To the NW of Home Farm a small bridge carries the main road to Bangor over the railroad formation. The formation emerges from a narrow cutting to the E of the road and follows the W face of the Penrhyn Estate wall for circa 500m to the north until it reaches Incline Cottage (Listed Building reference 4085). Situated at the summit of the Marchogion Incline, Incline Cottage was the original winder house for the Marchogion Incline. To the north of the cottage, the Marchogion Incline connects the contour section of railroad with the Afon Cegin section some 20m below. It is by far the best preserved of the surviving inclines and is a unique survival, designed for both counterbalance operation and for up-haulage by means of an adjacent horse-whim. The upper part of the Marchogion Incline comprises a massive slate and earth construction in the garden N of Incline Cottage that rises to first floor level where it would have interacted with the winding mechanism. The east face of this section has been lost and is bisected by the driveway to Incline Cottage. From here, the incline survives as a well-preserved but much overgrown cutting running parallel with the track that connects Incline Cottage and Nursery Cottage. The lower section survives as a well-preserved relict structure opening out into a marshalling yard in dense woodland. At the base of the incline the railroad connects with Pont Marchogion, a single-arched stone bridge with evidence of phasing that appears to have carried both a road on a raised level to the NE and the railroad on a lower ledge against the SW face. From here the railroad continues along a well-engineered ledge for a further 250m on the west bank of the Afon Cegin until it reaches the Cegin Viaduct (Scheduled Monument reference CN380), probably the oldest multi-arched rail bridge in the world. The monument is of national importance for its potential to enhance our understanding of the slate quarrying industry, specifically the evolution of transport systems and the development of international export. It is the progenitor for the Ffestiniog Railway and all subsequent descendants. At the time of construction, the Penrhyn Quarry Railroad was the longest overland railroad system in the world. Several well-preserved relict sections remain intact along with monumental structures such as Pont Marchogion. The less well-preserved sections and those which survive as low earthworks retain significant archaeological potential. The scheduled area comprises the remains described and an area around them within which related evidence may be expected to survive. The scheduled area is divided into 5 linear polygons that encompass the line of the railroad and associated structures: Area A varies between 3 and 20m in width and is c.650m in length orientated NNW-SSE between NGR 261330, 366730 – 261100, 367340. Area B varies between 1 and 9m in width and is c.660m in length between 261000, 368370 – 260730, 368950, the southern half of the area is orientated NW-SE and the northern half orientated N-S. Area C is c.10m in width and c.900m in length and orientated broadly N-S between 260160, 369230 – 259780, 369880. Area D is c.10m in width and 550m in length orientated N-S between 259770, 369930 – 259740, 370450. Area E is orientated broadly N-S between 259380, 3371360 – 259270, 372360, varies between 4 and 12m in width and comprises two sections – the section to the south of incline cottage is c.580m in length and the section to the north of Incline Cottage is c.500m in length.