A horse- and gravity-worked railway, 12.9 km long, engineered by James Brunlees, constructed under way-leave by the tenants of Gorsedda slate quarry, who included the German entrepreneur Henry Tobias Tschudy von Uster, to connect the Gorsedda slate quarry (NPRN 40557) with the slate-slab mill at Ynysypandy (NPRN 40572), and to provide rail access to the sea at Porthmadog harbour (NPRN 306317). From Tremadoc to Porthmadog it re-used the formation of an existing railway built to serve Llidiart Ysbyty iron-mine. The formation was later used by the Gorsedda Junction and Portmadoc Railways (NPRN 34661) to connect with a newly-built section from Prince of Wales slate quarry and Cwm Dwyfor copper mine.

The railway systems serving the two quarries and connecting them to Porthmadog harbour exemplify different approaches to construction – the well-engineered horse-and gravity-worked line of 1857 on a constant down-gradient to assist movement of the load, by James Brunlees (1816–1892) to Gorsedda quarry, and the very light and cheaply-built locomotive-worked formation of 1875 to Prince of Wales quarry, the Gorseddau Junction and Portmadoc Railways. Brunlees had already worked on the Londonderry and Coleraine Railway and on the Ulverston and Lancaster. Once he had completed the Gorsedda contract, Brunlees sent his assistant Daniel Makinson Fox (1830-1918) to survey the challenging São Paulo Railway in Brazil. Fox spent most of the rest of his career in Brazil.

Statement of Significance: 

The Gorsedda railway formed the link between the quarry, the Ynysypandy slate-slab mill and the sea, and survives as a relict component of this important slate-quarrying landscape. One of the second-generation horse- and gravity-worked systems serving the slate industry, it is also significant as the work of Sir James Brunlees, a major Victorian engineer who worked in Brazil, Switzerland and New Zealand. The Gorseddau Junction & Portmadoc Railways is a lightly-engineered system that reflects the short-lived optimism in the slate industry in the 1870s, and evolving views about the construction of inexpensive locomotive-worked industrial railways. 

This site is part of the Slate Landscape of Northwest Wales World Heritage Site, Component Part 4: Gorseddau and Prince of Wales Slate Quarries, Railways and Mill. Inscribed July 2020. 

Sources: 

• Louise Barker & Dr David Gwyn, March 2017. Gwynedd Slate Industry Transport Routes. (Unpublished Report: Project GC401 for Gwynedd Archaeological Trust)  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/   

Hannah Genders Boyd, RCAHMW, March 2022