Tunnel Portal and Tunnel

Cadw's description

Location

Located in the hillside to the north of Talysarn Hall.

History

The Nantlle Railway Company was incorporated by Act of Parliament in 1825 and opened in 1828. It was promoted by a group of slate quarry owners in the Nantlle vale to improve the transport of their products to the port at Caernarfon, following the construction of similar narrow gauge railways from the Bethesda and Llanberis Quarries to Penrhyn and Port Dinorwic respectively. The tramway was of 3ft 6in (1.07m) gauge and operated by horses until much of it was converted to standard gauge and incorporated into the main national railway network in the later C19. A short section of the line above Talysarn remained as a horse-drawn tramway until 1963. The tunnel itself is a late C19 structure, built in the later C19 to allow waste from the Talysarn Quarry to be tipped above. As the tip encroached further the line was diverted to a more southerly route, immediately behind Talysarn Hall, and the west portal of the tunnel is no longer visible. This diversion had been made by 1889 when it appears on the Ordnance Survey map of that date.

Exterior

Eastern tunnel portal built of squared slate rubble. Semi-circular arch with slate voussoirs, above which are a string course and parapet.

Interior

Not inspected at time of survey.

Reason for designation

Included as a substantial structure on the Nantlle Railway, an important early horse-drawn tramway, the tunnel itself is particularly significant for the evidence it provides of the massive expansion of the Dorothea and Talysarn Slate Quarries during the C19.