Dyffryn Nantlle is a sparsely populated glacial valley in Gwynedd. Roofing slates excavated at the nearby Roman fort of Segontium, originated from the valley and by the eighteenth century, Cilgwyn quarry was well-known for its brightly red slates.

Unlike the large enterprises run in Bethesda, Llanberis and Blaenau Ffestiniog, the slate quarries situated in Dyffryn Nantlle were run independently and on a much smaller scale, but the valley was still one of the world-leading producers of slate in the nineteenth century. The open cast mining and innovative transportation systems in use at the Cilgwyn and Penbryn quarries were of great interest to mining engineers from France and Germany. Engineers such as Hanns Bruno Geinitz, Rudolph Nasse and C. Lariviere repeatedly visited the quarries from the 1850s up to the 1880s and took detailed notes to encourage the installation of similarly efficient systems in their home nations, an early form of industrial espionage!

Record created as part of the AHRC-funded project 'Journey to the Past: Wales in historic travel writing from France and Germany'.
R. Singer (Bangor University) and S. Fielding (RCAHMW), 2017.