Penrhyn Quarry drainage adit

Slate arch of the adit portal


12 November 2011

Tanysgafell, Bethesda

SH 61561 66862; 53.18078°N, 4.07304°W


The once grand slate-arch portal of Penrhyn Quarry’s main drainage adit now stands forgotten, overgrown with ivy, and fenced off in the middle of a field.

The adit is 1837 yards long with a 5ft by 7 ft cross section and took five years to dig. Inscribed in the arch keystone is the date 1849. The outfall from the adit flows some 80 metres along a channel before emptying into the Afon Ogwen. At the far end, two De Winton hydraulic pumps used to drain the quarry levels below the adit. In 1907 these were superseded by electric pumps.

Adit portal


Fenced off portal and drainage channel leading to the Afon Ogwen

3 thoughts on “Penrhyn Quarry drainage adit

  1. I adore seeing these old things! My ancestors left about 1849 I think (I’ll go and check). 🙂 I so wish they would have stayed there, so I could live in Wales too! Gorgeous, gorgeous, gorgeous.Thanks so much, Graham. 🙂


  2. Fascinating photos. I always like it when the adits have date inscriptions, I think it show the pride in what they were doing, although it’s not common here in Blaenau Ff. 1849 is pretty early, too, in slate quarry terms! Shot no.2 is particularly intriguing.


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