Ynys Pandy slate mill (SH 550 434) View up valley. Three-storey mill where slate from Gorseddau Quarry was processed. Built 1856-7 by Evan Jones of Garndolbenmaen and probably designed by James Brunlees. It is ingeniously planned so that the natural fall of the site assisted the manufacturing process. A deep trench inside accommodated a large overshot water wheel (26 ft, 8m in diameter), and on the south side a long curving ramp brought branches of the tramway from Gorseddau Quarry into the mill at two different levels, serving the middle and upper floors. The grand, round-headed openings are closely spaced like a Roman aqueduct. The eastern gable is surmounted by a decorative feature incorporating a false chimney stack, and the west gable windows have at some time had window frames or shutters. Mill produced slab slate for floors, urinals etc.
In its heyday, in 1860, it was producing over 2,000 tons per annum, but seven years later production was down to 25 tons per annum (due to poor quality of the quarried slate) and the business went into liquidation in 1871. The building provided a venue for eisteddfodau until the roof was removed around 1906.
Sources: Coflein. Haslam, Orbach and Voelcker (2009), The Buildings of Wales: Gwynedd. Pevsner Architectural Guide, page 362.