The 1st, 2nd and 3rd editions of the historic 25-inch O. S. maps, published in 1889, 1900 and 1914 respectively, depict a slate mill and associated features at this location. The south-eastern part was erected in 1862, its roof trusses aligned along (NW to SE) the building. On the north-west side is a large waterwheel pit, and beyond this an extension of the mill dating from 1867. A shaft tunnel running under both parts of the mill transmitted power from the wheel to various machines, including Hunter circular saws (patented 1865 in Scotland). The wheelpit was later modified to accommodate a Pelton turbine, and later again replaced by an electric motor. The waterwheel also provided power to the 420 metre-long incline down to the valley floor, so that loads could be hauled up to the mill, as well as finished slabs being sent down by gravity. At the rear (south-west side) of the mill line of stone pillars which once supported a wooden launder suggest that there was a second waterwheel, possibly to provide more power for the mill.
W J Crompton, RCAHMW, 1 August 2018.