The 1st, 2nd and 3rd editions of the historic 25-inch O. S. maps, published in 1889, 1900 and 1914 respectively, depict a waterwheel pit at this location. It was constructed as part of a plan to build a new slate mill at this level to process slate being brought out of Rhos slate quarry (NPRN 305768) through a tunnel as the pit became deeper, but the mill was never built. It could have accommodated a 40ft wheel.
W J Crompton, RCAHMW, 2 August 2018.
