Level 9 adit was the main access to Rhosydd Slate Mine (Nprn40600). The adit was excavated between 1862 and 1871, providing drainage and transport from the working areas of the mine (all above this level at the time) to new processing facilities at Bwlch Cwmorthin. The adit is 677 metres long and rises 7.87 metres. It was 3 metres wide to accommodate a double line tramway with a shared centre rail, except at the ends and at a central passing loop where the adit was 4 metres wide. Haulage was provided by an endless wire rope, powered by a pitchback waterwheel of composite construction 7.3 metres diameter by 1.2 metres wide, part of which still remains in its wheelcase at SH 6652446223. Slate trucks were hauled in trains of about 12, with special "gripper" trucks (with a vice-like gripper underneath which gripped the rope when tightened by the screw above) at each end.
There are remains of track, wooden sleepers and the rope, and as the lower levels of the mine are now drowned up to Level 9, considerable amounts of water flow from the adit.
W J Crompton, RCAHMW, 12 March 2009.