stream The 1st edition of the historic 25-inch O. S. map (1888) applies the "Upper Boat Level" name to a complex area of mining which may date back to Roman times; but the Upper Boat Level proper was driven in the 1770s from the south-east bank of the Nant-y-bai at SN 7838744613. Water draining from the adit was channelled by a leat 170 metres long to a reservoir, augmented by another leat from the stream, to power a waterwheel-driven crushing house at SN 7823244647. A water-colour of 1792 by John `Warwick? Smith, now in the National Library of Wales, depicts these dressing-floors and water-wheel. At SN 7864944773 the 1st edition map shows another water-powered crushing house, with two reservoirs fed by a short leat from the Nant-y-bai on the hillside above.
W J Crompton, RCAHMW, 21 July 2016.