1. Furnace at the centre of a shake hole in the centre of a marshy peat bog area. Internal dimensions 2m x 1.5m x 1.2m deep. External structure is 7m x 4m x 2m high. Walls 1.2m thick. Signs of burnt and heated stone at the centre and a red staining, possibly from melting iron ore. The ground cover was bracken at the time of survey. G. Arnold, ArchaeoPhysica Ltd, 11/03/2009

2. A subsequent visit by a member of staff at Brecon Beacons National Park noted that this feature was located at SO 08992 12385, rather than the previously noted SO 089 124, and that it was not within a shake hole. The depression at the bottom of which the furnace is located being formed by the Dowlais Limestone Formation.

(Sources: Information received via e-mail on 11.10.2019; NMRW MS. KAM 02; F. Frowen, K. A. Martin and K. Palmer, 'Odyn Fach', Archaeology in Wales, 37 (1997), 124)
A.N. Coward, 14.10.2019