example included a sequence of no fewer than 16 reverse overshot water wheels, each pair of wheels feeding water to the next set in the sequence. Each wheel would have been worked like a treadwheel, from the side rather than at the top, but it would have been a hard and lonely activity for the miners working these wheels lifting water from the mine bottom. Since the fragment of a reverse overshot water wheel was found 160 feet below any known adit or stope, it must have been part of a similar sequence at Dolaucothi to that in Spain. Gold mining was sophisticated and technologically advanced at Dolaucothi, suggesting that the Roman army itself pioneered exploitation at the site. The construction of such dewatering machines is described by the Roman engineer Vitruvius writing in 25 BC, and their use for irrigation and lifting water in thermae was widespread. At another part of the mine, on Penlan-wen, water would have been in short supply; a siphon could have transferred water from the main aqueduct or one of its tanks, but remains unproven. The vein carries along the hill for some considerable distance, and has been trenched out. This method involved excavating the vein vertically down while keeping the top open. However, ventilation becomes a problem when fire-setting is used, so three long adits were driven in from the hillside to the north. They are much wider than normal galleries, suggesting that their primary purpose was to allow circulation of air through the trench and permit safe fire-setting. The upper two adits are still open to the trench, but the lowest one is currently blocked. Similar sites Although there is nothing directly comparable with Dolaucothi in Britain in terms of the extensive hydraulic systems, there are many other known Roman mines in Britain, some of which seem to show traces of hydraulic activity. They include the extensive remains of lead mining at Charterhouse in the Mendips, Halkyn in Flintshire, and many areas in the Pennines. Dolaucothi is most directly comparable with gold mines in the Carpathian mountains of Transylvania in modern Romania, at Rosia Montana, and with the Roman gold mines in north-west Spain, such as the very much larger site of alluvial mining at Las Médulas and Montefurado. The Romans may have used slave labour taken from the local area to work the mine, although the army itself was probably most