on the rough surface of the tables, the finer gold being caught in the rougher parts of the tables, and removed at the end of the process. The cascade would probably have been built towards the end of the 1st century when underground mining commenced following opencast development. Carreg Pumsaint This site yields some of the earliest evidence anywhere for the Roman use of water-powered trip hammers to crush ore (Burnham 1997). The ore was probably crushed on the famous Carreg Pumsaint, a block of stone erected many years ago before the Romans had left the site. There are parallels with similar stones at other ancient Roman mines in Europe, and the hollows in the block were formed by a trip hammer probably worked by a water wheel or a "water lever". Such a water-powered hammer would have been moved regularly as each hollow became too deep, so producing the series of overlapping oval hollows in its surfaces. The hammer head must have been of substantial size judging by the width of the hollows shown in the drawing. The stone is the only example so far discovered at the site, but is not unique, and Burnham refers to others of similar shape from Spain. As one side of the stone became worn, it was simply turned to reveal another side, so the block could be re-used several times. When found years after the Romans had left, in the Dark Ages, it gave rise to the legend of the five saints, who left the impression of their heads in the stone after being found asleep by the devil. Deep mining They followed the veins with shafts and tunnels, some of which still exist on the site. The remains of Roman dewatering machines were found during the 1880s and the 1920s when the Rio Tinto mines in Spain were being mined by opencast methods. At Dolaucothi, a similar discovery was made in 1935 during mining operations, and it included part of a reverse overshot water wheel which is now in the National Museum of Wales. It was found with burnt timbers, suggesting that fire-setting was used to help break up the hard quartz in which the gold was trapped. A similar but larger wheel was rediscovered during mine operations at Rio Tinto in Spain, and is now in the British Museum, where it is displayed prominently in the Roman gallery. The Spanish