so must be later in date. By contrast, several tanks found on the site did not show a vein, so were abandoned. The tank shown at right occurs not far from the north opencast and was probably intended to find the limits of the deposit located in the adjacent opencast (Tank A in the schematic diagram below). It clearly didn't find the vein, and was thus abandoned. The water supply may have been obtained from a small leat run from a stream up the main Cothi valley before the much larger aqueduct was constructed. Opencast mining Prospecting was successful and several opencasts are visible below the large tanks built along its length. The only exception is the final and very large tank, below which are two reservoirs. It is likely that this complex was used for washing powdered ore to collect the gold dust. More leats and tanks can be found below the line of the main aqueduct, some of which are shown on the map of the site. They surround the lip of the very large opencast and the tank shown at right is one which was built on the main aqueduct. It was successful in finding a vein, judging by the opencast below, but must have been modified later to feed a washing table built to the left-hand side (near the figure in the picture), probably to wash the crushed ore from the same opencast working. It is labelled Tank C in the schematic diagram. Similar tanks occur below as the Romans followed the large vein down to the road and the main opencast. Most of the opencast workings must therefore be Roman in origin, since one of the aqueducts has been confirmed by carbon 14 dating as to predate all modern workings. Just by the road itself the Carreg Pumsaint has been erected in the space beside a large mound, now thought to be a dump of waste material from mining activities. The existing ponds above and below the minor road from Pumsaint to Caeo, were probably part of a cascade for washing ore, the upper tank having yielded large quantities of Roman pottery from to at least 300 (Lewis, 1977; Burnham 2004). The upper pool is known as Melin-y-Milwyr, or the soldiers' mill, an intriguing name that implies that watermills may have been used here during the Roman period. Alternatively, it may have been a sequence