Water Wheel at Dyfi Furnace, Ceredigion, Wales. The Dyfi Furnace is in the village of Furnace, Ceredigion, Wales. The furnace built around 1755 was only used for about fifty years to smelt iron ore. By 1810 it had been abandoned and the waterwheel removed. Some time later a new waterwheel was installed - the one that has been renovated and is visible today - and the furnace became a sawmill. The furnace site was renovated around 2008.