Just off the M4 near Neath in South Wales is the site of the beautiful Aberdulais Falls. The gorge in which the river runs was formed by glaciers during the last ice age. Huge sink holes formed by water flowing beneath the glacier can still be clearly seen. The falls also represent one of the oldest industrial sites in Britain. Corn milling, dying of wool, copper smelting and tin plate making have all been carried on here over the centuries. The gorge and the falls have been altered considerably by all this activity, and in 1820 a Captain R.H. Gronrow wrote despairingly: "A natural cascade called Dyllais... was destroyed by an agent to Lord Jersey, the proprietor of the estate, in order to build a few cottages ans the lock of a canal. The rock down which this beautiful cascade had flowed from the time of the flood and which has created a scene universally admired was blown up with gunpowder by this man." A weir was built in 1830 to control this unpredictable, flash flood river. This continues to be used to stockpile water in a header tank, to provide a constant supply of water for the wheel.