This wheel was, at c.52 feet in diameter, the largest on mainland Britain, second only to the wheel at Laxey on the Isle of Man. The wheel was overshot, transferring the power through its rim, hence the light weight construction using metal spokes, like a bicycle wheel. This wheel replaced two earlier wheels in the same pit. These were arranged one above the other with the top wheel feeding the lower wheel. The big wheel was replaced in the early 20thC by turbines and electricity generators – a very early use of electricity to power a mill.