'Singrigg Mill Glyn North Wales', early 19th century.
© Science Museum / Science & Society Picture Library
Lithograph after an original drawing by W F Wells, showing a water mill in North Wales. The mill wheel is of the overshot type where the flow of water turns the wheel from above. Because of the role of gravity, this was found to be much more efficient than the undershot type, where water flows beneath the wheel. Printed by C Hullmandel.