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Tide mills will be found along shallow creeks, usually some miles from the coast, safe from the buffeting waves of the sea but well within reach of the tide. Behind the mill there will be a pond. Some mills have created these ponds by creating a bank right across the estuary, often capturing stream or river water as well as tidal water. Carew in Pembrokeshire is one of these and Eling Mill near Southampton. At Woodbridge a pond of over seven acres was constructed.
The incoming tide opened lock-type gates in the banks of the pond and filled the pond. As the tide fell, the first out-flowing water closd the gates and they were then held firmly in position by the pressure of the trapped or impounded water. When the tide had fallen suiciently - that is when the water wheel was completely clear of tidal water, then the miller opened the sluice gates at the mill race and the released water, rushing out, turned the wheel and therefore the machinery. The mill worked for approximately two hours either side of low tide. The miller's day depended upon the movement of the tide and his working hours were quite irregular. No two consecutive days would be the same for him. The variation of tides at different seasons added to his difficulties.
The sluice gates were so constructed as to allow breastshot operation on a high tide or early in the milling process and then undershot when both sluices would be raised to use up every last drop of available water.
In the diagram below you will notice two gates, A and B. Here they are both raised and the wheel is driven by undershot power. Drop gate B and the water would flow under A and over B to drive the wheel breast-shot.
The mill stones have to be recut at regular intervals, or the efficiency of the mill will be lost. They are lifted carefully and the miller or a specialist dresser can sharpen the cutting edges with the miller's bill.
Dressing the stones. A specialist task.