Editing Watermill (section)

=== Tide mills ===

A different type of watermill is the [[tide mill]]. This mill might be of any kind, undershot, overshot or horizontal but it does not employ a river for its power source. Instead a mole or causeway is built across the mouth of a small bay. At low tide, gates in the mole are opened allowing the bay to fill with the incoming tide. At high tide the gates are closed, trapping the water inside. At a certain point a sluice gate in the mole can be opened allowing the draining water to drive a mill wheel or wheels. This is particularly effective in places where the tidal differential is very great, such as the [[Bay of Fundy]] in Canada where the tides can rise fifty feet, or the now derelict village of [[Tide Mills, East Sussex]].{{citation needed|date=January 2015}} The last two examples in the United Kingdom which are restored to working conditions can be visited at [[Eling Tide Mill|Eling]], [[Hampshire]] and at [[Woodbridge Tide Mill|Woodbridge]], [[Suffolk]].

''Run of the river'' schemes do not divert water at all and usually involve [[undershot]] wheels the mills are mostly on the banks of sizeable rivers or fast flowing streams. Other watermills were set beneath large bridges where the flow of water between the stanchions was faster. At one point London bridge had so many water wheels beneath it that bargemen complained that passage through the bridge was impaired. {{citation needed|date=January 2015}}