What is a Tide Mill?
A tide mill is quite simply a water mill that derives its power from the rise and fall of the tides. Water impounded behind a mill dam can only be put to work after the water level outside of the dam has sufficiently dropped during the ebb tide. Wherever there was an absence of freshwater streams, or where freshwater streams had an inadequate drop in geographic elevation, tide mills were important early industrial resources in many coastal areas. [Richard A. Duffy]
Tidal Range--From Wikipedia, the free encyclopedia:
The tidal range is the vertical difference between the highest high tide and the lowest low tide. In other words, it is the difference in height between high and low tides. The most extreme tidal range will occur around the time of the full or new moons, when gravity of both the Sun and Moon are pulling the same way (new moon), or exact opposite way (full). This type of tide is known as a spring tide. During neap tides, when the Moon and Sun's vectors make a right angle at the Earth, the difference between high and low tides is smaller.
Geography
The typical tidal range in the open ocean is about 0.6 metres (2 feet). As you get closer to the coast, however, this range gets much greater. Coastal tidal ranges vary globally and can differ anywhere from 1.8 metres to 3 metres (6–10 feet). The world's biggest tidal differential occurs in the Bay of Fundy in Eastern Canada, where the sea level changes by up to 17 metres (55 feet) during the day. What is generally regarded as the next highest tidal range occurs in the Bristol Channel in the UK, where sea levels change by some 15 metres (49 feet). The smallest tidal ranges occur in the Mediterranean, Baltic, and Caribbean Seas.
The rising tide flows through the gates into the mill pond. When the tide turns and begins to flow out, the gates close automatically, trapping a large volume of water that may be used to power a water wheel.
