I recently did a story for a local magazine about an old overshot water wheel mill on Cow Creek in Gloucester Virginia. In the process of researching that mill, I found the Popular Grove Plantation Tide Mill in Haywood, Virginia. Both were grist mills that ground corn and other grains. The difference is that the Cow Creek mill was powered by water flow from a pond. At the Poplar Grove Tide Mill the action of the tide coming in and going out powered the mill. That concept intrigued me. It seemed so logical to harness the relentless free power of the tide. Some historians believe that the first tide mill in the Roman world was located in London on the River Fleet. Some archaeologists believe earlier tide mills discovered in Killoteran near Waterford in Ireland, dating back to the 6th Century. It is not known who invented the first tide mill. Some historians believe there is evidence they existed in the 7th Century BC. In the year 1086, there were eight tide mills on the River Lea. There were 76 tide mills in London in the 18th century, two of which were at London Bridge. At one time there were 750 tide mills operating along the shores of the Atlantic Ocean: approximately 300 in North America, including in colonial Boston over a 150-year span. What then exactly is a tide mill? This definition comes from the exhibit brochure moinhos de maré do ociente europeu 2005: “A tide mill comprises the building which houses the milling machinery, the mill-pond, where the tidal water is retained, and the dam or causeway which confine and controls it. Seawater enters the pond through large sluices or ‘sea gates’ which open under pressure from the rising tide, and close automatically after high water. By opening the internal sluice gate, the pressure of the water from the mill pond can be controlled as it flows through one or more narrow channels before hitting the paddle blades and setting the water wheel and the milling machinery in motion.” The tide mill I visited in on the property that is part of the Poplar Grove Plantation. Poplar Grove Plantation was the birthplace (1883) and home of Ms. Sally Tompkins. Ms. Tompkins was the only woman officer in the Confederate Army during the Civil War. She is well known for her charity to wounded civil war troops and for having run the hospital with the lowest mortality rate. Poplar Grove was at one time the country home of Beatle John Lennon and Yoko Ono, who owned it for less than a year before his tragic death. The estate was eventually given to a boy’s home. The present owner told reporter Sherry Hamilton of the Mathews-Gloucester Gazette Journal, “Slave labor was used to build a dam across a small lagoon along Poplar Grove’s shoreline, creating a pond for the tide mill, and that Washington’s troops used the mill during the siege of Yorktown. The house and mill are on the National Register of Historic Places and the Virginia Landmarks Register.” The tide mill is a two-story frame structure built after the American Civil War with a gable roof. Poplar Grove Tide Mill, a historic building located on the East River in Mathews, has a new mill wheel. The original wheel was destroyed during Hurricane Isabel in 2003, and local carpenter Wesley Sanger has built a new one to replace it. Bernadine Teague, the owner of Poplar Grove, said that Sanger delivered the wheel by vessel from his sawmill at Potato Neck on Winter Harbor, around New Point, and up the East River to Poplar Grove.” The Poplar Grove Tide Mill, according to the National Register of Historic Places to have originally been built in Colonial times. Like so many mills in the South, it was destroyed by Union Army raiders during the Civil War. After the war, it was rebuilt and operated until 1912. It is now the only tide mill left in Virginia. That the mill still exists, weather worn and suffering the ravages of time is a fragile monument to the ingenuity of the human mind. The concept of using the power of the tide to generator power has not been forgotten. It is alive and well and being developed in several areas. Perhaps the most, ambitious at last report, is a project in the Bay of Fundy. While it incorporates concepts only possible with modern technology, the basic source of the electrical power generator is the same action of the tide used for hundreds of years around the world and at the Poplar Gove Tide Mill and others like it. In 2016 a single massive tidal turbine was deployed on the coast of Nova Scotia, Canada, a first in North America. OpenHydro and Emera deployed the first of a series of massive turbines and connected it to the local grid. This is one of a very few projects in operation around the world at present. However, there are several more being developed including the Cape Sharp Tidal in the Bay of Fundy in Nova Scotia, Canada. A similar project in 2009 met with failure when the blades were destroyed by the powerful tides not surprising given the history of strong tides in the Bay of Fundy. The tidal range, one of the highest in the world recorded at 56 feet. An estimated 115 billion tons of water flow in and out of the bay during the tidal period. A stronger turbine was developed. The turbine is five-stories high and weighs roughly 1,000 tons. Another turbine is in the works which will produce a total of 16 MW. It should be understood that this project is a demonstration and test of the technology since it’s in no way economically viable otherwise. The cost of MWh delivered is roughly $530 or $0.53 CAD per kWh. The local power company produces power for less than half of what the tide generator costs. Even as a demonstration project, the current turbine generates enough electricity to power 500 homes with significant improvements occurring as the technology develops. An important part of the cost is attached to the development of custom tools and logistical equipment to build and deploy those massive turbines. Once the cost of the development of this equipment is amortized over several more turbines, it will start making more sense in term of cost of energy delivered. They expect to have about 300MW of capacity deployed in the Bay of Fundy serving nearly 75,000 customers. Environmental impact is also a top priority. As of this writing, the generator is online and working well. The Tide Mill Institute advises that Robert Gordon and Patrick Malone have just published a thoroughly researched and annotated paper, “ ‘Perpetual power’ from the Tides in Boston, Massachusetts, USA, 1813–1858.” According to its abstract, the 27-page paper describes how engineers “overcame daunting technological challenges” to harness the tides in Boston from 1822 to 1858, providing “continuous, uniform tidal power to Boston industries.” This energy-producing system operated as a modern utility by selling this energy to industrial customers. Inventors and artisans, too, took advantage of this energy source, and roads built on the dams around the tidal basins became important transportation links.” There is a great deal of information about tide mills available at: https://www.tidemillinstitute.org Boats can take advantage of water movement as well to generate electricity. Watt &Sea is just one of several firms making cruising hydro generators that can provide electric power while the boat is moving through the water. https://www.wattandsea.com This is a great start toward utilizing the movement of water to create power. It is a very old idea, but basically a very good one.