New Castle, its surrounding islands and eight to twelve foot tides, is an ideal location for a tidal mill. (Pic #1) During the 1700’s New Castle had two functioning tide mills: the Bell/Ritsen Mill and the Abraham Trefethan Mill, both located in the back channel. Substantial physical evidence of these tide (pic #2 a) mills still exists today. The mill ponds created by these earthen man-made dams connected the islands and the mainland. (2.b) Built into these dams were two wooden vertical wall-like gates. The mill only operated two times a day when the tide was low. As the tide rose outside of the mill pond, it pushed the gates open and entered the mill pond. The gates closed as the tide began to go out. Captured water from the mill pond was slowly released via a sluice system under the mill house. The water from the sluice system was directed over a turbine water wheel which powered the mill. Note: These dams and adjacent islands are available for marine research and nature walks via the acquisition a few years ago by the town of New Castle, with the help from the town, a Conservative Trust and private donations.