Pherrins River Was once called Ferrin's River which is the main tributary of Clyde River, empties into the Clyde River from the north at 0.9 kilometers below the outlet, frequently rises quite suddenly, swelling the waters of the latter so as to reverse its current and cause it to back up into Island Pond with great force for ten hours or more, until the pond is full, or the water subsides below, when it will again change and rush out.