The principle is to use a curved track and rolling counterweights where the work expended in raising the leaf is equal to the energy released by the falling counterweight. The toe end of the movable span is linked by cables to cylindrical rolling counterweights. The connecting cable passes over a tower column with a curved track. Moving the counterweights along the curved track thus raises or lowers the bridge. The work expended in raising the leaf is equal to the energy released by the falling counterweight. The toe end of the moveable span is linked by cables to cylindrical rolling counterweights. The rolling counterweight single-leaf bascule bridge with a deck girder movable leaf is the only example of the late 19th-century bridge type in the state of New Jersey and possibly the entire country. It was, at the time, a popular design for railroads in New Jersey for spanning canals.