John A. Roebling built his legacy on using suspension cables to support bridges and aqueducts, and he devised the technique of air spinning, still used to create much larger spans. This former aqueduct is the nation’s oldest existing wire cable suspension structure and the earliest of Roebling’s works still standing. Although much of the aqueduct has been reconstructed, the cables and almost all of the ironwork in the suspension system are original. In air spinning, 36-inch-thick wrought iron wires were shuttled across the river two at a time over stone piers, looped over anchor chain shoes, and returned to the opposite side, with each roll of wire spliced to the next until a bundle was formed; seven bundles made one cable. Each of the two 8.5-inch-thick cables contains 2,150 individual parallel wires, which are oiled, wrapped, and painted for protection, and each cable is 576 feet long. Together the cables support almost 2,000 of water. Iron rods suspend from the cables to hold the trusses that support the aqueduct, while wrapping wire compresses the wrought iron wires between the masonry piers to form the cables. At the anchor chain shoes, the cable wires separate into seven strands, and shoes and pins connect these bundles to anchorage chains. The anchorage system is encased in cement and stone and buried almost 20 feet below the surface to keep out air and moisture and prevent rust and decay.