the arch to at the ends next to the pylons. The arch has a span of and its summit is above mean sea level; expansion of the steel structure on hot days can increase the height of the arch by . The total weight of the steelwork of the bridge, including the arch and approach spans, is , with the arch itself weighing . About 79% of the steel, specifically those technical sections constituting the curve of the arch, was imported pre-formed from England, with the rest being sourced from Newcastle. On site, Dorman Long & Co set up two workshops at Milsons Point, at the site of the present day Luna Park, and fabricated the steel into the girders and other required parts. The bridge is held together by six million Australian-made hand-driven rivets supplied by the McPherson company of Melbourne, the last being driven through the deck on 21 January 1932. The rivets were heated red-hot and inserted into the plates; the headless end was immediately rounded over with a large pneumatic rivet gun. The largest of the rivets used weighed and was long. The practice of riveting large steel structures, rather than welding, was, at the time, a proven and understood construction technique, whilst structural welding had not at that stage been adequately developed for use on the bridge. Pylons At each end of the arch stands a pair of concrete pylons, faced with granite. The pylons were designed by the Scottish architect Thomas S. Tait, a partner in the architectural firm John Burnet & Partners. Some 250 Australian, Scottish, and Italian stonemasons and their families relocated to a temporary settlement at Moruya, south of Sydney, where they quarried around of granite for the bridge pylons. The stonemasons cut, dressed, and numbered the blocks, which were then transported to Sydney on three ships built specifically for this purpose. The Moruya quarry was managed by John Gilmore, a Scottish stonemason who emigrated with his young family to Australia in 1924, at the request of the project managers. The concrete used was also Australian-made and supplied from Kandos. Abutments at the base of the pylons are essential to support the loads from the arch and hold its span firmly in place, but the pylons themselves have no structural purpose. They were included to provide a frame for the arch panels and to give better visual balance to the bridge.