members were fabricated in on-site workshops, pre-drilled, test-assembled—exact dimensions were needed in a riveted structure—and then dismantled to be painted and carried to the site for erection. Each of the 331-foot-high (99.3-meter) cantilevers consists of two inward-sloping trusses fabricated from huge, internally stiffened tubular members up to 12 feet (3.6 meters) in diameter. They support 680-foot-long (204-meter) cantilever arms that are linked midspan by suspended girders of about half that length, making the distances between the towers about 1,700 feet (540 meters). The length of the bridge between the end piers is about 5,300 feet (1,600 meters). Together with the approach viaducts and arches at each end, the bridge carries the double-track railroad for 2,765 yards (2,490 meters), 150 feet (45 meters) above the surface of the Firth of Forth. The central gap was closed on 14 November 1889, and the Prince of Wales ceremonially opened the bridge on 4 March 1890.


Firth of Forth Railway Bridge, Scotland; Thomas Harrison, William Barlow, John Fowler, and Benjamin Baker, engineers, 1881–1890.

Further reading

Hammond, Rolt. 1964. The Forth Bridge and Its Builders. London: Eyre and Spottiswoode.

Koerte, Arnold. 1991. Two Railway Bridges of an Era: Firth of Forth and Firth of ‘Tay. Boston: Birkhäuser.

Petroski, Henry. 1995. Engineers of Dreams. New York: Alfred A. Knopf.

Florence Cathedral dome

Florence, Italy

The dome of the cathedral church of Santa Maria del Fiore (St. Mary of the Flowers) in Florence, Italy, was designed and built by Filippo Brunelleschi (1377–1446) in the beginning of the fifteenth century. Towering over the immediately surrounding buildings and still visible, almost 600 years later, from any part of the city, it is one of Europe’s greatest architectural and engineering achievements—a masterpiece of structural ingenuity.