The Forth Rail Bridge.

The bridge is, even today, regarded as an engineering marvel. It is 1.5 miles in length, and the double track is approx. 150 ft above high tide. It consists of two main spans of 1,710 ft, two side spans of 675 ft, 15 approach spans of 168 ft, and five of 25 ft. Each main span comprises two 680 ft cantilever arms supporting a central 350 ft span girder bridge.

More than 55,000 tons of steel were used, as well as 18,122 m³ of granite and over eight million rivets. The bridge was opened on March 4, 1890

Much of the engineering was without precedent, including calculations for incidence of erection stresses, provisions made for reducing future maintenance costs, calculations for wind pressures, the effect of temperature stresses on the structure, and so on.