�Constructing The Central Girder�, 1889.

SCOTLAND - SEPTEMBER 03: Photograph showing the construction of the central span to the Forth Railway Bridge, from 'The Forth Bridge In Its Various Stages Of Construction And Compared With The Most Notable Bridges Of The World', by Philip Phillips, published by R Grant & Sons of Edinburgh. A cantilever design, the Forth Railway Bridge was built to carry two tracks of the North British Railway across the the Firth of Forth between South Queensferry and North Queensferry. Constructed over seven years by engineers Sir John Fowler (1817-1898) and Sir Benjamin Baker (1840-1907) and completed in 1890 it was the largest steel bridge of its time. It is still regarded as an engineering marvel. (Photo by SSPL/Getty Images)