Caisson Pier Finished, 1885.

SCOTLAND - SEPTEMBER 03: A photograph of a completed caisson pier for the Forth Railway Bridge, Scotland, taken by an unknown photographer in 1885. This image is taken 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 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)