seen from South Queensferry.
See a zoomable version of these images in
'Forth Bridge Illustrations'
The first major engineering challenge in the building of the Forth Bridge was the construction of the stone piers to hold the main body.
Two piers were built using a dam, where water was excluded by means of cement bags and liquid grout poured in by divers.
At the south of the Inchgarvie pier and the Queensferry pier, the conditions of the river bed and depth of water meant that it was not possible to use a dam.
Instead, a pneumatic or compressed air method used wrought iron cylinders called 'caissons' to enable men to work underneath the river.
The six caissons, each measuring 70 feet in diameter and weighing in excess of 400 tons, were constructed on the beach at Queensferry. Each cylinder was floated into position then weighted with cement until it sat on the bed of the estuary.
Once in position on the riverbed, water was pumped from the space and replaced by compressed air.
The bridge was designed to withstand enormous pressure, not just from the weight of trains, but also from high wind speeds.
To further strengthen the bridge against the wind, the whole was laced together by lattice girders, which give the bridge its distinctive appearance.
Philip Phillips was a merchant seaman and photographer who documented the construction of the Forth Bridge from 1886 to 1887. He was the son of Joseph Phillips, a bridge contractor who specialised in ironwork.
Phillips' photographs capured the progress of the bridge at weekly and fortnightly intervals. His images were reproduced in the album 'The Forth Bridge illustrations' in 1889.
See also 'Caissons — dangerous work'
Photos of the bridge's constuction featured in our display, 'The Forth Bridge: Building an icon', at the Library from 1 April to 21 June 2015.