St Pancras station roof, London, 1868.
© National Railway Museum / Science & Society Picture Library -- All rights reserved
The roof of the train shed at St Pancras, designed by William Henry Barlow, seen here as construction reached its conclusion. 'This albumen print was made from a 12x10 inch wet collodion glas plate. The unknown photographer sensitised the plate and then climbed to the top of the scaffolding, carrying a bulky camera and tripod. The wet plate was exposed before it could dry and then the photographer returned to the ground as quickly as posible, where he developed, fixed and washed the negative.'