Original wooden viaduct at Landore, Wales, c 1850.

UNITED KINGDOM - JULY 29: Watercolour, showing a train on the viaduct over the River Tawe at Landore, Swansea, on the South Wales Railway. The railway was built by Isambard Kingdom Brunel (1806-1859) and was designed to run from Gloucester to Fishguard, from where it would connect with shipping to Ireland. The line was completed as far as Carmarthen in 1852, but was then extended to Milford Haven rather than Fishguard. Brunel used timber viaducts on several of his railways in the West Country and Wales, as they were inexpensive to build. They had a limited lifespan however, and needed to be replaced by stone or brick structures. (Photo by SSPL/Getty Images)