Thomastown viaduct, co Kilkenny (1846-50 & 1877)
South of Thomastown, near Jerpoint abbey in county Kilkenny, the Dublin to Waterford railway crosses the river Nore. Originally built by the Waterford & Kilkenny railway company, for its first thirty years or so it was formed of an incredible single-span wooden lattice deck, designed by captain William Scarth Moorsom and Robert Mallet. According to Michael Barry in his book Across Deep Waters: Bridges of Ireland, the Illustrated London News reported on the new viaduct in June 1850, describing it as ‘stupendous…the largest work of its kind in the three kingdoms.’ Moorsom penned an article in the Civil Engineer and Architect’s Journal in 1852 where he described it in more detail, noting it was constructed of Memel fir, and the final deflection in the centre of the span was calculated at 7.25 inches, less than the 9 inches expected, and therefore well within iys safe operating limits.
However, as noted by Joe Norton in his recent and very informative article on the viaduct for the National Inventory of Architectural Heritage, ‘from the start there was public unease about its safety…[it was recommended that] the railway company should start preparing for its replacement with a more permanent structure…Finally in 1875 the directors decided to replace the timber structure with one of iron.’ The new deck was built by Messrs. Courtney, Stephens and Bailey of Dublin, and completed by August 1877.
Here is the map link for the site.