THOMASTOWN RAILWAY VIADUCT (2004)

The Thomastown Railway Viaduct was notable as it had the longest single railway bridge span in the British Isles at the time of completion.  But it has also an interesting building history.

The Kilkenny to Thomastown railway line opened the 12th May 1848.  It was extended from Thomastown to Jerpoint Hill, opening 29th May 1850.  This relatively short section required the construction of the viaduct consisting of timber lattice girders supported on heavy masonry abutments to a design by engineer, Captain William Scarth Moorsom (1804-63).  It was two hundred feet long and seventy-eight feet above the river Nore.  Twenty-five feet wide, it was designed for two lines, although only one was built.  The timber was supplied by Messrs. J.P. Graves of Waterford and New Ross at a cost of £3,300 and construction was completed by the firm of J. and R. Mallet of Dublin.

However from the start there was public unease about its safety.  Michael Sullivan MP (d. 1878) brought these concerns to the railway company.  A series of tests were carried out; by a Captain Laffin in 1850, a Colonel Wynne in 1854 and finally in June 1858 by Captain Henry Whatley Tyler (1827-1908) of the Royal Engineers, appointed Inspector of Railways in 1853.  Tyler's report concluded that while it was safe, it needed constant monitoring and that the railway company should start preparing for its replacement with a more permanent structure.

 
A RENDERING OF THE ORIGINAL TIMBER CONSTRUCTION INCLUDED AS AN ILLUSTRATION TO ACCOMPANY AN ARTICLE TITLED "THE NORE VIADUCT AT THOMASTOWN" IN THE IRISH BUILDER, MARCH 15TH 1879 (pp.85-6)

Finally in 1875 the directors decided to replace the timber structure with one of iron.  The contract was awarded to Messrs. Courtney, Stephens and Bailey of Dublin, with construction starting in the autumn of 1876.  On the evening of 29th January 1877, a violent south-westerly gale damaged the old timber superstructure.  By early the following morning the gale increased again and by daybreak all the new construction had blown down, completely blocking the bridge.

It was quickly cleared to allow passage by foot, trains stopping short on both sides.  In his paper to the Institution of Engineers in Ireland, the engineer for the new viaduct, Charles Richard Galwey (1840-94) stated: "Every exertion was made to clear the line, but owing to the difficulty of handling such large masses of iron and the shortness of the days, this was not accomplished till the afternoon of the 2nd February".  Two days later engine traffic was allowed again across the bridge.

On 3rd August 1877 the new iron structure was tested with five engines and tenders, covering the whole span of the bridge and weighing in all nearly two hundred tons.  The results were satisfactory and the taking down of the old bridge followed, taking some three months.  Subsequent tests showed that much of the timber was rotten; although ironically it was the timber which Moorsom had suggested "should be avoided in the future" which was found to be in the best condition.  Some of the original timber piles could not be extracted so were broken off at riverbed level - where presumably they still survive.

Joe Norton

Department of Environment, Heritage and Local Government