Thomastown railway viaduct, Co. Kilkenny

Published in 18th–19th - Century History, Features, Issue 2 (Mar/Apr 2009), Volume 17

Engraving of the original 1850 timber lattice structure.

Engraving of the original 1850 timber lattice structure.

The Kilkenny to Thomastown line, part of the Waterford and Kilkenny Railway, opened on 12 May 1848; it was subsequently extended from Thomastown to Jerpoint Hill, opening on 29 May 1850. This relatively short section required the construction of a viaduct over the River Nore, consisting of timber lattice girders supported on heavy masonry abutments, to a design by engineer Captain William Moorsom. The viaduct was 200ft long and 78ft above the river. Twenty-five feet wide, it was designed for two lines, although only one was built. The timber was supplied by Messrs J. P. Graves, Waterford and New Ross, at a cost of £3,300.
From the start there was public unease about its safety, and Michael Sullivan, MP for Kilkenny City, 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 H. W. Tyler of the Royal Engineers. Tyler’s report concluded that, while the bridge was safe, it needed constant monitoring, and recommended that the railway company should start preparing for its replacement with a more permanent structure.
In 1875 the directors at last decided to replace the timber portion of the structure with iron. The contract was awarded to Messrs Courtney, Stephens and Bailey, and construction started in the autumn of 1876. On the evening of 29 January 1877, a violent south-westerly gale damaged the old timber superstructure. Early the following morning the gale increased again and by daybreak all of the new construction had blown down, completely blocking the track.

The iron bridge that replaced it in 1877 as it is today.

The iron bridge that replaced it in 1877 as it is today.

Debris was quickly cleared to allow passage by foot, with trains stopping short on both sides. In his paper to the Institution of Engineers in Ireland, the engineer for the new viaduct, Charles R. Galwey, stated that ‘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 2 February’. Two days later engine traffic was again allowed across the bridge.
On 3 August 1877 the iron structure was tested with five engines and tenders, covering the whole span of the bridge and weighing in all nearly 200 tons. The results were satisfactory and the removal of the old bridge followed, taking some three months. Subsequent tests showed that much of the timber was rotten. Ironically, it was not the ‘best Memel or Archangel fir’ but the pitch-pine timber used as a partial substitute, and which Captain Moorsom had suggested ‘should be avoided in the future’, that was found to be in the best condition. Some of the original timber piles could not be extracted and so were broken off at riverbed level—where presumably they still survive.

Joe Norton works in the National Monuments Section, Department of the Environment, Heritage and Local Government. Series based on the National Inventory of Architectural Heritage’s ‘building of the month’.

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