Loch Nan Uamh Viaduct

West Highland Extension Railway

(Institute Civil Engineers Historic Engineering Works no. HEW 0084/02)

The West Highland Railway, originally worked by the North British Railway, is one of the world’s most scenic railways. It could also be said to be the last considerable piece of railway building in Britain, its single track

snaking north-west 140 miles from Craigendoran on the Clyde to the fishing port of Mallaig. The 100-mile Craigendoran to Fort William section was begun in 1889 and opened in 1894, and the 40-mile Mallaig extension, was begun in 1897 and completed in 1901.

The Craigendoran–Fort William section was engineered by Formans & McCall, and the main contractor was Lucas & Aird, a prominent London firm whose driving force was John Aird, an MP of crofting stock. The summit is at Corrour, 1345 ft above sea level on Rannoch Moor. The

methods of crossing the waterlogged moor on brushwood were developed from traditional experience.

Spectacular viaducts include Glen Falloch (NN 3170 2020) 145 ft high, and two in the great Horseshoe Curve above Tyndrum (NN 3350 3620).

Financially the line fared precariously during construction and had to be rescued on one occasion by a director, J. H. Renton, using his private fortune. In gratitude his head was sculpted on a massive rock at Rannoch Station by navvies using only the tools of their trade. It is still there.

The Mallaig extension, built to support the fish trade, struggles westwards through inhospitable mountainous country and winding inlets of the sea. The line has gradigradients as steep as 1 in 40 and curves of 12 chains radius (800 ft) both of which impose drastic limits on speed of trains. Much of its length is on embankment, bridges or hewn out of the living rock in cuttings and tunnels. Today the line is a major tourist attraction with many

steam ‘specials’ in addition to regular services. In engineering terms the line is renowned for the early use of mass concrete in bridge construction. The structures were originally planned to be constructed in masonry, but

the local rock ( mica schist) was too hard and difficult to dress. Concrete offered a cheap alternative solution. In consequence of his usage of this material Robert McAlpine became known as ‘Concrete Bob’. The line’s most notable elements are Glenfinnan and Loch nan Uamh viaducts and Borrodale Arch. The railway was designed by Simpson & Wilson, consulting engineers, and the contractor was Robert McAlpine & Co.

R Paxton and J Shipway, 2007.

Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.

Loch nan Uamh Viaduct

(Institute Civil Engineers Historic Engineering Works no. HEW 0021/02)

The scenic location of this viaduct, at the foot of a rocky mountainside and bridging an inlet to the sea, has been described as Wagnerian. It has eight concrete arches of the standard West Highland Railway span of 50 ft arranged in two four-arch groups on either side of a 50 ft wide central pier. The reason for this unusual arrangement in preference to the more obvious and attractive arrangement of nine arches is not known.

In 2000, Professor Paxton and Radar World, commissioned by Sir Robert McAlpine Ltd, developed an innovative radar imaging technique which penetrated the 9 ft thick walls of this pier into its infilled cavity and identified the vertically positioned remains of a McAlpine horse and cart (behind the white spot in the view) which had accidentally fallen into the cavity a century earlier.

R Paxton and J Shipway, 2007.

Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.

Confirming a West Highland Railway viaduct legend by Professor Roland Paxton MBE

In 1984, when recording the 21-arch, mass-conctrete, Glenfinnan Viaduct for the Institution of Civil Engineers' Panel for Historic Engindeering Works, the legend of a Robert McAlpine horse and cart being buried in a pier after an accident during construction in c.1898 was addressed by Prof. Roland Paxton.

In 1987, Prof. Paxton and colleagues invetstigated the viaduct by inserting a camera into cavities within the piers in the viaduct big enough to hold a horse and cart. There were two: a fish-eye lens camera mounted of a long pole was inserted via inspection holes into each pier cavity and photographs taken at 45 degree intervals i.e. from 0 degrees (vertical) clockwise to 315 degrees. Dissappointingly, the images did not show any evidence of a horse and cart, although it was on interest that some upper timberwork left in place after construction still remained.

The Professor then heard from Dr Jim Shipway, great grandson of the designer, Alexander Simpson, that Ewen Macmillan of Borrowdale remembered local hearsay in his father's time that the accident had occurred at Loch-nan-Uamh viaduct. The central pier of Loch-nan-Uamh viaduct was the only one large enough to have accommodated the remains of a horse and cart. In 2001, eleven hours of intensive site work involving transmission of radio waves through walls up to 9 feet thick revealed the remains of the horse, propped vertically against the east wall of the cavity above the wreck of the cart. This seems consistent with the horse having been dragged down into the cavity from about track bed level as the viaduct was nearing completion by a loaded stone cart.

Information from Prof. R Paxton, July 2008.