Bill McAllister looks back on the wonder of Thomas Telford's work
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This year marks the 200th anniversary of Thomas Telford, a shepherd’s son and a stone mason with no formal engineering training, completing the Caledonian Canal.
It was an outstanding facet of a life of achievement and at peak times 3000 men worked on the massive project. Part of the government’s rationale for funding it was the need to create Highland employment after glens were emptied for sheep farming, triggering widespread emigration.
Telford was delighted to recruit a largely unskilled but highly willing Highland construction army, boosting the local economy. But when it came time to cut the peats or take in the harvest, many of them disappeared for weeks on end.
This led to Telford recruiting scores of Irishmen to keep construction going – which created often bitter disputes when the locals, the peats or harvest in, returned to the job after their ‘holidays’.
The sea lock at Clachnaharry, leading in to the Beauly Firth was one of his toughest challenges. The soft, shifting mud meant no piles could be driven. Telford admitted: “It became necessary to adopt a new method.”
Two headlands were built, using quarry waste from Redcastle and elsewhere along with boulder clay, stretching out 366 metres over the mudflats, to take the canal into sufficient depth of water. The oozing mud prevented work on the base of the lock gate. The solution was to join the embankments in one giant mound, a bridge of clay and boulders between the new headlands, which, over six months, was allowed to sink 16 metres through muddy depths.
This gave scope for a nine metre pit to be dug for the lock chamber – then a chain pump pulled by six horses drained the water and the space filled with mortar and rubble to form the lock foundations.
This was a highly innovative technique for its time. While building was going on, blocking material kept the sea at bay. This was removed in August 1812, allowing the sea to fill the new lock, which raised vessels two-and-a-half metres from firth level to that of the canal.
Thomas Rhodes, from Bradford, designed the original lock gates from oak, with cast iron framing. By 1906, these were replaced by steel and oak versions and by 1959, the gates were being mechanised.
Matthew Davidson, who had grown up with Telford, was in 1805 appointed the canal’s resident engineer at Clachnaharry and he supervised the sea lock success. Davidson was 64 when he died at Clachnaharry in 1819, succeeded by his son James.
Telford’s biographer Julian Glover wrote: “Telford created the backbone of our national road network. His constructions were the most stupendous in Europe for a thousand years and, astonishingly, almost everything he ever built remains in use today.”
Despite the death of his father when he was only two months old – Thomas lived in a one-bedroom Dumfries-shire cottage with his mother until he was 14 – Telford rose from poverty to become an international icon. His big break came from having gone to the same rural school as William Pulteney, who married well and became Britain’s richest man. Telford is reputed to have walked to London to become involved in the country’s biggest construction project, the building of Somerset House.
Pulteney pulled strings to have him appointed County Surveyor of Shropshire, a post Telford skilfully used as on-the-job training. Despite his lack of experience, he was appointed to build the Ellesmere Canal and managed it so successfully that when complete in 1793, other commissions flowed.
Telford, called ‘Laughing Tam’ by Caledonian Canal workers because of his cheery nature, would design or engineer 30 major bridges, more than a thousand minor ones, 33 canals, over a dozen harbours and thousands of miles of road, including the Scottish trunk network.
In 1788 he designed and created Ullapool for the British Fisheries Society. From 1804 he built Bonar Bridge, Roy Bridge and Craigellachie Bridge, the Dingwall to Wick and Inverness to Perth roads. Harbours he created included Nairn, Fortrose, Dingwall and Portmahomack.
But, as we shall see next week, it was another great Scottish engineer who paved the way for Telford’s historic Highland canal.
n Sponsored by Ness Castle Lodges.
