Bridges allow us to travel across obstacles like waterways, roads and valleys that would otherwise stop us from getting from one place to another.
The majority of bridges that John Smeaton built were across rivers and canals and they were all either constructed from stone or brick. Some of them are still standing today including Coldstream Bridge over the River Tweed and the nine arched Perth Bridge over the River Tay.
John was also called upon to complete emergency bridge repairs across the River Thames. In 1763 the central arch of London Bridge had been widened to allow larger boats to pass along the river. However, the extended arch increased the volume and rapid flow of water rushing beneath the bridge. This damaged the foundations so badly that the bridge became unstable and people were afraid to cross it.
The London authorities summoned John Smeaton to attend at once and he immediately made the trip down from Yorkshire. His solution to the problem was unexpected but ingenious. After inspecting the failing bridge, he advised that the stone pillars of the City Gates should be thrown into the river to stem the rapid flow of water. In a twist of fate, the stone City Gate pillars had been recently dismantled and sold to local merchants. Fortunately, they were promptly located, purchased back from the merchants, thrown into the water and London Bridge was saved.
Smeaton’s experience of building Hexham Bridge over the River Tyne stands in stark contrast to that dramatic success in London. In 1782, midway through Hexham Bridge’s construction, a violent storm caused the water to surge, the foundations gave way and the bridge collapsed. This was Smeaton’s first failed project and it caused him great unhappiness. Until that moment John prided himself on his disciplined approach to work and meticulous calculations. Writing about the experience he lamented:
“It cannot now be said that in the course of thirty years practice not one of Smeaton’s works have failed”.
The replacement bridge was not built by Smeaton but it was based on his previous designs and completed after his death by the engineer Robert Mylne in 1793. 200 years later the bridge still stands today.
The aesthetic of John Smeaton’s bridge designs was characteristically simple. He was led by the geometry, function and materials of the structure rather than a desire to create ornamental embellishments for their own sake. That’s not to say that he didn’t appreciate his own design skills though and once remarked on Coldstream Bridge after it was completed:
‘I find myself somewhat jealous of the beauty of the bridge. The dam being of equal height in every part, the bridge in the lowest water times will appear to stand in a level pool terminated by an extensive cascade, a noble sight’ Skempton p176