The Civic Society column with David Winpenny

The Ponte de 25 Abril suspension bridge in Lisbon. (Copyright - David Winpenny)
The Ponte de 25 Abril suspension bridge in Lisbon. (Copyright - David Winpenny)

The city of Ripon is surrounded by water. Please don’t be alarmed; this is not a flood warning but a statement of fact, for the city has water on nearly every side.

We have three rivers – the Ure, the Skell and the Laver – and a canal, as well as wetlands where gravel extraction has been completed and the land flooded.

Druids' Bridge, Nostell Priory ' a late clapper bridge. (Copyright - David Winpenny)

Druids' Bridge, Nostell Priory ' a late clapper bridge. (Copyright - David Winpenny)

And with water comes the necessity to cross it – and that usually means bridges (ferries exist, too, of course, but not round Ripon).

So we in Ripon know the value of our many bridges.

Ripon Civic Society not long ago had an excellent talk by Peter Hills on the city’s bridges, so we appreciate their historical origins and their present state.

Bridges are essentially utilitarian structures, and their shape and structure are dictated by their function. We may speculate that the earliest bridges were simple tree trunks that had conveniently fallen – or had been felled to fall over an otherwise impossible stream of water.

Sydney Harbour Bridge. (Copyright - David Winpenny)

Sydney Harbour Bridge. (Copyright - David Winpenny)

Then, perhaps came the idea that a flat piece of stone could be used to bridge a modest stream – and from that came the idea of the clapper bridge, where a causeway of several flat stones across a shallow stream is supported on stone uprights.

There are several ancient clapper bridges in upland areas of Britain; a late example, with its supporting piers built of many stones rather than just single-block uprights, is found at Postbridge on Dartmoor.

In the 18th Century, when there was a fashion for all things from the distant past, new, ancient-looking clapper bridges were constructed; there’s a good example, characteristically called the Druid’s Bridge, at Nostell Priory near Wakefield.

The Romans were the great bridge builders of the classical period; one of the titles of the Pope, taken over from the Roman emperors, is still ‘Pontifex Maximus’ – the great bridge-builder.

There are no complete Roman bridges in Britain, but there are several places where you can see the riverbank abutments that supported them, including near Chesters Fort in Northumberland.

If the Romans showed the British how to build arched bridges, it took some time for such structures to permeate our landscape.

There are some fine medieval bridges, including the unusual three-armed bridge at Crowland in Lincolnshire, that went over the confluence of two streams.

Commerce was often the incentive for building bridges, so we have many packhorse bridges on the routes formerly taken across moorland and through valleys by traders. These days the simple humpbacked structures are much admired and photographed for their picturesque look – though to their first users there were just a vital link in the supply chain.

The same is true of bridges built during the industrial revolution. We have a couple of brick bridges over the Ripon Canal, and such structures were vital to keep both the canals and the villages and agricultural communities around them operating.

Sometimes the canals themselves had to carried over valleys on aqueducts, the most spectacular being the Pontcysyllte in North Wales, completed in 1805 to carry the Llangollen Canal 126 feet above the valley.

In the same way, the railways needed bridges to carry them over valleys and other obstacles; their bridges and viaducts can be things of beauty in themselves – think of the 24 arches of the Ribblehead viaduct, or, nearer home, the Knaresborough viaduct.

Such structures are essentially engineering, made possible by advances in technology in the 17th and 18th centuries.

The world’s first completely-iron bridge was opened in Shropshire – at the place now named Ironbridge – in 1779. All other metal bridges, from the Royal Albert Bridge designed by Brunel to cross the River Tamar into Cornwall, to the Sydney Harbour Bridge, owe their existence to it.

Another innovation was the suspension bridge.

There had been simple suspension bridges from early history, in the Himalayas and in South America, where ropes slung between the banks supported a simple, narrow, flexible bridge.

Such bridges continue to be used in jungle and mountain areas – and also in Britain; the rope bridge at Carrick-a-Rede in Northern Ireland was first used in the 18th Century by salmon fishermen wanting seasonal access to a small offshore island; it is now a popular National Trust tourist attraction.

What we might recognise as the first modern suspension bridges, in which a rigid deck is carried on rods hanging from chains or wires, date from the early 19th century. An American patent of 1808 shows this new type of bridge, and there were suspension bridges in Britain soon afterwards.

The first to accept vehicles was the Union Bridge over the River Tweed, put up in 1820, to link England and Scotland; more modest was the bridge at Whorlton across the River Tees near Barnard Castle, erected a decade later – four years after Telford’s great Menai Bridge, the first important suspension bridge in the kingdom, was constructed to replace the dangerous ferry across the Menai Strait.

Today we have many great suspension bridges –the Humber Bridge, the Golden Gate Bridge in San Francisco (opened in 1937) and its imitator the Ponte de 25 Abril at Lisbon in Portugal, for example.

The world’s longest suspension bridge is currently under construction; it’s the Çanakkale 1915 Köprüsü across the Dardanelles in Turkey, planned to open in 2023. Until then you’ll have to travel to Japan for the longest – the Akashi Kaikyō Ō-hashi.

Most of these bridges are engineered without decoration – though some, like the Clifton Suspension Bridge in Bristol with its Egyptian theme, or the castellated Knaresborough Viaduct, have some architectural embellishment. But there are other bridges – smaller and more ornamental – that have more artistic pretensions.

We shall consider those next week.