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Celebrating Scottish innovation

Sir William Arrol and the Forth Bridge

For something as innovative as our new polymer five-pound note we wanted to celebrate. We’ve chosen the images for the front and the reverse of the note to commemorate the nomination of the Forth Bridge for inclusion in UNESCO’s World Heritage List. It’s also the 125th anniversary of the opening of the bridge in 2015. The other image we’ve chosen to use is of the engineer whose company built the bridge, Sir William Arrol.

Sir William Arrol

(13th February 1839 – 20th February 1913)

Sir William Arrol

Showing early promise

William Arrol started work in a cotton mill just outside Glasgow at the age of nine. By the age of 13 he was training to be a blacksmith. At the same time he attended night school and learned mechanics and hydraulics. In 1863 he started work at a bridge manufacturing company in Glasgow.

Building a career

He learned his trade and mastered all aspects of bridge building and, in 1872, started his own company, the Dalmarnock Iron Works. By the late 1870s he founded Sir William Arrol & Co., which went on to become a leading international civil engineering company.

Making visionary changes

His company redefined the way bridges were built, using steel and a newly developed riveting method. They built the Caledonian Railway Bridge over the River Clyde in 1878, which is still in use today. In 1882 the company was appointed to reconstruct the Tay Rail Bridge, which had sadly collapsed in 1879. When it was built, the Tay Rail Bridge was the largest of its type in the world.

Building a legacy

They built the Forth Bridge, which remains one of the most iconic and recognisable structures in the world. They then built Tower Bridge in London and they designed the foundations for the Finnieston Crane in Glasgow.

He was a visionary. A man who changed the world he lived in and whose ingenuity is still influencing our lives today.

The Forth Bridge

(4th March 1890 – present day)

The Forth Railway Bridge

Looking good for a 125 year old

The Forth Bridge is a true landmark, both physically and in terms of engineering. It is one of Scotland’s most iconic structures and is recognised around the world. Since it opened on 4th March 1890 it’s been an inspiration for everyone from engineers to advertisers, and from authors to filmmakers.

Breaking it down

It’s a cantilever railway bridge that spans the Firth of Forth in eastern Scotland. It crosses from South Queensferry on the Edinburgh side to North Queensferry on the Fife side. The bridge is 8,296 feet (2,528.6 metres) in length – that’s just over 1.5 miles. On an average day around 200 trains cross it. It’s estimated that there are 6.5 million rivets holding the steel frame together and that 39,000 tonnes of steel were used to build it.

Construction begins

Sir William Arrol’s company started work on constructing the Forth Bridge in late 1882. It was an astounding feat of engineering that is still seen as an engineering marvel today. The project team devised many innovative ways to build the bridge. At the project’s peak there were around 4,600 workers building the bridge. There were so many employees that the company hired a paddle steamer to transport them. They built a double track crossing that is elevated around 150 feet (46 metres) above high tide.

Cantilever construction

The bridge is built on the principle of the cantilever bridge. This means that a cantilever beam supports a light central girder. This engineering principle has been used for thousands of years in the construction of bridges.

The bridge is constructed of:

  • three main spans of 1,710 feet (520 metres)
  • two side spans of 675 feet (206 metres)
  • 15 approach spans of 168 feet (51 metres)
  • five of 25 feet (7.6 metres)

Each main span comprises two 680 feet (210 metres) cantilever arms supporting a central 350 feet (110 metres) span truss.

A quirk of fate

After the Tay Bridge collapsed in high winds in 1879 the Forth Bridge was given a ‘belt and braces’ design. This meant that the bridge was reinforced to give it extra strength. This accounts for some of the structure’s iconic steelwork. Had the Tay Bridge not collapsed then the Forth Bridge may not have had the same grandeur.

Still admired today

The Forth Bridge has been nominated for World Heritage Site status. UNESCO will examine the nomination and make its decision later in 2015. The bridge would become an even greater tourist magnet if the nomination is successful.

It’s sometimes known as the Forth Rail Bridge to distinguish it from the Forth Road Bridge. But to locals it’s the Forth Bridge (with the emphasis on ‘the’). It seems a very worthy inclusion on the UNESCO World Heritage list. And we’re delighted to feature it on our new polymer five-pound note.