What is Mathematical Bridge?
Mathematical Bridge is an iconic wooden footbridge at Queen’s College in Cambridge that was designed in the 18th century.
Mathematical Bridge History
Punt chauffeurs will tell you that the Mathematical Bridge was designed and built by the great scientist Sir Isaac Newton. They may even recall how it was originally built without a single nail, bolt, or fastening at the joints and how a group of arrogant scholars thought they could recreate Newton’s work by dismantling the bridge and putting it back together, only to find that they were unable to do so without bolts, which is why you can see them today.
Sadly, that’s all fiction. Along with King’s College Chapel, the Mathematical Bridge, often just called the Wooden Bridge, is one of the most recognisable features in Cambridge. Crossing the River Cam and linking Queens’ College, it’s a curious wooden structure, but given all the folklore, oddly there’s no mystery around the facts of its creation. Undoubtedly, the bridge was designed by William Etheridge and built by James Essex in 1748, a date which easily excludes Newton who died 20 years previously. It was also originally intended to have many fastenings, either as coach-screws, which weren’t visible, or fastenings covered by a wood shim. When the bridge was entirely rebuilt in 1905, coach-bolts were used: the nuts were visible on the outer elevation and the bolt heads visible on the interior. Although fastenings had always been there, their increased visibility after the rebuild most likely produced the myth of the failed re-assembly.
The bridge, whilst quaint, is also a famed engineering accomplishment. It’s an example of a voussoir arch bridge, whereby the entire arch is held in a state of compression via the force of gravity. Rather than bending the wood, which would weaken it, the bridge instead is comprised of many short lengths of straight timber which make up carefully constructed segments. These segments come together to form a rigid and self-supporting structure that spans the 15-metre river in a single arch. The design was not novel, however: James King had used the design to build Westminster Bridge in London, and the architect of the Mathematical Bridge, William Etheridge, also designed the even larger Old Walton Bridge soon after. The Mathematical Bridge’s fame is more a result of its picturesque appeal than its singular design or the various tall tales that surround it.
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