View source for Mathematical Bridge

{{Short description|Wooden arch bridge in Cambridge, England}}
{{Use dmy dates|date=October 2017}}
{{Use British English|date=October 2017}}
{{Infobox bridge
| name             = Mathematical bridge
| official_name    = Queens' Bridge, Wooden Bridge
| image            = File:Queens' College - Mathematical Bridge.jpg
| caption          = Mathematical Bridge at the [[University of Cambridge]] in 2016
| mapframe-zoom    = 15
| mapframe-caption = Location within Cambridge
| crosses          = [[River Cam]]
| material         = Wood, on stone abutments.
| number_spans     = One
| design           = [[Truss bridge]]
| followed         = [[King's College Bridge]]
| preceded         = [[Silver Street Bridge]]
| location         = [[Queens' College, Cambridge]]
| coordinates      = {{coord|52|12|08.0|N|0|06|54.2|E|scale:1000_type:landmark_region:GB-CAM|display=title,inline}}
| complete         = {{start date|1906}}<ref name="listing" /> (Current bridge)
| designer         = [[William Etheridge]]
}}
The '''Mathematical Bridge''' is a [[wooden bridge|wooden footbridge]] in the southwest of central [[Cambridge]], [[England]].
It bridges the [[River Cam]] about one hundred feet northwest of [[Silver Street Bridge]] and connects two parts of [[Queens' College, Cambridge|Queens' College]]. Its official name is simply the '''Wooden Bridge'''<ref>{{cite web |url = https://www.geograph.org.uk/photo/543110 |title = TL4458 : Mathematical Bridge, Queens' College |publisher = [[Geograph Britain and Ireland]] |date = 2007-09-02 |accessdate = 2012-11-02 }}</ref> or '''Queens' Bridge'''.<ref>{{Ordnance Survey|access-date=8 Jan 2021}}</ref> It is a Grade II listed building.<ref name="listing">{{NHLE|num= 1125515| desc  =QUEENS' COLLEGE, MATHEMATICAL BRIDGE | grade= II | accessdate = 2015-12-05}}</ref>

The [[bridge]] was designed by [[William Etheridge]], and built by [[James Essex]] in 1749. It has been rebuilt on two occasions, in 1866 and in 1905, but has kept the same overall design. Although it appears to be an arch, it is composed entirely of straight timbers<ref>{{cite web |url = http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=472 |title = Mathematical Bridge, Cambridge |publisher = Engineering Timelines |date = 2007-09-02 |accessdate = 2012-11-02 }}</ref> built to an unusually sophisticated engineering design, hence the name.

A replica of the bridge was built in 1923 near the [[Iffley Lock]] in [[Oxford]].<ref>{{cite web|title=Iffley Lock |url=http://thames.me.uk/s01620.htm |website=Where the Thames Smooth Waters Glide |accessdate=13 October 2014 |url-status=dead |archiveurl=https://web.archive.org/web/20140812030814/http://thames.me.uk/s01620.htm |archivedate=12 August 2014 }}</ref>

The original Mathematical Bridge was another bridge of the same design, also commissioned by James Essex, crossing the Cam between [[Trinity College, Cambridge|Trinity]] and [[Trinity Hall, Cambridge|Trinity Hall]] colleges, where [[List of bridges in Cambridge#Garret Hostel Bridge (1960)|Garret Hostel Bridge]] now stands.

==Mathematical explanation==
[[File:Mathematical Bridge tangents.jpg|thumb|left|The tangential members of the tangent and radial trussing are highlighted]]
The arrangement of timbers is a series of [[tangent]]s that describe the [[Arc (geometry)|arc]] of the bridge, with radial members to tie the tangents together and [[triangulation|triangulate]] the structure, making it rigid and self-supporting. This type of structure, technically '''tangent and radial [[truss]]ing''', is an efficient structural use of timber, and was also used for the timber supporting arches ([[centring]]) used for building stone bridges.<ref name="queens">{{Cite web |url=http://www.queens.cam.ac.uk/page-1684 |title=History of the Design |accessdate=2013-11-02 |publisher=[[Queens' College, Cambridge]] |url-status=dead |archiveurl=https://web.archive.org/web/20130921135000/http://www.queens.cam.ac.uk/page-1684 |archivedate=21 September 2013 |df=dmy-all }}</ref> Analysis of the design shows that the tangent members are almost entirely under compression, while the radial timbers are almost entirely subject to tension with very little bending stress, or to put it another way, the tangent and radial elements elegantly express the forces involved in arched construction.{{Clear|left}}
<gallery widths="200" heights="150">
MathematicalBridge1865.jpg|The Mathematical Bridge (approx. 1865) pictured shortly before it was partially rebuilt in 1866
Mathematical Bridge, Queen's College, Cambridge (South Face).jpg|South face of the Mathematical Bridge
cmglee_Cambridge_Mathematical_Bridge_from_Riverside_Building.jpg|The bridge from Queens' College's Riverside Building
</gallery>

== Myths ==
A popular fable is that the bridge was designed and built by Sir [[Isaac Newton]] without the use of nuts or bolts. Various stories relate how at some point in the past either students or fellows of the University attempted to take the bridge apart and put it back together, but were unable to work out how to hold the structure together, and were obliged to resort to adding nuts and bolts. In reality, bolts or the equivalent are an inherent part of the design. When it was first built, iron spikes were driven into the joints from the outer side, where they could not be seen from the inside of the parapets, explaining why bolts were thought to be an addition to the original. Newton could not have been directly involved since he died in 1727, twenty-two years before the bridge was constructed.<ref name="queens2">{{Cite web |url=http://www.queens.cam.ac.uk/general-information/historical-fun/queens-college/mathematical-bridge |title=Mathematical Bridge |accessdate=2013-11-02 |publisher=Queens' College, Cambridge}}</ref>

==See also==
*[[List of bridges in Cambridge]]
*[[Old Walton Bridge]], a larger bridge on the same principle, also designed by William Etheridge.

==References==
{{Commons category|Mathematical Bridge}}
{{Reflist}}

==Further reading==
* {{cite book |last=Ruddock |first=Ted |title=Arch Bridges and their Builders 1735-1835  |url=https://books.google.com/books?id=amQ9AAAAIAAJ |accessdate=2013-02-26 |year=1979 |publisher=Cambridge University Press |isbn=978-0521090216 }}

==External links==
* [http://www-g.eng.cam.ac.uk/cam-bridges/math.html Photograph] of the original 1748 model of the bridge, made by William Etheridge and still in possession by [[Clare College, Cambridge|Clare College]]

{{Bridges over the River Cam}}
{{Queens' College, Cambridge|state=expanded}}
{{Authority control}}

[[Category:Bridges in Cambridge]]
[[Category:Bridges completed in 1749]]
[[Category:Bridges across the River Cam]]
[[Category:Pedestrian bridges in England]]
[[Category:Queens' College, Cambridge]]
[[Category:Wooden bridges in the United Kingdom]]
[[Category:Truss bridges in the United Kingdom]]
[[Category:Arch bridges in the United Kingdom]]
[[Category:Buildings and structures of the University of Cambridge]]
[[Category:Grade II listed bridges in Cambridgeshire]]
[[Category:Grade II listed buildings in Cambridge]]