The Mathematical Bridge is the popular name of a wooden footbridge

Wooden bridge

A wooden bridge is a bridge that uses wood as a building medium. One of the first forms of bridges, the wooden bridge has been used since ancient times, among them the Holzbrücke Rapperswil-Hurden crossing upper Lake Zürich in Switzerland. The prehistoric timber piles discovered to the west of the...

 across the River Cam

River Cam

The River Cam is a tributary of the River Great Ouse in the east of England. The two rivers join to the south of Ely at Pope's Corner. The Great Ouse connects the Cam to England's canal system and to the North Sea at King's Lynn...

, between two parts of Queens' College, Cambridge

Queens' College, Cambridge

Queens' College is a constituent college of the University of Cambridge, England.The college was founded in 1448 by Margaret of Anjou , and refounded in 1465 by Elizabeth Woodville...

. Its official name is simply the Wooden Bridge.

The bridge

Bridge

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

 was designed by William Etheridge, and built by James Essex

James Essex

-Professional life:Essex was the son of a builder who had fitted the sash windows and wainscot in the Senate House , under James Gibbs; and also worked on the hall of Queens' College, Cambridge . He died in February 1749....

 in 1749. It has been rebuilt on two occasions, in 1866 and in 1905, but has kept the same overall design.

The original "mathematical bridge" was another bridge of the same design, also designed by James Essex, crossing the Cam between Trinity

Trinity College, Cambridge

Trinity College is a constituent college of the University of Cambridge. Trinity has more members than any other college in Cambridge or Oxford, with around 700 undergraduates, 430 graduates, and over 170 Fellows...

 and Trinity Hall

Trinity Hall, Cambridge

Trinity Hall is a constituent college of the University of Cambridge, England. It is the fifth-oldest college of the university, having been founded in 1350 by William Bateman, Bishop of Norwich.- Foundation :...

 colleges, where Garret Hostel bridge now stands.

Mathematical explanation

The arrangement of timbers is a series of tangent

Tangent

In geometry, the tangent line to a plane curve at a given point is the straight line that "just touches" the curve at that point. More precisely, a straight line is said to be a tangent of a curve at a point on the curve if the line passes through the point on the curve and has slope where f...

s that describe the arc

Arc (geometry)

In geometry, an arc is a closed segment of a differentiable curve in the two-dimensional plane; for example, a circular arc is a segment of the circumference of a circle...

 of the bridge, with radial members to tie the tangents together and triangulate

Triangulation

In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...

 the structure, making it rigid and self supporting. This type of structure, technically tangent and radial truss

Truss

In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

ing, is an efficient structural use of timber, and was also used for the timber supporting arches (centring

Centring

Centring , or centering , is the structure upon which the stones of arches or vault are laid during construction. Once the arch is complete, it supports itself, but until the keystone is inserted, it has no strength and needs the centring to keep the voussoirs in their correct relative...

) used for building stone bridges.

Myths

A popular fable is that the bridge was designed and built by Sir Isaac Newton

Isaac Newton

Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

 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. Note that Newton died in 1727, 22 years before the bridge was constructed.

See also

• List of bridges in Cambridge
• Old Walton Bridge
  Old Walton Bridge
  Old Walton Bridge is the name given to the first Walton Bridge built across the River Thames at Walton-on-Thames in Surrey, England. The wooden bridge was completed in 1750 and stood until 1783 when it was dismantled to make way for a brickwork replacement....
  
  , a larger bridge on the same principle, also designed by William Etheridge.