The Geometry of Bourges Cathedral

Robert Bork

doi:10.5334/ah.bz

Abstract

This article presents a geometrical analysis of Bourges Cathedral, based on the application of computer-aided design (CAD) techniques to the results of a recent and highly precise laser survey. This analysis reveals that the cathedral's original designer developed a tightly interlocking and strikingly unified design, in which the five-fold subdivision of the chevet ground plan set proportions that would be vertically extruded into an elevation that can be inscribed both within a square and within a series of progessively smaller equilaterial triangles. These results contribute to an ongoing debate about the use of ‘ad quadratum’ and ‘ad triangulum’ geometries in Gothic architecture, and they provide new evidence for the geometrical coherence of Gothic cathedral design. In methodological terms, meanwhile, this discussion demonstrates the potential of CAD-based geometrical analysis for the study of precisely surveyed medieval buildings. The sequence of images being analysed can be viewed as supplementary material at: http://dx.doi.org/10.5334/ah.bz.s1

Highlights

The following geometrical analysis of Bourges Cathedral can be read as a complement of sorts to the articles that grew out of the 2011 Leiden conference on architectural proportion
For the decade prior to that conference, I had been using computer-aided design (CAD) software to study the proportions of Gothic architectural drawings
As my paper for the conference explains, and as my book The Geometry of Creation explains in greater detail, drawings are excellent subjects for such study, in part because their proportions can be measured more readily than those of actual buildings (Bork 2014a; Bork 2011)

Summary

Introduction

The following geometrical analysis of Bourges Cathedral can be read as a complement of sorts to the articles that grew out of the 2011 Leiden conference on architectural proportion.

Results

Conclusion