Cunning Geometry: The Designing of Medieval Churches
Interdisciplinary Study of Medieval Technology, Science, and Art
SCENES FROM A DESIGN:
Michael T. Davis
WHEN PAUL DE MAN ASSERTED that history was composed of texts not events, he drew attention to the way in which a few moments out of trillions of possibilities are selected, ordered, and interpreted to explain the past or to map our location in the present. In the spirit of the PBS series Connections, one may weave far-flung links between, say, the printing press and the rocket or medieval monastic life and the contemporary electronic highway while remaining aware that the tale is an act of authorial magic that transforms caprice, luck, and intention alike into fluid narrative. Today, my son visited Saint-Peter's in the Vatican-he didn't climb up into the dome, but saw the Pieta. One day he or another writer may choose to remember this one afternoon as filled with disappointment (the unclimbed dome), pleasure (the Pieta) or new horizons (the Swiss Guards as a career choice). But however I July 1996 is chronicled, original events lurk behind and between the words.
In 1262, pope Urban IV set about erecting a church to his patron saint and a shrine to honor his birthplace in the city of Troyes, France. An aggregate of ephemeral 'events' including real estate purchases, stone carving, and arson went into the making of the structure which we can see to this day. This brief notice offers a preliminary explanation of one of the most important, yet unrecorded activities of the architectural process: the design of the building's plan. When I began my analysis of Saint-Urbain, I pursued a definitive description of the way the church must have been designed. What I have found instead is an architectural Rashomon. As in Kurosawa's cinematic masterpiece, the basic facts are clear: the plan is composed from a lucid scheme of squares, octagons, and rectilinear modules. It is in the way these geometric facts happened and how the figures fit together as a dynamic sequence that multiple possibilities of thought and action emerge. Not only rules of craft, a mason's training and skill, but also the intervention of the patron and the site shaped the performance of the design. Encoded into the 'text' of Saint-Urbain's plan and the shape of its spaces are the conception. the debates, the decisions, the meaning and the making of the church.
Beginning from the outside
On a mild fall day in 1262, a master mason strides onto the cleared worksite with a parchment plan in hand. The church is a tight fit here in the middle of the city he tells his oldest apprentice. With the Grande Rue on the north side and the Rue Moyenne running along the south flank, I had to start the design from the practical consideration of available space. We've also had to watch it on the east since pope Urban appropri ated some land from the good nuns ofNotre-Dame-aux- Nonnains and I hear they are still not happy about this project. But I think I've been able to satisj,9, everyone: the church will not clog the two main city streets which will please the merchants. it sits nicely in the parcel of land the pope's agents have purchased. The length and width of the church are based on squares, ad quadratum length and width of the church are based on squares, ad quadratum. It will be easy for us to lay out and will be quite beautiful. We should have the first couple of steps done by lunch, so let's get to work...
A square (ABCD) is constructed using the available distance between the two city streets (approximately 37 meters per side). Rotating the diagonal of this square (AC,BD) establishes the length of the entire building ( 52.35 meters at AE and BH). A second 37-meter square (EFGH) is laid out from the end point of the diagonal (fig.1). These two overlapping squares fix the alignments of the west facade buttresses (EH), the eastern edges of the choir salients (AB), the inner faces of the lateral porch buttresses (AE,BH), as well as the axes of the eastern piers of the nave (CD) and the western piers of the choir (FG). The center of the plan can be found easily.
As the next logical step, the Saint-Urbain master inscribes a pair of squares UKLM, NOPQ) within the first. In the choir, its 26.175 meter sides define the exterior surfaces of the diagonal walls of the main apse and lateral chapels (KJ,KL). These squares, turned forty-five degrees and aligned with the eastern and western limits of the site frame the body of the church. In short, the setting out of the exterior package of the papal shrine unfolds from the realities of its crowded urban location.