The arrangement at Bourges, which appears to have been mainly built, if not actually finished, in the first half of the thirteenth century, differs from that of Sens. The structure is one of five aisles, and in plan recalls Notre Dame de Paris, but the details are very dissimilar. The inner side aisles no longer support a gallery, nor are they of equal height with the outer aisles; they are raised so as to afford space for lighting (see [Fig. 43]). The main vault is sex-partite planned on squares; but the same illogicality exists here which we have already pointed out, and in connection with which we will risk appearing somewhat insistent, in the hope of directing special attention to it. It is more glaring here than elsewhere, the flying buttresses themselves being of exaggerated dimensions and of double span, embracing the two side aisles.
43. BOURGES CATHEDRAL. SECTION OF THE NAVE
Both at Bourges and Sens the space between the summit of the archivolts and the bases of the upper windows, known as the frieze, or, in modern parlance, the triforium, becomes a purely decorative feature. It consists of a narrow arcaded corridor, occupying in the interior of the building that portion of the wall space which in the exterior has been appropriated by the lean-to roof of the side aisles. At Sens there is merely a single gallery; at Bourges it becomes double, through the stepped arrangement of the side aisles (see [Fig. 43]), a variation in which we may trace an ingenious blending of the systems of Anjou and Poitiers with those of the Ile-de-France.
CHAPTER VII
THE CATHEDRALS OF THE THIRTEENTH CENTURY
The Cathedral of Rheims, which was begun soon after the destruction of the original building by the fire of 1211, is a supreme expression of the fusion of the three systems—those of Aquitaine, of Anjou, and of the Ile-de-France. It may be taken as the most perfect manifestation of persistent efforts to establish a method of construction based on equilibrium—the equilibrium, that is to say, of a building vaulted on intersecting arches, the thrusts of which are received by exterior flying buttresses.
The temerity, and even the dangers of such a system, are sufficiently demonstrated in the wonderful works of the thirteenth-century architects themselves. For, notwithstanding the skill and beauty of their many admirable combinations, they were unable to reduce their methods to scientific formulæ. The statical power of their structures remained an uncertain quantity, determined by the durability of the material and its exposure or non-exposure to the weather, the interior skeleton being formed of the same material as the exterior.