They are constructed with single aisles, like the cupola churches, with a series of bays, square on plan; but the arrangement of the vaults has been perfected by the logical use of intersecting arches in the place of pendentives, the architects of the day having realised by this time the progress we have explained and demonstrated in the preceding chapter.
These vast aisles, vaulted on intersecting arches, are of course allied to the cupolas; they recall their general outline, but the arrangement of the vaulting is different. The intersecting ribs are no longer merely decorative features; they have taken on all the active functions of the arc-doubleau and the formeret. Their union constitutes an elastic ossature, the weight being concentrated upon four points of support, which receive the impost of the arches, and compose a stone skeleton, each unit of which has been cut and dressed to fill the exact place it occupies in the whole.
12. LONGITUDINAL SECTION OF TWO BAYS IN THE NAVE OF LA STE. TRINITÉ AT LAVAL
If we compare the sections (Figs. [13] and [14]) of the churches of Angoulême and Angers, we may clearly trace the filiation between these buildings, the one dating from the first years of the twelfth century, the other from some thirty or even forty years later. We shall also note the advance made by the Angevin architects in the construction of groined vaults in the
place of domes with pendentives, a development worked out by the more perfect and reasoned application of the same architectural principle.
13 AND 14. COMPARATIVE SECTIONS OF THE CHURCHES OF ANGOULÊME AND ANGERS
15. VIEW IN PERSPECTIVE OF THE NAVE VAULT OF ST. MAURICE AT ANGERS