1. PLAN OF A CUPOLA OF THE ABBEY CHURCH OF ST. FRONT AT PÉRIGUEUX
2. PENDENTIVE (MARKED A) OF A CUPOLA OF THE ABBEY CHURCH OF ST. FRONT
[Fig. 3] is a section through one of the pendentives of St. Front, following the line A B in [Fig. 1]. It shows that the first six courses are cut so as to make what is called a tas de chargé; the upper surfaces are horizontal, the faces curved to the radius of the dome itself. After the sixth course the voussoirs are cut normally to the curve of the arch. The vaulting of religious buildings having long been the crux of mediæval architects, the construction of the St. Front cupolas must have been an event much noised abroad, for towards the close of the eleventh century a large number of churches with cupolas were built in imitation of the mother church at Périgueux.
3. SECTION OF A PENDENTIVE ON THE DIAGONAL A TO B IN PLAN, FIG. 1
The construction of the churches of Angoulême and Fontevrault in the first years of the twelfth century shows that the architects were attempting to cover spaces of ever-increasing span on the Aquitainian model, while at the same time they set themselves to lighten their vaults, and consequently to reduce their points of support.
[Fig. 4] gives the plan of one of the cupolas of Angoulême or of Fontevrault, both being built on precisely similar plan, with the exception of the number of bays to the nave.
4. PLAN OF A CUPOLA OF ANGOULÊME OR FONTEVRAULT