[Fig. 5] gives the section of a bay in one of these churches, and illustrates the considerable difference already existing between the mother cupola of St. Front and its offspring. The cupola on pendentives begins to show a certain attenuation, and we shall presently note a fresh step forward towards the solution of that problem so persistently grappled with by the mediæval architect—how to reduce the weight of the vault.
5. SECTION OF A BAY OF THE CUPOLAS OF ANGOULÊME
The Church of St. Avit-Sénieur furnishes a most instructive example.
The cupola of this building is strengthened by stiffening ribs. It becomes an annular vault, formed of almost horizontal keyed courses, sustained by transverse and diagonal ribs, which act the part of a permanent centering.
The Church of St. Pierre at Saumur marks a further step onwards in the construction of vaults derived from the cupola.[5]
[5] L'Architecture Romane, by Ed. Corroyer.
6. SECTION OF A BAY IN THE CHURCH OF ST. AVIT-SÉNIEUR