Side Aisle Vaulting
There now remain for consideration before closing this chapter, the ribbed vaults of the aisles and triforia of Gothic churches. Very naturally the general development of ribbed vaulting in the aisles closely parallels that in the nave. In by far the larger number of churches, the side aisle bays are square and covered with simple four-part cross-ribbed vaults. As in the case of the nave, those of early date have many clumsy features. Thus in the aisles of Saint Étienne at Beauvais [(Fig. 44)]—which, fortunately, retain a few bays of their primitive vaults dating from about 1125—the diagonals are heavy (cir. 20-25 cm. thick)[273] and either square with simple bevelled edges or of single torus section. No wall rib is found and the transverse arches, besides being very thick, are of round-headed form, highly stilted to bring them up to approximately the general vault level. The vault itself is slightly domed up at the crown and besides the
Fig. 43.—Senlis, Cathedral, Chapel Vault.
Fig. 44.—Beauvais, Saint Étienne.
Fig. 45.—Sens, Cathedral.
primitive characteristics just enumerated, its panels are composed of small stones roughly joined and in very uneven courses, while the ribs themselves are built up of short voussoirs, which are not combined at their springing in the familiar tas-de-charge of more developed Gothic work. The cathedral of Sens presents in its side aisles [(Fig. 45)], which date from the twelfth century[274] a slightly different system. The transverse arches are still heavy and semicircular but they are not stilted. The diagonals rise from corner corbels—a fact which may prove that the aisles were originally planned for groined vaulting and thus no provision made for the cross-ribs,—and they are also semicircular, thus giving the vault a decidedly domed up character. This makes these vaults at Sens very similar to Lombard work and it would seem as though their builders had the same object of saving centering by the use of ribs as obtained in Lombardy. There is one apparent advance over those at Beauvais in the presence of a wall rib, but this is of too wide a span to fit under its severy, and it would seem to have been designed to mark the wall intersection of groined rather than ribbed vaulting.
The early aisle vaults in England are generally similar to those at Beauvais, with even less doming or none at all. The earliest would seem to be those in Peterborough, Durham and the north nave aisle of Gloucester cathedrals, all dating, apparently, from before 1140. Although similar to those in Saint Étienne at Beauvais they differ in the comparative lowness of their transverse arches, which are but slightly stilted, and in the correspondingly reduced curve of the diagonals, which are less than semicircles and thus do not raise the crown of the vault. The explanation of this may very possibly be found in the desire of the builders to avoid cutting into the level of the triforium floor, especially at Peterborough, where this is a true gallery, and also in their familiarity with the flat crowned groined vault, which they had previously used in crypts and elsewhere. The form of the diagonals is in any case displeasing, as they spring from the shafts at an awkward angle and, furthermore, render the thrusts of the vault excessive.[275]
Many structural refinements were, of course, necessary before these crude vaults gave rise to the fully developed type, but these refinements followed in general the same order as those in the larger nave vaults. First came the introduction of the pointed arch and its use for the transverse and longitudinal ribs in place of the semicircular type. This change may be seen in such early vaults as those of Noyon cathedral (cir. 1150) where pointed arches are used throughout. The noticeable feature here is the great size of the transverse ribs compared to that of the diagonals. This same feature continues to appear in a gradually lessening degree in many of the churches of the transitional period, and even in the developed Gothic of the thirteenth century, as, for example, in Bourges and Amiens cathedrals. This may, perhaps, be explained by the function of this transverse arch which was not merely a centering for the vault panel, but carried a considerable amount of the weight of the exterior buttress piers and wall pilasters which were connected above the aisle roofs by the arch of the flying buttress. These heavy transverse ribs also aided materially in bracing the nave piers and tying them to the outer walls. Sometimes, as in the beautiful aisles of Rouen cathedral, all the ribs are of the same section, but whether they were all the same or not, such vaults as those at Rouen and Amiens set the standard for developed Gothic side aisles.