The side aisles of the school of Bourgogne are also worthy of mention. They are usually covered with groined vaults, in many cases of slightly domical form. Whether this method came directly from Lombardy where there exist early examples of its use, or whether it came in through the influence of Poitou and Auvergne which had come into close contact with Carolingian architecture, is an open question. It seems quite likely, however, that, since the Byzantine builders developed this type and transmitted it to the Carolingian builders of the Rhine valley, it should have passed from there into France and spread over the three northern-central schools as it did over Lombardy. Regardless of its origin, it became the standard type in all the important churches of the Cluniac region. Occasionally, as at Souvigny (Allier) (possibly eleventh century), the enclosing arches are of stilted round headed form, a type which is also found as far north as Vézelay (Yonne) La Madeleine (after 1140) [(Fig. 16)]. Neither of these churches, however, is near the center of the school,[99] and the pointed structural arch as used in the abbey church of Paray-le-Monial [(Fig. 14)] is the common form.
The system employed in Bourgogne marks the highest development attained in the use of a tunnel vault running the length of the nave. In the Ile-de-France a few instances might be cited[100] in which a system like one of those already described was used, and the same is true of certain Romanesque churches outside of France, but in none of them is any new structural method introduced. The tunnel vault was even used occasionally as late as the thirteenth century,[101] but the examples are generally small and insignificant.
Churches with Transverse Tunnel Vaults Over the Nave
Besides the methods which have just been described and which were so localized as to form veritable Romanesque schools, there remain a number of churches falling into two groups in which transverse tunnel vaults replace those running longitudinally either in the nave or aisles. The first and smaller group contains those in which such vaults were used over the nave. Of these, the most important example is Saint Philibert at Tournus
Fig. 16.—Vézelay, La Madeleine.