A similar purpose of providing apparent abutment would seem to account for the unusual form of the chevets of Bayeux cathedral (thirteenth century), and Sant’ Antonio at Padua (after 1232) in which all the radiants which ordinarily stop at the keystone are carried through against the face of the apsidal arch. At Bayeux there are two such ribs ([Plate II-l.])[386] and at Padua, three ([Plate II-m.]). The latter is also exceptionally interesting in the form of its chevet which is really a combination of the diagonal and the buttressing ribbed type.
Although there are occasional instances like the one at Barcelona, in which the transverse severy of a buttressing ribbed chevet is subdivided only by a ridge rib, it is far more common to find a more extensive subdivision of this bay when such subdivision was undertaken at all. Moreover, it is an interesting fact that many of the elaborated chevet vaults—for it may be noted here that the apse vault was elaborated just as were those in the remainder of the church edifice—are fundamentally based upon the simple chevet with buttressing ribs.
Of these vaults with added ribs, perhaps the simplest are those in which the western bay is subdivided by the introduction of a ridge rib running about half way to the crown of the apsidal arch and there met by two tiercerons rising from the imposts of this same arch ([Plate II-n.]). A good example appears in the cathedral of Bayonne (Basses-Pyrénées) (after 1213), and another in that of Saint Quentin (Aisne) (commenced 1257), while the same subdivision of this severy in combination with other subdivided cells is to be seen in the Marien-kirche at Stargarde (Germany) (fourteenth century) ([Plate IV-d.]).
A second and unusual division of this severy appears in the cathedral of Saint Jean at Perpignan (Pyrénées-Orientales) (1324-1509),[387] where the customary three-part bay containing the buttressing ribs also contains two diagonals precisely like those in a four-part vault ([Plate II-o.]). A similar arrangement, with the addition of a ridge rib ([Plate II-p.]), may be seen in the church of Saint Jean at Ambert (Puy-de-Dôme) (fifteenth and sixteenth centuries). Such subdivisions as these last two quite evidently had for their object not merely a reduction in the size of the spaces to be vaulted but also an effort to retain the buttressing-ribbed type of chevet and still obtain a window cell which would not have the warped surface characteristic of this form.
Fig. 71.—Chalons-sur-Marne (near), Notre Dame-de-l’Épine.