A still more elaborate subdivision of the rectangular vaulting bay appears in the chevet of Notre Dame-de-l’Épine near Chalons-sur-Marne (1419-1459) [(Fig. 71)], where this bay contains no diagonals at all but is divided by a series of tiercerons and short ridge ribs in a manner best understood from the plan ([Plate II-q.]). But it is the subdivision of the window cells of the apse proper which is of especial interest at l’Épine, for the method here employed was very widely extended in the later Gothic period. It consists in the introduction into each of these cells of a short ridge rib running from the central keystone to a point about half way to the window crowns where it is met by two tiercerons which rise from the impost of the principal ribs of the chevet on either side of the window. The apparent object of the system is to so subdivide the vault surface as to break up its compound or ploughshare curves and substitute smaller panels whose surfaces are simpler to construct exactly as in the similar nave vaults previously described. This purpose does not show to advantage at l’Épine, where the awkward adjustment between the vault panels and the window heads would seem to indicate that the apse was originally designed for a simple form of chevet with no added ribs. Better examples could be cited, among them Saint Severin at Paris. Such an arrangement of window cells as that in these vaults practically converts the chevet into a ribbed half dome pierced with lunettes which do not rise to its crown. This may clearly be seen from a study of the apse of Saint Jacques at Antwerp (probably sixteenth century), where the vault is unusual in the omission of all the true radiating ribs ([Plate II-r.]). As a matter of fact such ribs were no longer of value since they did not mark the intersection of two vault panels but merely lay along a surface which is almost precisely like a section of a half dome. The tiercerons are still important since they mark the intersection of the window lunettes and carry the weight of the vault down to the piers. They are therefore retained. Thus, while the absence of radiants in Saint Jacques might seem to make this vault structurally less correct than that of l’Épine in reality such is not the case.
Once it became the custom to introduce extra ribs into the chevet, this portion of the church underwent the same treatment as the vault of the nave or choir. Thus in England, to cite only extreme cases of elaboration, the later Gothic produced such vaults as those of Tewkesbury Abbey (between 1325 and 1350),[388] in France, such pendant types as that of Saint Pierre at Caen (probably early sixteenth century), and in Germany such a choir and apse as that of Freiburg cathedral (late fifteenth century) [(Fig. 72)].[389] The last named is especially interesting as showing the low point reached in rib vaulting for its ribs have almost no function as supporting members, some of them being actually free from the vault panels and are merely used to form a decorative pattern upon a vault which would stand equally well were they entirely removed. Such chevets are, in many cases, clever examples of stone cutting and decorative design but they are lacking in fundamental structural character.
The Number of Chevet Cells
Fig. 72.—Freiburg, Cathedral.
Thus far the discussion of chevets has been distinctly from a structural point of view, but there remain certain other differences between these vaults which are worthy of remark. In the first place, there is the matter of the number of cells comprised in the chevet. The standard during the best Gothic period was seven, though five was a frequent number and quite often nine are found ([Plate II-s.]), as for example, in the apse of San Francesco at Bologna, Saint Martin at Ypres, Belgium, and that of Béziers (Hérault), cathedral (1215-1300).[390] In the smaller churches and in the radiating chapels there are frequently three. Moreover, when the apse has a central pier,[391] there are an even number of bays and thus four and six-celled chevets are employed. That in Saint Pierre at Caen, for example, has four bays all on the curve, and that in Notre Dame at Caudebec-en-Caux (Seine-Inférieure) (fifteenth and sixteenth centuries) ([Plate II-t.]) has only two bays thus placed, a fact which gives an angular character to the apse which is far from pleasing.[392] As for the chevets with six cells, they are of very infrequent occurrence, though one is to be seen in Saint Pierre at Auxerre ([Plate II-u.]). A chevet with the unusual number of eleven cells is to be seen in the church of La Chapelle-sur-Crécy (thirteenth century).[393] In construction, this chevet is similar to one bay of such an eight-part vault as that at Provins, Saint Quiriace[394] with its easternmost cell divided into five parts.