Fig. 75.—Auxerre, Cathedral.
Still another interesting characteristic of certain chevet vaults is the presence of openings from one cell to the next in the lower portion of the panels between them. The simplest of these are to be seen in the cathedral of Auxerre (choir finished 1234) [(Fig. 75)], and it seems very reasonable from their square shape, comparatively small size, and their position at the beginning of the curve of the vault cells to assume that they were intended to hold wooden beams, used, quite possibly, as supports for scaffolding or centering for the rest of the vault. Whatever their use, they may be the prototypes of such larger openings as those in the cathedral of Bourges (after 1215) [(Fig. 76)], which may not only have been used in a similar manner but which, from their circular shape and moulded character, supply a certain amount of decoration to this part of the vault and even serve in a slight degree to distribute the light from its windows over a larger area.[399] An even greater amount of decoration is obtained by the use of tracery in the similar openings in the cathedral of Orleans (begun 1630), which are of larger size and of a generally triangular shape.[400] The final development of such tracery panels may be seen in the Brunnenkapelle of Magdeburg cathedral (fourteenth century)[401] where the apse vault proper becomes practically a flat ceiling the entire space between it and each of the ribs being filled with tracery.