Eight-Part Vaulting
There is one more important variant of the six-part vault which is especially interesting and unusual. It appears in the church of Saint Quiriace at Provins (Seine-et-Marne) (cir. 1160) [(Fig. 31)][202] and
Fig. 31.—Provins, Saint Quiriace.
consists in a division of the nave into great square bays each corresponding, not to two, but to three square bays in the side aisle ([Plate I-f.]). The divisions thus formed are covered by what is really an eight-part vault, which is precisely like six-part vaulting except that there are three instead of two window cells in either side of each bay. Needless to say the immense size of the transverse triangular severies thus created presented a structural problem of much difficulty, and it is not surprising that such a vault was but seldom imitated,[203] particularly as the great discrepancy in the size of the vault cells and the awkward angles formed by their crowns give a decidedly unpleasant appearance. Nevertheless, there is one instance, at least, in which this system was not only imitated but transformed into a ten-part vault. This was at Boppart, Germany,[204] where the thirteenth century church has vaults with four window cells and but a single pair of diagonals. To break up the two remaining triangular severies, added surface ribs were introduced ([Plate I-g.]).