Page:Charles Moore--Development and Character of Gothic Architecture.djvu/63

Rh Caen which afford instructive illustration of the beginnings of such constructions. Of these the vaults of the Abbaye-aux-Hommes are the earliest, dating from the early part of the twelfth century. They are beyond doubt among the earliest, if they be not the very earliest, sexpartite vaults that were anywhere built. But they are not Gothic vaults, notwithstanding their transverse and diagonal ribs, because the rib system is neither complete nor independent. It is not complete because there are no longitudinal or wall ribs; and it is not independent, though it is not incorporated with the shell of the vault, because the forms of the arches do not determine the forms of the vaults, but are themselves determined by these forms. The mind of the builder was preoccupied with the traditional methods of vaulting, based upon the intersecting principle, and the ribs of his vaults were accordingly made to follow the old forms; hence the transverse ribs are round arched, and the diagonals are elliptical—forms opposed to Gothic principles as exerting the maximum rather than the minimum of thrust. The lateral cells, however, take a new form, which is a step in the direction of Gothic, since it is necessitated by the positions and the curves of the intermediate and diagonal ribs, to which these cells have to accommodate themselves. In covering the triangular spaces enclosed by these ribs and the clerestory wall, it was impossible to avoid those twisted surfaces which have often been mistakenly regarded as among the defects, though they really are among the essential characteristics, of Gothic vaults. In this instance, however, the twisted surface is less pronounced than it would otherwise be, because the longitudinal arches are made to assume an upright elliptical form—which however, adds to the awkwardness of the whole effect. But with all their