Pointed the Architecture of the age was still more influenced by the greater development of vaulting. Vaults were not rare at the close of the twelfth century, but it was at the commencement of the thirteenth that the system was fully completed. It is very difficult to trace the development of the pointed style with certainty, since so many structures of the transitional period have entirely or partly fallen—since there is many a motif which is not preserved to us in its earliest examples, but only in later ones, and may thus bear a more recent date than that borne by extant inotifs which have sprung up later.
It is true that in France we meet with simple groined vaults in the side-aisles, in crypts, and in small spaces; that we also find them around the apse of the choir, where the vaulting is somewhat complicated, executed without diagonal ribs in such a manner that smaller, steeper pieces of tunnel-vaulting are curt out of the continuous circle formed by the apse, as, for example, in Notre Dame du Port at Clermont and in the Church of St. Julien at Briond (Auvergne, 114.o); and we also find trans verse arches, as in the choir of the collegiate church at Poissy, but in the nave itself we meet with groined vaulting in only a few structures of this date, as at Vezelay, and this may be attributed to foreign, and especially to Rhenish, influences.
It is known to every engineer that a groined vault, which is composed of two segments of semicircular tunnel-vaults, has in its lower third very sharply-marked angles, but that these become flatter and flatter as the crown is approached; so that the line of meeting of the various portions can scarcely be traced. It thus becomes difficult to cut the angle-stones of the ashlar work with that regularity which is desirable for sound workman ship. This difficulty increases with the dimensions of the vault. The precautions adopted in Germany for the security of the crown, all of which tended toward avoiding geometrical regularity, had no great following.
The difficulty is naturally greater the more the vault deviates from, the square shape and becomes oblong; therefore at Mayence, Worms, and Speyer a bay of the nave corresponds to two of the side-aisles. This naturally leads to the alternation of the pillars to correspond with the requirements, every second pillar being a main pillar, while the alternate ones may be called secondary. It is only exceptionally (Laach, Vezelay) that the arrangement of oblong central vaults and equal pillars is adopted. The technical difficulties in such cases render it desirable, and it is exacted by the aesthetic effect, that the groins should be marked. This was
effected by diagonal ribs.
Diagonal and where these were first employed can scarcely be known, but certainly earlier in France than in Germany, since in the nave of the Cistercian church at Heiligenkreuz, built 1135-1187, massive diagonal ribs occur. These not only make it possible for the eve to follow the lines of the groining to the crown, but also allow the com partments of the vaulting to be much lighter than they would have to be were there no ribs. To make these compartments still smaller, and further to express the relation between the intermediate pillar and the crown of the vaulting, a rib is thrown from the former to the latter. There are thus six separate sections, each of which forms an independent vault between the transverse and diagonal ribs. Proof of where this method originated is as difficult as it is in the cases before mentioned. France has a series of examples, as in St. Etienne and Ste. Trinite at Caen, but it is not certain whether this plan was adopted when the building was erected. The similarity of the pillars should not induce us to decide hastily.
While in Germany the alternation of pillars and columns can be seen even in unvaulted basilicas, though the arrangement of the vaulting furnished the motive for this alternation, the tunnel-vaulting used in Prance gave no occasion for constructing dissimilar pillars. Thus the similarity of the pillars had become so ingrained with the architectonic instinct that the necessity for the alternation was not felt even in hexa partite vaults, so that in the further progress of the development the alternation of the pillars formed the exception. Ste. Trinite (at Caen) perhaps exhibits the intention to use hexapartite vaulting, since when the height of the triforium was reached two shafts were attached at the sides of the shaft which is carried down to the ground.
Church of St. Germain des Pr the most interesting build ings in which the exterior is changed to express the necessities of the vaulting is the choir of the Church of St. Germain des Pres at Paris, con secrated in 1163. It is divided by monolithic columns into three aisles. The arcades are broad round arches with roll-mouldings, but at the end of the choir, where the spans are narrower, the arches arc pointed. Above these arcades runs a passage, and over this rise marble columns, which are now united by architraves, but were formerly spanned by pointed arches. The vaulting is pointed.