Bk. II. Ch. X. VAULTS. 571 Vaults. It has already been explained how essential a part of a Gothic church the vault was, and how completely it was the governing power that gave form to the art. We have also seen the various steps by M'hich the architects arrived at the intersecting vault, which became the typical form in the best age. In France especially the stone vault was retained throughout as a really essential feature, for though the En<rlish were so successful in the art of constructing ornamental wooden roofs, the practice never prevailed in France. In the best age the arrangement of the P'rench vaults was extremely simple. The aisles were generally built in square compartments, the vaults of which were first cir- cumscribed, each by four equal arches (Woodcut No. 426), of which A A were transverse ribs, or a7-c3 douhleaux as the French called them, and Avere used, as we have seen, in the old tunnel- A-aults. These arches, as spring- ing from the main points of IJC^- support, were the principal strencrtheners of the vault, b was called tQ former et, diuii was a rib built into the wall, of the same form as the transverse ribs, and so called because, being the first con- structed, it gave the form to the vault. Lastly, there were two more ribs springing from angle to angle, and intersecting one another at c. These were called or/ives, from the Latin word au(/ere, to strengthen, ^ Avhich was the object of their employment — and every builder knows liow essential is the strength given by them. In modern vaults — in cellars or dock-vaults for instance, if built of brick — it is usual to in- sert a course of stone on the edge of the intersection, for bricks used there would be liable to be crushed or fall out. But though this is now done flusli with the brickwork, the Mediaeval architects allowed this course to project, not only because such a form was stronger in itself, but because it gave the appearance as well as the reality of strength. The roof of the nave was composed of precisely the same parts, only that, being twice as wide as each compartment was broad, tlie length of the transverse ril)s and of the intersecting ogives was greater in proportion to the formerets than in the aisles. Another addition, and certainly an improvement, was the introduction of ridge-ribs (d d) 426. Diagram of Vaulting. The French aiititiuaries eni])loy this word as if it signified a pointed arch, whence they designate the style itself as ogival. There is no doubt, however, that the word has notliing to do with the form of the arch or the ogee, but is the name of a rib common to the round- arched as well as to the pointed style.
