Vault

(Fr. voute, Lat. volututs). The simplest and most ancient kind used over a rectangular area is the cylindrical, called also a barrel, and sometimes wagon vault; this springs from the two opposite walls, and' presents a uniform concave surface throughout its whole length. The term "cylindrical" properly implies the form of a segment of a cylinder, but it is applied to pointed vaults of the same description. Vaults of this character were used, by the Romans, and also by the builders in England to the end of the Norman style. The Romans also first introduced groining, formed by the intersection of vaults crossing each other at right angles, and some of their constructions of this kind were of very large size. In groined vaults the arches which cross each other do not always correspond in width; in such cases they sometimes spring from the same level, and consequently are of unequal heights; and sometimes the springing of the narrower vault is raised so that the tops are on the same level. Domical, or hemispherical, vaulting over a circular area was likewise practiced by the Romans, of which the Pantheon at Rome exhibits a magnificent example of one hundred and forty-two feet; in diameter. The decorations employed on Roman vaulting consist chiefly of panels, and fiat band so of ornament following the curve of the arch the application of ribs at that period was unknown.

In the Norman style cylindrical or barrel vaulting, as well as groined vaulting, is used; the former of these is either perfectly devoid of ornament, as in the chapel in the White Tower of London, or has plain and massive ribs at intervals following the direction of the curve of the arch. In groined vaulting the cross-vaults are not infrequently surmounted, or stilted when they are of narrower span than the main vault, though sometimes in such cases they are both made to spring from the same level; but in general the parts of the building are so arranged that both vaults are of nearly or quite the same breadth.

In the Early English style, when the use of the pointed arch was permanently established, the same form was also given to the vaulting; and groined vaults at this period were universally adopted. In buildings of this date ribs are invariably employed, especially on the groins. The simplest arrangement of them consists of the diagonal or groin ribs, cross-springers, and the longitudinal and transverse ribs at the apex of the main and cross vaults; but these two last in some examples are omitted. Additional ribs are sometimes introduced between the diagonals and cross-springers. In some buildings in England, and in many on the Continent, the vaulting is constructed with the main vault double the width of the cross-vaults, with the diagonal ribs embracing two bays or compartments of the cross-vaults, as in the choir of Canterbury Cathedral.

Decorated vaults, for the most part, differ but little from those of the preceding style. The longitudinal and transverse ribs are occasionally, but not often, omitted, and the number of those on the surface of the vaulting is sometimes increased; and in some examples ribs are introduced crossing the vaults in directions opposite to their curves, so as to form in some degree an appearance of network upon them. The short ribs which connect the bosses and intersections of the principal rib and ridge-ribs, but which do not themselves either spring from an impostor occupy the ridge, are termed liernes, and the vaults in which they occur lierne vaults.

In the Perpendicular style the general construction is much the same as in the Decorated, but the ribs are often more numerous, and pendants are not uncommon.

Towards the latter part of this style fan tracery vaulting was commonly introduced; this has no groins, but the pendentives are circular on the plan, and have the same curve in every direction, resembling inverted curvilinear conoids, and are generally covered with ribs and tracery branching out equally all round them. The middle of the upper part of the vault, between the pendentives, is usually domical in construction, and frequently, has a pendant in the center of each compartment.