The capping may be divided into two. The top half consists of a fillet, reversa and facia, and the lower half a supporting cyma recta, a bead and a cavetto curve. The plinth mouldings are the same as those of the Ionic pedestal with the addition of a torus beneath the ogee. The height of this torus is one-fourth the total height and is about equal to that of the cavetto and bead together.
When the pedestal is employed the arch becomes proportionately larger. In the Doric order the columns are then spaced seven and a half diameters apart; in the Ionic seven and three quarters, and in the Corinthian eight diameters centre to centre.
The archivolt, the radius of which is determined by the above spacing, is supported as before by an impost and pilaster. The base of the pilaster consists of a slightly projecting block equal in height to the plinth block of the pedestal.
The height of the arch varies slightly, inasmuch as the inner curve may be about a diameter from the architrave, but in the Corinthian order should not fall below the level of the necking moulding of the capital.
The Baluster
As already stated, the pedestal may be used as a part of a balustrading associated with balusters, and must conform to the proportions necessitated by the conditions. The usual height for balustradings, whether to steps, balconies, or before windows, is three feet two inches, though in special cases it may be slightly more.
The baluster is a species of small column. Its usual form is bulbous or vase-shaped, and it is furnished with a capital and base. A series of balusters is technically known as a balustrade.
The balusters are raised on a plinth, which corresponds to the plinth of the pedestal, and surmounted by a rail of horizontal mouldings, which correspond to the capping of the pedestal; hence the baluster is of the same height as the die.
The height of the baluster should be divided into five, then one-fifth will be the height of the base, and the capital exclusive of the necking will be another fifth. The extreme diameter of the bulbous shaft is one-third the total height of the baluster, and the diameter of the necking and the top of the shaft is about one-sixth. The capital has a square abacus slightly less in width than the plinth of the base. Below the abacus is