In many historical examples the upper columns are placed on pedestals, but this treatment, although useful when a balcony is desired, is not to be recommended as the extra width and projection which the use of the pedestal entails, gives an appearance of undue weight to be borne by the supporting columns. If balconies are necessary they may terminate with their own pedestals, which can be kept clear of the columns and should not exceed them in projection.
It may be as well to deal here with the treatment of pilasters, which may be defined as columns in bas-relief. Their projection may vary from one-half to about one-sixth their face width, though in antique examples it is sometimes much less than this. In the pilasters of the Pantheon at Rome it is one-tenth.
The projection is, however, partly determined by the order with which the pilaster is used, as an appearance of mutilation might easily be produced in the capitals of the Ionic and Corinthian orders. The Doric capital, being composed of moulded profiles, is not in any way affected by the amount of projection. Nor does the Ionic capital suffer when the volutes are in one plane except when used on an angle. But if the later Renaissance type with the volutes arranged at angles of 45 degrees is employed, the projection of the pilaster must not be less than half its upper diameter, so that the volute on the return face may be complete.
The Corinthian capital would be affected in the same way, and should also be not less than half a diameter in projection in order to obtain a satisfactory result.
The pilaster is usually tapered, and when associated with columns and supporting the same entablature it is essential to preserve universal alignment in the upper extremities and the architrave, but when used by itself the pilaster is often not tapered. At the angle of buildings, where both faces are displayed, it is an invariable rule that pilasters should be straight.
The details of capitals and bases are the same as those of the columns. When fluting is employed an odd number of channels should be used, usually seven on the front face.
[Illustration: No. 173. Doric Order. Treatment of coupled Column and Pilaster.]
Arcades, as already suggested, may be composed of a series of arches, supported on pilasters which flank the columns. The backs of the piers thus formed may be treated with pilasters, which can be repeated on the opposite wall, with the architrave frieze and cornice above.