This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The use of pilasters by the Romans was very different from the Greek custom, and the pilaster is given a much more important place in their architectural development.
The Roman pilaster in the later periods is practically the same as the column in its treatment of the capital and base, and therefore quite different from the Greek anta. The question of diminishing the shaft at the top is one that seems to have been left largely to the discretion of the designer, and no general rule can be given that will apply invariably. In some instances the procedure follows the same method as used in the column itself, and at other times the shaft is carried up in a plumb, perpendicular line from the base. In general, the same considerations that have been given in the discussion of the pilaster treatment in Part I may be either applied exactly as there outlined, or may be varied by the designer at his own discretion.
In most Classic instances the pilaster was treated exactly the same as the column. It was given the same cap and base; the shaft, of course, being plain and square in plan. As regards the pilaster dimension at the neck and base, there is considerable difference of custom among the oldest examples. In Roman practice the pilaster is sometimes treated with sides tapering in the same manner as the sides of the column and exactly to agree with it. At one time, the whole shaft will be treated with the exact diminution given to the accompanying column; at others, the pilaster is of the same width at the neck as at the base, the size being determined by the average between the diameter dimensions of the column at neck and base, approaching, if anything, more nearly the larger than the smaller diameter. In other cases-as, for example, where pilasters alone are used-they are generally made straight and of equal width throughout their entire height; but even then they are sometimes given an entasis the same as the column. The shafts of the pilaster are generally treated to agree with the columns with which they are used. They may be plain, fluted, or-especially in Renaissance work-paneled.
The projection of the pilasters from the wall was generally about from one-quarter to one-half their width; but sometimes a greater depth was required, in order that they should remain free from projecting belt courses or horizontal cornices that stopped against them. If given greater depth than this, a pilaster is apt to compare unfavorably with the column itself, and to give a clumsy, stiff effect, while causing the column by contrast to appear thinner. The pilaster should always be used against the wall behind a column, in order to receive the beam or entablature which it carries. Occasionally a round half-column or three-fourths column may be used for the same purpose in place of the pilaster, but this use is comparatively rare in old work. It has the obvious disadvantage that if an exact half-column 1s used, it appears to the eye of less size than the entire columns which stand free from their surroundings, while any horizontal courses cutting into it have a tendency to divide or cut off its apparent height and diameter.
Possibly an intimate and thorough acquaintance with a large variety of moulding sections, together with a nice appreciation of their proportions and use, is the most important result for which the student can hope from the study of the Orders. Certainly it is the most tangible return, the only one that can be considered as of greater importance being an unconscious development of the sense of proportion which cannot fail to result from an earnest study of the old examples. An intelligent appreciation of the reasons governing the various proportions of columns and the different sections of mouldings., will result in an equally subtile sense of proportion in regard to the outlines and the composition of the various parts of a building or group of buildings. This sense may also be developed by a study of the history of the various races and builders, and by a knowledge of the purpose for which the buildings were intended, of their comparative height and surroundings, of the location of the Order or mouldings on the building and the purposes they were intended to fulfill. If, in addition, the student is able, from the contrast between the effect of any executed moulding section as given to his eye and its actual contour in the section outline, to deduce the relation that the one bears to the other, he will have gone far on the road toward a mastery of architecture.