pilasters may be either plain or fluted, without regard to the columns. Thus, in the portico of the pantheon, the columns are plain, and the pilasters fluted ; but in that of Septimius Severus, the former arc fluted and the latter plain, the architects seeming to be governed by no other rule than their taste. The angles, or coins, of flu ted pilasters are frequently strengthened with a bead, as in the pantheon, and the flutes are generally of a semi circular section. Sometimes the faces of pilasters are sunk within a margin, and the panncls charged with fo liage, arabesque or grotesque ornaments, instruments of music or war, or of all these compounded. In the arch of the Goldsmiths, at Rome, the pannels are decorated with winding foliage and trophies of war.
When placed on the front or outside of a building, pilasters should project one-fourth of their breadth at the bottom ; but in the interior, or behind a row of co lumns, they should not project more than one-eighth of that breadth.
In a large recess, when an entablature is supported by an even number of insulated columns, with each end ter minating and resting on a wall or pier, a pilaster is very commonly placed against each wall or pier, to support the extremities of the architrave. When the entabla ture over the columns is recessed within the surface of the ,‘ all or pier, the pilaster projects tow arc's the column, sl.cwing its thickness on the front, with its breadth facing the void or adjacent column. In this case, the architrave may either profile against the sides of the aperture or recess, or it may return at each interior angle ; and again, at the exterior angles, proceed along each wall or pier.
When the intermediate columns and extreme pilasters are so ranged, as to project a small distance beyond the face of the wall at each end, the pilasters spew the same breadth towards the front as towards the void, that the entablature may remain unbroken, as in the chapels of the pantheon ; but if breaks be unavoidable, they must. be at the extremities, or most distant angles.
Pilasters are not only ornamental to a building, but they also tend to strengthen it gtc atly ; to m hid) we may add, that they become an obj,:ct of economy, as being less expensive than columns. to situations where they arc either placed behind a range of columns, or for the support of the extremes of an entablature across au open ing, they are also more concordant w ith the walls to which they arc attached.
Clustered pilasters, or those which have both exterior and interior angles, with their plains parallel and perpen dicular to the front, may be executed with good effect, when the order is plain, as in the Tuscan ; but in the Doric, Ionian, Corinthian, and Roman orders, where triglyphs and capitals meet but imperfectly in the inte rior angles, such a junction should be avoided as much as possible. The same may be observed of Ionic and Corinthian capitals of half pilasters meeting each other in the interior angles of rooms. In the Ionic order, a difference must be made between the capitals of pilasters and of columns ; for, in the latter, the projection of the ovolo is greater than that of the volutes ; but, the hori zontal section of the ovolo being circular, the ovolo is bent behind the hem or border of the N olu tes ; therefore, if a vertical section be conceived to pass through the axis of the column, perpendicular to the face, and another through the middle of the breadth of the pilaster, the corresponding mouldings being equal in both sections ; then, because the horizontal section through the ovolo is rectangular, as in the trunk, the ovolo would, if continued, pass over the volutes, or by terminating abruptly, shew the profile of the moulding, which is a palpable defect. It therefore becomes necessary, either to give the ovolo but a small projection, or to make it so prominent in the front, that its extremities may appear to retire behind the border of the volutes ; otherwise, the volutes must be twisted from their original plain surface, so that every part of the spirals may be projected towards the eye ; or the whole abacus, with the volutes, must be protru ded beyond the projection of the ovolo. The same incon venience will occur in the instances of the Corinthian and composite capitals, in which the upper part of the vase projects beyond the middle of the abacus, and would pass over the faces of the spirals or volutes of the capitals of the pilasters.
Orders upon orders.—In placing one order above ano ther, we shall be naturally led, by the known laws of gra vity, to give the strongest and heaviest the lower place, and the weakest and lightest the upper. Symmetry and strength will also direct us to keep all their axis in the same vertical line.