The portico is 98 feet 4.4 inches long, between the centre and mitre of the extreme or angular columns of the front, and 41 feet 54 inches in breadth, from the cen tre of the angular column to the middle of the pilaster, or ante of the solid part of the porch. There are eight columns in front, and three deep; but eight of the inner columns arc omitted, viz. four opposite the entrance, and two opposite each niche on each side of the entrance. The angular column is 4 feet 8-4 inches, and the other 4 feet 61 inches diameter. The middle intercolumniation is 10 feet inches, and the next 9 feet 5 inches. The height, including base and capital, is 19 modules 16i parts, which, taking the module from the angle column, makes the height equal to 46 feet, and the whole order 53 feet. The soffits of the pronaus are ornamented by pannelling of different forms. The great entrance is 36 feet 11 inch high, and 18 feet 44 inches wide. The jambs are each about 4 of the width of the door, and each work ed out of two pieces. The lintel is only one piece. In the pronaus on each side of the entrance is a large niche 17 feet 10 inches diameter. Besides the 16 isolated co lumns, there are three fluted pilasters on each side. Upon the square solid part of the porch, which projects from the circular body of the edifice, the diminution of the co lumns begins at the bottom. The bases, capitals, and entablature are of white marble. The shafts are of Egyp tian granite, each of one piece. The pilasters, with their bases and capitals, arc of white marble. The base round the outside of the building is of marble—all the rest of brick. The inside of the temple was incrusted with mar ble, as was the portico.
The circular body of the edifice is encompassed round the outside by three cornices. The top of the first is at the height of 38 feet 10 inches from the level of the up per step of the portico; from the top of the first to the ;op of the second cornice is 29 feet; from the top of the second to the top of the third is 26 feet inches; these taken together make 94 feet 41 inches. The cornices increase in size as they ascend ; the upper one being 3 feet 6 inches thick, and 3 feet 14 inches projection : the two upper ones have modillions cut in stone; all the rest are of brick. Above the upper cornice is a retreat of 8 feet 111 inches, which slopes 18,4 inches. Over this re treat is a socle or pedestal, 6 feet 9 inches high, which has a small cornice. Upon this is a retreat of 4 feet 4 inches. The degrees, or plinths, or steps of the dome, which are six in number, have a slope ; their edges are rounded, and they were covered with lead. The flat part at the top, which contains the opening, is 37 feet 5* inches. From the top of the upper cornice there is a small stair upon the outside of the dome leading to the top. On the outside of the circular body of the edifice, there appear arches in the brickwork in two tiers verti cally over the chapel recesses, and other recesses in the walls. If the cornices, which encompass the edifice, are correctly marked by Desgodetz, there is ncither re cess nor projection, to admit of the Corinthian and com posite orders, shewn in the elevation given by Montfau con from La Freri.
The small circular temple of Vesta at Tivoli, (see Plate CLXIII.) about five or six leagues from Rome, is built of Tiburtine stone, except the walls, which are of flint. A row of 18 Corinthian fluted columns surrounds
the cell, from the wall of which they stand 5 feet 3+ inches distant. They are 2 feet 4 inches diameter, and, includ ing the bases and capitals, 21 feet. 10 inches high. They stand upon a pedestal 7 feet 33 inches high; and, from the pavement upon which it stands to the top of the enta blature, the height is 33 feet. The inside diameter of the cell is 22 feet 2 inches, and the walls are 2 feet 14 inch thick. The door and windows are narrower at top than bottom.
The temple of Vesta, at Rome, is nearly on the same model. It is surrounded by 20 Corinthian fluted co lumns, 2 feet 11 inches diameter. They also stand upon a pedestal, and at the distance of 7 feet 2 inches from the outside of the wall of the cell. Their height, including the base and capital, is 31 feet 9 inches. The inside di ameter of the cell is 26 feet 2 inches. The wall is 2 feet 11 inch. The dado of the pedestal is plain, but the out side of the wall of the cell is rusticated.
The temple of Faunus at Rome, (sec Plate CLXIII.) built by the Emperor Claudius upon the Celia') Mount, is likewise of a circular form, but is, in many respects, different from those we have just described. The inte rior body of the building, which rises to a very consider able height, is supported by low coupled Ionic columns, with an entablature ; upon this a solid wall is carried up to rather more than equal to the height of the before men tioned order; at this height is placed a row of windows• with semicircular tops; the space within this is divided equally by a column, from the capital of which rise two small semicircular arches, having for their other abut ments the jambs of the general opening. The space or spandrel between these small arches and the circumscrib ing general arch, is pierced by a small circular opening, composing the same sort of windows which was after wards named Saxon, Norman, Gothic. The general wall of the building is carried above the top of the windows about double their height, where it is finished by a cor nice. This circular edifice has a division across it, which is carried to the height of the outer wall; the lower part of this division is formed by two isolated Corinthian co lumns, and two pilasters attached to the wall ; the co lumns are so placed, that the middle space is wider than those on each side. These columns are about once and a half the height of the Ionic column which supported the outer circular wall. Immediately from the capitals, arches are turned which support the cross wall ; in this wall arc five large openings with semicircular tops ; viz. two over each of the side, and one over the middle arch. Without the before mentioned Ionic columns, and at a distance equal to about half the diameter of the space they inclosed, is a row of small Corinthian columns, about three-fourths of the height of the Ionic ; these arc connected by semicircular arches raised immediately upon the capitals; over these arches is a solid wall, which, including the arches, is about the same height as the order. These surrounded the whole central build mg, and formed a series of arcades similar to those after wards introduced into the Christian churches.