1The Greeks make their forum square, with a spacious and double portico, ornamenting it with columns placed at narrow intervals, and stone or marble epistylia, and forming walks above on the timber framed work. In the cities of Italy, however, this practice is not followed, because the antient custom prevails of exhibiting the shows of gladiators in the forum.
2Hence, for the convenience of the spectators, the intercolumniations must be wider; and the bankers’ shops are situated in the surrounding porticos with apartments on the floors over them, which are constructed for the use of the parties, and as a depôt of the public revenue. The size of the forum is to be proportioned to the population of the place, so that it be not too small to contain the numbers it should hold, nor have the appearance of being too large, from a want of numbers to occupy it. The width is obtained by assigning to it two-thirds of its length, which gives it an oblong form, and makes it convenient for the purpose of the shows.
3The upper columns are to be made one-fourth less than those below; and that because the latter being loaded with a weight, ought to be the stronger: because, also, we should follow the practice of nature, which, in straight growing trees, like the fir, cypress, and pine, makes the thickness at the root greater than it is at top, and preserves a gradual diminution throughout their height. Thus, following the example of nature, it is rightly ordered that bodies which are uppermost should be less than those below, both in respect of height and thickness.
4The basilica should be situated adjoining the forum, on the warmest side, so that the merchants may assemble there in winter, without being inconvenienced by the cold. Its width must not be less than a third part, nor more than half its length, unless the nature of the site prevent it, and impose a different proportion; if, however, that be longer than necessary, a chalcidicum is placed at the extremity, as in the Julian basilica on the Aquiline.
5The columns of basilicæ are to be of a height equal to the breadth of the portico, and the width of the portico one-third of the space in the middle. The upper columns, as herein above described, are to be less than those below. The parapet between the upper columns should be made one-fourth less than those columns, so that those walking on the floor of the basilica may not be seen by the merchants. The proportions of the architrave, frieze, and cornice may be learnt from what has been said on columns in the third book.
6Basilicæ, similar to that which I designed and carried into execution in the Julian colony of Fano, will not be deficient either in dignity or beauty. The proportions and symmetry of this are as follow. The middle vault, between the columns, is one hundred and twenty feet long, and sixty feet wide. The portico round it, between the walls and columns, is twenty feet wide. The height of the columns, including the capitals, is fifty feet, their thickness five feet, and they have pilasters behind them twenty feet high, two feet and a half wide, and one and a half thick, supporting beams which carry the floor of the portico. Above these, other pilasters are placed,eighteen feet high, two feet wide, and one foot thick, which also receive timbers for carrying the rafters of the portico, whose roof is lower than the vault.
7The spaces remaining between the beams, over the pilasters and the columns, are left open for light in the intercolumniations. The columns in the direction of the breadth of the vault are four in number, including those on the angles right and left; lengthwise, in which direction it joins the forum, the number is eight, including those at the angles; on the opposite side, including all the angular columns, there are six columns, because the two central ones on that side are omitted, so that the view of the pronaos of the temple of Augustus may not be obstructed: this is placed in the middle of the side wall of the basilica, facing the centre of the forum and the temple of Jupiter.
8The tribunal is in the shape of a segment of a circle; the front dimension of which is forty-six feet, that of its depth fifteen feet; and is so contrived, that the merchants who are in the basilica may not interfere with those who have business before the magistrates. Over the columns round the building architraves are placed. These are triple, each of them two feet in size, and are fastened together. At the third column, on the inside, they return to the antæ of the pronaos, and are carried on to meet the segment on the right and left.
9Over the architraves, upright with the capitals, piers are built three feet high and four feet square, on which are laid beams well wrought, joined together in two thicknesses of two feet each, and thereon the beams and rafters are placed over the columns, antæ, and walls of the pronaos, carrying one continued ridge along the basilica, and another from the centre thereof, over the pronaos of the temple.
10Thus the two-fold direction of the roof gives an agreeable effect outside, and to the lofty vault within. Thus the omission of the cornices and parapets, and the upper range of columns, saves considerable labour, and greatly diminishes the cost of the work; and the columns in one height brought up to the architrave of the arch, give an appearance of magnificence and dignity to the building.