The architrave is relatively low, the result of an interesting peculiarity in the method of construction. Blocks of tufa long enough to span the intercolumniations were too weak to sustain the weight of the rest of the entablature. To meet this difficulty a line of thick planks was placed in old Italic fashion above the capitals of the columns, and on these were laid short tufa blocks. Thus in our illustration ([Fig. 14]), while the upper of the two bands of the architrave is seen to be of stone, the lower shows the modern timber supplied in the place of the ancient. That the planks were in reality no thicker than has been assumed in the reconstruction is proved beyond question by the later colonnade on the west side, which, although entirely of stone, corresponds throughout in its proportions with the older one; the architrave is equally narrow, and is likewise divided into two parts.
Fig. 14.—Remnant of the colonnade of Popidius, at the south end of the Forum.
This explanation is curiously confirmed by an architectural painting on the garden wall of one of the finest houses of the Tufa Period, the house of the Faun. Here we find pilasters and entablature, except the architrave, painted white; but the architrave is painted in two bands, of which the lower is yellow, as if to represent wood. Nothing would have been easier than to leave the architrave, moulded in stucco, of one color as if it were all of one material; but special effort was made apparently to indicate the appearance of a lower division of timber. From this we may infer that in actual construction no pains was taken to conceal the lack of uniformity in structural materials by laying a coat of white or colored stucco over wood and stone alike; on the contrary, the difference was not only recognized in the decoration, but even accentuated, as the timber, whether retaining its original color or painted with a suitable tint, presented a marked contrast with the stone the surface of which was covered with white stucco. If the strip of timber in the architrave had been perceptibly thicker than that of stone above it, the effect would not have been good; as the earlier Greek polychrome decoration was now no longer in vogue, the stripe of color above the capitals made a pleasing variation from the prevailing whiteness of the structure.
The Basilica at the southwest corner and the temple of Jupiter both conform to the same variation from the direction of the early north and south street that we have noticed in the case of the colonnade of Popidius; they belong, therefore, to the same remodelling of the Forum. It is quite possible that the erection of the temple, by limiting the area of the Forum on the north side, caused its extension toward the south beyond the earlier boundary. Originally the temple was isolated, the north end of the Forum on either side being left open; later, but still in the time of the Republic, a high boundary wall with passageways was built on both sides of it. Later still the two arches were erected in a line with its façade; afterwards, in the time of Tiberius, the wall at the right of the temple was replaced by the commemorative arch (I), and the smaller arch near the façade at the right was removed in order that there might be an unimpeded view of the great arch from the area.
The colonnade of Popidius may have stood for more than a century; the necessity of making thoroughgoing repairs no doubt became urgent. In the meantime, however, the taste of the Pompeians had undergone a change, and instead of repairing the old colonnade they began to replace it by a new one, a part of which is shown in [Fig. 15]. Better material, the whitish limestone, was used, and the construction was more substantial; the blocks of the entablature were fitted together so as to form a flat arch. Though the new colonnade followed closely the proportions of the old, effective details, such as the fluting of the columns, and the triglyphs with the guttae underneath, were omitted. The refined sense of form characteristic of the earlier time was no longer manifest; all is coarse and inartistic, the swelling on the shafts of the columns, for example, being carried too high.
Fig. 15.—Part of the new colonnade, near the southwest corner of the Forum.