In his book,[78] which is made up largely of drawings and diagrams, Vignola shows how the proportions of an order may be regulated by a module down to the smallest details. He explains how to construct Ionic volutes and other curves from centres, and how to describe the details of Corinthian and composite capitals by means of plan and elevation. He thus introduces a mechanical system modelled after the formulas of Vitruvius.
Fig. 43.—Vignola’s entablature.
But notwithstanding his ardent advocacy of the principles of ancient Roman art, Vignola, in his own practice, not only altered the proportions of the orders as Milizia says, but made many fanciful changes in them. He introduced details which have no counterparts in correct Roman design, and freely mixed those of different orders. An instance of this occurs in an entablature figured in his book,[79] which he calls his own invention. In this composition (Fig. [43]) we have a pseudo-Doric frieze between an architrave with multiplied faciæ, and a cornice on modillions. In the place of triglyphs this frieze has consoles with two channels, like those of a triglyph, on the curved face of each. To such travesties of classic design did the striving after novelty, which was curiously mingled with their ardour for the antique, lead the men of the later Renaissance. For an advocate of classic correctness such aberrations are the more surprising as they are expressly condemned by Vitruvius, who warns his readers against them as follows: “If dentiled cornices are used in the Doric order, triglyphs applied above the voluted Ionic, thus transferring parts to one order which properly belong to another, the eye will be offended, because custom otherwise applies these peculiarities.”[80] The Roman writer might, indeed, have given a better reason why the purity of the orders ought to be maintained, namely, because to each of them the fine artistic genius of the Greeks had given its appropriate details.
Fig. 44.—Half plan of Sant’Andrea.
In designing entire buildings Vignola shows no less freedom in unclassic and incongruous combinations. This is manifested in the earliest of his church edifices, that of Sant’Andrea di Ponte Molle outside of the Porta del Popolo at Rome (Figs. [44], [45], and [46]). It is a small, oblong, rectangular enclosure covered with a dome of oval plan on pendentives. The structural scheme is thus primarily Byzantine, but the architectural treatment is Roman. The dome is built in a praiseworthy form, and follows the construction of the dome of the Pantheon. An enclosing drum is carried up from the pendentives to a considerable height, and the haunch of the vault is well fortified by stepped rings of masonry. These rings are criticised by Milizia[81] as awkward and unnecessary because, he affirms, the vault might have been made secure without them. He probably means that it might have been bound with chains in the usual manner of the Renaissance. As in the Pantheon, the drum rises so high above the springing that but little of the dome is visible externally. The character of the rectangular substructure is puzzling to the eye of a beholder who looks for meaning and congruity in architectural forms. Wrought in shallow relief upon its façade is an order of Corinthian pilasters surmounted by a classic pediment, and the entablature of the order is returned on the sides of the building. The effect of the whole may be compared to that of a Greek temple with an attic supporting a dome built upon it. So awkward is the combination that it might be supposed to be a piece of patchwork in which a building of Greek temple form had been altered to gain more height within, were it not that we find in the architect’s own book the plan and section reproduced in Figs. 44 and 45, which show that the building as it now exists was originally designed in its present form.[82]
Fig. 45.—Longitudinal section of Sant’Andrea, from Vignola’s book.
On reflection we discover that the scheme suggests a derivation from the Pantheon. Not only is the dome shaped and adjusted as in that ancient monument, save for its oval plan, but the rest of the composition is pretty clearly from the same source. To realize this it is necessary only to eliminate, in idea, the portico of the Pantheon with the exception of its pediment, and to conceive this pediment as drawn back into the plane of the rectangular façade. The pediment would then surmount the order of Corinthian pilasters which adorn this façade, and the resulting composition would be substantially identical with that of the façade of St. Andrea. The minor differences are unimportant, as where Vignola has placed a pair of pilasters, instead of only one, at each end of the façade, has given the whole order more shallow relief, and has omitted the fluting on the pilasters. Even the niches on either side of the portal are reproduced from the Pantheon, though Vignola has pierced them with windows.