ROMAN ARCHITECTURE. Although, as was said under ARCHI TECTURE, the Romani; derived their architecture, as they did most of their arta, immediately from the Greeks, yet they undoubtedly borrowed the circular arch, and the fondness for oircularity in the plans of their buildings, from the Etruscans; and these features were ' what mainly brought about the modifications of style and ornamenta tion, the variety of form and the conetnictive peculiarities, which dis tinguish Roman architecture. We cannot here trace the progress of the rAri011111MoilitleatioMI: all wo shall attempt is to show the leading eLarseteristies of Roman arehiteeture, especially inarking its divergence trues that of the Greeks, referring the reader to the article Gaecies: AlICUITrt:TVIII: for a general view of the parent style, and to COLUMN far a particular account of the Orders.
With regard merely to the orders, Roman architecture presents chiefly a corruption of the Done and Ionia, for it may claim the Corinthian as almost entirely its own, the Roman examples of that order being not only numerous and varied, but at the same time exceedingly different in character from the almost solitary specimen of one with foliaged capitals which occurs in a Grecian building. [Greens AIICIITECTUKE_] But even as regards the application of the orders,there is a wide difference between the two styles ; in the Roman they are frequently employed as mere decoration, the columns being csgsged or attached to the walls, or in some cases (as that of triumphal arches) though the columns are lnsulated and advanced from the structure, they are in a manner detached from it, inasmuch as they do not support its general entablature, but merely projecting portions of it. Nor are these the only differences, for the frequent employ ment of pilasters as substitutes for columns—that is, as constituting the order without columns—the practice of super-columniation, or raising one order upon another, was by no means uncommon ; a prac tice that was indeed a matter of nece.sity in such enormous edifices as the Colosseum, if columna were to be employed at all.
From all this it will be evident that, as regards the orders alone, there is a very marked difference between Roman and Grecian archi tecture; yet such difference is by no means the whole. 11 there were no other distinction between them, that arising from the arch, and diverse applications of its principles to vaults and domes, would be' a very material one ; but we also meet with a variety and complexity in Roman buildings of which there are no example; in those of Greece.
With the exception of the Erechtheium, or triple temple on the Acropolis of Athens, Greek temples were merely simple parallelograms, differing from each other as to plan only in the number and disposi tion of the columns around the cella [Temente] ; whereas by the adoption of the circular form in their plans, whether for the whole or parts of a building, the Romans introduced an important element of variety into architectural design. To this shape in the ground-plan is to be ascribed the origin of the (holm, or concave dome, which haimouizes so beautifully with all the rest, and renders the rotunda shape at once the most picturesque and tho most complete for internal effect,—that in which both unity and variety are thoroughly combined. [Itoresna.] The Pantheon alone would suffice to con vince us that the Romans were not mere copyists, and that if the Greek orders deteriorated in their hands, they also added much to the art and greatly extended its powers by new sppliancea. As regards its exterior, the I'antheon preseuts what is certainly a strikingly picturesque (and what we consider to be also a consistent and appro priate, because a well•motived) combination, namely, that of a rectangular mass projecting from a larger circular one. In that example the body of the edifice, or rotunda limit, has no columns externally ; hut circular peristylar temples, or rotundas, whose cella was enclosed by an external colonnade, were not uncommon. Of this kind is the temple of the Sibyl, or, as it is otherwise called, that of Vesta, at Tivoli, an edifice of singular beauty, and highly interesting as it very peculiar and unique example of the Corinthian order. Edifices of this kind were covered with hemispherical domes, or with smaller sections of a sphere, which consequently did not show themselves much externally, as they were raised only over the cella, and therefore the lower part was concealed by the colonnade project ing around it. The dome of the Pantheon is hemispherical within, but is of very low proportions and flattened form without, for its spring commences at about the level of the first or lower cornice of the exterior cylinder, and is further reduced by the base of the outer portion of the dome being expanded and formed into separate cylin drical courses or gradini.