The earlier architecture of the Romans was doubtless chiefly derived from that of the Etruscans, who, like the Greeks, followed the trabeated principle. This origin is distinctly traceable in the plans of the Roman temples, which are never truly peripteral, or surrounded with a detached colonnade, like those of the Greeks, but have a deep portico at one end only, in front of the cella. Of this arrangement we have seen a beautiful example in the Maison Carrée at Nimes. But the Central Italians must have early received some impressions from the Hellenic art of Magna Grecia, and the way would thus be opened for the introduction at a later period of the finer developments of Greek architecture which were so universally followed during the Empire. Meanwhile the arch, the antagonistic element to the trabeated principle, was gradually progressing; and from its primitive obscure use in substructures, conduits, and similar engineering situations, it had forced itself into notice above ground, and had gained recognition in the elevations as a proper architectural element. Hence arose the combination, so conspicuous in the architecture of the Romans, of trabeated features, such as pilasters and entablatures, with the arched method of construction which they had adopted from an early period, and of which they ultimately shewed themselves such masters. The amphitheatres and the triumphal arches of the empire well illustrate this mixture of arched construction, as shewn in the round-headed wall openings, combined with trabeated decoration, in the form of horizontal entablatures supported on engaged columns or pilasters. This mixed style long prevailed, and examples of it are to be found in every part of the Roman world. But in later times, when purity of taste had begun to decay, the Romans gradually gave fuller scope to their noble constructive powers, and allowed them to find a worthier expression in their designs. This took place chiefly in their engineering works, such as the Pont du Gard, and in their interior architecture, as, for instance, in the great halls of the Baths of Diocletian and Caracalla, the Basilica of Constantine (or Maxentius) and other similar works, in some of which immense intersecting vaults were successfully executed. The simple barrel or tunnel vault is of very ancient origin, and was adopted by the Romans from the earliest times. They also freely employed round intersecting vaults for covering spaces of all sizes up to the great examples above referred to. But the most astonishing feat of the Romans in connection with vault construction is their adoption and application of the dome. In the Pantheon at Rome we have an example of that species of vault introduced at once in its perfect form in the largest example in the world. The portico of this temple belongs to the age of Augustus, and it is therefore thought by many that the rotunda and dome are of the same date. It is very remarkable that no smaller Roman domes of earlier date are to be found, and that this style should, as it were, be born in perfect manhood without having passed through the stages of infancy and growth. These no doubt existed, although we have as yet been unable to trace them. Possibly, as Professor Baldwin Brown suggests, the dome is of eastern origin, and its enlarged construction may have been worked out in some of the Hellenistic cities, such as Alexandria, where the earlier examples have now perished.

Along with the introduction of the above new and splendid development of vaulting in their interiors, the Romans still adhered in the decoration of their exteriors to the Italo-Grecian portico, with its entablature and pediment. It was not till the time of the Lower Empire that these elements came to be modified and slowly abandoned. The stages by which the trabeated forms were by degrees stripped off can, however, be distinctly traced. The arches and vaults employed in the baths, tombs, &c., no doubt conduced to that result. In these the arch became the important feature internally, and naturally in course of time it assumed a more prominent position externally also. Archivolts, or curved architraves running round the arches, such as were in common use in buildings like the Colosseum, had gradually intruded themselves amongst the Greek pilasters and entablatures of the exterior elevations; while in later edifices, such as the palace of Diocletian at Spalatro, the straight architrave was omitted, and only the arched one retained. The early Christian sarcophagi shew the same important step. In these a common design consists of an arcade containing the figure of an apostle in each arch, and these arches or archivolts spring directly from the caps of the columns, without any straight architrave being employed. Of this a good example has been given above, page 63.

In all transitional styles it is difficult, and indeed scarcely possible, to draw the line where one style terminates and another begins. This is especially difficult in connection with the passage from Roman to mediæval architecture. The latter was in fact for centuries not a different style but simply a continuation of that of the Empire.

After the adoption of Christianity the purposes to which the Christian buildings were applied was certainly very different from that of their prototypes, but the architecture was the same. The circular domed edifices raised by the Romans as mausoleums were imitated by the Christians in their circular baptisteries; while the style of construction employed in the great basilica or pillared hall lighted by a clerestory, was exactly copied in the nave or large vessel of the Christian Church. The continuity of style is complete; there is no break. The same Corinthian or Ionic pillars, the same entablatures, the same roofs and vault are used in both. So close is the resemblance between the Christian circular baptisteries (several of which we shall meet with in Provence) and Roman circular monuments, that the former are generally regarded as Roman temples converted to Christian uses. The early churches are usually called basilicas, and have hitherto been supposed to be derived from the Roman basilica. But Professor Baldwin Brown, in his recent interesting and learned work “From Schola to Cathedral,” endeavours to prove that this is not the case. The basilica had no doubt the form of a pillared hall with central and side aisles, the former lit by a clerestory, but it had no apse, or if there was one it did not occupy the prominent position of that feature in the early churches. The origin of the apse, which was an essential feature in all churches, containing as it did the seat of the Bishops in the centre and those of the presbyters on either side, is attributed by Professor Baldwin Brown to the memorial cellae erected by Pagans and Christians alike in the cemeteries. These often assumed a domed or apsidal form, and were much resorted to on saints’ natal days, for commemorative festivals and religious ceremonies, held in the cemeteries above the spot where the martyr’s bones reposed in the catacomb below. At a later time, when these relics had been transferred to crypts below the altars of the churches, the apse was a feature naturally introduced to complete the resemblance to the original tomb. As regards the nave, the scholae or halls of meeting of private societies are regarded by Professor Baldwin Brown as the principal model of the early church. Under the emperors the Christians were allowed to form burial guilds, and these, like other guilds, had their scholae. The schola often had an apse containing the seat of the president; and the above author is of opinion that the large churches built after the conversion of Constantine are rather enlarged scholae than copies of basilicas.

However this may be, the type of the early Christian church or basilica presented to view an elongated hall with two or four rows of pillars, dividing it into three or five aisles, with a lofty triumphal arch at the end of the central nave, leading into a wide open space raised some steps higher than the nave, and in which stood the altar. Beyond this was the invariable apse with its semi-domed ceiling adorned with mosaics, and containing, elevated by a few steps above the floor, the throne of the Bishop, and the seats of the Presbyters. The whole building was covered with an open wooden roof.

Some of these early churches have been preserved or restored in Rome—such as San Paolo fuori le Mura, Sta Maria Maggiore and San Clemente.

There is every reason to believe that the above was the usual form of early churches in the West. At Ravenna, which was the principal city in Italy during the Lower Empire, being the seat of the Exarch, the representative of the Emperor in the West, there are fine examples of the various kinds of early Christian religious edifices, dating from the fifth to the seventh century. The great Church or Basilica, used for the assembly of the whole congregation, is represented in St Apollinare Nuovo. It has the usual row of columns on either side of the nave, separating it from the side aisles, and supporting a flat upper wall splendidly decorated with mosaics, the whole being ornamented with Roman details. The upper portion of the wall is pierced with clerestory windows, and at the east end is the great apse.

The Baptistery or Ceremonial Church is as usual octagonal and is domed. Here also the walls are covered with fine mosaics.

Another extremely interesting building at Ravenna is the church of San Vitale. This edifice (whether designed as a monument or as a church is uncertain) is octagonal and domed, very much after the style of the temple of Minerva Medica and similar Roman structures.

San Vitale has a special interest from its having formed the model adopted by Charlemagne for the church which he erected at Aix-la-Chapelle, to serve also as his own mausoleum. It thus constitutes an example of a Roman design reproduced in Ravenna, under the late Empire, as a Christian structure, and again serving as a model for a mediæval mausoleum as late as the eighth century. This shows distinctly the continuity of Roman design and its direct influence on the art of later times.