The early Christian basilicas, at any rate in the west, had very seldom, if ever, galleries over the side aisles, and their interior is always dominated by the semi-dome of an apse that terminates the central nave, whereas, with the doubtful exception of Silchester (Archaeologia, liii. 549), there is no instance known of a vaulted apse in a columned civil basilica of the normal kind.

Fig. 6. Basilica of Timgad.

Fig. 6. - Plan of Basilica adjoining the Forum of the Roman city of Timgad, in North Africa.

(From Gsell's Monuments antiques de l'Algerie, by permission of A. Fontemoing.)

When buildings were first expressly erected for Christian worship, in the 3rd or perhaps already in the 2nd century A.D. (Leclercq, Manuel, ch. iii. "Les édifices chrétiens avant la paix de l'église"), they probably took the form of an oblong interior terminated by an apse. After the time of Constantine, when the numbers of the faithful were enormously increased, side aisles were added, and in this way the structure came to assume an appearance similar to that of the civil basilica. A striking confirmation of this view has recently come to light at S. Saba on the Aventine at Rome, where a small and very early church, without aisles, has been discovered beneath the floor of the present basilica.

There are, on the other hand, instances in which private basilicas in palaces and mansions were handed over to the Christians for sacred uses. We know that to have been the case with the basilicas of S. Croce in Gerusalemme and S. Maria Maggiore at Rome, which originated in the halls of the Sessorian and Liberian palaces respectively, granted by Constantine to the Christians. We may adduce also as evidence of the same practice a passage in bk. x. ch. 71 of the theological romance known as The Recognitions of Clement, probably dating from the early half of the 3rd century, in which we are told that Theophilus of Antioch, on his conversion by St Peter, made over "the basilica of his house" for a church. But however this may have been, with, perhaps, the single exception of S. Croce, the existing Christian basilicas were erected from the ground for their sacred purpose. At Rome the columns, friezes and other materials of the desecrated temples and public buildings furnished abundant materials for their construction. The decadence of art is plainly shown by the absence of rudimentary architectural knowledge in these reconstructions.

Not only are columns of various heights and diameters made to do duty in the same colonnade, but even different orders stand side by side (e.g. Ionic, Corinthian and Composite at S. Maria in Trastevere); while pilasters assume a horizontal position and serve as entablatures, as at S. Lorenzo fuori le Mura. There being no such quarry of ready-worked materials at Ravenna, the noble basilicas of that city are free from these defects, and exhibit greater unity of design and harmony of proportions.

Fig. 7. Basilica of Silchester.

Fig. 7. - Plan of Basilica adjoining the Forum of the Roman city at Silchester, Hants. (From Archaeologia, vol. liii.)

An early Christian basilica may be thus described in its main features: - A porch supported on pillars (as at S. Clemente) gave admission into an open court or atrium, surrounded by a colonnaded cloister (S. Clemente, Old St Peter's, S. Ambrogio at Milan, Parenzo). In the centre of the court stood a cistern or fountain (cantharus, phiale), for drinking and ablutions. In close contiguity to the atrium, often to the west, was the baptistery, usually octagonal (Parenzo). The church was entered through a long narrow porch (narthex), beyond which penitents, or those under ecclesiastical censure, were forbidden to pass. Three or more lofty doorways, according to the number of the aisles, set in marble cases, gave admission to the church. The doors themselves were of rich wood, elaborately carved with scriptural subjects (S. Sabina on the Aventine), or of bronze similarly adorned and often gilt. Magnificent curtains, frequently embroidered with sacred figures or scenes, closed the entrance, keeping out the heat of summer and the cold of winter.

The interior consisted of a long and wide nave, sometimes as much as 80 ft. across, terminating in a semicircular apse, with one or sometimes (St Paul's, Old St Peter's, St John Lateran) two aisles on each side, separated by colonnades of marble pillars supporting horizontal entablatures (Old St Peter's, S. Maria Maggiore, S. Lorenzo) or arches (St Paul's, S. Agnese, S. Clemente, the two basilicas of S. Apollinare at Ravenna). Above the pillars the clerestory wall rose to a great height, pierced in its upper part by a range of plain round-headed windows. The space between the windows and the colonnade (the later triforium-space) was usually decorated with a series of mosaic pictures in panels. The colonnades sometimes extended quite to the end of the church (the Ravenna basilicas), sometimes ceased some little distance from the end, thus admitting the formation of a transverse aisle or transept (St Paul's, Old St Peter's, St John Lateran). Where this transept occurred it was divided from the nave by a wide arch, the face and soffit of which were richly decorated with mosaics. Over the crown of the arch we often find a bust of Christ or the holy lamb lying upon the altar, and, on either side, the evangelistic symbols, the seven candlesticks and the twenty-four elders.

Another arch spanned the semicircular apse, in which the church always terminated. From Carolingian times this was designated the arch of triumph, because a cross was suspended from it.

Fig. 8. S. Apollinare. Fig. 8. - S. Apollinare in Classe, Ravenna.