secular basilica. The apse with its semi-circular range of seats and its altar reproduces the judicial tribune, with its seats for the praetor and his assistant judges, and its altar on which oaths were taken. The open galleries, which in some of the earliest Christian basilicas at Rome form an upper story to the aisles, recall the galleries above the colonnades which surrounded the central hall of some of the larger secular basilicas. Again, the atrium or forecourt through which the Christian basilica was often approached has been supposed to be derived from the forum in connexion with which the secular basilica was frequently built.

§ 2. However, while the atrium of the Christian basilica is merely an outer court, the secular basilica, when planned, like the Basilica Ulpia at Rome, with direct relation to a forum, was a principal building in connexion with the forum, but not a building of which the forum was a mere annexe. Further, when we begin to seek for a complete identification of the Christian with the secular basilica, we are met by the obstacle that the secular basilica had no fixed plan. If we try to trace any principle of development in its plan, we find that this development is directly inverse to that of the Christian basilica. The secular basilica, in earlier examples a colonnaded building with its central space open to the sky, became at a later time a roofed hall, either, as in the case of the basilica at Trier, without aisles, or, like the basilica of Maxentius or Constantine in the Roman forum, with a series of deep recesses at the side, the vaulted roofs of which served to counteract the outward pressure of the main vault. The Christian basilica, if it were a mere imitation of this type of building, would follow the same line of development; but, as a matter of fact, the highest type of Christian church is always a colonnaded or aisled building. And, even if the Christian apse derived its arrangement from the apse or apses which projected from the ends or sides of the secular basilicas, there is again a difference. The apse with its altar was the main feature of the interior of the Christian church: it was the place in which the chief rite of Christian worship was performed before the eyes of all. In the secular basilica the apse was devoted to special purposes which set it apart from the main business of the body of the building: it was an appendage to the central hall, not necessarily within view of every part of it. In fact, the relation of the apse to the main building was totally different in the two cases.

§ 3. It seems probable, then, that the identity between the two buildings is mainly an identity of name, and that Christian builders, in seeking for suitable arrangements for public worship, may have borrowed some details from the arrangements of the secular basilica. It is natural, however, to look for the origin of a religious plan in buildings devoted to religious purposes. The Roman temple supplied no help for the plan of buildings which were required for public worship. Of recent years, it has been customary to assume that the Christian basilica took its form from the inner halls of the private houses of those wealthy citizens who embraced Christianity in its early days. Such halls may have been used for Christian services; and if their plan was adopted for the Christian basilica, the mature state of the basilican plan at its first appearance can be explained. The atrium or entrance hall of the house is represented on this hypothesis by the forecourt of the basilica; the peristyle, or colonnade round the inner room, becomes the aisles and the space screened off at the entrance for those not entitled to take full part in the service; the colonnade at the further end survives in the arcaded screen which existed, for example, in old St Peter's at Rome; the apse takes the place of the tablinum, where the most sacred relics of family life were preserved; and the transept, which is found in some of the early Roman basilican plans, represents the alae, or transverse space, which existed between the tablinum and the main body of the hall. But these close analogies are the result of an assumption by no means certain. It is always probable that the basilican plan had its origin in a plan originally aisleless. Some, intent on its religious source, explain it as a development of the plan of the Jewish synagogue. Others, regarding assemblies of Christians for public worship as, in their essence, meetings of persons associated in common brotherhood, have derived the basilica directly from the aisleless scholae which were the meeting-places of the various confraternities or collegia of ancient Rome. In these there is an apse at one end of the building; and, if we imagine aisles added by the piercing of the walls with rows of arches and columns, we have at once the essential features of the basilican plan. Each theory has its attractions and its difficulties; and to none is it possible to give unqualified adherence. It may be stated, as a tentative conclusion, that the basilican plan probably had its origin in an aisleless form of building, and thus pursued a course directly opposite to the development of the secular basilica. But it seems clear that, in many details of the plan, especially as we see it in Rome, the peristyled hall was kept in mind; while in two features, the arrangement of the apse and the occasional appearance of galleries above the aisles, the secular basilica was taken into consideration. The policy of the early Christian Church, when its services were sanctioned by the state, was to adapt existing and familiar forms where they could be suitably reproduced.

Fig. 1. Plan of old St Peter's: (1) atrium or fore-court; (2) nave with double aisles; (3) site of screen-colonnade; (4, 4) transepts; (5) apse with crypt below.

§ 4. The plan of the old basilica of St Peter at Rome, founded by Constantine the Great, and destroyed early in the sixteenth century to make way for the present church, explains the principal features of the basilican plan in its developed state. (1) In common with other early basilicas in Rome, and in other parts of western Europe, the entrance was at the east, and the altar at the west end, so that the celebrant faced the congregation during the divine office. (2) The church was approached through a cloistered atrium or fore-court, in the middle of which was a fountain, the place of purification for those intending to enter the church. (3) At the west end of the cloister three doorways opened into the nave of the church, and one on either side into the side aisles. (4) The nave communicated with the aisles by a row of columns beneath an entablature: there were also outer aisles, communicating with the inner by columns bearing rounded arches. (5) The side walls of the nave, above the entablature, were not pierced for galleries, but were covered by two rows of mosaic pictures, one above the other, on each side, the upper row corresponding to the height of the space between the outer and inner roofs of the aisle. Above this, the walls rose into a clerestory, pierced with round-headed windows at regular intervals; and a high entablature supported the great tie-beams of the wooden roof. (6) The quire of singers, divided from the rest of the church by low screen walls, probably occupied the centre of the western portion of the nave. (7) A tall open arch divided the nave from the transept, which was of equal height with the nave, and projected south and north as far as the walls of the outer aisles. Here