All subsequent churches, whether Romanesque, Gothic, or Renaissance were constructed on but slight modifications of this original plan, which, in fact, was itself evolved from that of the Roman temple. Illustration: PLAN OF THE OLD BASILICA OF ST. PAUL’S BEYOND THE WALLS. A - Apse T - Transept N - Nave X - Narthex] The first basilicas erected for Christian worship had double aisles; this form was, however, soon discontinued, probably owing to the difficulty of observing the offices of the clergy from the outer aisle. Of these St. Peter’s, St. Paul’s beyond the walls, and St. John Lateran were the finest examples. The first-named was built upon the site of the present cathedral, and was removed in the sixteenth century to make room for it. Its dimensions were of notable size, being about 380 feet long by 212 feet in width. It was preceded by an atrium, or open court, surrounded by a colonnade, in which the Christians met to transact their affairs. The basilica of St. Paul’s was destroyed by fire in the early part of this century, and a new structure resembling the old was erected in its place on a scale of great magnificence. The columns of its Corinthian colonnade and the floor are of polished marble and the wooden roof lavishly ornamented with carving and gilding. The transept is enriched with mosaics, and contains a baldachin over the altar, in which malachite and other choice stones have been used unsparingly. A typical basilica was generally arranged as follows: The atrium or quadrangular open court, surrounded by porticos, preceded the main building, or was replaced by a porch composed of columns sustaining a low roof which was called the narthex. Within, the structure was divided into a nave, side aisles, transept, and apse. The nave (derived from “navis,” a vessel, symbolical of that of St. Peter) was loftier than the adjoining aisles, the upper wall being usually panelled with pictures and pierced at the top by a range of windows, from which the Gothic clerestory was derived later on. In one or two instances where the side aisles had a second story or upper gallery for the women, the panels and windows were placed in the outer wall. The interior lines of columns were usually of the Ionic or Corinthian orders, having been taken from older buildings, but if new they were of stouter proportions than the Classical models. These columns supported either a continuous architrave or circular arches. Wooden doors, often covered by chased bronze, were hung in the main entrance and the wall above was usually pierced by a round window or bull’s-eye, afterward developed into the rose window. At the other end of the nave a wide arched opening, called the triumphal arch, connected it with the transept. An enclosure, separated from the body of the church by a balustrade, at the upper end of the nave, contained the seats of the choristers and the reading-desks.