Fig. 12.—Vaulted Chamber with Columns.
The cubicula had vaulted roofs, and were sometimes plastered or cased with marble and paved with tiles, or, though rarely, with mosaic. These, however, were generally additions of later date than the original construction, as were also the semi-detached columns in the angles, with stucco capitals and bases, as indicated in [Fig. 9], and shown more clearly in the following engraving, which is a perspective view of the lower chamber
in [Fig. 9]. The walls and ceiling were often covered with fresco paintings, frequently of elegant design, to be hereafter described.[15] Sometimes, as in some examples in the Catacomb of St. Agnes, tufa or marble seats are ranged around the chamber, and chairs are hewn out of the solid rock.[16] These chambers were used probably for the instruction of catechumens. Occasionally the cubiculum terminates in a semicircular recess, as in the upper chamber in [Fig. 9]. These probably gave rise to the apse in early Christian architecture, of which a good example is found in the Church of St. Clement, one of the most ancient Christian edifices in Rome. Niches and shelves for lamps, an absolute necessity in the perpetual darkness that there reigns, frequently occur, such as may be seen in Italian houses to-day. Without the least authority, some Roman Catholic writers have described
these as closets for priestly vestments and shelves for pictures.
Fig. 13.—Cubiculum with Arcosolia.
A peculiar form of grave common in these chambers, as well as in the galleries, is that known as the arcosolium, or arched tomb. It consists of a recess in the wall, having a grave, often double or triple, excavated in the tufa, or built with masonry, like a solid sarcophagus, and closed with a marble slab. These are seen in the plan, [Fig. 9], in the section, [Fig. 10], at G and E in [Fig. 15], and in perspective in [Figs. 11] and [12]. Sometimes the recess is rectangular instead of arched, and is then called by De Rossi sepolcro a mensa, or table tomb. Sometimes the arch was segmental, especially when constructed of masonry.[17] An example of both sorts is seen in the accompanying engraving of a cubiculum in the Catacomb of St. Prætextatus. The narrow door into the corridor is also seen, and the stucco capitals and bases of the columns. In course of time these arcosolia were