Besides this constant change of size, colour, and arrangement, there is a great variety in the surface treatment. We have the shallow channelling into continuous mouldings of the skirtings, some portion of which has a stiff fret sunk in the surface in addition. Then there are panels on either side of the great door, and on the faces of the projections from the great piers in the aisles, coming just above the eye, (Fig. 48) of plain russet-red or brown which bear severe abstract patterns, made out by slight sinking into the surface. The centre in some cases is overlaid with an oval or square of another precious material such as red or green porphyry or the “onyx”; the whole of the sunk portions may have been filled by inlays, or in some the sinking alone may have formed the design. The upper part of the bema is incrusted with slabs patterned in this way, and here the sunk portions are entirely inlaid; several parts of this are represented by Salzenberg. In this work “casements” are sunk into the rosso or other deep coloured field, and green porphyry and other materials, set off by yellowish-white lines and spaces are inlaid in geometrical panels, or friezes of stiff foliage. [Illustration: FIG. 47.--Portion of Marble Lining of Aisles. Scale about 1/50.] Our Fig. 47 shows the arrangement of the marble plating on the great piers towards the middle compartment of the aisles; in this we have shown one of the enriched panels now only sunk, as inlaid. Fig. 48 gives outlines of others of these panels. The marble used in the aisles is as follows. First comes the moulded skirting of white Proconnesian, then a 3′·3″ band of the streaked variety of the same marble. A band of verde antique 2′·0″ wide follows, above which is a row of slabs alternately verde antique and Synnadan. A second similar row of slabs comes above a band of rosy cipollino. The frieze below the cornice is of marble sectile work. The passages through the piers are lined with slabs of streaked Proconnesian marble, nearly fourteen feet high. The gynaeceum has two bands at the bottom and an upper band of rosy cipollino; the wall space between is covered with a row of vertical slabs of streaked Proconnesian, except the central space on north side where the slabs are of rosy cipollino. In the spandrils of gynaeceum arcade at the west are roundels of oriental alabaster. [Illustration: FIG. 48.--Marble Panels with Sunk and Inlaid Panels. Scale about 1/30.] [Illustration: FIG. 49.--Inlaid Marble Slabs above Royal Door. Scale about 1/50.]