All the doors opening into or from the narthex, with one exception, are cased in bronze on a wood foundation about five inches thick, formed into panels. They are all hung in two leaves, and the back edges against the frame are rounded continuing top and bottom as pivots on which they revolve. The nine doors entering the church are comparatively plain, each leaf being divided into three panels. The central doors entering the narthex are two panels high, each of which bore a large cross; these were applied separately, the upper one under a round arch on pilasters, and the lower beneath a gable also supported by pilasters. The lower cross is planted on a rock, from which flow the four rivers, symbol of the Gospel preached to the ends of the earth. Part of a verse in the mosaic of the apse at Nola as given by Paulinus makes this symbolism clear. “Christ the rock Of all the church, the base of rock sustains From which as living streams four fountains flow; The four evangelists, whose words are gone Through every land.” The margins, framing the panel of this pair of doors, are decorated with elliptical hollows and pairs of small rosettes alternately (see Fig. 66). [Illustration: FIG. 66.--Central Bronze Door entering Narthex. Scale about three feet to an inch.] The two doors right and left of this central door are less in size; here each leaf is again divided into two panels. The top one has a relief of a chalice from which rises the stem of a cross with crisp acanthus foliage on either side. The lower panel has a large plain cross. These reliefs are all applied to the panels, the crosses being made up of four arms, which are separately inserted into a central boss. The horizontal arms, and in many instances the whole crosses, have been removed by the Mahommedans. The styles and rails of these doors are inlaid with strap-like forms and gammidae in silver, and engraved with a representation of a setting of gems (see Fig. 67). These inlaid straps, with seal-like ends, exactly repeat the forms found on door-hangings. See Fig. 13. At S. Sophia the forms have certainly been taken from similar veils. The large simplicity of the design of these beautiful bronze doors suggests that they may be of Justinian’s time. The doors still further from the centre, right and left, that is to say the two end doors of the five entering the narthex, have each leaf divided into three panels. The top and bottom panels are charged with crosses; and the centre one, which is smallest, bears an annular boss; the styles are studded with discs. The south door of narthex, and also the end doors in the west wall of the nave are similar to these; the others in this wall, including the great central door from the narthex, have the big panel in the centre and two smaller ones with circular boss top and bottom (see Fig. 68). [Illustration: FIG. 67.--Bronze Door of Narthex. Scale about four feet to an inch.]