The windows in the conchs of the exedras are now closed up, the grouped windows in the great tympana on the north and south are diminished to insignificant openings, and the large arched openings at the sides or the end divisions of the aisles seem even in Byzantine times to have been reduced in size; at least the remains of piers, shown in Salzenberg’s Plate xiii., indicate that there was originally an opening with pilasters, similar to those at the eastern end of the side aisles.[270] It is said that Justinian gave instructions that combustible materials should be avoided. If so, these instructions were followed even to the windows and doors, for the lattice-work of the former is of marble, and the panels of the latter are of bronze, or rather they are covered with bronze. Salzenberg[271] gives the inside elevation and section of a window on the south side of the gynaeceum, with details on a larger scale. The opening in the wall is brick-arched, and the framework consists of upright posts, with a thin horizontal architrave dividing the window into two parts. Between these posts were fitted the breast-wall and lattice-work. The posts are narrow towards the outside, and the ends of the architrave rest on thin pieces against the jambs. The ‘breast-wall’ at the bottom of the opening and the ‘lattice-work’ are formed of marble, three inches thick. The openings pierced in the slabs are about seven or eight inches high, filled with panes of glass. Between the panes the marble has a width of three and a half inches, slightly splayed on the inside. A second row of slabs fills the lower part of the windows pierced with openings, surrounded by wider margins.[272] The great semicircular west window is divided vertically by two columns with plain capitals and bases; the horizontal division from column to column is similar to the crowning member of the breast-wall of the other windows. The lower part is filled with marble slabs, which conceal the roof of the western gynaeceum. Each panel is ornamented with a cross upon a circle, and within the latter is a monogram. The small windows are simply filled with marble lattice for the glass. Inside the apse windows of the east end are other windows having coloured glazing; but these are evidently Turkish. Marble door jambs were placed in the openings left in the walls, just as the posts were inserted in the windows; the middle, or Royal Door, from the narthex to the nave, is of bronze. All the frames were moulded, and above are fixed door-hooks, like bent forefingers; these held rings and leather fastenings, from which were suspended the customary door-hangings.