ing of the gallery vaulting, and the nave walls, up to the gallery
level, were once faced with marble. This is proved by the presence in
the walls of many marble plugs and some iron holdfasts, as well as by
remains of the moulded base of the facing.

At the eastern extremity of the aisles there are chambers formed by
walls built, as the vertical straight joints and difference of materials
employed indicate, at various periods. The chamber at the end of the
northern aisle has an archway, now built up, in its eastern wall, and
seems to have served as a vestibule. It is in these chambers that
Salzenberg supposes the staircases leading to the galleries stood, but
it is evident from the character of the walls and vaulting that no such
staircases could ever have existed there.

The galleries extend over the narthex and over the whole length of the
aisles. Access to them is now obtained by a wooden staircase and landing
of Turkish construction, but how they were reached in Byzantine times is
not evident. Possibly the fragments of wall on the exterior face of the
south wall of the narthex and the traces of vaulting beside them may be
the remains of a staircase. Or a staircase may have stood to the west of
the narthex over the vaulting of the atrium, where projecting spurs of
walls appear.

The vaulting of the gallery over the narthex was originally similar to
that of the narthex itself, but only the cross-groined vaults at the
corners are Byzantine; the three central compartments are Turkish. Five
windows in the western wall looked into the atrium, and as many openings
in the eastern wall into the nave and side galleries. Below the former
range is a string-course corresponding to that which runs round the
interior of the building at gallery level.

The gallery over each aisle consists of two open portions under the dome
arches, divided from each other by the dome piers, which are pierced to
connect the different parts of the gallery with each other, and with the
gallery over the narthex. In the side walls there is a range of windows
at gallery level; five on each side of the eastern nave bay, three in
the south wall of the western nave bay, but none, at present, in its
northern wall. Above these windows are two ranges of windows in each
lunette under the dome arches, a system of five and three in the eastern
bay, and of four and two in the western bay. All these windows, now
square-headed, had originally semicircular heads.