nd of the northern and the southern gallery are chapels covered
with domes and placed above the prothesis and the diaconicon. As stated
already, the aperture in the roof of the chamber in the south-eastern
dome pier opens into the floor of the southern chapel, and probably a
similar aperture in the roof of the corresponding chamber in the
north-eastern pier opened into the floor of the chapel at the east end
of the northern gallery. The presence of chapels in such an unusual
position is explained by the desire to celebrate special services in
honour of the saints whose remains were buried in the chambers in the
piers, as though in crypts.

The domes over the chapels are hemispherical and rest directly on the
pendentives. They are ribless and without drums. The arches on which
they rest are semicircular and, with their infilling of triple windows,
are Byzantine. We may safely set down all four angle domes as belonging
to the original design, though the arches by which they communicate with
the galleries are pointed, and are therefore Turkish insertions or
enlargements.

On the exterior the eastern wall of the church is fairly well preserved.
The three apses project boldly; the central apse in seven sides, the
lateral apses in three sides. Although the central apse is
unquestionably a piece of Byzantine work it does not appear to be the
original apse of the building, but a substitute inserted in the course
of repairs before the Turkish conquest. This accounts for its plain
appearance as compared with the lateral apses, which are decorated with
four tiers of five niches, corresponding to the window height and the
vaulting-level within the church. As on the apses of the Pantokrator (p.
235) the niches are shallow segments in plan, set back in one brick
order, and without impost moulding. In the lowest tier three arches are
introduced between pilasters, with a window in the central arch. Above
the four tiers of niches is a boldly corbelled cornice, like that in the
chapel attached to the Pammakaristos. One cannot help admiring how an
effect so decidedly rich and beautiful was produced by very simple
means.

[Illustration: PLATE XLV.
(1) S. THEODOSIA. DOME OVER THE STAIRCASE TO THE GALLERIES.
(2) S. THEODOSIA. THE NARTHEX, LOOKING NORTH.
_To face page 172._]

Details of the tiled floor and of several carved fragments are given in
Fig. 76.

For some time after the conquest the building was used as a naval
store