The dome, bema, and the barrel vault in the
lower story (p. 285) seem to be laid with true radiating joints. The
springing of the barrel vault is formed of four courses of stone laid
horizontally and cut to the circle, and above them the entire barrel is
of brick. The dome arches of the Sanjakdar Mesjedi (p. 270) are formed
of three distinct rings, not bonded into one another. They radiate to
the true centre, and the pendentives are, as usual, in horizontal
courses. The transverse arches of the outer narthex in S. Saviour in the
Chora are also built with true radiating courses.

The gynecaeum of the side-chapel of the Pammakaristos (p. 153) has never
been plastered, and consequently the laying of the brickwork can be seen
there to advantage. The little stair leading up to the gallery is
covered with a sloping barrel vault built in segments perpendicular to
the slope of the stair and could easily have been built without
centering. The same remark applies to the cross vault at the head of the
stair, which is similarly constructed in 'slices' parallel to each side
(p. 154). The arches of the gynecaeum itself, the vaults, and the two
little domes, seem to have true radiating joints. The ribs of the domes
are formed in the brickwork, and are not structurally separate. In these
last examples, and in all door and window openings, in which the joints
invariably radiate from the centre, a certain amount of centering was
inevitable.

[Illustration: PLATE III.
(1) THE MYRELAION (SINCE IT WAS BURNT). INTERIOR, LOOKING EAST.
(By kind permission of H. M. Dwight, Esq.)
(2) SULEIMAN AGA MESJEDI, BESIDE S. SAVIOUR PANTOKRATOR.
_To face page 24._]

On the other hand a little passage in S. Saviour in the Chora between
the church and the parecclesion (p. 311), is covered with a barrel vault
evidently built without centering. The space is first narrowed by two
corbelled courses of stone and, above them, by three projecting courses
of brick. From this springs the vault, built from each end in strongly
inclined segments. These segments meet in the middle, leaving a
diamond-shaped space filled in with longitudinal courses. Like the
stairs in the Pammakaristos, this passage is very narrow, some 85 cm.,
yet the builders thought it necessary to corbel out five courses before
venturing to throw a vault without centering.

Near the Pantokrator is an octagonal building, now Suleiman Aga Mesjedi
but generally regarded as a Byzantine l