reafter returned to the palace.

_Architectural Features_

In the description of the architectural features of the church and for
the plans and most of the illustrations in this chapter I am under deep
obligation to Mr. A. E. Henderson, F.S.A. The information gained from
him in my frequent visits to the church in his company, and from his
masterly article on the church which appeared in the _Builder_ of
January 1906, has been invaluable.

In design the church is an octagonal building roofed with a dome and
enclosed by a rectangle, with a narthex along the west side. This was a
favourite type of ecclesiastical architecture, and is seen also in
another church of the same period, San Vitale of Ravenna, in which
Justinian and Theodora were interested. There, however, the octagonal
interior is placed within an octagonal enclosure. The adoption of a
rectangular exterior in the Constantinopolitan sanctuary is a
characteristic Byzantine feature.[107] S. Vitale was founded in 526, a
year before SS. Sergius and Bacchus.

[Illustration: PLATE XIII.
(1) SS. SERGIUS AND BACCHUS. FROM THE SOUTH-EAST.
(2) SS. SERGIUS AND BACCHUS. IN THE GALLERY OVER THE NARTHEX.
_To face page 70._]

As an examination of the plan will show, the architect's design has not
been followed with strict accuracy, and the result is that both the
enclosing square and the interior octagon are very irregular figures.
Furthermore, the two portions of the building have not the same
orientation, so that the octagon stands askew within its rectangular
frame. How this lack of symmetry should be explained, whether due to
sloven work or the result of the effort to adapt the church to the lines
of the earlier church of SS. Peter and Paul, with which it was united,
is difficult to decide.

The court which stands before the Turkish portico in front of the west
side of the building represents the old atrium of the church, and to the
rear of the portico is still found the ancient narthex. At the south end
of the narthex is a stone staircase leading to the gallery. The arch at
the foot of the staircase is built of fragments from the old ciborium or
eikonostasis of the church. The great height (0.24 metre or 9 inches) of
the steps is found, according to Mr. Antoniadi, also in S. Sophia.

The exterior walls, which are mostly in brick and rubble masonry,
exhibit poor workmanship, and have undergone considerable repair,
especially on the east. On the south ther