d the Diaconissa,
was to split marble slabs so as to form patterns in the veining, and
then to place them upright on the wall. It is probable that the finest
slabs were first placed in the centre points of the wall, and that other
slabs or borders were then arranged round them. The centre slabs in the
Chora are of exceptional beauty. The usual design consists of a dado of
upright slabs surmounted by panelling to the cornice level, the panels
being outlined with plain or carved beads. In the Diaconissa the notched
dentil form is used for the beads; in the Chora, a 'bead and reel.' The
arches have radiating voussoirs, or, in the Diaconissa, a zigzag
embattled design, found also in S. Demetrius of Salonica, though two
hundred years must have separated the buildings. In the Chora the arch
spandrils and cornice are inlaid with scroll and geometrical designs in
black, white, and coloured marbles.

The surfaces above the cornice and the interior of the domes gleamed
with mosaic, representing, as seen in the Chora, figures on a gold
background. The mosaic cubes are small, measuring 5 mm. to 7 mm., and
are closely set. This is about the same size as the mosaic cubes in S.
Sophia, but smaller than those at Ravenna, which measure about 10 mm.

_Painting._--In the majority of churches this full decoration with
marble and mosaic must have been rendered impossible by the expense, and
accordingly we find examples like the parecclesion at the Chora
decorated with painting, following exactly the tradition of marble and
mosaic. This painting is in tempera on the plaster, and is executed with
a free and bold touch.

_Conclusion._--Byzantine architecture is essentially an art of spaces.
'Architectural' forms, as we are accustomed to think of them, are
noticeably absent, but as compensation, colour was an essential and
inseparable part of the architecture. The builder provided great
uninterrupted spaces broken only by such lines and features as were
structurally necessary--capitals, columns, string-courses, and over
these spaces the artist spread a glittering robe of marble or mosaic.
No school has ever expressed its structure more simply, or given fuller
scope to the artist, whether architect or painter.

Byzantine architecture is not only a school of construction, it is also
a school of painting. Most of the churches of Constantinople have
unfortunately lost the latter part of their personality. They are mere
ghosts, their skeletons w