glory is the adaptation of the dome, which hitherto had only appeared on round buildings, to a rectangular building by means of a series of lesser domes filling up the angle spaces and mounting one above another, till the great central dome soars over all, and the whole cluster looked at from beneath has the effect of cavernous vaults in a vastness of lofty space. The Byzantine architecture which followed also adapted the dome to rectilineal lines, sometimes by having the building beneath it octagonal, or by means of other devices, but never with any approach to the glory of St. Sophia.
While this structural triumph of genius is the chief peculiarity of St. Sophia, another feature of Justinian's basilica, being more easily imitated, has become a marked characteristic of Byzantine architecture. This is its wealth of decorative splendour. In the decoration of St. Sophia the richest materials—gold, silver, ivory, precious stones—were used with incredible prodigality. The great dome was constructed with white tiles from Rhodes, one-fifth the weight of ordinary tiles. Soon after it had been completed it was thrown down by an earthquake. It was rebuilt more strongly, and it has stood through nearly fourteen centuries till our own time. The ambo placed near the centre, made of most beautiful marbles and surmounted with a dome and cross of gold, consumed one year's Egyptian revenue. The choir was separated from the nave by a solid silver screen. The altar was of gold set with jewels beneath a gold dome and cross sustained by four silver columns. The interior surfaces of domes and walls were completely covered with immense mosaics, consisting of majestic figures, on a ground in some places of gold, in others of a deep blue colour; some of these however were later than the time of Justinian. At night, when the whole building was lit up with the scattered radiance of 6,000 candelabras, the effect must have been superb. Justinian appears to have been more proud of his basilica at Constantinople than of the conquests of his great general Belisarius,
