The art of mosaic existed, of course, long before Constantine. But glass mosaics containing a film of gold were the invention of the later empire, and the Byzantine architects made vast use of them. What a museum of this splendid art Constantinople must once have been we can only guess. Ravenna, however, early became important for the study of mosaics, for in the capital of Justinian many of his masterpieces were destroyed during the iconoclastic controversy. And to-day Salonica, Venice, Sicily, and a few widely scattered monasteries contain the chief remaining specimens. In Constantinople, where palaces, churches, public monuments and private houses without number were tapestried with mosaic, there are in 1914 only four buildings where anything is visible of this lost art. The attendants of St. Sophia used to make quite an income by selling mosaics which they picked out of the walls of the galleries. This infamous commerce has now been checked, but there is no telling what ravages were committed while it flourished. The earthquake of 1894 was also disastrous for the decoration of the mosque, correspondingly enlarging the area of plaster in the nave. The vaulting of the aisles and galleries, however, the soffits of the arcades, and the inner narthex still contain a greater extent of mosaic, and presumably older, than exists elsewhere in the city. The church of St. Irene, long a Turkish armoury and now a military museum, also contains, in the narthex, a little mosaic which may be of Justinian’s time. That of the apse belongs to the restoration of the church during the iconoclastic period. And in a chapel of the eighth-century church of the All-blessed Virgin, now Fetieh Jami, where the figures of Christ and twelve prophets still look down from a golden dome, we have work of a much later period—probably the fourteenth century. But a far finer example of the work of that period is to be seen in Kahrieh Jami, once Our Saviour in the Fields. [Illustration: Kahrieh Jami]