The mosaics of the Middle Ages were of a purely ornamental character down to the time of Constantine. Then, when the protection of a Christian emperor enabled the Christians to express themselves without fear, the doctrines of the church and the stories of the life of Christ and the histories of the saints, as well as many other instructive religious subjects, were made in mosaics, and placed in prominent places in churches and basilicas. Mosaics are very durable, and many belonging to the early Christian era still remain. The mosaics at Ravenna form the most connected series, and are the best preserved of those that still exist. While it is true in a certain sense that Rome was always the art centre of Italy, it is also true that at Ravenna the works of art have not suffered from devastation and restoration as have those of Rome. After the invasion of the Visigoths in A.D. 404, Honorius transferred the imperial court to Ravenna, and that city then became distinguished for its learning and art. The Ravenna mosaics are so numerous that I shall only speak of one series, from which I give an illustration (Fig. 19). This mosaic is in the church of S. Vitalis, which was built between A.D. 526 and 547. In the dome of the church there is a grand representation of Christ enthroned; below Him are the sacred rivers of Paradise; near Him are two angels and S. Vitalis, to whom the Saviour is presenting a crown; Bishop Ecclesius, the founder of the church, is also represented near by with a model of the church in his hand. On a lower wall there are two pictures in which the Emperor Justinian and the Empress Theodosia are represented: our cut is from one of these, and shows the emperor and empress in magnificent costumes, each followed by a train of attendants. This emperor never visited Ravenna; but he sent such rich gifts to this church that he and his wife are represented as its donors. [Illustration: FIG. 19.--JUSTINIAN, THEODORA, AND ATTENDANTS. _From a mosaic picture at S. Vitalis, Ravenna._] After the time of Justinian (A.D. 527-565) mosaics began to be less artistic, and those of the later time degenerated, as did everything else during the Middle or Dark Ages, and at last all works of art show less and less of the Greek or Classic influence. When we use the word miniature as an art term, it does not mean simply a small picture as it does in ordinary conversation; it means the pictures executed by the hand of an illuminator or _miniator_ of manuscripts, and he is so called from the _minium_ or cinnabar which he used in making colors.