JUSTINIAN AND THE BYZANTINE EMPIRE 147 nave terminates is roofed over with a half dome filled with mosaics. A mosaic is a design or picture made of small cubes of stone or glass of different colors set in the floor or wall or ceiling of a building. Those of ancient Roman times are usually patterns or pictures set in pavements and are rather dull and colorless compared to the later Byzantine ones seen in the domes and upon the walls of Christian churches. San Vitale, another church of the sixth century at Ravenna, illustrates the round or concentric style of early Christian architecture. It is octagonal in shape with a central dome surrounded by a lower aisle. Here again are to be seen splendid mosaics, including those of Justinian and Theodora, and beautiful capitals in the double Byzan- tine form of a lower part adorned with floral or other designs and an impost above upon which the arches rest. The little fifth century mausoleum of the Empress Galla Placidia at Ravenna has already been described in another connection, but may be mentioned again as one of the earliest distinct examples of a building in the shape of the Latin cross, although some of the early basilicas at Rome seem to have approximated to that shape by having transepts at the very end just before the apse and altar. Later on, in the Middle Ages, in the time of Romanesque and Gothic archi- tecture in western Europe, cathedrals came to be regularly built in the form of a Latin cross. For several centuries after Justinian, Constantinople led the world in art. Almost all fine work in gold, silver, or bronze, in ivory carvings or colored enamels, Byzantine that one finds in museums of western Europe art as dating from before the twelfth century, is pretty sure to be of Byzantine workmanship. The influence of Byzantine architecture, with its concentric plan, its domes and cupolas, its capitals and mosaics, its Oriental tinge, may be seen in southern France and elsewhere besides Italy. In the Byzan- tine painting, sculpture, and mosaic, faces, costumes, and draperies change to suit the times, and since the motive of art is Christian and Oriental rather than classical, the
