194 COMPARATIVE ARCHITECTURE. 2. ARCHITECTURAL CHARACTER. The general architectural character depends on the development of the dome, induced by the adoption of circular and polygonal plans for churches, tombs, and baptisteries. This is in contrast with the Romanesque style, which developed the vault in Western and Northern Europe (page 224). The change from the old Roman forms was of course gradual, but in the course of 200 years the East asserted itself, and under Justinian the Church of S. Sophia (a.d. 532-537) was erected, and remains the greatest achievement in the style — the interior being perhaps the most satisfactory of all domed examples. Although no line can be stated as separating distinctively the Early Christian and Byzantine styles, yet, as already stated, the Basilican type is characteristic of the former and the vaulted church with pendentives of the latter. A Byzantine building consists generally of a brick carcass or " shell," constructed after the size of the marble shafts had been assured. The walls of this shell were finally sheeted internally with marble, and the vaults with colored mosaics on a golden background. In fact no church was founded during this period in which mosaic was not intended to be employed, and the decora- tion of S. Sophia and the churches of Nica;a and Thessalonica show the perfection to which this was carried out. The core of the wall was generally of concrete, as in the Roman period, but the manner in which the bricks of the casing were arranged contributed greatly to the decoration of the exterior. They were not always laid horizontally, but sometimes obliquely, sometimes in the form of the meander fret, sometimes in the chevron or herring-bone pattern, and in many other forms of similar design, giving great richness and variety to the fa9ades, as may be seen in the churches of Thessalonica. Externally an attempt was made to render the rough brick exteriors of Roman times more pleasing, by the use of bands and relieving arches of an ornamental character. Byzantine art and influences were carried westward by traders, and are found at S. Mark, Venice, S. Vitale, Ravenna, S. Front, Perigueux, and elsewhere, largely directing the architecture of these districts. The dome, already referred to, is the prevailing motif or idea of Byzantine architecture, and had been a traditional feature in the old architecture of the East, and M. Choisy, in his " Art de Batir chez les Byzantins," traces the influence of this tradition of domical construction on Greek architecture to show how from this fusion the later imperial architecture became possible. Domes were now placed over square apartments, their bases being brought to a circle by means of "pendentives" (Nos. 79,
