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Rh aiding to carry the roof. A really structural gallery of this kind is a beautiful feature. The most perfect part of this church is now the columnar front of the narthex. The columns and entablature are of marble elaborately carved. This carving, in accordance with a principle which afterwards became still more marked, is sharply cut into the general block-form of the mouldings and capitals, the serrated edges of the leaves are in sharp triangular forms, and details are accentuated with holes formed by a drill. On the white marble and under the bright light this delicately fretted surface decoration tells like pierced work; indeed a little later it became customary to undercut much of the surface patterns so that the capitals were surrounded by a thin layer of pierced pattern work only attached here and there to the background: the result was often wonderfully vivid and delightful. Marble door frames were set between the columns of the narthex, forming a screen; this, like all such expedients in Byzantine architecture, is done in a perfectly direct and simple manner. Without pretence and without bungling the builders did what was required in a free and great way; but it was done in noble materials under the guidance of a fine tradition. Byzantine architecture at its best gives us a romantic feeling of freedom with a classical sense of order; it followed a law of liberty.

Another typical building is the church of SS. Sergius and Bacchus at Constantinople, built about 526. The plan of the central area is an octagon with semicircular recesses projecting from the alternate sides; there are eight strong piers but the interspaces are set with columns which bear a marble entablature forming a gallery beam which follows the tradition just described. The outer walls form a square, from which to the eastward projects the apse of the bema. The central area is covered by a dome which is protected by leadwork but not by any independent roof. The church of S. Vitale at Ravema closely resembles that of SS. Sergius and Bacchus, but it has hemicycles of columns projecting from every side of the octagon except where the bema opens to the east.

Both these churches were built before Justinian essayed the colossal task at St Sophia, which became one of the greatest building triumphs in the whole history of architecture. The reign of Justinian was a time of astonishing architectural activity; nothing of the kind was to be experienced again, until the twelfth and thirteenth centuries marked, by the erection of countless cathedrals, another flood-time of art. The superb plan of St Sophia must have been led up to by a great number of experiments in smaller churches, many of which have been destroyed unrecorded. The church of Sergiopolis, the ruins of which still exist, has great hemicycles of columns on either side of the "nave," and Wulff has recorded two fragmentary plans from ruined churches at Tralles, one of which had some affinity with the church at Sergiopolis, while the other had a great apse from which five apsidal niches projected.