From the time of Constantine to that of Justinian, one hundred and fifty years, is a period of formation. Under the reign of Justinian, Byzantine art reached its height. Prominent among its factors is the use of mosaic, the influence of which spread insidiously through its whole system, until in the later work the cornices and entablatures of classic design withered into long thin lines of moulding; projections which disturbed the effect of color by the shadows they cast were discarded; voussoirs disappeared under a mosaic veil; surfaces resolved themselves into broad expanses of infinitely varied tones, bounded by narrow but strongly contrasting bands and borders of marble. All ornament had resolved itself into surface decoration, or as nearly that as possible. In 539 Belisarius took Ravenna in the name of the Emperor Justinian, and to celebrate this event Justinian decided to erect a magnificent monument in the city. He chose to replace, by a more important structure, the small church dedicated to S. Vitale, and built by Neon in the reign of Theodoric. The wonderful basilica of Sta. Sophia at Constantinople was just completed, and the novelty of its plan and immense effect Produced by its dome, a method of construction entirely novel in Roman architecture, doubtless excited the admiration of the Emperor and led to the adoption of a similar plan for S. Vitale. S. Vitale 18 by no means a copy of Sta. Sophia, but unquestionably was strongly influenced by it. It was founded in 540, and consecrated in 547. It is octagonal in plan, with an inner structure of eight large piers, arranged in a circle, connected by arches which support a pendentive dome. Following the custom then in vogue, its interior is incrusted throughout with elaborate mosaics in a wealth of color. The most elaborate design and richest color is used in the apse, which was the centre of display in all Byzantine churches. [Illustration: XXI. Capital from the Apse of the Church of S. Vitale, Ravenna, Italy.] XXI. CAPITAL FROM THE APSE OF THE CHURCH OF S. VITALE, RAVENNA, ITALY. This is one of the most beautiful and most characteristic capitals of the Byzantine style. Its form and decoration are both typical of the style. The flat treatment of the interlace of the vine motive is very generally used, and can be seen in great variety in S. Vitale and elsewhere. The ornament is here enriched with gold and color. In the double capitals of Ravenna the upper member, or cushion, is usually ornamented with symbolic designs drawn from various sources, both Pagan and Christian. [Illustration: XXII. Capital from the Church of S. Vitale, Ravenna, Italy.] XXII. CAPITAL FROM THE CHURCH OF S. VITALE, RAVENNA, ITALY. Here again is the rhomboidal double capital of a much more severe design than that of the preceding plate, but with a remarkable delicacy and refinement of treatment. [Illustration: XXIII. Capital from the Church of S. Vitale, Ravenna, Italy.] XXIII.