An interesting lateral branch of Byzantine architecture is seen in the monasteries erected by Coptic Christians in Egypt, in the 6th-9th centuries, recently explored by the Metropolitan Museum of Art of New York. The domes and surface-carvings of these buildings strongly in fluenced the development of the Arabic art of Cairo. The great mosque at Jerusalem, known as that of Omar (more properly the Dome of the Rock, Kubbet-es-Sakrah) is probably a re construction of the church built on Mount Moriah by Justinian. The decline in the size and splendor of the Byzantine churches built after the 6th century was due to the slow decay of the empire itself in both political and military prestige and power. Those erected in Greece and the Danubian provinces were often of almost microscopic size. The Cathe dral* at Athens measures 37 by 32 feet; the dome of another church in the same city is but seven feet in diameter. Many of the later churches have three apses, one at the end of each aisle; and in all the examples after the 7th century the dome is carried on a high drum pierced with windows, forming a ((lantern,* whereas in the earlier churches the windows penetrate the base of the dome itself. Another innovation was the introduction, into the wall of the main structure, of arched windows coupled in pairs under a discharging arch, often with a mullion or midwall shaft •between the two. This feature, together with the central lantern or high cupola over the crossing, was adopted by the Romanesque church-builders of Italy and France in the 11th and 12th centuries, and both became important features in the Western Romanesque style. The partial copying in France of Saint Mark's, and perhaps of Hagia Eirene, at Perigueux and Cahors has been re ferred to. Besides these there are in Aquitania and in the valleys of the Loire and Charente a large number of domed churches of the 12th century due to Byzantine influence, partly by way of Venetian commerce, partly (according to Enlart) by way of Cyprus where the Crusad ers established important Latin Christian com munities.
Of the Byzantine secular architecture there are hardly any remains. Doubtless the palaces of the emperors were of great splendor, but the only extant ruin of any importance is that of the palace of the Porphyrogenitus near the Blachernw at Constantinople, of which the walls of the great hall are still standing, but with no vestige of its interior decoration. The vaulted cisterns of the city are still intact, and at Ravenna the front wall of the so-called pal ace of Theodoric. There are a number of Byzantine fortifications in ruins in various cities of the empire, and Byzantine military architecture was of great importance; but these examples are so ruinous or have been so often and so completely rebuilt in later ages that further notice in this article is unnecessary.
Bibliography.— The best general handbook of Byzantine architecture in English is by Sir T. G. Jackson, 'Byzantine and Romanesque Architecture' (Cambridge 1913). There are excellent accounts of the style in F. M. Simp son's (A History of Architectural Develop ment) (Vol. I, London 1911) ; in R. Sturgis'
of Architecture) (New York 1901), and in Vol. II of his