Dome

Dome (Ital. duomo). Since the time of the Renaissance this term is commonly applied to the external part of the spherical or polygonal roof, of which the cupola (cupo, or cup) is the internal part. In Italian usage, however, it has a wider signification than even the first, being used to denote the cathedral or chief church of a town, the house (domus) par excellence, or house of God; and in Germany, dom or domkirche is a cathedral. In tracing the historical origin of the dome, we are usually in the habit of regarding it as originating with the architecture of the Eastern empire, because it was at Constantinople and in the Byzantine provinces that its use in ecclesiastical structures was principally adopted. But it was the Romans who developed the dome, as well as all the other applications of the semicircular arch. Of their success in applying it to large buildings, we have abundant proof in the ancient domes still to be seen in Rome and its neighbourhood. The dome of the Pantheon is still probably the most magnificent dome in existence, and others of smaller size are to be seen in the temples of Bacchus, Vesta, Romulus, Hercules, &c. From Rome it went to Constantinople, and from the same source, also, according to Fergusson, came the few insignificant attempts at domes in the Western empire. The external form of the dome of the church of St Sophia at Constantinople, which became the typical Christian structure of the kind, will be seen in the illustration appended to BYZANTINE ARCHITECTURE (see also ARABIAN ARCHITECTURE, and the illustration of the Taj Mahal at AGRA). The dome of San Vitale, at Ravenna (q.v.), is said to be still more ancient than that of St Sophia, and is a very remarkable structure of the same class. On the church of St Mark, at Venice, there are no less than five domes, the centre one, as is usual in Eastern structures, being much larger than the others. The interior of these domes is covered with Mosaics (q.v.). So far from being peculiar to the few churches we have mentioned, domes occur in those of almost every town along the western shore of the Adriatic, and form, in fact, the chief architectural feature of that side of Italy. From St Mark's the dome was introduced in the 11th century into Périgueux in the south of France, and thus influenced the architecture of a considerable part of that country. The construction of domes in modern times was revived in Rome, by the building of that of Our Lady of Loretto in 1507. But the three most celebrated modern domes are those of St Peter's (q.v.) at Rome, of St Paul's in London, and of the Pantheon in Paris. The following are the dimensions of some of the most important existing domes:

In modern times, domes have been constructed with iron of still larger dimensions. Thus that of the Great Exhibition in Vienna was 360 feet in width, and that of the Albert Memorial Hall in London, which is oval, measures 219 by 185 feet in diameter. For a class of ancient dome-roofed structures, see BEEHIVE HOUSES.