Domes
The dome was supported on four piers, united by arches, and the change in plan from these piers to the dome necessitated vaultings from the inner angles to reconcile the diagonal dimension to the diameter of the imposed circle. These vaultings spreading from the angles are technically known as Pendentives. The
No. 35. Byzantine. Section and plan of St. Vitali, Ravenna.
No. 36. Byzantine Capitals from Ravenna.
four arms of the cross constituting transepts, nave and chancel were also surmounted by either complete or semi-domes.
The Byzantine dome differs from the Roman type in matters of detail, thus the interior surface is plain instead of the intersecting ribs with resulting coffers as in that of the Pantheon. In this latter the lighting of the interior is accomplished by a central opening or eye, but in some Byzantine examples, notably St. Sophia (built for Justinian by Anthemius) the lighting is the result of windows ranged round the base, constituting what is known as the ariel type of dome.
The dome of St. Sophia is segmental instead of hemispherical as in the Pantheon, being only one-sixth of the diameter in height, the diameter being 106 ft. 7½ ins.
The architectural features generally were considerably modified, particularly with regard to mouldings, which were almost eliminated. The entablature was also at times dispensed with, and arches springing direct from the capitals of supporting columns were general; a feature which is characteristic of the later Romanesque. The capitals became simple in form, being mostly inverted pyramidal or cushion shapes, in which the abacus is considerably enlarged and as a rule unmoulded.
The carved details reveal simplicity of execution, being merely cut back from the surface, the relief being uniform and greatly in contrast to the plastic feeling of the Roman work. Though the leaves employed were of the acanthus type, they were quite devoid of modelling, being merely channelled with V-shaped grooves; the eyes between the lobes being round and suggestive of the use of the drill, the execution being a reversion to the archaic Greek.
No. 37. Byzantine Panels. St. Appollinare, Nuovo, Ravenna.