The ideal of each is a cross with a central dome. The difference is that in the Church of the Apostles the limbs of the cross were each covered by a complete dome of equal dimensions with the central one (Fig. 422), while those of St. Sophia are covered each by a semi-dome only of equal diameter with the arches carrying the central dome ([Fig. 423]); so that if we consider the latter to spring from the top of its pendentives, which it in effect does, its springing is on a level with the crown of the surrounding semi-domes.
| Fig. 422. Church of the Apostles. | Fig. 423. St. Sophia. |
In reality, however, this idea is not carried out to completion, as only two of the semi-domes have been erected, the other two arches of the central dome being filled in with an arcade in many storeys. This incompleteness, however, is greatly more than compensated—firstly, by the vastness of the scale—the central dome, if measured on the diagonal, being 150 feet in diameter—and, secondly, by other semi-domical projections branching out from the walls which support the great semi-domes, three from each, excepting that on the western side, one is devoted to the entrance, and is not domed. Even these secondary projections are mostly arcaded, so as to allow the eye to pass onward into a yet inner chamber ([Fig. 424]). So that, simple as is the primary ideal, the actual effect is one of great intricacy and of continuous gradation of parts, from the arcades last alluded to, up to the stupendous dome which hangs with little apparent support, like a vast bubble, over the centre, or, as Procopius, who witnessed its erection, described it, “as if suspended by a chain from heaven.”
Fig. 424.—Plan, St. Sophia, Constantinople. (From Fergusson.)
The dome is lighted by forty small windows, which pierce it immediately above the cornice which crowns its pendentives, and which, by subdividing its lower part into narrow piers, increases the feeling of its being supported by its own buoyancy.
The interior thus generated, covered almost wholly by domes, or portions of them, each rising in succession higher and higher towards this floating hemisphere in the centre, and so arranged that one shall open out the view towards the others, and that nearly the entire system of vaulting may be viewed at a single glance, appears to me to be, in some respects, the noblest which has ever been designed, as it was certainly the most daring which, up to that time at least, if not absolutely, had ever been constructed.