The entire church is internally encrusted with richly-coloured marbles and gold mosaic, with figures, just as at St. Sophia’s;[65] and the floor is of marble and porphyry tesselation, varying in scale from the most vast slabs to the finest mosaic work. The interior was, no doubt, a joint imitation of St. Sophia’s and the Apostles’ Church, rivalling the former in its sumptuous decoration, and imitating the latter in its plan. To those who have not visited the East, this interior gives a very faithful idea of the splendour of a Byzantine church, and I must say that I have myself seen nothing more impressive (Fig. 441). I will only further (before proceeding to another branch of my subject) notice one other church--the little church of Santa Fosca (Fig. 442), on the island of Torcello, close to Venice. This church is not domed, or has only a wooden dome, but was clearly planned for a proper domical covering. Its plan is like that of St. Nicodemus, at Athens,[66] already alluded to, and is perhaps one of the most beautiful in existence, and one best adapted of all domical arrangements to modern use. Before I proceed farther I must call your attention to a fresh step in advance. [Illustration: Fig. 441.--Longitudinal Section, St. Mark’s, Venice. (_From Fergusson._)] The next step in the development of domes is the adoption of _pointed_ arches for their support, often accompanied by an increase in the height of their own section beyond that of a semicircle. The fact that the pendentive dome is, as it were, suspended in mid-air, so that a perpendicular line dropped from any part of its circumference passes through empty space, renders it imperative that the arches which sustain it in this airy position should be extremely strong, and should have as little outward thrust as possible; and it is equally desirable that the courses of stone forming the pendentives should not form very acute angles with the haunches of these arches. These considerations seem to have led the Mahometan architects soon to substitute _pointed_ arches for _round_ as the supports of their domes; a step in which they were followed at a later period by the greater part of those Western European architects who adopted the pendentive dome. There can be no doubt that this was a very advantageous change. Mr. Fergusson says: “A little reflection ... will show how difficult it is to adapt the curves of a pendentive dome to a circular arch, and how weak the arrangement is when done.... With a pointed arch, however, even when the pendentives follow its lines, there is some thickness in every part, and no curve need slope forward at a greater angle than 45 degrees.” [Illustration: Fig. 442.--Plan, Santa Fosca, Torcello.]