A Text-Book of the History of Architecture / Seventh Edition, revised

by A. D. F. Hamlin

FIG. 71.—DIAGRAM OF PENDENTIVES.

DOMES. The dome, as we have seen, early became the most characteristic feature of Byzantine architecture; and especially the dome on pendentives. If a hemisphere be cut by five planes, four perpendicular to its base and bounding a square inscribed therein, and the fifth plane parallel to the base and tangent to the semicircular intersections made by the first four, there will remain of the original surface only four triangular spaces bounded by arcs of circles. These are called pendentives (Fig. 71 a). When these are built up of masonry, each course forms a species of arch, by virtue of its convexity. At the crown of the four arches on which they rest, these courses meet and form a complete circle, perfectly stable and capable of sustaining any superstructure that does not by excessive weight disrupt the whole fabric by overthrowing the four arches which support it. Upon these pendentives, then, a new dome may be started of any desired curvature, or even a cylindrical drum to support a still loftier dome, as in the later churches (Fig. 71 b). This method of covering a square is simpler than the groined vault, having no sharp edges or intersections; it is at least as effective architecturally, by reason of its greater height in the centre; and is equally applicable to successive bays of an oblong, cruciform, and even columnar building. In the great cisterns at Constantinople vast areas are covered by rows of small domes supported on ranges of columns.

The earlier domes were commonly pierced with windows at the base, this apparent weakening of the vault being compensated for by strongly buttressing the piers between the windows, as in Hagia Sophia. Here forty windows form a crown of light at the spring of the dome, producing an effect almost as striking as that of the simple oculus of the Pantheon, and celebrated by ancient writers in the most extravagant terms. In later and smaller churches a high drum was introduced beneath the dome, in order to secure, by means of longer windows, more light than could be obtained by merely piercing the diminutive domes.

Buttressing was well understood by the Byzantines, whose plans were skilfully devised to provide internal abutments, which were often continued above the roofs of the side-aisles to prop the main vaults, precisely as was done by the Romans in their thermæ and similar halls. But the Byzantines, while adhering less strictly than the Romans to traditional forms and processes, and displaying much more ready contrivance and special adaptation of means to ends, never worked out this pregnant structural principle to its logical conclusion as did the Gothic architects of Western Europe a few centuries later.

DECORATION. The exteriors of Byzantine buildings (except in some of the small churches of late date) were generally bare and lacking in beauty. The interiors, on the contrary, were richly decorated, color playing a much larger part than carving in the designs. Painting was resorted to only in the smaller buildings, the more durable and splendid medium of mosaic being usually preferred. This was, as a rule, confined to the vaults and to those portions of the wall-surfaces embraced by the vaults above their springing. The colors were brilliant, the background being usually of gold, though sometimes of blue or a delicate green. Biblical scenes, symbolic and allegorical figures and groups of saints adorned the larger areas, particularly the half-dome of the apse, as in the basilicas. The smaller vaults, the soffits of arches, borders of pictures, and other minor surfaces, received a more conventional decoration of crosses, monograms, and set patterns.

FIG. 72.—SPANDRIL. HAGIA SOPHIA.

The walls throughout were sheathed with slabs of rare marble in panels so disposed that the veining should produce symmetrical figures. The panels were framed in billet-mouldings, derived perhaps from classic dentils; the billets or projections on one side the moulding coming opposite the spaces on the other. This seems to have been a purely Byzantine feature.

CARVED DETAILS. Internally the different stories were marked by horizontal bands and cornices of white or inlaid marble richly carved. The arch-soffits, the archivolts or bands around the arches, and the spandrils between them were covered with minute and intricate incised carving. The motives used, though based on the acanthus and anthemion, were given a wholly new aspect. The relief was low and flat, the leaves sharp and crowded, and the effect rich and lacelike, rather than vigorous. It was, however, well adapted to the covering of large areas where general effect was more important than detail. Even the capitals were treated in the same spirit. The impost-block was almost universal, except where its use was rendered unnecessary by giving to the capital itself the massive pyramidal form required to receive properly the spring of the arch or vault. In such cases (more frequent in Constantinople than elsewhere) the surface of the capital was simply covered with incised carving of foliage, basketwork, monograms, etc.; rudimentary volutes in a few cases recalling classic traditions (Figs. 72, 73). The mouldings were weak and poorly executed, and the vigorous profiles of classic cornices were only remotely suggested by the characterless aggregations of mouldings which took their place.