I will now proceed with my subject. After the Church of the Holy Wisdom, all subsequent domed churches of the Byzantine class seemed to shrink from a hopeless competition, and to content themselves with moderate dimensions. Among those remaining at Constantinople, that of St. Irene (Fig. 426) perhaps comes next in date. Its central dome, like that of St. Sophia (Fig. 427), is flanked by arcaded aisles, which, however, do not extend to the vaulting, but simply carry galleries. These wings, therefore, as well as the eastward extension, are covered by barrel vaults, the latter being terminated by a semi-domical apse--while westward is a second dome, like the central one in plan, excepting that, being less in dimension east and west, its base is an ellipse instead of a circle. The actual domes, however, differ much more widely; for, while the western one is a flat disc continuing the surface of its pendentives, the central dome is raised above them on a high drum pierced like a clerestory with many windows. [Illustration: Fig. 426.--St. Irene.] [Illustration: Fig. 427.--St. Sophia.] The Church of the Holy Theotokos, or of the Mother of God, is of much later date. The church proper has but a single dome of any importance, though there are several others over the narthex (Fig. 428). This dome covers the intersection of two barrel-vaults, is supported simply on four columns, and rises high above its pendentives on a drum pierced by windows (Fig. 429). The architecture of this church is very elegant, differing in date, it is probable, but little from that at St. Mark’s at Venice. Others do not differ sufficiently from these types to make it worth while here to describe them. It may, however, be mentioned that in the later Greek churches the domes, or some of them, rose often so high as to become rather elegant towers, arcaded externally. This is the case with several of the churches at Athens. [Illustration: Fig. 428.--Plan, Church of the Holy Theotokos.] [Illustration: Fig. 429.--Section, Church of the Holy Theotokos.] [Illustration: Fig. 430.--Plan and Section, St. Nicodemus, Athens.] Among the churches of that city we find one type of great elegance, the Church of St. Nicodemus (Fig. 430), in which the dome occupies the width of what we should call the nave and its aisles; each side of the square over which it stands being divided into three unequal arches, over which it rises on a lofty drum, and is carried on eight pendentives. This forms a most elegant interior, susceptible of many varieties; and, from the spacious central space which it affords, seems the most valuable type on which to found a domed design for a modern church.