[105] Constant. Porphyr. pp. 87-88. [106] Similar to the parakypticon at the east end of the southern gallery in S. Sophia. Reiske (_Comment. ad Constant. Porphyr._ p. 195) defines it as 'Fenestra, quae in sacrificatorium despicit e catechumeniis.' Cf. on the whole subject, Antoniadi, [Greek: Ekphrasis tês Hagias Sophias], vol. ii. p. 291, note 101; p. 331, note 190; p. 332. [107] The plan of SS. Sergius and Bacchus is similar to that of the cathedral of Bosra (511-12), which was also dedicated to the same saints. Fergusson, _History of Ancient and Mediaeval Architecture_, vol. i. p. 432. [108] Gyllius, _De Top. C.P._ ii. c. 16. If the design represented vine leaves and grapes, it surely did not allude to the god Bacchus, but to the vine in the gospel of S. John. The small columns on the piers are Turkish. [109] Antoniadi, _S. Sophia_, vol. ii, pp. 7-9, draws attention to the development of buildings with sides turned into exhedrae, from their simplest form to their culmination in S. Sophia. He refers for illustrations to plans in Dehio und Bezold, _Die kirchliche Baukunst des Abendlandes_, vol. i. pp. 23-31; _Atlas_, vol. i. plate i. figures 1, 2, 3, 4, 7; plate iii. figures 1, 2, 7. [110] C. Diehl, _Theodora_, pp. 242, 342. [111] The ratio of the height of the gallery above the floor of the church to the height of the summit of the dome is, according to Antoniadi, 1/3.5, the same as in S. Sophia as built by Anthemius. [112] 'Pulvins,' says Rivoira (_Lombardic Architecture_, p. 11, English translation), 'serve the purpose of providing the springers of the arches with a base corresponding to the wall which they carry, while allowing the support beneath to be much slighter without injuring the stability of the structure.' [113] Rivoira, _ut supra_, p. 62: 'The volutes in the Pseudo-Ionic capital intended to conceal the abruptness of the transition from the square of the pulvin to the round.' [114] _De aed._ i. p. 187. [115] 'The centres of the radii of these concave compartments are formed by having three points given the groins on either side and the angle of the octagon in the centre. With these points for each compartment the radius is given, and an arc turned giving the concavity required for each web at its springing.'--A. E. Henderson in the _Builder_, January 1906, p. 4. [116] In S. George of Ezra in Syria (515), as Mr. E. M. Antoniadi informs me, the dome overhangs or oversails the angles of the octagon.