“Now when they were going to build the thysiasterium and let in the light through glass windows, the Deviser (_mechanikos_) suggested that the apsoid (_muax_) should have one light. Then he changed his mind, and suggested that it should have two, so that it should not be heavy, because no wooden ties (_ikriomata_) were placed there as in the narthex, and on the sides of the church. But the rest of the craftsmen were opposed, saying that one arch (_kamara_) would light the holy place. Then the chief builder (_protooikodomos_) was at a loss what to do, because the emperor said at one time that there should be one arch (_apsis_), and at another time two. Whilst the master (_maistor_) was thus pondering and anxious, on the fourth day, at the fifth hour, appeared an angel of the Lord, like the emperor, with royal robes and red shoes, and said to the craftsman, ‘I will that there be a triple light, and that the conch be made with three windows,[223] in the name of the Father, the Son, and the Holy Ghost.’ He then disappeared quickly. Then the master, struck with wonder, rushed to the palace, and said to the emperor, ‘You keep not to your word. Until to-day you wanted one window, and then two, to light the bema; but now, when the work is all but finished, you come to me and say, three windows shall light the bema, as a symbol of the Trinity.’ Now the emperor knew that day that he had not left the palace, and he recognised that an angel of the Lord had spoken. He said, ‘As I have bidden thee, so do.’ “All the piers (_pessoi_) inside and outside were made strong by iron bars (_mochloi_), so that they were bound together, and made immovable; the joints of the piers were made with oil and _asbestos_; and upon them was placed a plating of many marbles (_orthomarmarosis_). “The emperor sent Troilus the Cubicular, Thedosius the Prefect, and Basilides the Quaestor, to Rhodes to have bricks (_besala_) of Rhodian clay, made all equal in weight and length, with the words engraved on them, ‘God is in the midst of her, therefore shall she not be moved; God shall help her, and that right early.’[224] And they sent bricks of measured sizes to the emperor, twelve of them weigh one of ours; for the clay is light, spongy, fine, and white; hence arose the common idea that the dome is built of pumice stone (_kiserion_); but this is not so, though it is light and of a white colour.