Wulff is of opinion that the letters were originally filled in with lead, and, from the evidence of this lead infilling, dates the church as late as the fifteenth century. But it is equally possible that the letters were marked out by drill holes which were then connected with the chisel, and that the carver, pleased by the effect given by the sharp points of shadow in the drill holes, deliberately left them. The grooves do not seem suitable for retaining lead.
In the course of their history both churches were altered, even in Byzantine days. The south church is the earlier structure, but shows signs of several rebuildings. The irregular narthex and unsymmetrical eastern side chapels are evidently not parts of an original design. In the wall between the two churches there are indications which appear to show the character of these alterations and the order in which the different buildings were erected.
[Illustration: PLATE XXXV. (1) S. MARY PANACHRANTOS. EAST END OF THE SOUTH CHURCH. (2) S. MARY PANACHRANTOS. EAST END OF THE NORTH CHURCH. _To face page 132._]
As has already been pointed out, the north side of the ambulatory in the south church, which for two-thirds of its length is of practically the same width as the southern and western sides, suddenly widens out at the eastern end and opens into a side chapel broader than that on the opposite side. The two large piers separating the ambulatory from the central part of the north church are evidently formed by building the wall of one church against the pre-existing wall of the other. The easternmost pier is smaller and, as can be seen from the plan, is a continuation of the wall of the north church. Clearly the north church was already built when the north-eastern chapel of the south church was erected, and the existing wall was utilised. As the external architectural style of the three apses of the south church is identical, it is reasonable to conclude that this part of the south church also is later in date than the north church. For if the entire south church had been built at the same time as the apses, we should expect to find the lateral chapels similar. But they are not. The vaulting of the central apse and of the southern lateral chapel are similar, while that of the northern chapel is different. On the same supposition we should also expect to find a similar use of the wall of the north church throughout, but we have seen that two piers representing the old wall of the south church still remain. The narthex of the south church, however, is carried up to the line of the north church wall.