(5) The tower S is later than the tower N, for their common wall, H, is strictly the north-eastern side of the tower N, as the similarity of the masonry of H to that of the other sides of N makes perfectly plain. This similarity is manifest not only in the general features of the work, but also in the insertion of marble shafts into the wall H; in one instance partially, after the odd fashion adopted so extensively in the open sides of the tower N. Furthermore, the manner in which the walls of the chamber F and the L-shaped chamber in the tower S impinge upon the wall H shows that the former were built against the latter, and that they are posterior in age. (6) The stairway-turret E, as the loopholes in its sides prove, stood, at one time, in the open light and air. If so, it must be older than the apartments _b_, F, L, in the tower S, which enclose it. (7) The passages communicating between the stairway and the chambers in the tower N render it almost certain that the stairway-turret was constructed at the same time as that tower. Thus, also, a short and private way from the Palace of Blachernæ to the country beyond the city bounds was provided; for it may be confidently assumed that at the foot of the stairway there was a small gate, corresponding to the gate _l_, and the postern _x_ at the mouth of the tunnel Z. (8) When the stairway-turret was enclosed by the vestibule _b_, the chamber F, and the =L=-shaped chamber, the lower loopholes of the turret were built up as superfluous, while the upper ones were widened to form entrances to the L-shaped chamber. Accordingly, the tower S is an old stairway-turret enclosed within later constructions. (9) In view of some great danger, access to the tower S from without the city was blocked by building up the postern _x_, the tunnel Z, the gate _l_, and the vestibule _b_, to their actual level. The portion of the passage still left open was too narrow to be forced by an enemy, and yet was convenient to be retained for the sake of ventilation, or as a way in and out in some emergency. At the same time, a breach was made in the wall _g_ to place the elevated floor of the vestibule into communication with the stairway-turret E. (10) What precise object the chambers C in the body of the city wall were intended to serve is open to discussion. In the opinion of Dr. Paspates, who was the first to explore them, they were prison-cells. Possibly the lowest series of these chambers may have been employed for that purpose; but, taken as a whole, the suite of apartments between AA and BB do not convey the impression of being places of confinement. Their spaciousness, their number, the free communication between them, the size of the windows in the two upper stories, the proximity of the windows to the floor, are not the characteristics of dungeons.