Before leaving the chamber the explorer should notice the shaft of a pillar which protrudes from the south-western wall, like the shafts of the pillars built into the open sides of the tower N. Returning once more to the vestibule _b_, we proceed to the breach in the wall _g_, and enter E. That the breach was made on a systematic plan is clear from the half-arch _f_, which was constructed to support the building after the wall _g_ had been weakened by the opening made in it. E was a stairway-turret, in which an inclined plane, without steps, winded about the newel, _e_, upwards and downwards. The turret is filled with earth to the present level of the vestibule _b_, so that one cannot descend the stairway below that point; but there can be no doubt whatever that the stairway conducted to the original floor of the vestibule _b_, and to the gateway _l_, and thence to the tunnel and postern in the counter-fort. Whether it led also to an entrance to the chambers C C C cannot be discovered under existing circumstances. The object of the breach in _g_ was to establish communication between the stairway, the vestibule _b_, and the tunnel Z, after the original means of communication between them had been blocked by raising the floors of the tunnel and the vestibule to their present level, in the manner already described. The stairway winds thirteen times about its newel, and ascends to within a short distance of the summit of the turret. The summit was open, and stood on the level of the court of the Palace of Blachernæ; but the opening could be reached from the stairway only by means of a ladder removable at the pleasure of the guardians of the palace, and was, doubtless, closed with an iron door for the sake of greater security. The walls of the turret were pierced by four loop-holes; two, placed one above the other, looking towards the north-west, and two, similarly arranged, facing the north-east. Those on the lower level are closed, but the two higher ones have been enlarged, and admit to the fine =L=-shaped chamber in the upper story of the tower, the chamber above F and the vestibule _b_. [Illustration: The =L=-Shaped Chamber in Upper Story of Tower =S=.] The chamber measures some 39 feet by 33 feet, and was lighted by a large square window in the north-western wall. A circular aperture in the floor communicated with F; and a corresponding aperture in the vaulted ceiling opened on the roof of the tower. The walls are furnished with numerous air-passages, to prevent dampness, and are covered with a thin coating of plaster. The vault of the ceiling, if we may judge from the small cavities for joists below the spring of the arch, was concealed by woodwork. Indeed, a portion of one of the cross-beams is still in its place.