Twenty inches above these crowns is a plain chamfered stringcourse, and upon this the arcade of the triforium, each arch being exactly above, and of the same diameter with, that below. These arches spring from piers 30 inches square, and 4 feet 3 inches high, without either base or cap. As the apsidal arches are not stilted, the piers are taller, so that the crowns still range. The nave roof is a barrel vault, commencing imperceptibly at the crown level of the triforial arches, and ending eastwards in a semi-dome. The height to the crowns of the nave arches is 13 feet 6 inches, to those of the triforium 23 feet 9 inches, and to the crown of the vault 32 feet. The vault abuts against the west wall, in which is a plain round-headed recess, 18 inches deep, 12 feet diameter, and 13 feet 6 inches high. The aisle is 6 feet 6 inches broad. Opposite to each nave column is a flat pilaster, advanced three steps from the wall surface, and having a plain chamfered abacus, or string-cap, and from each springs a broad flat rib. The aisle is thus divided into thirteen bays, four on each side, and five in the chevet, the sides of these latter being convergent. Each bay is hip-vaulted, the vaults being groined, and entirely in rubble work. The aisle is 13 feet 6 inches high. The wall of each bay is recessed, and the recesses form an arcade. In the southern recesses are four windows, of which two open between, and two upon the exterior pilaster strips. Four of the five apsidal bays also have windows, one being to the east. There are two doors: one in the north aisle, opening into the eastern room on the third stage of the keep, and one in the west wall of the south aisle, leading by a short mural gallery to the well-stair in the south wall, and into the great or western chamber of the keep. The triforium is 7 feet 6 inches diameter. It is a mere plain gallery, without pilasters, stringcourse, or moulding of any kind, 8 feet high to the spring of its side barrel-vault, which gives 3 feet 9 inches more. In its south wall are three windows, one opening in the face of an outer pilaster; and in the apse are five. In the north wall, and at the west end of the south limb, are the openings of the mural gallery which surrounds the keep at this, the council-chamber level; the chapel, as has been stated, rising through the two upper stories to the roof. The walls of the aisle are 4 feet thick; of the west and east ends, 5 feet. Of the triforium, the north, south, and east walls are 4 feet, and the west wall 5 feet 6 inches thick.