The interior of the towers is more richly treated than is usual. Over the tower-arch is a small arcade of four members with clustered shafts, and with a string below, while the other three walls are plain up to the windows, each of which is flanked, as on the exterior, by two blind lancets. The arcading thus formed has clustered and banded shafts (not detached), behind which ran a passage, now blocked, and below the sill, and a little distance apart, are two strings, to the lower of which the sills of all the windows save two descend in steps. The windows are not splayed, and those which now look into the aisles are unglazed, and their flanking lancets are of unequal width. All the arches are much moulded and ornamented with the dog-tooth, and the central shaft of each cluster has a fillet. In each corner a detached shaft springs from a round corbel above the lowest string and rises to the impost of the arches, being banded twice on the way; and from its capital another shaft runs up to the ceiling. The doors to the spiral staircases open into little square lobbies which have vaults with groin-ribs springing from corbels.[56] In the north tower is a modern stained window of some merit. The two bays of Archbishop Roger's work incorporated in the towers, taken together with another Transitional bay at the east end, make it possible to imagine the whole interior of what must have been the most remarkable nave in England. It was unusually broad. From the ground to the first string (about 16 feet) there was plain wall. Above this was a triforium (if it can be so called[57]) of the unusual height of about 28 feet, and there were thus no windows except in the clearstorey, and there only in alternate bays. According to Sir Gilbert Scott the triforium and clearstorey were probably continued across the west wall. The bays were alternately broad and narrow, and there is room for five of each sort. The westernmost bay shows in the triforium stage a round arch comprising four pointed arches. Of these the two in the middle are raised above the others on shafts of two stages, in the upper of which the capital is circular and its moulding is continued along the tympanum to the _apices_ of the two lower arches. The tympanum is relieved by a sunk quatrefoil in a serrated circle, and so is the space under either of the two central sub-arches. The passage in this bay has been built up, and the bay itself shortened, probably when the tower arches were made. [Illustration: CONJECTURAL PLAN OF ARCHBISHOP ROGER'S CHURCH BY SIR G. G. SCOTT. See _p._ 16. (By permission of the Archaeological Institute.)] In the adjoining narrow bay, the comprising arch is pointed, there are only two sub-arches, and there are no quatrefoils, except in the tympanum on the north side. Doors have also been inserted in this bay to communicate with the passages behind the arcades in the towers.