The #North Transept# is most interesting. Its west wall contains two round-headed windows with billet moulding, the northern one blocked up; and at the north-west corner is a cluster of cylindrical shafts running up to about the same height as the walls of the aisle. Why they terminated here it is hard to say; they may mark the termination of the original Norman wall. This wall may not have risen above this height, or the upper part may have been taken down and rebuilt when the large Perpendicular window was inserted in the north end of the transept. At the north-east corner of the transept stands a richly-ornamented turret of Norman date. Round the lower part of this the arcade of intersecting arches which runs round the whole transept is carried; above this, round the turret, runs an arcading of semicircular-headed arches springing from pairs of shafts; above this the wall is decorated with diaper work; and finally, another arcading, this time of round-headed arches rising from single shafts, encircles the turret. The turret is capped by a sloping roof of stone attached to the transept wall. This turret is worthy of close attention, because it shows how the Norman builders hated monotony; each stage has its own decoration unlike that of any other; and, moreover, there are variations in the shafts of the arcading--some are plain, some decorated in one way, some in another. The same love of variety may be seen here that lends so great a charm on a larger scale to Flambard's glorious nave at Durham. No doubt this north transept had attached to its east wall an apsidal Norman chapel similar to that which still exists on the eastern side of the south transept, but this had to make way for an addition of two chapels, which we may assign, from the character of their architecture, to the latter end of the thirteenth century. The northern chapel is lighted by a three-light window with three foliated circles in the head, which is rather sharp pointed, and the southern one by a two-light window with one foliated arch. These are beautiful examples of plate tracery. Above these chapels is a small chamber lighted by a window of similar character. This is supposed to have been the tracing room, where the various architectural designs for the building were drawn.