After the Norman period above described, a distinct change of style is observable. This is prominently seen in the piers and arches of the crossing (see Figs. 233 and 235), which are of an advanced transition style, and appear to have been introduced in lieu of the old Norman piers. Possibly, however, the older piers are preserved and encased in the new. The latter (Fig. 239) are arranged in the form of clustered shafts, approaching first pointed in plan. The bases and caps of the shafts are of transition character, being very like those of Jedburgh Abbey, a good transition example. Some, however, have a tendency to foliage, but all are much damaged. The arches are in distinct orders, like first pointed work, and the inner order of those next the nave and choir is enriched with a large boldly relieved chevron ornament (see Fig. 233). The windows in the choir nearest the main arches of the crossing, and the triforium openings into the transept, appear to have been altered and rebuilt at the time of this operation. The upper part of the north transept was probably raised and its windows inserted at this time, as they are of transition character; but the raising of the south transept and introduction of the rose window in it is of a somewhat later date. This circular window (see Fig. 235) is very similar to that in the east window of the choir. The chapels on the east side of the transept are also of the transition period. Both internally, including the vaulting, and externally, including the pointed windows (see Figs. 229 and 230), the work of these chapels is very advanced transition in style. Of course, it must be understood that the style is referred to, not the date. The transition style may not have penetrated to Orkney till a long time after it had been abandoned further south, possibly not till the middle of the thirteenth century. The space between the south chapel and the choir aisle has been built up and formed into a small vaulted chamber, which has no [Illustration: FIG. 238.--Kirkwall Cathedral. South Doorway of Nave.] opening communicating with the chamber in the south chapel. It enters from a window in the aisle changed into a door. The use of this chamber is unknown. The large windows in the triforium of the transept, adjoining the crossing, are cut across by the aisle roofs. This arises from the aisle roofs having been raised at a late period. The vaulting of the original choir, and the vaulting shafts, with their corbels (see Section, Fig. 226), probably also belong to the transition period. The completion of the nave, as far as the original west wall, was probably next undertaken. The piers (as above mentioned), although round on plan like the original ones, have round moulded caps like those further east. The arches over the piers were, no doubt, executed at the [Illustration: FIG. 239.--Kirkwall Cathedral.]