The main piers consist of a circular column, five feet in diameter, with smaller attached half-columns on three sides to carry the moulded arches between the main piers and the arches between the latter and the aisles. The piers have caps of the usual Norman modified cushion pattern, and the arches were moulded and arranged in several orders. The arcade immediately over the main arches has a row of single round shafts, with spreading Norman caps, which carry a series of moulded arches, occupying the position of the triforium. The upper arcade, which takes the place of the clerestory, has shafts of triple form, with wide-spreading bases and caps of Norman and transition design. On the latter rest the round boldly-moulded arches. The arches opposite the windows in the outer wall are slightly larger than the others. It will be observed that there is no main vaulting shaft carried up over the main piers, as is almost invariably the case, for the purpose of strengthening the wall. On the contrary, the triforium arcade is continuous, and no provision is made to support the side wall, except the single shafts of the running arcade, which have a very weak effect. In the usual arrangement the triforium arches are separated by a substantial piece of wall, including a vaulting shaft, and the triforium arch, which is generally subdivided into several subordinate arches, is introduced between the vaulting shafts. That is a much more substantial form of construction, and also more satisfactory to the eye, than the plan adopted here of a simple continuous arcade. [Illustration: FIG. 317.--Kelso Abbey. North End of Transept.] The clerestory is designed on the same principle as the triforium, and consists of a continuous arcade, without the interruption of the vaulting shafts. In the view of the exterior of this portion of the choir (Fig. 313), the outside of the windows of the clerestory is visible, being simple round-headed openings, with flat buttresses between them. The remainder of the wall is plain, but, judging from the level of the triforium window, the vaulting of the aisle, which was very high, and partly covered the windows, seems to have been added at a later date. The choir was 28 feet in width from centre to centre of the piers, only two of which survive. The crossing is square, and measures 28 feet from centre to centre of the piers; but of these the north-east one is wanting. The piers are about nine feet square, that at the south-east angle standing detached in consequence of the opening into the south aisle, while those at the north-west and south-west angles are incorporated with the walls.