Clustered columns of unpolished Purbeck marble on a quatrefoil plan, with smaller detached shafts of lustrous marble at the cardinal points, support, on either side, the ten great arches of the first story of the nave. These polished shafts are generally in two pieces, with a brass ring covering the joint; Francis Price discusses, at great length, this constant feature of the whole building, and points out, that although most of the shafts were probably not in place until after the masonry was fairly set, yet frequently subsequent settlement has crushed them; although, in the nave, the main piers in small blocks laid according to the natural bed of the stone, are still perfectly sound. The large arches are gracefully moulded with masses of carved foliage at the intersections. [Illustration: THE NAVE--SOUTH SIDE.] In the nave of this cathedral we have a very uncommon feature in the connected base of the main columns, which was doubtless introduced to aid in distributing the weight over a larger surface, and so to overcome the treacherous character of the foundation. The triforium, which, from its style, naturally suggests comparison with Westminster, and the Angel Choir of Lincoln, is simple, but extremely beautiful. Each of its rather flat-pointed arches, equalling in span that of the main arch below, is subdivided into pairs, which again each inclose two smaller ones. These are decorated with trefoils and quatrefoils, alternately with cinquefoils and octofoils. Immediately above the carving, at the intersection of the main arches, is a corbelled head, from which rises a triple vaulting-shaft with foliated capitals, on a line with the base of the clerestory. This upper story has, in each bay of the vaulting, simple lancet windows grouped in threes. The arches here, as in almost every instance throughout the building, are supported by Purbeck marble shafts. The nave aisles are lighted by double lancet-windows in each bay. The most noticeable feature of these aisles is the stone bench which extends the whole length of the building on both the north and south sides. [Illustration: NORTH AISLE.] The west wall is panelled in three main arches, with an upper story reaching to the height of the triforium base, and containing an arcade of four arches, subdivided each into two smaller trefoiled ones, with cinquefoil heads. Above these is the triplet lancet of the great west window. The effect of the nave looking west is clearly shown in the photograph here reproduced.