The choir and aisles were roofed with fine groined vaulting. That of the side aisles was simple, but the vault of the choir was ornamented with ridge ribs and several intermediate ribs, or tiercerons, springing from vaulting shafts, supported on corbels and provided with carved caps, and all the vaults were studded with carved bosses. The effect of the vaulting of the apse was specially beautiful. Each bay of the choir had clustered piers (Fig. 1017), with finely carved capitals. Above these was a string course, then a piece of plain wall in the space usually occupied by the triforium, and the whole was crowned with the traceried clerestory [Illustration: FIG. 1017.--Trinity College Church. Piers of Choir.] windows. A good general view of the interior, taken a short time before its destruction, is given by Billings.[52] Owing to the removal of the building, it has been impossible to make original illustrations for this work, but we are fortunate in being able to publish copies of a series of sketches made by the late James Drummond, R.S.A., in 1845. These picturesque sketches give a good idea of the nature of the structure, both internally and externally. Fig. 1018 is a view of the exterior of the south side of the choir, showing the three bays into which the aisle was divided by buttresses, from which flying arches extended to the upper part of the choir. The buttresses had simple set-offs, and were crowned with pinnacles, which, for the most part, seem to have been greatly decayed. In the depth of the buttresses next the south transept a porch was formed, which was roofed with fine groined vaulting. This porch is also well shown in Fig. 1018. The arch is moulded, and dies against the buttresses, and is crowned with a reversed curve and a flowered finial. There were carefully carved canopies and corbels for statues on the face of the buttresses on each side of the porch, and the other buttresses seem to have had similar niches. A round-headed doorway in the porch gave access to the choir, and had a square-headed window over it. The aisle windows had double splayed jambs and arches (Fig. 1019) both in the exterior and interior of the wall openings, but the original tracery had been broken, and its place was supplied with one upright mullion in the centre and a transome (Fig. 1020). This sketch also shows the south end of the south transept, which preserved its four mullions, of varied thickness, and its tracery. The latter is of a kind not uncommon in late Scottish churches. Fig. 1021 shows the exterior of the north transept, and the north side of the choir and the sacristy. The north end wall of the transept corresponds [Illustration: FIG. 1018.--Trinity College Church. South Side of Choir.]