Lithgow, who built the north porch, and the completion of the nave was carried out by Bishop Tervas. A striking peculiarity of the interior of the nave is a series of large corbels (see Figs. 961 and 962), which project from the spandrils of the triforium arcade. The object of these corbels appears to have been to enable a passage, which is formed in the interior of the clerestory windows, but does not run through the wall in a straight line from end to end as is usual, to be carried round the solid piers introduced between the windows. These projections recall, by the small corbels arranged in rows into which they are divided, the corbels generally used for the support of the bartizans of castles. Each of the large corbels springs at its lowest point from the sculptured grotesque figure of a man or animal. Dr. Lees states (p. 209) that these figures “were mostly the work of Thomas Hector, a sculptor who lived at Crossflat, and whom the abbot retained for his skill in his art.” One of the corbels on the south side (near the west end) represents a man wearing the garb of Old Gaul. It may be mentioned that a somewhat similar gallery exists in Rouen Cathedral. It is carried round the piers of the nave on the side next the aisles, and is supported on shafts springing from corbels. This gallery has a light stone parapet resting on it. The design is of the thirteenth century, and is elegantly carried out; but it has, notwithstanding, a rather heavy appearance. It must be admitted that the projecting corbels at Paisley are clumsy, and considerably mar the effect of the interior. There appears to have been a parapet in front of the clerestory passage opposite the windows, and a similar parapet may have been carried round the large corbels, otherwise walking round them would have been dangerous. This would add still more to the heaviness of their appearance. Vaulting shafts are carried up between the windows of the clerestory, but the buttresses being very light, a vaulted roof has apparently not been contemplated. The present plaster vaulting is modern. The north wall of the nave aisle, except the doorway of the north porch, which is of first pointed work, has been rebuilt in the fifteenth century. The ingoing of the window jambs and arches consists, both on the inside and outside of the wall, of a great hollow, with the tracery set in the centre of the wall. The large north porch (shown in Billings’ work) was taken down in 1863, in order to be erected anew, in what was considered a finer style. The porch contains the tomb of Bishop Lithgow, who selected this porch as his burial-place, and was interred there in 1433. Some of the tracery in the aisle windows is good for the period, like that in some of the windows of Dunkeld Cathedral, which building (as above mentioned) has considerable affinity with Paisley Abbey Church.