[Illustration: FIG. 592.--St. Mungo’s Cathedral. North Side of Nave.] evident from the smallness of the buttresses of the clerestory (Fig. 593) that the walls were not calculated to resist the strain which such a vault [Illustration: FIG. 593.--St. Mungo’s Cathedral. View of South Side, looking West.] would have brought against them. The present vaulting beneath the central tower is modern, as also are the plaster ceilings of nave and choir. The vault of the north aisle of the choir has ribs of an early form, while those of the south aisle are of a later design (Fig. 594). On the panels of the latter vault there are a number of figures, comprising the symbols of the evangelists, &c. The bays of the nave are divided by clustered piers of smaller size and later shape than those of the choir (see Fig. 587), and the moulded caps (which follow the outline of the shafts and hollows of the piers) are also of later character. Each bay of the triforium and clerestory (Fig. 592) is divided into two openings, and has shafts running up through the whole height, which unite the two stories into one, a design which produces a striking effect. The triforium openings of the nave, although not without great vigour, are perhaps the most rudely executed features in the whole building. The jamb and arch mouldings accommodate themselves to each other in an awkward manner, and the fitting in of the uncouth trefoil tracery is quite a contrast to the fine finishing of the clerestory above. It is not easy to account for the careless work in the triforium, as the upper part of the nave appears to have been all executed about one period. The coarse workmanship is much more striking in the building than can be shown by drawings on a small scale. [Illustration: FIG. 594.--St. Mungo’s Cathedral. Ribs in North, East and South Aisles of the Choir.] The windows of the aisles, in the choir and part of the nave, are very much alike and very simple in design, and some of them are grouped and contain rudimentary rather than real tracery. Some of these are visible in the choir in Fig. 593, and Fig. 595 shows one in the north aisle of the choir, which may be taken as a specimen. It consists of three lancets separated by mullions, which might rather be described as portions of the wall with small buttresses attached, and the whole enclosed within one arch, having the spandril above pierced with a quatrefoil and two trefoils. The tracery of the windows on the south side of the nave is simple, but completely formed (see Fig. 590), each window having two mullions and three trefoils in the arch head. Those of the clerestory have each a central mullion divided in the arch into two branches (Fig. 596).