There have been cross walls dividing some bays of the outer aisle into chapels. Of these some fragments can be traced in the south aisle, and a few of the piscinas and ambries still remain. The chapter house (Fig. 552) appears to have been originally built about the same time as the east part of the choir, the buttresses being similar in design, but it was afterwards considerably altered. As it now stands, the chapter house is practically a structure of the late pointed period. It is the only example remaining in Scotland of a similar detached octagonal edifice, with central pillar and vaulted roof (Fig. 553). It is 37 feet in internal diameter on the ground floor; but the walls have the peculiarity that, about 8 feet above the floor, they are corbelled out, and overhang towards the interior. On the side opposite the entrance where the bishop’s seat stood the corbelling is carried on an arcade of five arches, enriched with third pointed ornaments. On the other sides the corbelling is horizontal, with foliaged caps and corbels at intervals, and detached leaf ornaments in the mouldings. It is apparent from the alteration of the masonry of the exterior that the windows have been inserted in an older structure. Probably the chapter house suffered so severely at the hands of the “Wolf of Badenoch” that it had to be almost rebuilt. The interior of the walls appears to have been relined with ashlar work when the restoration took place, new vaulting being erected and enlarged windows introduced at the same time. The new facing of the interior of the wall is carried round all the sides, except that in which the entrance doorway is situated. There it stops short, and the old wall is visible. This lining accounts for the unusual projection of the upper part of the wall above mentioned (see Fig. 553). The designer of the restoration of the chapter house has apparently thought that the original floor space might thus be retained without diminishing the stability of the structure, which is well buttressed on the exterior, and he has ingeniously calculated that the additional weight thrown by the corbelled out thickness on the interior of the walls would serve as a counterpoise to the outward thrust of the vaulting. The latter springs from a single vaulting shaft in each angle of the building, resting [Illustration: FIG. 552.--Elgin Cathedral. Chapter House from South-West and South Aisle of Choir.] [Illustration: FIG. 553.--Elgin Cathedral. Chapter House: Interior.] on a carved head, and having a foliaged cap. The vaulting has ridge ribs and liernes, and is evidently founded on English examples. The intersections of the ribs are provided with ornamental bosses. The windows are large, and were divided with mullions and tracery of the middle pointed style, most of which is now demolished.