It is difficult to determine when these alterations took place, and possibly they did not all happen at one time. We are informed that a new choir was erected by Richard, Bishop of Dunkeld, towards the end of the thirteenth century. It seems not unlikely that the remodelling may have taken place about that time, and it is well known that almost no building was carried on in Scotland from that period till the fifteenth century. Besides, the frequent disturbances caused to the abbey by the English fleet during the fourteenth century rendered building operations at that time impossible. The church, however, seems to have been spared, as it is on record that the lady chapel to the south of the choir was added to it in the beginning of the fifteenth century. The general appearance of the cloister ambulatory (see Fig. 746) would at first sight lead one to suppose it to be of an old date. The small round-headed windows without caps and with chamfers on edge (see Fig. 743), their wide recesses, with stone seats, and the round vault of the ambulatory, have an archaic look; but on close inspection, it will be noticed that the west wall is built against and partly bonded into the original south-east buttress of the tower (see Fig. 743), thus showing that this wall is more recent than the tower. This fact also confirms the view given above that the space opposite the south wall of the choir (where the old window is) was open, and that at least the upper floor, where the dormitory now is, was a later addition. [Illustration: FIG. 750.--The Abbey of Inchcolm. Details of Chapter House, &c.] The chapter house (Fig. 748) seems also to have been erected towards the end of the thirteenth century. It is in the first pointed style, as the mouldings of the caps, bases, window jambs, &c. (Fig. 749) show. It is one of the very few octagonal chapter houses in Scotland, that of Elgin Cathedral being the only other with which we are acquainted. The octagon is regular and the ribs of the vault, which spring from a round shaft 4½ inches in diameter in each angle, meet in a carved boss in the centre, having a circular aperture from which a light might be suspended. The bases of the angle shafts are of first pointed character, and rest on the stone bench. The ribs of the vault have a hollow in the centre (see [Illustration: FIG. 751.--The Abbey of Inchcolm. Interior of Chapter House, from North-East Window.] [Illustration: FIG. 752.--The Abbey of Inchcolm. Doorway of Chapter House: Interior.]