Above the vaulting of St. Mirin’s Chapel, and in the angle formed by the sloping roof, there is introduced a chamber, with a pointed barrel vault, about 12 feet wide and nearly 10 feet high, to the apex of its sharply pointed vault. The three sides of this chamber thus nearly form an equilateral triangle. Like the chapel below, it is 48 feet in length. It is lighted by trefoil headed windows in the gables. Access to this chamber, which may have been occupied by one or more priests, is obtained from the adjoining buildings. It is to be regretted that the south and south-east sides of St. Mirin’s Chapel are concealed from view by buildings of a poor description. It will be observed that the construction of the roof of St. Mirin’s bears considerable analogy with that of Lincluden Abbey, although later in its features. There is a similar double vault over both these buildings, with a small chamber between them. At Lincluden the lower vault was (if it ever was completed) of a genuine groined construction, while at St. Mirin’s the ribs were only imitative. The roof of St. Mirin’s Chapel was clearly intended to be formed of stone slabs, resting on the pointed arch, but has never been carried out, the present roof being slated. On the floor of this chapel there now stands an ornamental altar tomb (see Fig. 965), which was found lying in fragments near the abbey by Dr. Boog, one of the ministers of the parish, who, in 1817, had it brought here and put together again. It supports a recumbent female figure, believed to be the effigy of Margery, daughter of King Robert I., and mother of Robert II. The head of the figure is surmounted by a large cusped canopy, placed in n horizontal position, on the end of which is carved a crucifixion. The pedestal is covered with a series of Gothic compartments, in each of which there is carved a shield, enriched with heraldic blazons and figures of ecclesiastics. The panels at the west end (Fig. 967) contain--the first the fess chequé of the Stewarts between three roses; the third the fess chequé, surmounted of a lion rampant, and the central one, two keys saltierwise, between two crosiers in pale. Mr. Semple[15] is of opinion that the monument is made up of fragments from various quarters. On each side there are nine full compartments of [Illustration: FIG. 966.--Paisley Abbey. Piscina in St. Mirin’s Chapel.]