The upper chamber is undoubtedly the work of Bishop Cameron. The central pillar has two shields in the capital. That fronting a person entering contains the royal arms, surmounted by a crown (see Fig. 600); and the shield on the opposite side contains Bishop Cameron’s arms. There is here an analogy with the central pillar of the chapter house of Elgin Cathedral, where the royal arms and those of the bishop by whom it was completed are carved on the capital. The Cameron arms also occur in the cap of the wall shaft opposite the coat above referred to, and likewise over the fireplace (see Fig. 600). [Illustration: FIG. 602.--St. Mungo’s Cathedral. Rood Screen and Entrance to Choir and Lower Church.] The sacristy contains, as shown in the sketch (see Fig. 600), stone built projecting cupboards and a large fireplace. The arms of Bishop Cameron on the mantel above the latter contain an example of how heraldry and architecture may be made to work together; one of the members of the cornice over the fireplace being continued across the shield, so as to form one of the fesses of the Cameron coat. A wide wheel stair close to the entrance connects the chapter house and the vestry above. A shield containing a bull’s head, the arms of Bishop Turnbull, is inserted in the outside of the west wall, near the top. The wing may have been completed by that prelate. [Illustration: FIG. 603.--St. Mungo’s Cathedral. Archbishop Blackadder’s Arms on Altar.] Mr. Honeyman[69] conjectures that the Rood screen (Fig. 602) which is erected between the eastern piers of the central tower was built by Bishop Cameron. It contains a staircase in the space in the north side, and in the opposite side are cupboards for containing church vestments. In front of the screen there are two fine stone altars, that on the south side being known as the altar of St. Mary of Pity, and that on the north side as the altar of the Holy Cross. The arms and initials of Archbishop Blackadder (Fig. 603) are carved on the ends of both of these altars. The rood screen with its two altars, although evidently a late work, adds considerably to the picturesque effect of the interior of the cathedral. It has a large, deeply-recessed and moulded doorway in the centre, the arch of which is of elliptical form, and has the jamb mouldings (Fig. 604) continued, without caps or break, round the arch head. On each side of the doorway the surface of the wall is covered with shallow panels having trefoiled arch heads. A corbel in each of these panels (now cut off) once supported a statue, and these would add much to the effect of the structure. The cornice is large, and is surmounted by an open parapet containing quatrefoils, and having standards running up in the centre of each alternate quatrefoil. The standards are ornamented with small pinnacles, and are supported on corbels, each of which contains two human figures, which recall similar carvings at Rosslyn Chapel, but are of finer execution.[70]