The choir roof, which consists of a pointed barrel vault (see Fig. 1080), is divided by strengthening ribs into compartments corresponding with the bays, and each compartment is decorated differently (see Fig. 1078). The dividing ribs are moulded, and have large projecting cusps in the form of fleurs-de-lys, &c., on the soffit. The compartments of the roof are entirely “powdered with stars” or rosettes, set square or diagonally. The construction of the aisle roofs is peculiar, although something similar is frequent in castles, as will be afterwards alluded to. A regularly constructed straight arch with proper radiating joints, concealed behind upright joints, spans each aisle (see Fig. 1079) from pillar to wall shaft. These horizontal arches or lintels have flat relieving arches over them, which in some instances are visible. The aisles are roofed with a series of [Illustration: FIG. 1077.--The Collegiate Church of Rosslyn. East End of Choir, above Roof of Aisles.] pointed barrel vaults thrown between the above straight arches, and running at right angles to the axis of the building (Fig. 1081). This is [Illustration: FIG. 1078.--The Collegiate Church of Rosslyn. Interior of Choir, looking East.] one of the most unusual features of construction in the edifice. The straight arches or lintels, as they may be called, are all most profusely [Illustration: FIG. 1079.--The Collegiate Church of Rosslyn. Interior of West End of North Aisle.] carved with foliage or figure carving (Fig. 1082), the amount of decoration on each being, as usual, of corresponding artistic value. On the arched roofs of the north and south aisles, to the east of the [Illustration: FIG. 1080.--The Collegiate Church of Rosslyn. Transverse Section.] [Illustration: FIG. 1081.--The Collegiate Church of Rosslyn. East Aisle and ’Prentice Pillar.] doorways and of the east aisle, there is carved in each bay an engrailed cross, the one limb running along the crown of each arch, and the other downwards from this on each side. But in the north and south aisles, in the three bays west from the doorways, the engrailed band is only continued along the crown of the arch, the other limb being omitted, which may possibly be meant to distinguish the more sacred part of the edifice. The eastern chapels are the only part of the building in which there is groined vaulting. The compartments are oblong, and have pointed cross arches (Fig. 1083), the diagonals meeting at the apex. Elaborately carved pendants, about 4 feet long, occupy the place of the usual boss; while at the springing of the arches, against the east wall, great projecting horns, resting on curved corbellings or cones above the caps of the wall shafts, radiate outwards and downwards, one horn to each rib, so that they are in groups of three. [Illustration: FIG. 1082.--The Collegiate Church of Rosslyn. Details of Carving of Straight Arches.]