The first view of the interior is striking and impressive. (Fig. 224.) The long perspective of the great round pillars and arches on each side of the nave, surmounted by the round arched triforium and clerestory, and the lofty roof covered with simple vaulting, give an impression of size and height which is larger than is borne out by after measurement. This appearance of great size has often been remarked of St. Magnus’, and, no doubt, arises from the height and length of the edifice as compared with its width, which between the piers is only 17 feet, while the length of the nave is 111 feet, and the height to the apex of the vault is about 50 feet. The cathedral is found to be complete in all its great divisions. (Fig. 225, Plan.)[166] The nave has side aisles, which are vaulted, and the side walls are arcaded with interlacing Norman arches. The choir is, unfortunately, excluded by a glass screen from the general view of the cathedral, owing to the east end being still used as the parish church. The choir is of considerable length, being 85 feet 6 inches long by 47 feet 6 inches wide, and has main piers, triforium, and clerestory, of about the same height as the nave. It is also vaulted, and has vaulted side aisles. The longitudinal section (Fig. 226) shows the comparative heights of the nave and choir. The transept is 90 feet long by 17 feet wide, and has a great appearance of height, but is not vaulted. It has no aisles, but has a vaulted chapel projected to the east from each division of the transept. Fig. 227 is a section through the transept from north to south. The choir contains six bays, and the nave eight bays. When the exterior is examined, it is found to present at a glance a general history of the structure, and the changes which have taken place in it. The layers and masses of the different coloured stones which have been used in the edifice at different times tell their own tale. Fig. 228 [Illustration: FIG. 224.--Kirkwall Cathedral. The Nave, looking West.] [Illustration: FIG. 225.--Kirkwall Cathedral. Ground Plan.] shows the north elevation of the whole cathedral.[167] The oldest work (which, however, comprises several periods) is constructed with dark slaty stone, having red freestone dressings. This masonry comprises the whole of the outer walls of the choir, the transept, and the greater part of the nave. It is evident, however, that this style of masonry includes not only much Norman work, with its round arches and flat buttresses, but also some later work, which has pointed windows and boldly-projected buttresses. The Norman work (Figs. 228 and 229) may be observed in the transept, and several bays of the nave and choir nearest the transept, while the pointed work is specially noticeable in the eastern half of the choir.