David MacGibbon, The ecclesiastical architecture of Scotland from the earliest Christian times to the seventeenth century…
“ 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. ”
