The abbey or cathedral, which is now to be described, is classed along with the buildings of the third pointed period, as the greater part of the work connected with it belongs to a late date. When the great distance of the Island of Iona from the centre of operations of mediæval architecture is considered, it is not unnatural to find those deviations from the rules and practice of the art which are so frequent in Scottish architecture even more accentuated here than is usual. The connection of the locality with the Celtic art of Ireland and the west of Scotland has also had considerable influence in moulding the style of the carving and decoration of the Cathedral of the Isles.[36] These facts, although rendering the building somewhat difficult to class along with the general architecture of the recognised periods of Gothic in Scotland, yet add much to the interest of this isolated and unique structure. It should also be noticed that the cathedral shows signs in all directions of having been much altered and added to; but as the style of the masonry of the walls is much the same throughout, whatever its date, it is somewhat difficult to trace the points of junction of the work of the various periods. This masonry of all dates consists of large blocks of red granite of irregular shape, set with flat untooled face to the outside, and with filling-in of smaller pieces of granite and slaty stones between the larger blocks. The monastery (Fig. 982) consists of the church, which contains a [Illustration: FIG. 982.--Iona Cathedral. Plan.] choir, 62 feet 6 inches long by 23 feet wide, with a south aisle; a nave, 60 feet 9 inches long by 22 feet 6 inches wide; north and south transepts, [Illustration: FIG. 983.--Iona Cathedral. The Choir, looking East.]