The chapel at Dunstaffnage Castle, and the Church of St. Columba[57] at Skipness, are somewhat exceptional, from the amount of dog-tooth ornament exhibited by the former, and the two-light traceried windows at the east end of the latter, which clearly indicate their thirteenth century origin; while at other churches on the West Coast the lancet windows and similar first pointed features lead to the conclusion that many of them belong to the same period. These island chapels are, doubtless, survivals of the first pointed structures which were erected in the thirteenth century throughout the country, but which have been subsequently removed to make way for larger churches. As the most of the Scottish cathedrals and large monastic churches were planned during this or the preceding century, it may be well here to mention some particulars regarding their arrangements. In most of the conventual edifices the choir, including the presbytery, is short as compared with the nave. Thus, at Arbroath, the arcades of the choir are as 3 to 9 in relation to those of the nave; at Jedburgh, as 2 to 9; at Melrose, as 2 to 8, in the present ruined condition of the church, but originally probably as 2 to 12; at Dryburgh, as 2 to 6. Kelso is a remarkable exception, the choir having been much longer than the nave, the latter being of a single bay. The cathedrals, however, show a proportion more in accordance with the usual practice in England. Elgin Cathedral has in the choir (including the presbytery) 6 bays, and the same number in the nave; St. Andrews had 5 in the choir to 12 in the nave, Glasgow has 5 to 8, Dunblane has 6 to 8, Dunkeld has 4 to 7. Another peculiarity of the Scottish churches is that in several the choir is without aisles, as at Brechin, Dunkeld, and Sweetheart Abbey; and in others, as at Melrose, Iona, Elgin, St. Andrews, &c., the side aisles do not extend so as to include the presbytery, the object evidently being to admit of side lights in the latter, which thus becomes a kind of rectangular apse. Transepts are frequently, if not entirely, absent, as at Glasgow, where the transept is very short, and at Dunblane and Dunkeld, where there are none. When a transept exists, as at Melrose, Pluscardine, &c., there is frequently a side aisle on the eastern side only, for the purpose of containing chapels with altars facing in that direction. This arrangement was common in Cistercian churches, but in Scotland it is not confined to that Order. In some churches where there is a transept, the shortness of the choir has made it necessary to carry the choir screen across the intersection and some distance down the nave. This is very apparent at Melrose, where the rood screen enclosing the choir crosses the nave about the centre, and is evidently part of the original design, as the rood screen has formed a portion of the structure of the nave piers.