transept; but the steps to the sanctuary are believed to have been where shown on the plan. As already mentioned, the clerestory and vaulting of the six eastmost bays of the nave was probably executed soon after the choir was finished, the outer wall of the clerestory being built with the same whitish stone as the heightened part of the choir. The windows are small and of plain-pointed form, like those of the choir. Some of them have the appearance of having been cut up into the vaulting, as if they had been inserted or heightened after the vaulting was built. It is to be remarked that while the parapets of the nave and choir are on the same level on the exterior, the vaulting of the nave is several feet lower than that of the choir. The three western doorways (Fig. 241) and the pointed doorway in the south transept (see Fig. 231) must be assigned to a period rather later than the choir. The wall containing the three west doorways is built out [Illustration: FIG. 241.--Kirkwall Cathedral. West Doorways.] of the square with the nave walls. It is supposed to have been erected outside the church, with the view of lengthening it, while the original west front stood at a point distant one bay from it. The new west wall seems to have been left unfinished for a considerable time, the upper part of the west front having, from its style, evidently been built at a much later period than the doorways. When the new west wall was completed, the old west front would be removed. This necessitated the building of the westmost pair of piers. While this operation was in progress, the next pair of piers and arch above have yielded, and the piers remain much inclined to the west. [Illustration: FIG. 242.--Kirkwall Cathedral. Interior of West Doorways.] The three west doorways and that in the south transept are specially remarkable from their presenting probably the finest examples in Great Britain of the use of coloured stones in the construction. This is chiefly observable in the exterior, but is also carried out in the interior of these doorways (Fig. 242). The north doorway (Fig. 245) and central doorway (Fig. 244) of the west front have the colours arranged in concentric rings in the arches, red and yellow alternating. In the south doorway (Fig. 243) the same colours radiate and alternate, and in the doorway of the south transept the red and yellow stones are arranged chequerwise. (See Fig. 231.) Fig. 246 shows the plan of the central doorway. [Illustration: FIG. 243.--Kirkwall Cathedral. Plan and Elevation of South Doorway of West End.] [Illustration: FIG. 244.--Kirkwall Cathedral. Elevation at Central Doorway of West End.] [Illustration: FIG. 245.--Kirkwall Cathedral. Plan and Elevation of North Doorway of West End.] The shafts have all been detached, as shown in the plans. They have been renewed; but, as Sir H. Dryden suggests, no doubt correctly, they were probably at first in red and yellow stone alternately.