The twelfth century was in Scotland as elsewhere the great church-building period, and the number of churches in the south and east that reflect the Norman movement is very large. All the large ones were conventual. Parish churches of the period are generally small and aisleless--the most of them being single oblong chambers, with an eastern chancel, sometimes with an eastern apse, and occasionally with a western tower.[12] Towards the close of the period, the ornament became very elaborate, especially in the arched heads of doorways. A common feature was the arcade running round the walls below the windows, either in the exterior, interior, or both; the caps and arches are generally carved elaborately and richly with ornaments, the chevron or zig-zag enrichment being a characteristic feature. The windows are always single and simple in detail.[13] Some of the towers connected with such churches are amongst the earliest instances of Norman work which survive; they are simple in design, square on plan, and are carried up, without break or buttress, to the parapet, where they are finished with a gable roof, forming the saddle-back arrangement still preserved in the Muthill Tower.[14] The break in the height is formed by string courses, which mark the unequal stories. A small wheel-stair usually leads to the top, and the doorway is occasionally several feet from the ground. Such are the leading features that can be traced in the buildings connected with the period. 2. SCOTTISH TRANSITION STYLE The term "transition" is by general agreement reserved for the architecture of the end of the twelfth century, when the Norman style gradually gave place to the first pointed Gothic style. In England this period extends from about 1180 to 1200; in Scotland it extends considerably into the thirteenth century. The characteristics of the style are the gradual introduction of the pointed arch and its use along with some of the decorative features of the Norman style. "The pointed arch shows the advent of the new style, but the ornaments of the old style continue to linger for a time. The first pointed style was not complete till these old ornaments were abandoned, and the more vigorous enrichments of the new style were introduced. The other constructive features of the Norman style gradually changed at the same time as the arch. The buttresses by degrees assumed the projecting form of the first pointed style, and the pinnacles and spires of the latter style were in course of time introduced."[15] 3. SCOTTISH FIRST POINTED PERIOD