But whatever may have been the actual purpose or purposes to which they were applied, the fact which is of importance in our investigation is that these Earth-houses, though ranging in area from Berwickshire to the north coast of Sutherland, are all of one special character, long, low, narrow galleries, always possessing a certain amount of curvature, sometimes greatly, and at other times doubly curved, always widening and increasing in height from the low and narrow entrance inwards, usually built with convergent walls and roofed with heavy lintels, which are always lower than the surrounding level of the ground, so that the whole structure is subterranean. Occasionally they present variations in structure as in the case of one at Murroes, in Forfarshire, which, instead of being built, has its walls constructed entirely of flagstones set on edge. Similarly, the example at Kinord, in Aberdeenshire (Fig. 258), has its walls constructed of single boulders set on edge or on end, and it presents the further peculiarity of the chamber being divided into two branches at the farther end. One at Pirnie, in the parish of Wemyss, in Fife, and another at Elie, had steps leading down to the entrance. [Illustration: Fig. 258.—Ground plan and sections of Earth-house at Kinord, Aberdeenshire.] Occasionally they occur in considerable groups, as at Airlie, in Forfarshire, where there is a group of five. One of these is of great size, its length being 67 feet, and its average breadth, from the farther end to within about 12 feet of the entrance, 7½ feet. The height at the entrance is only about 22 inches, and the floor slopes down for about 20 feet till a height of about 6 feet is obtained. The walls are built of rough undressed boulders laid in pretty regular courses, and they converge from a width on the floor of a little over 7 feet to about 4 feet at the roof. The covering stones are of great size, many of them 7 or 8 feet in length and 4 feet wide. It contained the usual traces of cookery in the accumulation of ashes and bones of animals upon the floor. The only other relics found in it were a brass pin, a stone mortar-like vessel, and fragments of querns. The other four examples in the same neighbourhood are known to have existed, but have neither been measured nor described.