but occasionally the walls are made with flags set on end. The narrow entrance, probably concealed by a stone door, sloped down to the floor level of the chamber, but before reaching the latter there was occasionally a second door, often placed at the point where the direction changed. Sometimes a passage branched off from one side of the gallery and led to another chamber, usually of a circular or oval shape. These chambers were frequently roofed in a dome fashion, on the beehive principle, much in the same manner as those of the chambered cairns. Though all built on a uniform plan they are found to vary greatly in dimensions, that at Tealing, Forfarshire, measuring 80 feet in length, 5 feet 8 inches in height, 2 feet 6 inches in width at entrance, and 8 feet 6 inches next the inner end; while the corresponding measurements of one at Kinnord are only 21, 112, 3 and 212 feet.
It is the general opinion of archæologists that these subterranean chambers were always associated with surface habitations, whose structural materials, being made of timbers, have disappeared through natural decay and changes due to the cultivation of the land. Striking evidence of such an association was observed in 1859, at Cairn Conan, near Arbroath. Here, an underground structure presented the peculiarity of having, in addition to the usual long curved gallery, a circular beehive chamber attached to it by a low
