Having thus obtained a distinct conception of the type, we now proceed to determine its range or area. For this purpose it is necessary to ascertain what structures exist in Scotland, or out of it, possessing these typical features. [Illustration: Fig. 171.—General plan of Broch and its fortifications on Cockburn Law, Berwickshire.] On the northern declivity of Cockburn Law, in Berwickshire, there is a natural platform projecting from the shoulder of the hill over the valley of the Whitadder water, about 250 feet above the bed of the stream. On this platform there is an irregularly oval enclosure (Fig. 171), the outlines of which are formed by the remains of two parallel earthworks and an outside ditch. The space thus enclosed is occupied by the remains of various smaller enclosures, some circular and others irregular in form. They are nearly all so ruined that nothing can be made of their details. But the principal structure within the enclosure is still capable of such examination as will suffice to determine its typical relationship with the Brochs of the extreme north. It is circular, consisting of a wall 17 feet thick, enclosing an area of 56 feet in diameter. In the thickness of this wall are two elongated oval-shaped chambers, one of which is 33 feet long and 7 feet wide, the other 23 feet long and 7 feet wide. In 1793 the roofs were still on them, and it was then seen that they were covered with a rude vaulting of overlapping masonry. Both these chambers open to the inner area. The only access to this area from the outside is the main doorway, which passes straight through the wall, and is flanked by a guard-chamber constructed in the thickness of the wall on either side. To the left of the doorway are the remains of the staircase, with an elongated chamber opposite the foot of the stair. No remains of galleries exist owing to the absence of the whole upper part of the structure, but the presence of the stair implies that they once existed. The masonry is massive in character (Fig. 172), and the structure is also remarkable for its great size, being three times the width of Mousa and twice that of the Glenelg Brochs. But its features of form and character, and all the arrangements of its details, so far as they now exist, are those of the typical Broch structure; and, taken together, they form a group of features and arrangements which do not exist in any other type of structure. [Illustration: Fig. 172.—Masonry of Broch on Cockburn Law.]