Let us now group the main features of this singular building. It is a circular tower, composed of a dry-built wall 15 feet thick, enclosing a court 20 feet in diameter. The wall rises to a height of 45 feet, and has no opening to the outside except the doorway which gives access to the court. Opening from the court are a series of chambers on the ground floor constructed in the thickness of the wall and rudely vaulted with overlapping masonry. Above these are successive ranges of level galleries, also in the thickness of the wall, each going round the tower, and placed so that the roof of the one below always forms the floor of the next above. These galleries are crossed successively by a stair from which access to them is obtained by facing round in the ascent and stepping across the vacant space forming the well of the stair. The three lower galleries only are lighted, and the windows are placed in vertical ranges so close to each other as to be separated only by their upper and lower lintels.
Each of these features, taken by itself, is specially remarkable, and the presence in the one building of such a group of features that are wholly unfamiliar to us invests it with a character that is distinctly peculiar. From this examination of its character, it becomes obvious that although the construction and arrangements of the building are clearly those of a place of strength, it is incapable of association by way of relationship with any variety of castle known in historic times. But a wider survey of the remains of the ancient strongholds of the people who have occupied the land in times of which we have no distinct or detailed historic record will show that it has relationships so close as to amount to an almost actual identity with many similar structures in different parts of Scotland.
[Illustration: Fig. 163.—View of external aperture of doorway of Broch in Glenbeg. (From a Drawing by J. Romilly Allen.)]
[Illustration: Figs. 164, 165.—Ground plan and section of elevation of doorway and passages through the wall of Broch in Glenbeg. (Drawn by J. Romilly Allen.)]
For instance, in the small valley of Glenbeg, which runs nearly parallel with Glenelg, in the west of Inverness-shire, there are two such structures. One is situated on the edge of the meadow which lies in the bottom of the valley. It is greatly destroyed; more than half the circle of the wall is gone, and part of the height of the portion that remains is wanting. The internal diameter of the tower, at the level of the rubbish which encumbers the floor, is 33½ feet, and the thickness of the wall 11 feet. The doorway (Fig. 163), which is the only opening to the outside, is 3 feet 5 inches wide at the head, the lower part concealed with rubbish. About 4 feet inside the outer plane of the wall there is a rebate for a door (Fig. 164), with checks in the shape of large slabs set edgewise in the wall. Within these checks the passage widens to 5 feet, and the roof rises as shown in the section, Fig. 165. On the south side of the passage there is a guard-chamber opening from it, and constructed in the thickness of the wall. Three galleries and part of a fourth remain, but the stair is gone. The galleries are lighted by vertical ranges of windows looking to the interior. The greatest height of wall remaining is not over 30 feet, but 7 feet of its height were taken by the contractor for the Bernera Barracks in 1722. It must therefore, before that time, have been nearly as high as Mousa now is.