LECTURE IV.
(28th October 1881.)
THE ARCHITECTURE OF THE BROCHS.
In this Lecture I have to deal with the products of a school of architecture, Celtic in its character, and absolutely peculiar to the Scottish area.
On the small uninhabited island of Mousa, lying off the east coast of the mainland of Shetland, there stands a solitary stone structure, massive in size, peculiar in appearance, and still more peculiar in character. It is a tower of circular form, wide and lofty, but constructed of undressed stones laid upon each other without mortar or other binding material, so that the mass of its uncemented wall coheres simply by its own vertical pressure.
Its situation is peculiar. The island is small, not over a mile in length, and less than half a mile in width, bare, flat, and rocky. The tower is placed on a small promontory on the west side of the island at the point nearest to the mainland. It stands about 20 feet back from the edge of the rocks, which slope irregularly to the tide-mark about 20 feet below. There are slight remains of an intrenchment on the sides which look landward, those facing the rocks and the sea are protected by the natural features of the ground.
Fig. 160.—Exterior View of the Broch of Mousa, Shetland.
The material of which the tower is built is the fissile flag of the island. The stones are flat, sometimes as much as 2 feet in thickness, but mostly much less, and they rather diminish in size towards the top of the tower. The stones bear no mark of a tool, and the masonry is not coursed, but compactly fitted together. The wall goes up with a curve like that of a lighthouse, and its external appearance (Fig. [160]) is suggestive of great solidity and strength. This suggestion of solidity, which is due to the bulk of the building rather than to the character of its masonry, is further intensified by the absence of external openings, the whole exterior surface being unbroken by a single aperture except the doorway. It is on the level of the ground on the S.W. side, and is about 5 feet 3 inches high by 2 feet 11 inches wide, passing straight through the thickness of the wall, but widening considerably at a distance of about 7 feet from the outside and rising in the roof. Entering by this tunnel-like passage through a wall 15 feet 6 inches thick, the visitor finds himself in the interior of a circular well-like court, open to the sky above, but completely surrounded by a wall of that thickness and 45 feet in height. From the inner circumference of this court (as seen in the ground plan, Fig. [161]) there open at various places other doorways leading into oval chambers constructed in the thickness of the wall nearly on the ground level. These chambers are three in number. One placed to right of the entrance is 16 feet in length, 5 feet 9 inches wide, and 9 feet 9 inches high. Its doorway is small, 3 feet high and 2 feet wide, passing through 4 feet of the thickness of the wall. A second chamber opposite the main entrance is 14 feet long, 6 feet 10 inches wide, and 10 feet 6 inches high. Its doorway is also small, 3 feet 4 inches high and 2 feet 9 inches wide, passing through a thickness of 4½ feet of walling. The third chamber, situated to the left of the main entrance, is 14 feet long, 5 feet 6 inches wide, and 9 feet 6 inches high. Its doorway is 3 feet 2 inches high and 2 feet 3 inches wide, passing through 4 feet of walling. All these chambers are irregularly oval in form on the ground plan. They are roofed in a peculiar manner. At variable distances from the floor the walls begin to be brought inwards by projecting each stone slightly beyond the face of the stone below it. In this way the distance between the opposite walls is gradually lessened as they rise in height until they come near enough to admit of single stones being laid across the space between wall and wall. This style of converging the walls inwards to obtain support for a roof of single stones is not new to us. We have met with it in the beehive houses of the early Christian monasteries and in the inverted boat-shaped roofs of their churches, built of uncemented stones on a rectangular ground-plan. It is the style of roof which is common to all dry-built structures that are roofed, whether they be of Pagan or of Christian time, because it is the style that is best suited to the material and the manner of construction. The builders of this edifice had no stones long enough to span chambers of six feet wide, and if they had had them long enough they would have been too weak to bear the superincumbent weight of a wall forty feet in height. Therefore they made their chamber-roofs semi-vaulted, while the doors and passages, which were narrow, were simply spanned with strong flat lintels. These chambers on the ground floor are lighted by window-like openings above the doorways, which rise one over the other, and serve not only to admit light and air, but to distribute the weight to be borne by the lintels. In each of the chambers there are small ambry-like recesses in the walls, but no fireplace or chimney. They are small, dimly-lighted, dungeon-like rooms, but neither smaller, worse-lighted, or more dungeon-like than many rooms in the lime-built castles of the nobles of the Feudal ages.
Fig. 161.—Ground Plan of the Broch of Mousa, Shetland. (From Plan by Sir Henry Dryden.)
Half-way between the chamber facing the main entrance and the one to the left of it there is a doorway placed at a height of four feet above the ground level. This doorway, which is higher and wider than those which lead into the chambers, is slightly larger than the main entrance itself, being 5 feet 4 inches high and 3 feet wide. It leads to a stair constructed like the chambers within the thickness of the wall. At the foot of the stair there is an oval chamber, from one end of which the stair rises in a steep slope, but following the curve of the wall to the top. The steps are single flat stones, varying in width from ten inches to two feet, undressed, and laid above each other so that they give a tread of about five inches and nearly the same of a rise. The upper part of the tower which is traversed by the stair is differently constructed from the lower part. To the height of about eleven feet above the ground level the wall of the tower is carried up solid except for the vacancy occasioned at intervals in its thickness by the chambers and their accesses. But above this height the wall is carried up with a vacancy in its centre (as seen in the section Fig. [162]) so as to form a series of circular galleries placed one immediately over another, and crossed successively from the lowest to the highest by the rise of the stair which gives access to them.