Fig. 181.—Diagrammatic Section of the Broch of Borrowston, showing the well in the area. (From Archæologia Scotica, vol. v.)
Fig. 182.—Broch at Manse of Harray. (From a Plan by Mr. George Petrie, 11⁄16 inch to 1 foot.)
The Broch of Borrowston, in Shapinsay (Fig. [181]), also in Orkney, consisted of a wall 13 feet thick, enclosing a central area 33 feet in diameter. Within the central area of the Broch there was a well 10 feet deep, the lower part dug out of the solid rock, and the upper part faced with dry-built masonry. The Broch of Okstrow, at Birsay in Orkney, which consisted of a wall 12 feet thick, enclosing an area 45 feet in diameter, had a well within the area and a drain from it leading out to the outside of the structure. The Broch near the Manse at Harray (Fig. [182]), excavated by Rev. Dr Traill, consisted of a wall 12 feet thick, enclosing an area about 33 feet in diameter. It was surrounded by outbuildings, which were not properly explored. There were no guard-chambers on either side of the passage (B), which shows the checks for the door, at 6 feet within the outer face of the wall. To the left of the main entrance is the usual chamber (H) at the foot of the stair (G), of which 19 steps remain; and two other oval chambers (E and F), placed at nearly equal distances in the circumference of the wall, complete the resemblance to the general type. Near the middle of the area a subterranean passage terminating in five steps led to a well (D) 9 feet deep excavated in the rock. The subjoined sectional diagram (Fig. [183]) shows the construction of the well, which still retained water when the excavation of the Broch was made. The Brochs of Skinnet, Harpsdale, and Kettleburn in Caithness, had each a well within the central area. The well of the last-mentioned Broch is still utilised as the existing water supply for the cottars, who live in houses close by constructed of the stones removed from the site of the ancient structure.
Fig. 183.—Section of the Well in the Broch at Manse of Harray.
(From a plan by Mr. George Petrie.)
The central areas of several Brochs have been provided with drains to convey the surface water outside the building. This same Broch of Kettleburn had a drain which passed out under the foundation of the wall of the tower. It was what is now called a self-cleansing drain, the flat stones forming the water channel being set together in the form of the letter V. Sir Henry Dryden remarks the presence of drains in the Broch of Clickamin. I found a square drain leading from the court of a Broch which I excavated at Brounaben, in the parish of Wick.
The facts that many of these structures were thus provided with drainage, and that they had also secured a water-supply within the enclosed area of the building, are not only significant indications of intelligence and forethought applied to the arrangement of constructional details, but when taken in connection with all the other arrangements of the structure external and internal, they complete a series of characteristics which point definitely to one object as the chief intention of the Broch-structure, viz. security obtained by the simplest of all means—a construction of uncemented stones which could neither be easily forced nor readily reduced.[[74]]
Reviewing the typical characteristics of the special form of structure which has come to be known in recent years by the local northern name Broch, we see that it is a hollow circular tower of dry-built masonry, rarely more than 70 or less than 40 feet in its total diameter, and occasionally at least 50 feet high. Its circular wall, which may be from 9 to 20 feet thick, is carried up solid for about 10 feet, except where it is pierced by the entrance, or partially hollowed by the construction within its thickness of oblong chambers with rudely-vaulted roofs. Above this height the wall is carried up with a vacancy of about 3 feet wide between its exterior and interior portions. At every 5 or 6 feet of its height this vacancy is crossed by horizontal ranges of slabs inserted as ties between the outer and inner shells of the wall, so that their upper surfaces form a floor to the space above and their under surfaces become a roof to the space below. These spaces thus form horizontal galleries about 6 feet high and 3 feet wide, separated from each other vertically by the slabs of their floors and roofs. They run completely round the tower except that they are crossed successively by the stair which gives access to them. They are lighted by ranges of peculiarly-constructed windows placed vertically over each other, and all looking into the central area enclosed by the wall of the tower. This area or court varies from 20 to 45 feet in diameter. At various points of its interior circumference are placed the openings which give access to the chambers on the ground floor within the wall, and to the stair which ascends to the galleries. The only aperture on the outside of the tower is the doorway formed by the external opening of the tunnel-like passage through the wall which gives access to the central court. It is always on the ground level, square-headed, usually with slightly inclined sides,[[75]] 5 to 6 feet high, and rarely more than 3 feet wide, passing straight through the thickness of the wall, and thus varying from 9 to 18 feet in length. Some 4 feet or thereby within the outer end of the passage there is a rebate of the masonry faced with strong slabs inserted edgewise in the wall, and forming checks for a door, behind which are the bar-holes, and behind them the opening of a guard-chamber built in the thickness of the wall.