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]
That this object was practically attained by these simple means we have evidence in one case from the direct testimony of record. It is related in the _Orkneyinga Saga_, that Erlend, who (about A.D. 1155) carried off the widow of Maddad, Earl of Athol, took her north to Shetland, and took up his residence in Moseyarborg—the Broch of Mousa, described at the commencement of this Lecture. It is said that her son Harald, Earl of Orkney, pursued Erlend, and besieged him in the Borg, “but it was difficult to take it by assault,” and the siege failed because “Erlend had made great preparations.” This is the only record of the actual use of a Broch as a place of defence, and it bears out the inference drawn from an examination of the nature and arrangements of the structure, that it was difficult to take by assault, and equally difficult to reduce by siege, if the defenders were provided with supplies. It is also stated in the Saga of Egil Skalagrimson, that about two centuries and a half before this time (or somewhere about A.D. 900), Bjorn Brynjulfson, fleeing from Norway with Thora, Roald’s daughter, because her father would not consent to their marriage, was shipwrecked on the island of Mousa, landed his cargo and lived in the Borg during the winter, celebrating his marriage in it, and afterwards sailed for Iceland.—_The Orkneyinga Saga_ (Edinburgh, 1873), p. cxi. and chap. 92.