In my Introductory Chapter I have remarked that none of the Irish writers appear to have paid much attention to the mechanical principles on which the wooden islands were constructed. A similar remark is equally applicable to the writers on Scottish crannogs. Dr. Stuart had got hold of the general idea that the mortised transverses were used for the purpose of steadying the uprights, and that the outer structures were adapted to resist the action of the surrounding water. The following are his words: "Of the first class, or the crannog proper, the ordinary construction was by logs of wood in the bed of the lake supporting a structure of earth or stones, or of a mixture of both, the mass being surrounded by piles of young oak-trees in the bed of the lake, the inner row of which kept the island in shape, and the external rows acted as defences and breakwaters."[43] But these views convey only a partial notion of a more comprehensive system, the meaning of which I was only able to perceive after my experience at Buston. Notwithstanding that I made the structural arrangements of the Lochlee crannog a particular point of study, I failed to adduce a satisfactory theory for the details recorded; and, beyond showing that the two inner circles of uprights, with their radial and circumferential transverses which immediately surrounded the log pavement, formed a kind of breastwork or wall some 3 feet high, I made no advance on Dr. Stuart's theory. I could offer no explanation of the other large mortised beams found external to this circle, nor of the network of oak beams--some with mortised holes, and others with tenons to fit into continuous beams--which became manifest on making the deep shaft, and appeared to permeate the whole structure of the island. The advantage of carefully recording every fact, however trivial or obscure, has never been better illustrated than in this very article (that on the Lochlee crannog), as, with the more recent light thrown upon the subject, there can be no doubt that these structures, as well as the mortised beams (one of which contained three holes) lying on the western margin of the crannog, were some of the radial beams of an encircling girdle, still _in situ_, which surrounded and knit together the island in a precisely similar manner to that at Buston, as described at page 197. At Buston also, the inner circle, as evidenced by its mural remains, formed part of the enclosure surrounding the log pavement, and thus corresponded with, and served the same purpose as, the breastwork at Lochlee. Again, on the south side of both crannogs, the circles were more numerous, and occupied a larger area than on the north side, but with this difference,--that at Lochlee the midden covered the greater portion of this space, which at Buston was converted into an open and partially paved promenade.