The Clyde Mystery | Page 9

layers of horizontal woodwork some portions of heather, bracken, and brushwood were detected, and below this came a succession of thin beds of mud, loam, sand, gravel, and finally the blue clay which forms the solum of the river valley. {28b} The piles penetrated this latter, but not deeply, owing to its consistency; and so the blue clay formed an excellent foundation for a structure whose main object was resistance to superincumbent pressure.
Outside the circle of piles there was, at a distance of 12 to 14 feet, another wooden structure in the shape of a broad ring of horizontal beams and piles which surrounded the central area. The breadth of this outer ring was 7 feet, and it consisted of some nine rows of beams running circumferentially. Beyond this lay scattered about some rough cobble stones, as if they had fallen down from a stone structure which had been raised over the woodwork. The space intervening between these wooden structures was filled up in its eastern third with a refuse heap, consisting of broken and partially burnt bones of various animals, the shells of edible molluscs, and a quantity of ashes and charcoal, evidently the debris of human occupancy. On the north, or landward side, the outer and inner basements of woodwork appeared to coalesce for 5 or 6 yards, leaving an open space having stones embedded in the mud and decayed wood, a condition of things which suggested a rude causeway. When Mr. Donnelly drew my attention to this, I demurred to its being so characterised owing to its indefiniteness. At the outer limit of this so-called causeway, and about 25 feet north-east of the circle of piles, a canoe was discovered lying in a kind of dock, rudely constructed of side stones and wooden piling. The canoe measures 35.5 feet long, 4 feet broad, and 1.5 foot deep. It has a square stern with a movable board, two grasping holes near the stem, and three round perforations (2 inches in diameter) in its bottom. On the north-west border of the log-pavement a massive ladder of oak was found, one end resting on the margin of the log-pavement and the other projecting obliquely into the timberless zone between the former and the outer woodwork. It is thus described in the Proceedings of the Glasgow Philosophical Society:{29}
'Made of a slab of oak which has been split from the tree by wedges (on one side little has been done to dress the work), it is 15 feet 3 inches long, 2 feet broad, and 3.5 inches thick. Six holes are cut for steps, 12 inches by 10 inches; the bottom of each is bevelled to an angle of 60 degrees to make the footing level when the ladder is in position. On one side those holes show signs of wear by long use.'
An under quern stone, 19 inches in diameter, was found about halfway between the canoe and the margin of the circle of piles, and immediately to the east of the so-called causeway already described.
I carefully examined the surface of the log-pavement with the view of finding evidence as to the possibility of its having been at any time the habitable area of this strange dwelling-place; but the result was absolutely negative, as not a single particle of bone or ash was discovered in any of its chinks. This fact, together with the impossibility of living on a surface that is submerged every twelve hours, and the improbability of any land subsidence having taken place since prehistoric times, or any adequate depression from the shrinkage of the under-structures themselves, compels me to summarily reject the theory that the Dumbuck structure in its present form was an ordinary crannog. The most probable hypothesis, and that which supplies a reasonable explanation of all the facts, is that the woodwork was the foundation of a superstructure of stones built sufficiently high to be above the action of the tides and waves, over which there had been some kind of dwelling-place. The unique arrangement of the wooden substructures suggests that the central building was in the form of a round tower with very thick walls, like the brochs and other forts of North Britain. The central space was probably occupied with a pole, firmly fixed at its base in the 'well,' and kept in position by suitable stays, resting partly on the stone 'cairns' already described, partly in wooden sockets fixed into the log-pavement, and partly on the inner wall of the tower. This suggestion seems to me to be greatly strengthened by the following description of some holed tree-roots in Mr. Bruce's paper to the Scottish Antiquaries: {30}
'Midway between the centre and the outside piles of the structure what looked at first to be tree-roots or snags were noticed partly imbedded in the