These are by no means isolated observations on this point, and when we consider how readily the exposed woodwork of an uninhabited crannog would be destroyed, either by the hand of man or the natural processes of decay, we need not wonder that it is only the stumps of the piles and generally submerged portions of these singular structures that remain to the present day.
The construction of a crannog must have been a gigantic operation in those days, requiring in many cases the services of the whole clan. Having fixed on a suitable locality—the topographical requirements of which seemed to be a small mossy lake, with its margin overgrown with weeds and grasses, and secluded amidst the thick meshes of the primæval forests—the next consideration was the selection of the materials for constructing the island. In a lake containing soft and yielding sediment of decomposed vegetable matter, it is manifest that any heavy substances, such as stones and earth, would be totally inadmissible, owing to their weight, so that solid logs of wood, provided there was an abundant supply at hand, would be the best and cheapest material that could be used.
The general plan adopted was to make an island of stems of trees and brushwood laid transversely, with which stones and earth were mingled. This mass was pinned together, and surrounded by a series of stockades, which were firmly united by intertwining branches, or, in the more artistically constructed crannogs, by horizontal beams with mortised holes to receive the uprights. These horizontal beams were arranged in two ways. One set ran along the circumference and bound together all the uprights in the same circle, while others took a radial direction and connected each circle together. Sometimes the latter were long enough to embrace three circles. The external ends of these radial beams were occasionally observed to be continuous with additional strengthening materials, such as wooden props and large stones, which, in some cases, appeared also to have acted as a breakwater. The mechanical skill displayed in their structure was specially directed to give stability to the island and to prevent superincumbent pressure from causing the general mass to bulge outwards.
South of the Scottish border the remains of lake-dwellings are too much decayed or imperfectly observed to furnish many reliable data bearing on this subject. So far, however, as the evidence goes it would appear that the artificial island in Llangorse and the lacustrine dwellings in Holderness were true fascines; the former, indeed, having all the appurtenances of the typical crannog.
The crannogs were made accessible by various means. Some had moles or stone causeways, the existence of which, in some instances, became known only upon the drainage of the lake. Hence it is conjectured that these approaches might have been always submerged, and so supplied, on emergencies, a secret means of communication with the shore. This idea was suggested by the tortuous direction which many of them assumed, as for example the causeway discovered in the Loch of Sanquhar which had a zig-zag direction and so could only be waded by persons intimately acquainted with its windings. Others were approached by a wooden gangway, the evidence of which now consists only of the stumps of a double row of piles. Others again were completely insulated and accessible only by boats. One feature regarding some of the wooden gangways deserves particular attention. Both at Lochlee and Lochspouts the piles were found to be tightly embraced at their lower extremities by a curiously constructed network of transverse beams. As the surface of these elaborate structures was buried from 3 to 7 feet beneath the lake-bed, my first impression was that they might have been used, like the submerged stone causeways, as a concealed means of communicating with the shore. To test this suggestion I had a special excavation made along the line of a gangway at the Miller's Cairn in Loch Dowalton. (B. 426, p. 102.) After digging through 3 feet of the consolidated and hardened mud, we came upon a stratum of fine blue clay, extremely tenacious, and little liable to displacement. The pointed stakes of the gangway, which penetrated into this clay only a few inches, here met with a firm resistance. It then occurred to me that the ingeniously arranged wooden beams at Lochlee and Lochspouts served merely the same end as the blue clay at the Millers Cairn, and that they were to be found only in localities where there was a great depth of mud incapable of affording a sufficient basis of resistance to the piles. Such difficulties have been encountered by the constructors of pile-dwellings in all countries; and it is curious to note the variety of methods by which they were overcome. The Swiss lake-dwellers sometimes surrounded the piles with heaps of stones which now go under the name of steinbergs; at other times split planks were laid on the soft mud into which the piles were mortised. The former plan was adopted on rocky shores too hard for piles to be driven in, and the latter where there was a great depth of soft mud, as at Wollishofen and other stations adjacent to the town of Zürich. In North Germany, as Persanzig, Aryssee, and other localities, the log-house principle, which greatly economised the materials, was adopted in the construction of the subaqueous foundations. It appears to me that this was the principle adopted in the structure of the great Irish crannog of Lagore, as Sir W. Wilde distinctly states that it was "divided into separate compartments by septa or divisions that intersected one another in different directions." It was in these compartments, which were filled with bones and black mud, that the antiquities were found; so that the crannog-dwellers must have used them as kitchen-middens. Originally they contained only water, but in the course of time they became filled with food refuse and other débris. House-cleaning was thus reduced to a minimum, while the laws of sanitation were not more violated than in the underground cess-pools of many of our modern dwellings. A curious statement by Wilde in regard to the disposal of bones at Lagore is that "the remains of each species of animal were placed in separate divisions, with but little intermixture with any others."
It may be also mentioned that the log-house structures described by Pigorini as lining the inside of the surrounding dyke in the terramara of Castione were perfectly analogous, only in this case the compartments were filled with clay and rubbish, so as to act better as contraforte to the clay wall.
Canoes are so invariably found associated with crannogs that their discovery in lakes and bogs has been considered by Dr. Stuart as an indication of the existence of the latter. This may be true in some cases; but in others, such as Closeburn, Lochwinnoch, and Loch Doon, three of the examples cited by him, it is more probable that the canoes were used by the occupiers of the mediæval castles in the vicinity of which they were found. From these and other instances that have come under my notice I have come to the conclusion that dug-out canoes do not indicate such great antiquity as is commonly attributed to them, nor do they therefore necessarily carry us back to prehistoric times.
There is no peculiarity in the structure or form of these dug-outs which distinguishes their age or nationality. There is a good collection of them in the Museum of the Royal Irish Academy. Some have pointed prows and square-cut sterns; others have both ends pointed; some have cross bands, like ribs, left in the solid oak at regular intervals, as if to strengthen the vessel; while others are uniformly scooped out without any raised ridges. They vary much in size and shape. The largest is thus referred to in the small handbook to the Museum:—"Down the centre of the room extends the largest known canoe, formed of a single tree. The remains measure 42 feet in length, and the canoe was probably 45 feet long, by 4 to 5 feet wide, in its original state. It was recovered from the bottom of Loch Owel, in West Meath, and cut into eight sections for purposes of transport. There is a curious arrangement of apertures in the bottom, apparently to receive the ends of uprights supporting an elevating deck."
One of the canoes found at Lochlee, the remains of which are still preserved in the Burns' Museum at Kilmarnock, measured when disinterred 10 feet long, 2½ broad, and 1¾ deep. There were nine apertures in its bottom, arranged in two rows, four on each side, with the odd one at the apex. These holes were perfectly round, and exactly one inch in diameter; but when the boat was found they were quite unobserved, being all tightly plugged up, and it was only long afterwards that the plugs, upon drying, dropped out and so revealed their existence.
During the summer of 1874 a canoe ([Fig. 177]) was discovered in Loch Arthur, or Lotus Loch, in the stewartry of Kirkcudbright, in the vicinity of a small artificial island, which is thus described by Rev. James Gillespie:—