Several authentic stone crannogs in Scotland, as to which we have information, possessed no central pole, but had a stone causeway, still extant, leading, e.g. from the crannog to the shore of the Ashgrove loch, “a causeway of rough blocks of sandstone slabs.” [47b] If one stone crannog had a stone causeway, why should this ancient inhabited cairn or round tower not possess a stone causeway? Though useless at high water, at low water it would afford better going. In a note to Ivanhoe, and in his Northern tour of 1814, Scott describes a stone causeway to a broch on an artificial island
in Loch Cleik-him-in, near Lerwick. Now this loch, says Scott, was, at the time when the broch was inhabited, open to the flow of tide water.
As people certainly did live on these structures of Langbank and Dunbuie during the broch and crannog age (centuries 5-12) it really matters not to our purpose why they did so, or how they did so. Let us suppose that the circular wall of the stone superstructure slanted inwards, as is not unusual. In that case the habitable area at the top may be reduced to any extent that is thought probable, with this limitation:—the habitable space must not be too small for the accommodation of the persons who filled up the eastern third of an area of from twelve to fourteen feet in breadth, and in some places a foot in thickness, with a veritable kitchen-midden, of “broken and partially burned bones of various animals, shells of edible molluscs, and a quantity of ashes and charcoal . . . .” [48]
But Dr. Munro assures me that the remains discovered could be deposited in a few years of regular occupancy by two or three persons.
The structure certainly yielded habitable space enough to accommodate the persons who, in the fifth to twelfth centuries, left these traces of their
occupancy. Beyond that fact I do not pretend to estimate the habitable area.
Why did these people live on this structure in the fifth to twelfth centuries? Almost certainly, not for the purpose of directing the navigation of the Clyde. At that early date, which I think we may throw far back in the space of the six centuries of the estimate, or may even throw further back still, the Clyde was mainly navigated by canoes of two feet or so in depth, though we ought to have statistics of remains of larger vessels discovered in the river bed. [49a] I think we may say that the finances of Glasgow, in St. Kentigern’s day, about 570-600 a.d., would not be applied to the construction of Dr. Munro’s “tower with its central pole and very thick walls” [49b] erected merely for the purpose of warning canoes off shoals in the Clyde.
That the purpose of the erection was to direct the navigation of Clyde by canoes, or by the long vessels of the Viking raiders, appears to me improbable. I offer, periculo meo, a different conjecture,
of which I shall show reason to believe that Dr. Munro may not disapprove.
The number of the dwellers in the structure, and the duration of their occupancy, does not affect my argument. If two natives, in a very few years, could deposit the “veritable kitchen midden,” with all the sawn horns, bone implements, and other undisputed relics, we must suppose that the term of occupancy was very brief, or not continuous, and that the stone structure “with very thick walls like the brochs” represented labours which were utilised for a few years, or seldom. My doubt is as to whether the structure was intended for the benefit of navigators of the Clyde—in shallow canoes!