Note 460 — Chapter III · STRONGHOLDS.

"I remarked that at Dun Mac Sniochain the materials of the hill itself were not vitrifiable, but that a very fusible rock was present at a short distance, or scattered in fragments about the plain. The same is true here, (Dunadeer); and in both cases the forts are not erected out of the materials nearest at hand, which are infusible, but collected with considerable labour from a distance. It is hence evident that the builders of these works were aware of the qualities of these various rocks; and it is equally evident that they chose the fusible in preference to the infusible, although with a considerable increase of labour. The obvious conclusion is that they designed from the beginning to vitrify their walls."—Highlands and Western Isles of Scotland, vol. i. p. 292.