_Proc. Soc. Antiq. Scot._, vol. iv. p. 350. A section and elevation of the rampart showing the oak-beams in position are given in Plate IX. of the same volume.
Memoire sur les ouvrages de fortification des Oppidum Gaulois de Murcens, d’Uxellodunum et d’Impernal situes dans le department du Lot. _Congrès Archeologique de France_, xli. session. Paris, 1875, p. 427.
The late Mr. Ramsay, Director of the Geological Survey, records a circumstance which has an obvious bearing on the question of the possibility of such vitrifaction. Near Barnsley, in Yorkshire, the country affords no good material for road-metal the sandstones made from the debris of granitic gneiss pounding up rapidly under cart-wheels. "To obviate this defect the following process is adopted:—The stone being quarried in small slabs and fragments is built in a pile about 30 feet square and 12 or 14 feet high, somewhat loosely; and while the building is in progress brushwood is mingled with the stones, but not in any great quantity. Two thin layers of coal about 3 inches thick, at equal distances, are interstratified with the sandstones, and a third layer is strewn over the top. At the bottom, facing the prevalent wind, an opening about 2 feet high is left, something like the mouth of an oven. Into this brushwood and a little coal is put and lighted. The fire slowly spreads through the whole pile and continues burning for about six weeks. After cooling, the stack is pulled down, and the stones are found to be vitrified. I examined them carefully. Slabs originally flat had become bent and contorted, and stones originally separate glazed together in the process of vitrifaction."—_Proc. Soc. Antiq. Scot._, vol. viii. p. 150.
[Illustration: Fig. 251.—Section of Hill-Fort of Dunsinnane, showing underground chambers within its area. (Not to scale.)]
The Hill-Fort of Dunsinnane (a section of which is shown in Fig. 251) is an oval circumvallation crowning the summit of a conical hill, some 800 feet in height. The rampart is now chiefly composed of earth intermixed with boulders, and is in some places about 20 feet wide at the base, rising to a height of from 6 to 8 feet. Fragments of vitrified matter, cementing masses of small stones together, are found in the rampart. The space enclosed is about 150 yards long by 70 yards wide and almost level. Towards its south-east side were two underground chambers 20 feet in length, from 6 to 8 feet in width, and 5 to 6 feet high. The chambers communicated with each other, near their extremities, by two passages low and narrow, not much exceeding 2 feet in width and 3 feet high. The floors of the chambers were paved with rough slabs. The walls were built with undressed stones, which at the height of 2 to 3 feet above the floor began to converge until the roof was spanned by flagstones laid across. The floors were covered with ashes and refuse, consisting chiefly of the bones of horses and cattle, and horns of deer. A quern was found by the side of one of the passages, and in another were parts of three human skeletons. Near the entrance to the circumvallation a bronze spiral finger-ring, described as of exquisite workmanship and formed like a serpent, was found.[107]