The Hill-Forts which are constructed of stone sometimes consist of a single wall drawn round the brow of a hill, and enclosing the more or less level area which forms its summit. One of this description at Garrywhoine, in Caithness, is an oval enclosure about 200 paces long by 65 in breadth. The foundation of the wall is about 14 feet thick, and in some places 3 or 4 feet of its height remains. In the thickness of the wall on the east side the remains of two chambers are visible. There were two entrances to the area of the fort, one at the north end and the other at the south end of the hill. The entrance at the north end has three of the great corner-stones of the gateway still in position. They are single stones or flat boulders about 5 feet high, set on end, having their broad faces in line with the exterior and interior faces of the wall, and the ends in the line of the entrance which is 7 feet wide. Only one of the stones similarly placed remains at the south entrance. The dilapidation of this remarkable example of a stone cashel was due to the construction of a mill-dam in the valley below, the stones having been rolled down the hill to form the embankment. I notice it because it is the only Hill-Fort I have seen which still retains the stone-pillars of its gateway, and because the story of its demolition illustrates the fate of many of the most perfect and interesting remains of our country’s antiquity.
A more complex variety consists of two, three, or more walls drawn concentrically round the upper part of a conical hill, at short distances apart, as in the case of the example known as the White Caterthun in the parish of Menmuir, Forfarshire. The area enclosed is a long oval about 450 by 200 feet. The enclosing wall has been of enormous size. Its remains have spread themselves over a width in some places of nearly 100 feet, and they now form a somewhat rounded embankment of from 4 to 6 feet high, encompassing the summit of the hill. About 150 feet lower down on the slope of the hill is another wall, equally ruined, and below it are the remains of a third. Beyond this there is an enclosure of an oblong form and of less massive construction, abutting against one side of the outer wall of the fort.[[99]] A fort of smaller size, but presenting somewhat similar features of construction, crowns the spur of Ben Ledi which overlooks the ford at Coilantogle, a little below the outlet of Loch Vennachar. The hill is precipitous on one side, and the walls do not encircle it completely, but the external faces of three encircling walls are in some places visible for a considerable distance round the less precipitous part of the hill. Abutting on the outer wall, on the side which is most accessible, is an oval enclosure less massively constructed, as at Caterthun.
There is another variety of these Hill-Forts which has attracted more attention on account of the singularity of the phenomena which they present. These are the Vitrified Forts, so called because in their walls there is always more or less of the scorified or vitrified appearance which is the result of the action of fire upon masses of loose stones. Although there has been perhaps more written about these singular structures than about any other class of antiquities, there is really little known of their special phenomena, and less of their real character.[[100]] In point of fact the real knowledge relating to the form, measurements, and composition of the structures and the observation of the phenomena they present has been entirely overlooked in fruitless discussions as to the modes in which the vitrifaction of the walls has been produced, and the reasons which may be conjecturally assigned for it. The result is that to this day, so far as I am aware, there is not a single scale-plan with sections, of a single one of them. When such plans and sectional drawings are available in sufficient numbers, we shall be able to say that the materials exist for the commencement of a systematic investigation of the nature and typical relations of the structures.
The fort on Knockfarril, which overlooks the valley of Strathpeffer, in Ross-shire, encloses an oval area of about 120 paces in length by about 40 in breadth. It was first described by Mr. John Williams in 1777.[[101]] Sections were then made through it from side to side, and Mr. Williams states that on the north side he found the ruins of the wall 12 feet high, although he came to the conclusion that this was a section of the width of the wall which had fallen flat outwards. With regard to the phenomena of vitrifaction, he states that the whole wall has been run together into one solid mass, but in another place he states that at the outskirts of the ruins and at the bottom of the hill there was a great quantity of large stones which had not been touched by fire, and from this he concluded that there had been some kind of stone buildings going round on the outside of the vitrified walls. It is to be observed that when he speaks of the whole wall being run together into one solid mass, he is not stating a fact, which he has observed, but a conclusion which he has formed from a partial examination. “I am of opinion,” he says, “and it appears by the ruins that the whole of the surrounding wall on Knockfarril has been run together by vitrifaction much better than the most of the kind I have seen.” He states also that immediately on the inside of the surrounding walls there were ruins of buildings in which the vitrifaction was much less complete, and these he imagined to have been a range of habitations reared under the shelter of the outer wall.
Craig Phadrig, near Inverness, when examined by Williams, presented the peculiarity of two vitrified walls, the remains of which could be traced quite round the inclosed area, while the remains of a third were visible at the entrance at the east end. The outer wall was founded on the rock, about 6 or 8 paces distant from the inner wall. Its greatest height did not then exceed 4 or 5 feet, but he found large masses of it adhering to the rock where it was first run. The area enclosed was from 80 to 90 paces long by about 30 broad.
The fort at Finhaven, near Aberlemno, in Forfarshire, is an irregular oblong with rounded corners, about 150 paces in length by about 36 in breadth. The walls are greatly dilapidated, and but a small part of their height is now visible. They appear to have been about 10 feet in thickness, and in some places there is still 4 or 5 feet of the height remaining. The vitrifaction is very unequal, and many parts of the wall scarcely show the action of fire, while in others the melted matter has run down among the interstices of the stones.
Dun Mac Uisneachan, in Loch Etive, was described by Dr. Maculloch in 1824, and more recently by Dr. R. Angus Smith, who made extensive investigations of the area of the fort in 1873-4.[[102]] It occupies the top of an oblong hill which is either very steep or actually precipitous on all sides. The area enclosed is about 250 yards long by 50 yards broad. It is encompassed on the verge of the hill by a wall which is still in some places from 5 to 6 feet high. The points made out by the investigation are thus stated by Dr. Angus Smith—(1) the weaker parts of the dun or defensible position were walled, the outer wall or part of wall being vitrified; (2) the wall of the western part is double; the outer being vitrified, the inner built in layers of flat stone, 9 feet being the distance from surface to surface; (3) the walls were built without mortar as in all these forts; (4) vitrified portions of walling were found overlying portions built in the ordinary manner and unvitrified. This I regard as the most interesting and important point ascertained by Dr. Angus Smith’s investigations regarding the construction of the so-called Vitrified Forts. It shows distinctly that the wall of a Vitrified Fort is not always, and in every part, a vitrified wall; and it suggests that instead of taking this for granted, in every case in which signs of vitrifaction are observed, the inquiry ought to be directed to the determination of the extent of such partial vitrifaction, wherever it is found to have been partial. Another interesting result of his researches was the discovery of the remains of dwellings within the area of the fort. They were rectangular constructions, having dry-built walls about 2 feet thick. A large refuse-heap of bones of the common domestic animals was found near them. Some querns, a portion of an iron sword, an iron ring about 2 inches diameter, and a convex plate of bronze 1¼ inch diameter, ornamented with concentric circles, the hollows of which were filled with red and the centre with yellow enamel, were found in the course of the excavations. The character of this relic, with its red and yellow enamels, is closely allied to that of the similarly enamelled bronzes which have been already described, some of which have been found in constructions of a very peculiar type which have yet to be noticed.
The latest examination of Vitrified Forts is contained in a paper by Dr. Edward Hamilton,[[103]] in which he gives detailed descriptions of two such structures in Arisaig, one of which is situated on a promontory in Loch na Nuagh. It is an irregular oval occupying the whole summit of the promontory, and measuring about 100 feet in length by about 50 feet in breadth. The enclosing wall varies from 6 feet in thickness and 7 feet in height to about 5 feet in thickness and 3 feet in height. In this case also the wall was not vitrified down to the foundation. Underneath the vitrified portion there was a depth of 3 feet of walling formed of water-worn boulders quite unvitrified. The internal part of the upper or vitrified portion of the wall was also unvitrified. From these appearances Dr. Hamilton concludes that the vitrifaction was the result of fire applied to the upper part of the wall externally.
From a consideration of these examples it is evident that the Vitrified Forts do not differ in any essential point of their character from the forts that are not vitrified—if vitrifaction be not a feature in the method of their construction. The results of former investigations have not produced evidence sufficient to carry the conclusion that the vitrifaction was accomplished at the time of their construction, or that it was a method of construction. The determination of this question lies at the end of an exhaustive investigation, and can only be obtained from evidence furnished by the phenomena of the structures themselves.
There is one fort in Scotland, at Burghead, in Morayshire, which presents the peculiar feature of being partially constructed of logs of oak alternating with layers of stones. The peculiarity of its dry-built stone rampart is thus described by Dr. Macdonald:—“To strengthen it, beams of solid oak (still measuring from 6 to 12 feet in length) take here and there the place of stones, and similar beams inserted end-ways pass into the mass behind.”[[104]] We only know the Vitrified Forts from their greatly dilapidated ruins, and it is a legitimate object of investigation whether any of them may yet present evidence of having been constructed with logs and stones in the manner exemplified at Burghead. This method of construction is characteristic of the Celtic or Gaulish forts of France. The rampart of Murcens, on the river Lot is constructed like that of Burghead, of unhewn and uncemented stones. In its mass, at regular intervals, there have been laid courses of oak logs disposed longitudinally and transversely as “binders” and “headers.” The spaces between the logs are filled with stones, and where they cross each other the transverse logs are fastened to the longitudinal rows by massive iron nails. There are two rows of logs laid parallel to the face of the wall and a little apart within its thickness, and these are crossed at every 3 or 4 feet by logs lying transversely and extending the whole thickness of the wall, so that their opposite ends appear in its exterior and interior faces. This is repeated at every 3 or 4 feet of the height of the wall. The same method of construction, with a greater proportion of timber to the mass of the wall, appears in the fort of Impernal, also on the river Lot.[[105]] It is obvious that by the application of fire to ramparts constructed on this principle, a partially scorified and partially vitrified appearance would be given to their ruins.[[106]] In the early annals the burning of fortified places appears as the common method of reducing them, and the legendary prophecy of the coming of Birnam Wood to Dunsinnane possessed a peculiarly fateful meaning if its walls were built not of stones alone but of stones and logs.