The archæology and prehistoric annals of Scotland

by Sir Daniel Wilson

But the most remarkable British fort to the north of the Tweed, if not indeed in the whole island, is that which crowns the summit of Caterthun, looking across the valley of Strathmore. Two neighbouring heights are occupied with British forts. The larger of these, called the White Caterthun, from the colour of its walls, is an elaborate, skilfully constructed stronghold, which must have formed a place of great strength when held by a hardy and well-armed native garrison. It is of an oval form, inclosing an inner area of four hundred and thirty-six feet in length, by two hundred feet in breadth. But this only constitutes what may be regarded as the citadel. Beyond it a succession of ramparts and ditches surround the height at lower elevations, including a much larger area, and affording scope for a more numerous body of defenders. The hollow is still visible, though now nearly filled up, which was once the well of the fort, and probably this strength was maintained as a rendezvous and place of temporary retreat for the entire population of the surrounding district. The White Caterthun has been repeatedly engraved, and its construction and details will be best understood by a reference to the plans and sections in Roy's Military Antiquities.[458] The Brown Caterthun, which crowns another hill about a mile to the north, is also a specimen of ingenious native fortification. Its ramparts are nearly circular, and a series of concentric intrenchments extend down the slopes of the height.[459] Both of these native military works have been constructed with immense labour. The astonishing dimensions of the rampart of the former, composed of an accumulation of large loose stones, upwards of a hundred feet thick at the base, and fully twenty-five feet thick at the top, with its extensive lower earth-works and ditches, excite surprise and wonder in the mind of every observer. General Roy remarks after a careful survey of it,—"The vast labour it must have cost to amass so incredible a quantity of stones, and carry them to such a height, surpasses all description."

Another remarkable hill-fort of the same class is at the Barmekyn of Echt, in Aberdeenshire; and at Dundalaiv, on an unusually steep and rugged height in Glenshiora, Badenoch, is one smaller, but perhaps more striking, from the superior masonry of its walls. These are from twelve to fourteen feet in thickness, and being built of thin flat schistose slate, the walls remain in parts fully fourteen feet high, and apparently as perfect as when first erected. The inclosed area of this ancient fortress also contains a well, and considerable ingenuity has been shewn in strengthening the weaker points of the position. Altogether, it is the most perfect relic of a British stronghold of the class that I know of in Scotland.

The so-called "Vitrified Forts" of Scotland which have been the subject of so many ingenious and baseless theories, form another interesting class of native works. Attention was first drawn to them by Mr. John Williams, in his "Account of some remarkable Ancient Ruins, lately discovered in the Highlands and northern parts of Scotland," published in 1777. Mr. Williams had been employed by the trustees of the Scottish estates forfeited in the last rebellion, to superintend some operations in his capacity of a civil engineer, and in the course of this he for the first time investigated the singular remains to which he gave the name of Vitrified Forts. So entirely new was the discovery that it was generally received at first as an extravagant fiction, and no London publisher could be persuaded to undertake the publication of Mr. Williams's Account. His facts, however, proved indisputable, and theorists thereupon undertook to combat his conclusions, and to assign to the supposed forts a volcanic origin. The appearance of some of the most remarkable of these works is well calculated to sustain such a theory. The fortified area on the Top-o-Noth, near the village of Rhynie, Aberdeenshire, for example,—one of the most remarkable specimens of a vitrified fort in Scotland,—could not be more accurately described than by comparing it to the crater of an extinct volcano.

Since the first announcement of Mr. Williams's remarkable discovery there has been no lack of observation or controversy on the subject, though not always with very satisfactory results. In 1825 the Society of Antiquaries of Scotland directed special attention to it, and the results of a series of careful investigations are published in the fourth volume of the Archæologia Scotica, made chiefly under the direction of the late Dr. Samuel Hibbert, one of the secretaries of the Society, and further qualified for the duty as an experienced practical geologist. The fruit of these investigations may be thus stated:—Dr. Hibbert arrives at the conclusion that the vitrification is an incidental and not a designed effect,—having formed no part of the process of erection of the forts or cairns on which it is now traceable, but resulting accidentally from the frequent kindling of beacon-fires as the signals of war or invasion, as well as from bonfires which formed a part of festive or religious rejoicings; and indeed from numerous independent causes, probably no less widely dissimilar in dates than in origination. The nature of the sites, also, where vitrification has been detected proves that it is by no means confined to fortified positions; nor when it does occur on such is it generally found diffused throughout the ramparts of stone, or even restricted to their limits. Dr. Hibbert accordingly rejects the name of vitrified fort for the more comprehensive and untheoretical one of vitrified site, as most descriptive of remains which appear to include small inclosures for the protection of beacon-fires; sites of bonfires periodically lighted at the ancient places of rendezvous for tribes or clans; and hearths of fort-beacons and signal-fires, occasionally occupying not the ramparts but the ditch.

The only argument which tends to throw any doubt on the result of Dr. Hibbert's conclusions is that of Dr. Macculloch,—a shrewd observer, little inclined generally to extend toleration to any antiquarian hobbies but his own,—who affirms, that in situations where the most accessible materials for constructing a stone fort are such as are incapable of being vitrified, suitable materials have been selected and brought with considerable labour from a distance.[460] But the evidence of design in the choice of such materials is by no means apparent. The examples referred to by Dr. Macculloch only confirm the fact, already familiar to the chemist and geologist, that there are very few districts in Scotland where rocks do not occur capable of being more or less vitrified. This subject is fully illustrated by an interesting series of experiments carried on by Sir James Hall, towards the close of last century, with a view to test some of the geological theories in reference to the igneous formation of rocks, which then furnished a fertile theme of controversy between the disciples of Werner and Hutton.[461] All the varieties of trap are so peculiarly susceptible of fusion, that they have been recently selected as the most efficient and economical flux in the smelting of copper ores. I am indebted to Dr. Francis Hay Thomson, the inventor and patentee of the ingenious application of the common rocks to this novel purpose, for communicating to me the results of his experiments. His invention chiefly consists in "the application of what are commonly called whinstones, and of other stones similar to whinstone—such as trap, basalt, sienite, and the like, being fusible silicates, as a flux in the smelting of copper ores." He has found all these materials capable of easy and complete fusion in a reverberatory furnace; but a much more moderate degree of heat would suffice to produce the conglomerated masses usually found on vitrified sites, where the larger stones are merely inclosed and cemented together by the fused matter. In reply to inquiries as to the probable effect of bale-fires kept blazing repeatedly on the same ramparts or heaps of stones, where a gradual accumulation of ashes from the burning pile must fill up the intervening spaces, and supply a flux capable of combining for the ultimate fusion of the whole, Dr. Thomson remarks:—

"Granite is per se very infusible; that of Aberdeen almost entirely so, in consequence of the presence of an overplus of silica. Sandstone is per se quite infusible, being almost entirely silica. Your supposition may, however, be correct, for the addition of the alkali produced from the wood-ashes would much assist the fusion of all kinds of stone that might be used in building these forts. Whinstone contains at least four per cent. of pure soda, fifteen of iron, and from twelve to twenty of lime. All these form a most fusible mixture, and the silica present is only in such proportion as is necessary for vitrification. Limestone is of itself not fusible except at a very high temperature; but the addition of either iron or soda with silica renders it at once vitreous. Although I am not certain as to the exact degrees of heat requisite for the fusion of these materials, I may mention that, in an ordinary reverberatory furnace, I have fused five cwt. of whinstone in one hour and a half, the product being a dark mass similar to bottle-glass; and I have no doubt, were proper precautions taken, that large slabs might easily be moulded for building purposes."

The degree of heat attainable in a reverberatory furnace manifestly greatly exceeds any temperature that could be produced by an exposed fire of wood; but the usual appearance of the vitrified masses found on the sites of forts or beacon-hills is such as proves them to be the product of a more moderate heat. The larger pieces are not fused into a homogeneous mass, but blocks of trap, granite, and sandstone, or occasionally all three in juxtaposition, are enveloped in a vitrified coating of irregular thickness, and bound into a solid piece by this extraneous substance. The alkali supplied by wood-ashes is abundantly sufficient to produce such a result. Carbonate of potash in contact with trap will readily melt at a red heat, and has a power of uniting with the constituents of the trap to form a fusible compound which hardens into glass in cooling. Fire-clay, which is altogether infusible, and less liable to be affected by heat than most of the known natural rocks, is employed on this account in making the chemists' crucibles; but if an alkali is melted in a fire-clay crucible, it forms a vitreous covering on the surface, and where large quantities are used even goes through the crucible. This is a fact familiar to the chemist, and so impossible is it to keep fused alkalis in contact with silicates, that only crucibles of platina or silver can be used for the analysis of silicious minerals. In this way even sandstone, though per se infusible, is perfectly capable of vitrification, and indeed is, under certain circumstances, peculiarly susceptible of it, as its great porosity admits of the ready absorption of the melted alkali.

This susceptibility of the degree of fusion usually observable on vitrified sites, which trap and others of the common rocks of Scotland possess, has long been recognised by able chemists; and when it is taken into consideration along with the very diversified and dissimilar circumstances under which vitrification has been observed, the conclusion seems inevitable, that it is an incidental and not a designed result of the application of fire. But neither the interest nor the importance of this inquiry is exhausted when we have established the undesigned origin of vitrified sites. The question still remains,—Are they peculiar to Scotland? because, even if we reject the idea that the cementing of stone buildings by means of fire is among the artes deperditæ Scotiæ, still the discovery of so many vitrified sites in nearly every district of Scotland, would seem to indicate the practice of peculiar customs and observances during those early centuries in which the primeval forests furnished an unlimited supply of fuel. It is at all times a precarious and unsatisfactory basis of argument which depends chiefly on the absence of contrary evidence. Nevertheless it is worthy of some note, that although upwards of seventy years have elapsed since Mr. Williams published his account of vitrified forts, no single example, so far as I am aware, has been discovered south of the Tweed.[462] This cannot be ascribed to the subject being one of mere local or temporary interest. It has excited much controversy, not only among English antiquaries, but among the students of various kindred sciences; and while the geological features of some districts preclude the possible existence of such structures, it will, I think, involve very important conclusions as to the peculiar customs of the early Caledonians, if it be recognised as an established fact, that neither in the Welsh Highlands nor in the stone districts of England, are any traces of vitrified forts or sites visible. It has been the fashion of late years to give the whole question the go-by in very summary terms as one that has already commanded undue notice. Such, however, is a more convenient than satisfactory mode of dealing with the inquiry. Dr. Hibbert has appended to his "Observations on Vitrified Forts," a list of forty-four sites already noted, extending over twelve Scottish counties, including the most northern and the most southern districts of the kingdom. To these others have since been added, both north and south, in the Orkney Islands, and in the vicinity of Jedburgh, near the English border. It will suffice, meanwhile, to note these facts, in the hope that English Archæologists may, on fitting occasion, seek a reply to the inquiries which they involve:—Were the southern Britons, whether Celtic or Saxon, or the intruding Scandinavians or Gauls, wont to kindle bayle or beacon-fires on cairns, forts, or elevated sites, with such frequency as to leave similar traces to those which are so common in Scotland? Or must we infer that these abundant remains are the result of ancient rites and customs peculiar to the races of the northern kingdom?

Dr. Hibbert has already invited the investigations of Scandinavian Archæologists, with a like view, anticipating, from the notices of Olaus Magnus, Snorro, and others, that vitrified sites should be found on the mountain tops in Norwegian provinces. Nineteen years have elapsed since Scottish Antiquaries appealed to those of Scandinavia for a reply. They have not been unmindful of the interests of archæological science in the interval, but still we wait in the uncertain negative which their silence furnishes; casting, meanwhile, some curious thoughts backward on the old Scottish festival of Beltane, and its apparent affinity to the rites of the Assyrian Baal.[463]

To attempt to assign a date for these primitive forts or vitrified sites would be manifest folly, but even to apportion them to one or more of those less definite periods is difficult. Some of them doubtless pertain to the earliest era of combined action, of which they would form one of the first results, while others may belong to a comparatively recent period; and, in particular, such border sites as those of Cowdenknowes and Howden Moor[464] perchance date no farther back than to those eventful times of watch and ward on the Scottish borders, quaintly referred to in the Act of James the Second's Parliament, in 1455, "for bailes making" to warn of the approach of the Southron foe: "Ane baile is warning of their cumming, quhat power that ever they bie of; twa bailes togidder at anis, they are cumming indeed; four bailes, ilk ane beside uther, and all at anis as foure candelles, suithfast knawledge that they ar of great power and meanis far."