Above fifty of these vitrified forts in all have been found, dispersed over the shires of Inverness (in which they are most numerous), Ross, Creinarty, Banff Moray, Argyle, Aberdeen, Perth, Forfar, Kincardine, and Bute. Two or three have also been discovered in the southern counties of Wigton, Kirkcudbright, and Berwick. The moat celebrated are that on the hill of Knookfarril, or Knockfarril na Phian, that is, the Place of Fingal on Knockfarril, on the south side of the valley of Stmtlipeffer, two miles to the west of Dingwall In Rosa-shire ; that, already mentioned, on the hill of Craig Phaidrick. two miles west of Inverness; that on the hill of Noth, in Aberdeenshire; that on Dun 3IacSnioeliain, in Argyleshire ; that on the hill of Dunadeer, in Aber deenshire; that near Creich, in Sutherland ; that near the church of Amwoth, In Kirkcudbright.; that on the hill of Dunskeig, at the entrance of Loch Tarbert, in Argyleshire; that on the castle hill of Finhaven, four miles to the east of the town of Forfar ; that on the hill of Laws, near the village of Drumsturdymuir, a few miles to the north-east of Dundee; that at the entrance of the bay of Carradale, in Cantyre; that in the pariah of Kingarth, in the Isle of Bute; that (very slightly vitrified) on Barryhill, in the parish of Meiglo, Perth shire; those on Castle Finlay and Donavan, iu Nairnshire; that called Tordun Castle, about three miles from Fort Augustus; that on the west aide of Gleneves, In Lochaber, about three miles south from Fort William.
Setting aside the theory of the volcanic or otherwise accidental origin of the vitrified forts, which appears to be untenable, seeing that they are manifestly artificial struetures, we have still two suppositions between which to choose In accounting for the appearance they present. The vitrification may have been part of the process of their erection, and designed as a substitute for the ordinary cement ; or it may have been the result of accident afterwards. The latter view was suggested by Lord Woodhouselce so early as 1783, and has since been supported by Dr. Ilibbert and Sir George 3Inekensie; the fernier, which was that taken by Williams and other early investigators, has boon ably defended In recent times by the late Dr. John Maocullooli. It is Impossible for
us here to enter at length Into the considerations which have been advanced on both sides : they amount for the most pert to hut alight and unsatisfactory probabilities. Dr. Hibbert's notion Is that thu in cleaures were intended for the protection of beacon fires; and he has endeavoured to show that the elevations on which they are erected aro so chosen as that one of these ;finale could always be seen from another. His views are adopted by Mr. Wilson in his valuable ' At-chit:elegy of Scotland,' before referred to. Dr. Macculloch. on the other hand, maintains that this is not the fact. Besides, lie observes that the extent of most of tho enclosures is far beyond what could have been required for any beacon fire : the area of that at Amwoth, for instance, is not less than 2700 square yards. How also, it is asked, should it have happened, es In generally the me, that the walls should be vitrified on both surfaces, the exterior as well as the interior, if the effect was produced merely by the flame of a beacon lighted up within the inclosure / That they were intended for defensive military posts, Dr. Maccullech further contends, is manifest from the whole character of the works—both the vitrified walls and the surrounding defences, all of which, he says, " vary in form and size according to the ground they stand on, and are so contrived, just as a military work would be iu the hands of a modern engineer, that they may command all the points of access, and prevent the enemy from advancing anywhere under cover." M-tcculloch further sought to show that the material of which the walls are built has evidently been eelected with a view to its capability of being vitrified. But, as Mr. Wilson observes, his statements ' only confirm the fact, already familiar to the chemist and geologist, that there are few districts in Scotland where rocks do not occur more or leas capable of being vitrified." The materials that have been commonly used are granite or moorstone, limestone, sand stone, and what is called pudding-stone, all of which have the quality of being more or less easily fusible by fire. None of these forts are found south of the Tweed ; they appear indeed to be peculiar to Scotland.