In these stormy hills, indeed, it is difficult to suppose that anything less imperishable than the gneiss, or granite, of which the blocks forming the circular forts are composed, would have preserved the original plan. In flatter and more turfy districts of Scotland, as well as in England, there are mounds seeming to be artificial, and cast in circular terraces, as if they had been put on a turning lathe and bevelled down. There is one of these—perhaps the most remarkable in Britain—at Old Sarum, and it was generally supposed to have some connection with the franchise of that scheduled corporation. How these could have been very available for forts it is difficult to imagine; and to devise any other purpose to which they can have been applicable would be still more difficult. But when it was reported in England, as it was about seventy years ago, that there were some ancient hill-forts in Scotland made of glass, the antiquaries, not having a prescience of the Crystal Palace before their eyes, turned from puzzling themselves about the earthen mounds in England, to burst forth in scornful laughter about the glass fortresses of Scotland. But people who have had much experience in the ways of this world, learn how the same word may, without the slightest misapplication, be used for very different things. The dingy slag-like lumps, with a vitreous fraction, found in the heather of some Scottish fortified hills, has undoubtedly a claim to the vitreous character, perhaps as strong as the glittering diaphanous squares which are to let in all the sun, and exclude the wind and rain, at Sydenham. That they were the creation of fire is certain; and though the geologists sought at first to make out a case of volcano, yet it became evident that it was administered by the hand of man; for the materials, which had been calcined and vitrified so as to resemble in a considerable degree the scoriæ of a glass-house, were built into walls round the summits of steep circular hills;—those with which we are acquainted have much the appearance, from their extreme steepness and regularity, of having been scarped. And then come the questions—were the vitrified masses produced by some accident, such as the burning of a stronghold? or were they a deliberate method of cementing stones together by fusion? or, perchance, were they the wide circuits within which might be consumed some whole forest of trees, cut down and piled together within a ring of stone, whether as a vast beacon, reddening the sky from the Tweed to Cape Wrath, or a sacrifice to the ancient God of fire?—Questions these which we respectfully decline taking the responsibility of answering.