----- 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. ----- Footnote 100: For this reason we are unable to compare the vitrified forts of Scotland with the scorified and vitrified ramparts which have been occasionally remarked as occurring in other countries of Europe. I know no example in England, but a considerable number have been noticed in France (_Memoires de la Soc. Antiq. de France_, vol. xxxviii. p. 83), one of which, at Peran in Brittany, has only the upper part of the walls vitrified, a circumstance which has also been noticed with respect to several of the Scottish forts. From the fact of a Roman roofing tile having been found firmly attached to the melted stones of the vitrified part of the wall of this fort, it is inferred that the period of the vitrifaction was subsequent to the Roman conquest. Scorified ramparts in Bohemia have been described by Dr. Jul. E. Fodisch in the _Proc. Soc. Antiq. Scot._, vol. viii. p. 155. It has been frequently stated that they do not occur in Ireland, but Dr. Petrie has noted four in Londonderry and one in Cavan (Stokes’s _Life of Dr. Petrie_, p. 223). -----