Vitrified forts are stoneenclosures whose walls have been subjected tovitrification through heat.[1] It was long thought that these structures were unique to Scotland, but they have since been identified in several other parts of western and northern Europe.
Vitrified forts are generally situated on hills offering strong defensive positions. Their form seems to have been determined by the contour of the flat summits which they enclose. The walls vary in size, a few being upwards of 12 feet (3.7 m) high, and are so broad that they present the appearance ofembankments. Weak parts of the defence are strengthened by double or triple walls, and occasionally vast lines oframparts, composed of large blocks of unhewn and unvitrified stones, envelop the vitrified centre at some distance from it.[2] The walls themselves are termed vitrified ramparts.[3]
Nolime orcement has been found in any of these structures, all of them presenting the peculiarity of being more or less consolidated by the fusion of the rocks of which they are built. This fusion, which has been caused by the application of intense heat, is not equally complete in the various forts, or even in the walls of the same fort. In some cases the stones are only partially melted andcalcined; in others their adjoining edges are fused so that they are firmly cemented together; in many instances pieces of rock are enveloped in a glassy enamel-like coating which binds them into a uniform whole; and at times, though rarely, the entire length of the wall presents one solid mass of vitreous substance.[2]
It is not clear why or how the walls were subjected to vitrification. Someantiquarians have argued that it was done to strengthen the wall, but the heating actually weakens the structure. Battle damage is also unlikely to be the cause, as the walls are thought to have been subjected to carefully maintained fires to ensure they were hot enough for vitrification to take place.[4][5]
The expert consensus explains vitrified forts as the product of deliberate destruction either following the capture of the site by an enemy force or by the occupants at the end of its active life as an act of ritual closure.[6] The process has no chronological significance and is found during both Iron Age and early medieval forts in Scotland.[6]
SinceJohn Williams, one of the earliest of Britishgeologists, and author ofThe Natural History of the Mineral Kingdom, first described these singular ruins in 1777, over 70 examples have been discovered inScotland.[2] The most remarkable are:
For a long time it was supposed that these forts were peculiar to Scotland; but they are found also in theIsle of Man (Cronk Sumark);County Londonderry andCounty Cavan, Ireland; inUpper Lusatia,Bohemia,Silesia,Saxony, andThuringia; in the provinces on theRhine, especially in the neighbourhood of theNahe; in theUcker Lake; in Brandenburg, where the walls are formed of burnt and smeltedbricks; in Hungary; in several places in France, such as Châteauvieux (nearPionnat), Péran,La Courbe,Sainte-Suzanne,Puy de Gaudy, andThauron; also rarely in the north of England.Castle Hill,Almondbury in Huddersfield, West Yorkshire.[2]Broborg [sv] is a vitrified hill-fort inUppland, Sweden.[7]
The 16 September 1980 episode ofArthur C. Clarke's Mysterious World features a segment in which the archaeologist Ian Ralston examines the mystery of the vitrified fort Tap o' Noth and tries to recreate how it might be accomplished by piling stones and setting a massive bonfire, repeating the work ofV. Gordon Childe andWallace Thorneycroft in the 1930s.[8] The experiment produced a few partially vitrified stones, but it was asserted that no answers were gleaned as to how large-scale forts could have been crafted with the approach tried in the programme.[9]
One or more of the preceding sentences incorporates text from a publication now in thepublic domain: Munro, Robert (1911). "Vitrified Forts". InChisholm, Hugh (ed.).Encyclopædia Britannica. Vol. 28 (11th ed.). Cambridge University Press. pp. 149–150.
