272 Dr. Mac CuLLOCH &« the Vitrified Forti of Scotland. 



a design to vitrify can be deduced from this specimen, except that 

 of the great heat required to fuse it, which applies as well to this 

 case as to that of Dun Mac Sniochain. 



Having in these two instances detected the existence of a vitrifi- 

 able substance in the rocks from which the walls were constructed, 

 I was in hopes that all the other vitrified forts would be found to 

 occur In the vicinity of vitrifiable rocks. No mineralogical notice 

 has accompanied the accounts of those which have been observed 

 in Aberdeenshire, in Ross-shire, and other situations, nor had I an 

 opportunity of inspecting them. But I have since learnt that three 

 or four exist in Arisalk, a country consisting of gneiss and granite 

 rocks only. The refractory nature of these substances would almost 

 lead us to doubt that the buildings are actually vitrified, unless 

 hornblende or other unnoticed vitrifiable matters abound in them. 



It is but of late that similar structures have been detected in the 

 southern parts of Scotland. Three of them are found in Galloway ; 

 but I had an opportunity of examining only that which lies in the 

 parish of Amworth. It is a rectangular and simple wall, occupying 

 the summit of a steep and strong but low hill, and exhibiting the 

 usual general appearances. 



As the whole of this part of the country consists of common 

 grauwacke and grauwacke-slate, I was I confess incredulous about 

 the reported vitrification, on account of the refractory nature of 

 those substances. 



On examining the wall, it appeared that although it bore very 

 generally the marks of fire, the vitrification had occurred in very 

 few places and in distant patches. I was at a loss to account for 

 this circumstance, till on accurate examination of the surrounding 

 rocks, I found some places where the grauwacke assumed a peculiar 

 character, exhibiting distinct grains of imbedded carbonate of lime. 



