Dr Hibbert's Observations on Vitrified Forts. '.191 



the vicissitudes of the weather better perhaps than any other 

 artificial cement that had ever yet been discovered." 



Thus, in coinciding with Williams, that vitrification was in- 

 tended as a cement to strengthen the walls of forts, he only 

 differed from him in the more correct view which he took of 

 the real structure of these defences, or in the theoretical use 

 which he made of an extraneous vitrescible matter. He pro- 

 perly remarked of the vitrified fort of Knockfarril, that its 

 wall was continued quite round the area, being adapted to the 

 form of the hill, so as to stand on the brink of a precipice, all 

 round, with the exception of the places of entrance. Such 

 being its construction, he next supposed that vitrification was 

 effected by the aboriginal Britons after the following manner : 



" Through all the northern parts of Scotland, a particular 

 kind of earthy iron ore of a very vitrescible nature much 

 abounds. This ore might have been accidentally mixed with 

 some stones at a place where a great fire was kindled, and 

 beino- fused by the heat, would cement the stones into one solid 

 mass, and give the first hint of the uses to which it might be 

 applied. A few experiments would satisfy them of the possi- 

 bility of executing at large what had been accidentally discover- 

 ed in miniature. This knowledge being thus attained, no- 

 thing seems to be more simple and natural than its application 

 to the formation of the walls of their fortified places. Having 

 made choice of a proper place for their fort, they would raise 

 a wall all around the area, building the outside of it as firm 

 as they could of dry stones piled one above another, the inter- 

 stices between them being filled full of this vitrescible iron ore ; 

 and the whole supported by a banking of loose stones piled 

 carelessly behind it. When the wall was thus far completed, 

 with its facing all round reared to the height they wished for, 

 nothing more was necessary to give it the entire finishing, but 

 to kindle a fire all round it sufficiently intense to melt the vi- 

 trescible ore, and thus to cement the whole into one coherent 

 mass, as far as the influence of that heat extended. As the 

 country then abounded with wood, this purpose would he 

 readily effected by building a stack of wood round the whole 

 outside of the wall, and then setting it on fire. It was pro- 

 bably with a view to enable them to build thia stack of wood 



