Dr. Mac Culloch on the Vitrified Forts of Scotland. 261 



was done with a view to strengthen the work, or else that it was 

 an effect of the rude manner in which they were supposed to be 

 erected. It would have been an extraordinary system of defence 

 which should have heaped up a pile of loose stones on the outside 

 of a wall. Modern warfare is satisfied when its ordnance has 

 produced such an addition to the face of an enemy's bastion. 

 A little attention also to the angle which loose stones assume when 

 they are at liberty, might have shown that such a system would not 

 cnly have prevented the defenders from approaching their own 

 walls, but would in fact in small works, such as those of this fort,, 

 have occupied a very considerable portion of the included area. 



It is the dilapidation of the unconsolidated parts of the building 

 which has produced this appearance. The thickness of the walls of 

 this fort, as nearly as it can be appretiated, is, as I have already stated, 

 twelve feet. They bear the marks of vitrification throughout their 

 whole extent, but in some places it is more complete than in others. 

 In no case does it seem to have extended more than a foot or two from- 

 the foundation, and the most perfect slags are found at the bottom of 

 the wall. As we proceed upwards, we find a mixture of porous slag 

 with stones which having been but partially fused have adhered toge- 

 ther in a mass. Higher still we meet with stones which though un- 

 vitrified are roasted by the action of the heat, and at length the marks of 

 fire diminish until they almost entirely disappear, leaving only a heap 

 of loose and unconnected stones. The loose part of the wall 

 having fallen through time, has caused that accumulation of rubbish 

 which we find about the vitrified parts. On account of this mixed 

 construction, we have no means of ascertaining the original height 

 of these works ; but if a judgment may be formed from the quantity 

 of loose stones which are found at the base of the walls, it was. 



