-aSo antiquities in Scotland, -^ug. 29; 



a stone was entirely vitrified, and another part of it 

 unvitrified through every part of the wall. 



This phenomenon most clearly proves, that' the 

 vitrification itself was not a volcanic production, 

 but a work of art. And the free stone quarry, be- 

 low the foandation of the wall, is the clearest de- 

 monstration, that the hill itself on which the fort, 

 stands, is not formed by a volcano; for free stone has 

 never yet, that I know of, been suspected to be of a 

 volcanic origin. 



The appearance of the heart of this broken down 

 wall, so exactly resembled thatof a lime kiln I once 

 saw, that had been in part vitrified during the bur- 

 ning of it, that it immediately occurred to me, that 

 the phonomcna in both cases might be attributed to 

 a similar cause. — In the lime kiln, the lime stone be- 

 ing very much mixed with »arid, and consequently 

 very vitrescible, there were irregular horizjont^\ 

 layers, or streaks of vitrified matter, with spaces*, 

 more or lefs between, in which some part of the 

 stone had not been so much burnt as to be capable 

 of falling down into lime, with the additicm of wa- 

 ter, while other parts of it fell down into lime, so- 

 that it remained a mixed mafs, exactly resembling^; 

 the other. 



The cause of this phenomenon in the lime kiln, - 

 we well know was the irregularity in tiie force of 

 the winds that prevailed during the time the kila^ 

 was burning. When the wind was very high, it*: 

 acted as a bellows upon the fuel put among the 

 stones for the purpose of calcining them, and by con- 

 sequence, it burnt then with so much force as to 



