Dr. Mac Culloch on the Vitrified Forts of Scotland, 2.69 



adduced are sufficient to prove that some of the fused substances must 

 have been brought to that condition in a heat not less than 60 degrees 

 or upwards of Wedgwood's scale. Such then, at least, is one tem- 

 perature at which the walls of this fort have been fused. It may have 

 been much greater. It is perfectly evident that if a temperature of 

 60" existed in one part of the wall, pyrites lying near it must have been 

 decomposed. There could be no such discordancy of temperature 

 existing simultaneously, and so near, in a mass of this construction. 

 Hence then it follows, that the wall could not have put on its 

 present appearance by one heating, if it were all actually built pre- 

 viously to the application of the heat. This precludes the possibility 

 of the supposition contained in Mr. Tytler's hypothesis. Had the 

 fire, which he supposes the cause of vitrification, been produced by 

 the burning down of the wooden part of the compound wall which 

 he has imagined, it could not have happened that a vitrification 

 requiring a temperature of 60° should have taken place in one part, 

 while in another such a substance as pyrites remained unchanged. 

 The great heat requisite to effect the vitrification of the pudding- 

 stone, is an additional argument against this hypothesis, as It could 

 not have been produced by any quantity of wood capable of enter- 

 ing into such a wall, unless the wood had predominated to an 

 extent Incompatible vi'lth any Idea we can form of Its architecture. 

 It Is not indeed easy to conceive a plan capable of producing these 

 effects, and certainly none more feasible than the suggestion of Mr; 

 Williams. With him I should rather be Inclined to suppose that a 

 sort of furnace was constructed of a double earthen wall, In which 

 the materials were placed, with such a quantity of wood as was suf- 

 ficient to excite a strong heat, and that this operation was repeated 

 till the wall had gained Its wished for elevation. The earthen fur- 

 nace In which the Africans fuse their ores, seems to countenance 

 this supposition. The Imperfect ustlon of the upper parts may be 



