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



easily conceived to have arisen from a partial neglect of the fire 

 after the wall had nearly attained its requisite height ; nor is there 

 any reason why it should not have been increased in height by the 

 addition of cold stones after a firm foundation had been obtained. 



One other circumstance in the appearance of the burnt stones is 

 deserving of notice before quitting this subject. The changes which 

 the mica slate has undergone, appear to be such as could not have 

 been produced but by long torrefaction, or by such a repetition of 

 the heat as I have supposed to be the result of design. The tran- 

 sient effects which would follow from burning down a wooden 

 wall, would scarcely have been sensible on stones of so refractory a 

 nature, which exhibit changes in many instances as great as if they 

 had been exposed for a long time to the heat of an ardent furnace. 



Such are the observations to which a consideration of the fort of 

 Dun Mac Sniochain has given rise. 



As this was the only one of these mysterious fabrics which I had 

 seen when the above remarks suggested themselves to me, I was 

 afterwards glad to have an opportunity of examining the fort on 

 Craig Phadric, it being that one on which most labour had been 

 bestowed, and that which I thought might possibly either confirm 

 or refute my notions on the subject. 



Its general appearance and military structure having been fully 

 and carefully described, I shall only indulge in a very few remarks 

 on its physical composition. 



The hill of Craig Phadric, on which it stands, is one of a numerous 

 set of pudding-stone rocks, which may be traced from Fyers, anti 

 for aught I know, beyond it. At Fyers they lie above the primary 

 rocks, which they doubtless separate as usual from the secondary 

 strata, as they may be seen near Inverness, succeeded by sandstone- 

 breccia and common sandstone. On the top of the rock there is a 

 deep deposit of rounded stones, consisting of fragments of the older 



