STONE CIRCLES. 117 



In addition to these memorials of the past, ancient camps 

 and fortifications crown many of our hills. 



In some parts of Scotland the old hill fortresses present 

 the remarkable peculiarity, first noticed by Mr. John Williams 

 in 1777, of having been subjected to considerable heat. 

 Until 1837 these vitrified forts were supposed to be peculiar 

 to our island, but in that year Professor Zippe called atten- 

 tion to the existence of similar remains in Bohemia, and 

 since that time vitrified forts have been discovered in various 

 parts of France and Germany.* 



Lastly, the country is intersected by great dykes, or lines 

 of embankment, such, for instance, as the Wansdyke, the 

 Devil's Dyke at Newmarket, and Offa's Dyke, which runs 

 from the Bristol Channel to the Dee, thus roughly dividing 

 England from Wales, which were no doubt partly boundary- 

 lines and partly fortifications, like the Eoman Wall or the 

 still more remarkable Wall of China. 



Stone circles, or cromlechs, consist of rough upright 

 stones, arranged in a circle. The usual diameter is about 

 100 feet, but some are much larger, the principal circle at 

 Abury, for instance, being 1200 feet across. The stones 

 are placed at equal distances, and the number of them had 

 probably some significance. " The two inner circles at Abury, 

 the lesser circle at Stennis, and one at Stanton Drew, each 

 consisted of twelve ; the outer circles at Abury, the outer 

 circles of uprights and transoms at Stonehenge, the large 

 circle at Stanton Drew, and the circle at Arbor Low, each 

 of thirty ; those of Eollrich and Stennis, of sixty ; and the 

 large enclosing circle of Abury, of one hundred stones. Four 

 circles at Boscawen, and adjacent places in Cornwall, have 



* References to the various me- papers by Mr. Stuart and Dr. 



moirs in which these are described Fodisch in the Proc. Soc. Antiq. 



are given by Virchow, Zeit. f. Eth- Scotland, vol. viii. 

 nologie, 1870, p. 258. See also 



