384 Proceedings of the Royal Physical Society. 



The area over which the Ballantrae volcanic rocks and 

 the Radiolarian Cherts are known to exist in the Southern 

 Uplands is about 2000 square miles ; but during the last few 

 years a narrow strip of rocks containing a volcanic zone, 

 Eadiolarian Cherts, and black shales, has been mapped by the 

 officers of the Geological Survey at intervals along the High- 

 land border from near Stonehaven, on the east coast, to the 

 island of Arran. In this belt there is a similar succession 

 and arrangement of these rocks to that of the Ballantrae 

 rocks in the Southern Uplands. They were first differentiated 

 from the Highland schists by Mr Barrow, who mapped their 

 outcrops in Forfar and Kincardine shires.^ Mr Dakyns,^ 

 and afterwards Mr Clough, mapped them in extreme detail 

 where they occur in the neighbourhood of Callander and 

 Aberfoyle, in Perthshire and Dumbartonshire,^ and in 1899 

 Mr Gunn announced their occurrence in Arran, where they 

 occupy a similar position to that which they hold elsewhere 

 along the Highland border line.^ The black shales associated 

 with these rocks have not yet afforded any identifiable 

 Graptolites, though they shov/ markings which may have 

 been their remains, but this may be owing to the fact that 

 the rocks are much shattered, cleaved, and even meta- 

 morphosed in places. There is a strong presumption, 

 nevertheless, that these rocks are the reappearance of the 

 Ballantrae horizons on the north side of the newer Palaeozoic 

 rocks of the central valley of Scotland, in which case the area 

 over which the Ballantrae rocks occur in Scotland alone must 

 be at least 4000 square miles. An even greater development 

 of these peculiar rocks, and doubtless a continuation of the 

 same belt, occurs next to rocks like the Highland schists of 

 Perthshire in County Tyrone, in Ireland, so that the area 

 over which they occur must be very wide.^ If the identifi- 

 cation of the Ballantrae rocks with those of the Highland 



1 Ann. Rep. Geol. Sur., p. 266, 1893. 

 '^Ibid., p. 266. 



^ Ibid.y 1895, p. 26; 1896, p. 28; Mem. Geol. Sur., "The Silurian Rocks 

 of Britain," pp. 422, 429. 



^ Mem. Geol. Sur., "Summary of Progress for 1899," pp. 66-71, 82. 

 ■' A. Geikie, "Ancient Volcanoes of Britain," vol. i. p. 240. 



