DURING THE TERTIARY PERIOD IN THE BRITISH ISLES. 



67 



across the fault, and pursue a W.S.W. line through the contorted crystalline rocks of the 

 Highlands. About two miles south, another dyke continues its normal course across the 

 belt of upturned Old Ked Sandstone ; but when it reaches the fault it bends round and 

 follows the line of dislocation, sometimes coinciding with, sometimes crossing or running 

 parallel with that line at a short distance (see fig. 12). 



Mr Clough has supplied me with notes of some remarkable examples recently observed 



Scale: one mck= one mile 



Fig. 17.— Map of the chief Basic Dykes between Lochs Riddon and Striven (C. T. Clough). The large E. and W. dyke 

 is a continuation of that which reaches the shore of the Firth of Clyde at Dunoon. 



by him in eastern Argyleshire, where broad bands of basalt or other allied rock run in a 

 N. and S. direction, and are formed by the confluence of N.W. and S.E. or N.N.W. and 

 S. S.E. dykes, where they are drawn into a line of fault. These broad bands, he says, are 

 not usually traceable for more than a mile or so, for the dykes of which they are made up 

 will not be diverted from their regular paths for more than a certain distance, so that 

 one by one the dykes leave the compound band to pursue their normal course. He adds, 

 that the occasional great thickness of those compound bands depends partly on the size 



