174 



GEOLOGY OF ARRAN. 



basaltic bed is traversed by a greenstone dike five yards wide, 

 and ranging W.N.W. This, as well as other dikes, traverse 

 to the very summit of the cliffs, intersecting the overlying 

 columnar greenstone, which is thus older than the greenstone 

 of the dikes, but newer than the claystone already noticed as 

 clearly erupted. We have thus here erupted rocks of three 

 ages. 



80. The sandstone, gradually ascending southwards, now 

 rises to the edge of the cliff, and the overlying trap retires 

 inland, but continues to occupy higher terraces over the sand- 

 stone. In front, near the cottages, the shore line is low, and 

 from this point southwards the trap appears in many interest- 

 ing relations with the sandstone, to which we can only 

 invite the observer's attention, without attempting to describe 

 them. The trap is an injected bed, and occurs in some 

 places overlying, in others in repeated alternation with, the 

 sandstone, and again the two rocks come together at the 

 same level. The dikes, too, are very singular; they make 

 strange turns and bifurcations, and one consists of alternate 



Fig. 33. 



bands of trap and sandstone. Presently after, a low cliff 

 begins and runs westwards by Kildonan Castle. This inter- 

 esting old keep (fig. 33) stands on the front of a flat terrace, 

 which runs back northwards to the trap hills, and faces the 



