EXCURSION XIV. 173 



talus of fallen blocks a very perfect counterpart, though on 

 a small scale, of the great basaltic fagades of Mull and the 

 Antrim coast. Inland, the ground rises in successive ter- 

 races formed by the sheets of greenstone laid one over the 

 other like the steps on a pyramid. Under the cliffs the 

 scenery is wild and romantic, and the place altogether 

 affords the best field in Arran for the study of the basaltic 

 rocks. The peculiarities of soil and shelter have favoured 

 the establishment of a few uncommon species of plants. On 

 the level of the beach S. of the talus we first come on a 

 great bed of claystone, very like the great Corriegills bed, 

 hard, splintery, and breaking into small prisms. It is seen 

 in the sandstone slopes above, but does not intersect the 

 columnar facade of greenstone overlying the sandstone this 

 fixes the relative age of these two erupted rocks. The sand- 

 stone now first appears on the shore, and is immediately 

 traversed by a trap dike four yards wide, ranging N. 10 W., 

 and this, as well as the claystone, produces a decided alteration 

 on the structure of the sandstone. But there is nothing on 

 this part of the coast that equals in interest a pavement of 

 basalt which extends for 200 to 300 yards in breadth, and 

 from the sea line to the base of the cliffs. This causeway 

 forms the nearest approach we have anywhere seen to the 

 basaltic pavements of Staffa and the Giant's Causeway. The 

 rock is not all a pure basalt; much of it has a fine porphyritic 

 structure. The pillars are less perfect, less various in form, 

 and are without the cup and ball articulation, the test of a 

 perfect pillar; and many cracks crossing the surface somewhat 

 mar the uniformity of the prismatic structure. This latter 

 defect is perhaps owing to the action of the tide, which covers 

 the greater part of the bed; a portion of which, indeed, seems 

 to have been already removed by this cause. As this great 

 lava stream rushed through the sandstone strata, pieces were 

 torn off, borne along, permanently entangled in it, and are now 

 found isolated in the basalt and altered to a crystalline 

 structure. But there was another later irruption the 



