MINERALOGY OF ARRAN. 345 



stratum of this kind is a sort of chalky limestone, which Calcareous 



contains rounded pieces of quartz, fragments of schistus, 



&c, so as to constitute a species of pudding stone. Many 



parts of the stratum contain few of these extraneous bodies, 



and would make excellent lime. Further on, a sort of 



pudding stone, red sandstone, and shiver, occupy the 



coast. 



Where the limestone rests upon the schistus, three whin- Schistus inter- 

 stone, veins intersect the schistus, and the strata that rest wn instone. 

 upon it. Where these veins run in the schistus, the cheeks 

 on each side are penetrated by the whinstone ; and frag- 

 ments of the schistus are found immersed in the whinstone 

 veins. One vein divides into two, like the letter Y ; and 

 pieces of slate are found immersed in the whinstone, at the 

 angle of separation. 



The Scriden rocks are strata of breccia, or puddmgstone, Rocks fallen 

 of most enormous thickness, and leaning upon the side °f mountain 

 the mountain at an angle of about 45- > . About a hun- 

 dred years ago, immense masses fell from these rocks, and 

 now encumber the beach, rendering it difficult and dan- 

 gerous to pass along shore. The concussion shook the 

 earth, and the sound was heard in Bute and Argyleshire. 

 On climbing towards the summit, found the whole of this 

 enormous mass of strata, which reaches almost to the top 

 of the mountain, had shifted from its original position ; 

 and that its transverse sections were separated from each 

 other, so as frequently to leave spacious gaps between. 

 In many cases too, the upper masses ride upon the ends of 

 those below them ; which, having no visible support, ex- 

 cite the most lively apprehension thaf the whole is about to 

 fall, and crush the beholder to atoms. The Scriden rocks 

 are reckoned the extreme point of Arran, towards north- 

 east. 



Red sandstone, with sometimes pudding stone, continue Sandstone and 

 along the coast, and ascend to the top of the mountain pu in *» stone » 

 where they meet the schistus. 



Near the Cock, these strata are intersected by a great intersected by. 

 vein of porphyry, the south-east side of which consists of porp yr)r ' 

 rhomboidal, sharp-angled crystals of feldtspar, inserted in 

 a red ground. On the opposite side, the ground is mostly 

 Vol. XVII. — Supplement. 2 A blue 



