ARRAN. GEOLOGY. OVERLYING ROCKS. 411 



enumerate them, since scarcely any one presents appear- 

 ances different from those already described in this work. 

 They sometimes consist of plain basalt, at others of a 

 porphyritic basalt, or of greenstone ; and occasionally, all 

 these several substances occur in one vein. They are 

 very abundant in Whiting bay, where they traverse the 

 sandstone in all directions ; at times passing through it 

 in a course parallel to the beds. On the shore near 

 Corygills, one, of large size, and nearly vertical, is found 

 running S. W. ; being very conspicuous, and accompanied 

 by others of less note lying in various directions. This 

 example has already been noticed in speaking of the great 

 vein of porphyry with which it is associated ; and it is 

 further accompanied by another equally large, which 

 crosses the same vein at a considerable angle, extending 

 for some distance along the shore. On these I shall only 

 remark in general, that many of them are laminated, and 

 that these laminae being of unequal hardness, they yield 

 in an irregular manner to the action of the sea. Very 

 often they may be observed to waste most readily where 

 in contact with the sandstone ; apparently from a difference 

 of composition prevailing at the junction of the two sub- 

 stances. In some cases the sandstone has become indu- 

 rated at the same place ; but that is only to be detected 

 after similar exposure to the sea ; when a thin edge will 

 be found projecting an inch or more above the general 

 level of the rock, and accompanying the course of the 

 vein. 



These veins occur frequently along the northern shore 

 in the space formerly described as occupied by the 

 secondary strata. In one place not far from Scriden, 

 a mass of sandstone is found included between two of 

 them, where it becomes of a dark blue colour ; the 

 same hue also occupying those parts of the bed which 

 lie immediately on the outside of the veins, while, in 

 further progress, it resumes the usual red complexion. 

 Between the exits of the lorsa and Machrie rivers, 



