104 GEOLOGY OF ARRAN. 



stone is not well seen. So far as can be judged there is little 

 alteration on the sandstone. On the lower side a dike of 

 hard, blue, fine greenstone is in contact with the vein ; but 

 the portion touching the dike is shivery and crumbling. 

 Passing upwards to the new Lamlash road, indications of the 

 vein are seen on the north of a claystone bed, which is 

 quarried, on the west side of the road. On the east side, 

 some way above the road, the bed of claystone, formed below 

 of rhombic blocks, but slaty above, is worked extensively for 

 road metal ; and on the north side of this quarry the pitch- 

 stone vein is seen coming against the claystone, and partly 

 covered by it ; a wing, as it were, of the claystone bed 

 stretches partly over the pitchstone, so that it does not 

 reach the surface a curious relation rarely to be seen 

 among the Arran dikes. It is quite possible, therefore, 

 that it may be covered wholly or in part by the claystone 

 bed or vein below the road, since it is exactly in its line of 

 bearing. This relation of the two beds lends countenance to 

 the idea that these claystones are but altered sandstones. It 

 is remarkable that there is no trace whatever in the river bed 

 of this claystone vein. The pitchstone is traceable all along 

 the hill -side towards the N.E. to the crest of the moor; 

 whence it bends round nearly S.E., and reaches the base of 

 Dun-Dhu, as already pointed out. This course implies un- 

 dulations somewhat greater than any we have yet seen in 

 dikes, some of them being fully 30 ; but on the Corrie shore 

 they reach 80 ; and it is therefore quite conceivable, since 

 the continuity is made out so far, that our pitchstone vein 

 may bend round again after leaving Birk Glen, and re-appear 

 at Brodick school-house. Still it would be satisfactory to 

 find it at some intermediate point. 



This pretty Birk Glen would be fit for cultivation ; but it 

 has been long kept in its present state of wildness as an 

 excellent cover for woodcock. We may return from it by 

 the new road ; but there is more variety in descending the 

 stream and passing through the ornamental grounds connected 



