THE CRAIG-DHU GRANITE. 19 



sandstone ranging along the lower part of the hill, the granite 

 on the upper part and southwards over the summit. The con- 

 tact is seen at only one point, which is on the hill side due south 

 of the summit level of the road. Here the granite seems to rise 

 through and overlie the sandstone; the rocks are intimately 

 blended and assimilated in structure; the sandstone is less dark 

 and more crystalline, while the granite has more the look of a 

 crystalline sandstone than is usual with it. The limits above 

 traced mark out an area much lai-ger than that hitherto 

 assigned to the granite. The weathered surface of the rock 

 over all the area is generally white; but the prevailing 

 colour in a fresh fracture is red. It is fine-grained, with 

 little mica in proportion to the quartz and felspar, and is 

 very similar to the fine-grained variety of the interior. 

 Drusy cavities often occur, lined with crystals of quartz and 

 felspar, and large crystals of mica are not infrequent. Mr. 

 Eamsay states (Guide to Arran, p. 1 2) that " It sends forth 

 veins into the adjacent sandstone; while specimens of the 

 sandstone, much altered by the effects of intense heat, may 

 even be found enclosed in the granite." We have not 

 noticed these cases of intrusion, nor are the precise spots 

 mentioned. We have, however, seen such in connection 

 with the porphyry of Windmill Hill, Jfco which the granite 

 succeeds on the west, and also in connection with the new 

 granite tract to be next noticed. 



T/te Craig -Dhu Granite. 



12. The other granite tract lies on the south side of the 

 Shiskin road, south-east of the farm-house of Glaister. 

 Here the hill, whose base is skirted by the road all the way 

 down from the " String," overhangs the valley of Mauchrie 

 water in a steep cliff called Craigmore, Craig-Dhu, or The 

 Corby's Rock. This cliff is the outer edge of a small plateau 

 or table-land, cut off from the higher ground behind, towards 

 Ard-Bheinn, by a deep hollow, which completely isolates it. 



