10 GEOLOGY OF ARRAN. 



Maoldon and the base of Goatfell, it gradually widens 

 presents bold precipices on both sides of the lower part of 

 Glen Rosa and along the south border of the granite nucleus, 

 between Loch Ghnuis, Dougrie, and Imochar, attains its 

 greatest development. Here the thickness of the slate band 

 between the granite and old red sandstone cannot be less 

 than 2000 or 3000 feet; whereas above Corrie it forms but 

 a thin band. The granite here closely approaches the old 

 red sandstone, but is nowhere in contact with it. The pre- 

 vailing dip of the slate over the whole district is the same 

 as that which it maintains in adjoining tracts beyond the 

 limits of Arrau namely, south or south-east at a high angle; 

 it is not arranged in mantle-shaped strata around the granite 

 nucleus, but is inclined towards it in some places, and off 

 from it in others. Thus, along the north side of the 

 nucleus, from North Sannox to Catacol, the dip is south or 

 towards the granite, at angles varying from 65 to 75. Thi s 

 is of course unconforuiable to the granite centre ; but a like 

 dip and inclination on the south side give conformability ; 

 and here, accordingly, from Maoldon by Glen Rosa and 

 Dougrie, and perhaps even as far as Thundergay, the slate 

 is seen to recline against the sides of the granite mountains 

 in a kind of mantling stratification. In many spots there is 

 great contortion and irregularity, indicating the operation of 

 violent forces, attendant on the upheaval of the granite, and 

 in several places, as above Corrie, and near Catacol, the 

 strata come against the granite end on, or nearly at right 

 angles. Reference will again be made to several of these 

 cases, as well as to local variations in the mineral character 

 of the slate. 



Granites of Hie Nucleus. 



G. The coarse and fine granites, as above traced, are found, 

 wherever they co-exist, in the same relative position ; the 

 coarse underlies the fine-grained. The outward aspect and 

 structure of the two kinds are very distinct, though the com- 



