ARRAN. GEOLOGY. SCHIST. 365 



on the mountain mass. It is therefore evident that 

 there can no longer be a common dip between the 

 two series ; since the general tendency of the micaceous 

 or south-western, is the reverse of that of the north- 

 eastern, or argillaceous strata. It is also obvious, that 

 the dips can no longer be conformable to the prevailing 

 tendency of the whole line as it occurs in the great 

 tract already mentioned. 



With respect to the common direction of the whole 

 schistose mass of Arran, it is evident from the preceding 

 remarks that it can possess none, and therefore admits 

 of no comparison with that of the analogous schists 

 on the mainland. But it was proved that the mutual 

 boundary of the two series was in this island directed 

 from the south-east to the north-west, in an order the 

 reverse of that of the two conterminous and analogous 

 series on the mainland ; and by that boundary the change 

 of direction which the whole mass has undergone may 

 therefore be estimated. 



Finally it may be remarked, that notwithstanding these 

 differences both in dip and direction, the place geogra- 

 phically occupied by the schist of Arran, lies on the 

 prolongation of the general line of these strata as they 

 traverse Scotland ; and thus their identity in general 

 connexion is no less established, than it is by their com- 

 munity of structure, and of relation to the secondary 

 strata. 



The only differences therefore to be accounted for, are 

 those in the direction and in the dip. In attempting 

 to explain these it must be remarked, that no granite 

 occurs either among or near these strata in any part 

 of their linear course. In Arran, where it does occur, 

 all regularity disappears. If to have traced a series so 

 singular and so perfectly identified, through so long a 

 space, every where regular where granite does not occur, 

 but losing that regularity where this rock is found, is not 

 deemed sufficient to prove that the granite is the cause of 



