356 ARRAN. GEOLOGY. SCHIST. 



for ten yards. It will be a question for future considera- 

 tion, whether this irregularity, either in the contacts of 

 the two classes of rock, or in the positions of the schistose 

 beds separately considered, do not bespeak a common 

 relation of the granite to the whole deposit ; namely, that 

 of intrusion at a time posterior to the original stratification. 



To the north of Loch Ransa, the position of the schistose 

 beds is for a small space very regular, and their protruding 

 edges can readily be examined on the shore, while the 

 angle of their dip may also be ascertained. But although 

 this angle is, from the causes just assigned, of no use 

 in tracing the continuity or relation of these rocks, it 

 here serves to discriminate the schistose from the se- 

 condary strata which lie above them ; the example now 

 under review, which is well known to all those who have 

 visited Arran, presenting a very well marked instance of 

 that position which is called unconformable. Neither the 

 position of the one set of rocks nor of the other is so regular 

 as to permit any great nicety of admeasurement, were such 

 nicety of use ; but at the point which I examined, the dip 

 of the schistose strata is about forty degrees S. S. E. 

 and that of the secondary strata about thirty degrees 

 W. N. W. On cfther occasions where the connexion 

 between the primary and the secondary strata have 

 come under review, it has been shown that the un- 

 conformable position must be considered as accidental ; 

 and it will hereafter be seen, that, in Arran also, the 

 secondary strata which are, in t^he place now under review, 

 unconformable to the schist, are, in another, parallel to it. 



At the point last mentioned, the schist retires from 

 the shore to give way to the secondary rocks ; which com- 

 mence at this place, occupying a considerable portion also 

 of the hills that skirt the higher mountain group. But 

 it is still found between these strata and the granite, 

 extending far to the southward and occupying a con- 

 siderable space; and would doubtless present to an accu- 



