Ch. VII.] GRANITIC AND SCHISTOSE ROCKS. 123 



the prolongation of the Alpine chain in the direction above 

 indicated.* 



Thus we learn that the absence of either the granitic or 

 schistose rocks, or of both, at the surface, does not indicate 

 that they are altogether wanting ; for they are frequently 

 found to exist at a lower level, being only concealed by a 

 subsequent and more recent formation. In the Brora dis- 

 trict, for example, rocks of the oolitic series are in contact 

 with the granite ; and the primary slates might be supposed 

 to be absent, if they had not been detected in small patches 

 at Clyne Kirk and near Loch Brora. It is, therefore, 

 very probable, that the granite is always surrounded by 

 primary slates, as is commonly the case : that the latter are 

 not always visible, may be attributed to the form of their sur- 

 face, or to an extraordinary accumulation of the newer 

 deposits. 



By these remarks, it is by no means intended to advocate 

 a universal order of succession among the rocks ; but only 

 to contend that the primary slates do succeed the granitic 

 rocks, when they are not visible at the surface ; and that this 

 circumstance can be explained by the analogy of those places 

 where the slate sometimes rises high on the granite, and at 

 other times falls to a low level in an undulating line ; thus 

 permitting newer formations to occupy its hollows, and to 

 come into contact with the granite. 



The next point for consideration is the angle at which the 

 primary strata are placed when in the vicinity of granite. 

 In Arran, this position of the beds of schist can be deter- 

 mined with certainty in many parts of this junction ; and 

 they may in general be said to recline against it : yet if, in 

 some cases, a given bed of schist be prolonged towards the 

 granite, it will be found to indicate the contact of the edges, 

 instead of the faces ; while, in tracing the linear direction of 

 the strata in a third set, they will tend to abut endwise 



* Geol. Trans. New Series, vol. iii. p. 305. Professor Sedgwick, and Mr, 

 Murchison on the Eastern Alps. 



