on the Mountain Cruachan. 129 



at 24 miles, with no variation of character ; but of its breadth be- 

 tween north and south I am unable to speak, the country being 

 absolutely trackless and uninhabited. 



It appears to me however that it extends, perhaps with some 

 interruption, from the schistose rocks to Ben Vualach by which it is 

 connected with the granite district of Loch Ericht ; and there is 

 equal reason to suspect that to the westward of this it will be 

 found similarly connected with the granite of Ben Nevis. 



Where it terminates, at the head of Loch Rannoch, it forms 

 hills of moderate elevation, and these are immediately followed 

 and covered by a succession of schistose rocks, consisting of quartz 

 rock, micaceous schist, and an obscure variety of gneiss which I have 

 already had occasion to describe in another place.* The junction 

 of the two may be observed in different places, in all of which it 

 is invariably accompanied by the appearances already noticed at 

 Balahulish, namely, fragments of the different schists imbedded in 

 the granite. 



The schist which is here imbedded in the granite is often composed 

 of black scaly mica with a high lustre. Towards the junction of the 

 fragment with the surrounding rock it generally contains crystals 

 of hornblende. The fragments vary much in size, and I must add 

 that they differ completely in aspect from those accumulated plates 

 of mica which are found in the granite of Aberdeen, as well as in 

 many other granites. In other cases the imbedded fragments con- 

 sist of the same quartz rock and gneiss which form the general 

 body of these schistose rocks. If any mineralogists are unwilling 

 to consider them as imbedded fragments, it can only be said that 

 if they were really detached fragments they could possess no other 

 aspect than that which they now have. The head of Loch Spey, 



* Vide Paper on Quartz Rock, Vol. 4. 



