264 GNEISS. 



N. Schistose felspar containing- crystals of born- 

 blende interspersed. Glen Tilt. 



O. Actinolite occupying the place of hornblende. 

 Sutherland. 



P. Compact felspar, argillaceous schist, and any 

 one or more of the other ingredients of gneiss. Lewis. 

 Loch Carron, 



Of all these I may remark, that the geological 

 position and general features are the same as those 

 of the most ordinary gneiss, and that they often 

 pass into the regular varieties. It is perhaps 

 superfluous to remark, that although I have thus 

 distinguished the varieties of gneiss by fixed divi- 

 sions, there are, as in all cases of compound 

 rocks, intermediate gradations which cannot be 

 decidedly referred to either. But I may observe 

 that many other combinations probably exist, and 

 that an ideal catalogue of much greater extent 

 might easily have been formed. The present 

 enumeration has been rigidly limited to the 

 varieties actually observed. 



No division is here made of those varieties 

 which contain c^eeasienaK minerals, however 

 abundant, or in whatever manner disposed. 



