GNEISS ISLANDS. GENERAL REMARKS. 



INTRODUCTORY REMARKS ON THE GNEISS ISLANDS. 



THE first group, in the order of examination that I have 

 adopted, is that of the Gneiss Islands. The greatest body 

 of this rock occupies the outer chain of the Western Isles, 

 which is so nearly identical from one end to the other, 

 as to admit of little variety in description. The next 

 portion, in point of dimension, forms the chain of Coll 

 and Tirey ; while lona, separated from these by a wide 

 channel, may almost be considered as independent. Rona, 

 and the northern part of Rasay, present a tract equally 

 independent, and far removed from all the others. 



The general bearings of these several divisions will be 

 found to conform more or less accurately to the leading 

 lines of the coasts of Scotland, as I have before remarked 

 of the islands in general; subject, at the same time, to 

 that deviation which has been already noticed. Yet it will 

 be seen that I have been unable to determine the actual 

 bearings of the strata in the outer chain, popularly known 

 by the name of the Long Island, I do not, however, 

 hold this to be a reason for assuming the non-existence 

 of such a continuous bearing in its stratification, but 

 should rather consider the directions of the coast lines 

 as sufficient indications of what I have been unable to 

 prove from an examination of the strata. This deficiency 

 may possibly have arisen from my own inattention; but 

 it will at any rate prove, that the observations have not 

 been biassed by theoretic views. I am rather inclined to 

 attribute it to the contortion and displacement of the 

 strata which the gneiss invariably presents wherever I have 

 examined it, throughout the course of that extensive 

 chain. Hence, it becomes impracticable to trace the 



