68 GENERAL COMPARISON OF 



there can be little doubt that they are detached portions 

 of that formation of gneiss which constitutes the chief 

 part of Morven, with the adjoining district of Ardgowar, 

 and the islands of Tirey, Coll, and lona. The approach 

 of the strata of Morven to the eastern shore of Mull, may 

 be traced in the southern Glas islands ; and it is probable 

 that they pass hence to the opposite side of the island, 

 beneath the sea and the superincumbent trap. If the 

 want of correspondence in the bearings be considered an 

 objection to this view, it must be recollected that similar 

 deviations are not unfrequent, and that there is moreover 

 some uncertainty respecting the real bearings of the pri- 

 mary strata of Mull. 



In comparing the detached portions of the secondary 

 rocks of Mull, we must be guided partly by general analo- 

 gies, and partly by corresponding circumstances in those 

 already examined in the northern Trap islands, and in 

 those which occur in the adjoining continent. 



The rocks of this division already described in treating 

 of those islands, are found also in Airdnamurchan and in 

 Morven ; and in circumstances which, without the aid of 

 analogy, would Iea4 us to conclude that they followed 

 in the same regular order. As those of Airdnamurchan 

 are however of little value in this comparison, I shall give 

 a sketch of those of Morven only ; the correspondence of 

 this tract to Mull being in every respect so perfect as to 

 leave no doubt respecting their geological continuity.* 



The far larger portion of this district consists of gneiss, 

 occupying the same north-easterly position which is predo- 

 minant throughout the western coast of Scotland. No 

 primary sandstone is here found, that rock having termi- 

 nated to the southward at Glen Elg. The western side of 



* Plate XX. fig. 12. In this, as in other similar sections, the propor- 

 tions are sacrificed to the necessity of bringing all the essential circum- 

 stances within moderate bounds. A map of Morven is not within the 

 limits of this work. 



