134 POSITION AND NATURE OF [Ch. VII. 



strata can be traced at Loch Laigh, the shore fortunately 

 lying in a direction oblique to the line of junction. It pre- 

 sents a very distinct view of appearances of considerable value 

 towards the history of granite, which, however frequent in the 

 mainland of Scotland, are nowhere to be seen under more 

 favourable circumstances. There are two kinds of granite in 

 Mull, the one of a pale flesh colour, and the other of a high 

 red: these rocks are large-grained, yet compact, and their 

 mica is black. The strata consist of an alternation of mi- 

 caceous schist and quartz-rock ; and in some places the former 

 puts on the characters of a schistose gneiss. When these 

 rocks come in contact with the granite, they assume the fol- 

 lowing appearances: The quartz-rock becomes red, and is 

 found to contain felspar in large proportion, often resembling 

 fine-grained gneiss ; and it thus frequently passes into granite 

 by a transition nearly imperceptible. The mica-slate, in the 

 same situation, becomes a true gneiss. These changes, how- 

 ever, are very partial, commonly confined within a few feet of 

 the junction, and gradually vanishing as they recede. At a 

 distance from the granite the strata are thin and regular, but 

 next this rock they are variously disposed : in some places 

 they continue in the same direction, and in others their ends, 

 or even their sides, are united to the granite, and so firmly 

 adherent, that they cannot be separated ; and this irregularity 

 is greatest where veins pass from the granite into the strata, 

 It is worthy of remark, that the junction sometimes takes 

 place between the granite and the mica-slate ; at other times, 

 between the former and the quartz-rock. This is an im- 

 portant circumstance, since these beds being parallel, the 

 granite is not parallel to them ; being found in contact some- 

 times with one, and sometimes with the other, stratum. 



Here, also, as frequently happens at the junction of these 

 rocks, fragments of the strata are detached from the main 

 body and imbedded in the granite : and in some cases these 

 are so distinct, that the parts whence they were separated may 

 be traced, and the fragments, in imagination, re-united. 



