JF. S. Eudleston — Fird Inipremons of Assynt. 393 



The Eastern Eangre.— This is the real field of battle, out of which 

 three issues at least have to be decided. 1. Is there aa Upper 

 Quartzite? 2. What is the nature and geological position of the 

 " Logan " rock ? 3. Is the Upper Gneiss really a newer formation 

 properly overlying the Quartzite-dolomite ? 



1. Is there au Upper Quartzite ? — There are quartzy beds in the 

 "intermediate series," and possibly, in some places, in the Dolomite 

 itself; but the real question is, whether the important rock masses 

 referred to the Upper Quartzite are not repetitions of the series below 

 the FuGoid Beds. One thing is pretty clear, that, in this district at 

 least, where there is no " Logan " rock, there is no Upper Quartzite. 



Thus at Craig-a-Knockan the sequence seems clear enough. The 

 Quartzite dips steadily to the eastward from Coul More, and is 

 regularly overlaid by the " intermediate series " with its Fucoids, 

 " yellow beds," quartzy beds and impure dolomites, and the whole 

 is surmounted in the clifi'-section by the Dolomite just as at Strouch- 

 rubie. The great diiference consists in the fact that the Upper Gneiss 

 comes on at once, so that there is no room for an Upper Quartzite. 

 Of course it is open to the believers in an Upper Quartzite to say 

 that it was never developed, or has been denuded off previous to the 

 deposition of the overlying beds at this particular spot. 



But let us now revert to more disturbed ground, and, in fact, to 

 Murchison's type section at the head of Loch Assynt, known as the 

 Cnoc-an-drein section.^ This commences in the bottom of the longitu- 

 dinal hollow between the two ranges, and ascends in an east-north- 

 east direction. It is to the lower portion only that I would direct 

 attention. Matters are not so clear as in the Stronchrubie and 

 Craig-a-Knockan escarpments, where, as we have seen, no Upper 

 Quartzite presents itself. Here, at a short distance from the Post 

 Office of Inchnadampb, the dusky dolomites associated with a pecu- 

 liar kind of diorite succeed the intermediate series, and these again 

 are succeeded by the pale grey dolomites dipping moderately E.N.E. 

 The ground is broken, but gradually rises, the dips being inwards. 

 A bed of igneous rock is again seen to intervene, and then a sudden 

 rise in the ground is observed to be composed of compact quartzite, 

 with approximately the same dip as most of the underlying beds. 



The whole thing seemed all right, and I could not deny that 

 appearances were in favour of there being an Upper Quartzite at 

 this place, though my first question was, what has become of the 

 peculiar grit and conglomerate which underlies the presumed Upper 

 Quartzite of Ben More ? We continued to pass over successive beds 

 of this Quartzite all dipping into the hilL In it there are three beds 

 of igneous rock, each of which may be recognized by certain pecu- 

 liarities, though on the whole the type is not dissimilar from what 

 occurs in the dolomite.- Just above the third igneous bed the 

 Quartzite suddenW becomes vertical, and ultimately assumes a dip 

 opposite to the one below, so that, as one continues to ascend, the 



' Q J.G.S. vol. xvi. p, 217, and vol. xxx\ii. p. 242. 



^ Subsequent examination would lead one to suppose that porphyritic structure is 

 more frequent in the iuterbedded igneous rocks of the Quartzite. 



