Vol. 55.] IN THE REGION OF LOCH AWE. 475 



varies considerably, but it may be stated generally that even in their 

 most altered condition the clastic nature of the rock is always 

 evident, and the alternations of bedding due to diflferences of texture 

 are apparent. The smaller pebbles may, however, be considerably 

 crushed and granulitized, and the larger grits show flattening and 

 drawing out. In some instances nevertheless, they appear to have 

 hardly suffered at all, microscopic examination failing to detect 

 signs of crushing. They seldom fracture along definite planes like 

 ordinary schistose rocks, and mica is not common in them. When 

 it occurs it is never in sufficient quantity to alter the gritty nature of 

 the rock, nor to form planes along which the rock will split. When 

 mica is present, it is always a white mica. 



The following microscopic slides from these unaltered grits 

 were described by Mr. Teall : — 



(5695) Cnoc-na-Moine (139 N.W.-W.). — Medium-grained grey 

 quartzose grit or quartzite. Large grains of quartz and turbid felspar, 

 together with micro-crystalline quartz, chlorite, etc. Quartz- 

 felspar-grit. 



(5696) 1 mile north-west of Inverliver (131 S.W.-W.). Fine- 

 grained greenish schistose rock. Quartz, felspar, sericitic mica, 

 chlorite, etc. Fine-grained schistose grit. 



Both the Ardrishaig and the Loch Awe Series have shared in the 

 foldings and crumplings which have been so fully described by 

 Messrs. Gunn, Clough, and myself in the south-eastern extension 

 of this district in Cowal. 



The beds have been intensely folded, and the folds are often so 

 closely packed that it is common for both limbs of the fold to hade 

 in the same direction. In the area to which this paper refers these 

 packed foldings are so numerous that no reliable estimate of the 

 dip of the stratigraphical divisions as a whole can be based on such 

 data. The mapping of the ground, for instance, between Loch 

 Fyne and the Sound of Jura has shown that the Loch Awe Series 

 is lying in a gentle trough of the Ardrishaig Series. In following 

 a section from Ardrishaig to Craignish, we find the Ardrishaig 

 Series near Lochgilphead being replaced by the Loch Awe Series, 

 which occupy an horizon here 5 miles in width, after which the 

 Ardrishaig Series comes up again. Although these Loch Awe beds 

 are lying in a very gentle trough of the Ardrishaig Series, the dips 

 are at a very high angle, continually increasing till, on an axis 

 corresponding roughly to the prolongation of Loch Awe, they 

 become vertical, and from this axis to Loch Craignish the dip 

 gradually lessens till it assumes the normal angle of about 30° at 

 Loch Craignish, much the same amount as at Ardrishaig, but the 

 beds dip in contrary directions. The dips, however, in such a folded 

 area merely indicate the hade of the limbs of the folds, which bear 

 no relation to the inclination of the division as a whole. In this 

 area of the Loch Awe basin it happens that, where the dips are 

 nearly vertical, the beds, taken as a whole, are nearly horizontal. 

 A remarkable instance of this structure is observed on the north 



