88 Revieivs — Geological Survey of Scotland — • 



intruded. Mr. Teall gives the following description of tbeir ap- 

 pearance under the microscope : " Uralitic hornblende, a saussuritic 

 aggregate of water-clear felspar and granular epidote, irregular 

 patches of sphene (leucoxene) and aggregates of chlorite." 



In chapter vii the minerals of the schists are enumerated and 

 partly described, whilst much attention is paid to the direction of 

 stretching. Chapter viii is devoted to the general physical structure 

 of the schists, together with remarks on metamorphism. The most 

 conspicuous feature of the schist area, as may be inferred from 

 previous remarks, is the great anticline of foliation running in 

 a direction about 35° W. of S. through the heads of Loch Goil, Loch 

 Striven, and Loch Riddon, and the hills about a mile north-west of 

 Tighnabruaich. There is no doubt that this anticline is a true arch 

 of an early foliation ; but scarcely perhaps an anticline of bedding. 

 The authors (and more especially Mr. Clough) apparently conclude, 

 after much weighing of the evidence, that at least five of the groups 

 on the north-west side of the anticline are unrepresented on the south- 

 east side, notwithstanding some apparent points of resemblance. 



Lines of actual rupture contemporaneous with the schist-making, 

 comparable to the " thrusts " of the north-west of Scotland, probably 

 do not occur anywhere in Cowal, except on the smallest scale, such 

 as strain-slips with throws not exceeding a few inches. Tho 

 numerous faults which have been mapped and which have effective 

 throws, are all later than the schist-making, and break up the 

 minerals and planes of schistosity instead of helping to form them. 

 To the question regarding the agents which produced the general 

 metamorphism of the district, Mr. Clough considers that it would 

 be premature to reply ; but he does not consider that there is any 

 exposure of igneous rock which would account for it. The alteration 

 effected by the Glen Fine granite, for instance, does not extend for 

 more than a mile, and is of quite a different character. 



The direction of the boundary fault between the Schists and the 

 Old Ked Sandstone is nearly parallel to that of the centre of the 

 anticline. This fault cuts off a shred of Upper Old Red Sandstone 

 rocks, which thus appear at the extremity of the peninsula that 

 terminates in Toward Point. They consist, in the main, of red 

 breccias and sandstones mixed with occasional blood-red and 

 variegated shales ; calcareous sandstones and magnesian limestones 

 are numerous on a certain horizon. One of the sections which best 

 illustrates the relations between the red marls and the metamorphic 

 schists occurs on the shore just to the south of Inellan pier. 



Chapters x to xiv are devoted to the igneous rocks (unfoliated). 

 A small part of the igneous complex of Garabhal Hill, etc., comes 

 within the district. These are, in fact, granitites with a tendency 

 to pass into a coarse dioritic rock ; the granitic rocks are generally 

 characterized by abundant porphyritic crystals of orthoclase felspar. 

 Considerable attention is paid to the character of the metamorphism 

 near the edge of the plutonic rock, chiefly with a view to contrast 

 the metamorphism special to its neighbourhood with that further 

 away near the anticline of Cowal. 



