'Vol. 55.] IN THE KEaiON" OF LOCH AWE. 481 



planes, due to the development of sericitic mica. The mica, how- 

 ever, does not occur in definite recognizable crystals, but yet in 

 sufficient quantity to give to a fresh surface a distinct lustrous sheen. 

 On the weathered surface no mica is seen at all, and the rock 

 cannot be distinguished from a clay-slate. Although the rock is 

 cleaved, the bedding is quite distinct and clear, slight variations in 

 colour and texture making the bedding prominent even in a homo- 

 geneous condition. The surfaces of the cleavage-planes are smooth, 

 and usually quite free from puckerings. Besides the thin limestones, 

 very fine-grained quartzites and quartz-schists are intercalated. 

 These are well seen in the burn-sections immediately west of Tervin. 

 Proceeding along this strike, they are now met with in Eilean Beith 

 and Fraoch Eilean. Here they are green, highly calcareous slates, 

 associated with very fine-grained quartzites and hornblende-schist, 

 all in precisely the same comparatively unaltered condition as at 

 iSTew Inverawe. Still following the strike, they are next seen on the 

 mainland at Lag-na-Linnge on the east coast of Loch Awe, where 

 they occur as greyish-green phyllites associated with thin limestones, 

 and in the same unaltered condition as where first seen across the 

 loch at New Inverawe. Prom the east side of Loch Awe they may 

 now be traced continuously to the eastward without the interruption 

 of large sheets of water. As they approach Dalmally some zones 

 still retain their unaltered appearance, but the beds on the whole are 

 more crystalline. Instead of the uniform greyish-green tint on a fresh 

 face as seen at Inverawe, the colour is less uniform, because of the 

 development of scales of chlorite and the differentiation of the chlorite 

 from the mica. A mile still farther east, in the burn that passes 

 the Inn at Dalmally, they are no longer phyllites, but are in the 

 condition of mica-schists, with mica well developed on foliation- 

 plancs, and the white sericitic mica and green chlorite markedly 

 differentiated. Here biotite begins to appear in long blades and 

 irregular blotches ; the biotite is not affected by later movements. 

 Proceeding still farther eastward, the micaceous beds assume a more 

 silvery appearance by the increased development of mica. The 

 beds are also now intensely puckered, steady dips being no longer 

 discernible. Although the zodo as a whole persists in an even 

 course, the foldings and puckerings within the zone are enormous ; 

 the beds are also beginning to become far more indurated, and 

 weather out in crags ; farther west they are so soft that hollows 

 are readily formed out of them. Approaching the neighbourhood 

 of Ben Laoigh, they are not only intensely puckered and more 

 highly crystalline, but are considerably hardened. At Socach, 

 about 8 miles east of Dalmally, these processes of deformation have 

 gone so far that one is reminded of similar metamorphic characters 

 in the anticlinal district of Cowal ; they are coarsely crystalline, big 

 flakes of white mica and green mica or chlorite being interleaved. 

 They contain here also a large amount of extravasated quartz, folded 

 and cjushed. Unaltered biotite is developed, especially in the 

 calcareous portions. Small garnets may also occur in the indurated 

 calc-sericite. An excellent section of this coarsely-crystalline 

 Q.J.G.S. No. 219. 2 1 



