part 2J THE SOUTH-WEST HI&HLANDS OF SCOTLAND. 91 



attenuation in the other, and this, of course, would at once betray 

 the direction of movement. It is disappointing, therefore, to find 

 Clough quite definite in his asseition that fig. 2 represents the 

 general state of affairs in both limbs of his Carrick- Castle 

 Fold. (At the end of Chapter VII, 1897, p. 82, Clough, for quite 

 other reasons, contemplates the inversion of the earh^ folds and 

 accompanying foliations of Cowal by the Carrick- Castle Fold. 

 Such inversion, if superinduced ujDon a previous inversion, might 

 well account for the absence of anything approaching schuppen- 

 struktur. But Clough whoU}^ neglects this suggestion of his 

 elsewhere in his account, and I do not think that it should be 

 regarded as an integral part of his interpretation.) 



The intensive study of our North- West Highlands by Dr. 

 Peach & Dr. Home, and the contemporaneous investigation of the 

 more ample exposures of Scandinavia by Tornebohm, alike 

 emphasize another imjDortant aspect of the matter. On approach- 

 ing a mountain -chain from the front, one commonly finds the 

 original structures of the rocks of the foreland increasingly de- 

 formed. Locally, the condition of the rocks of the South- West 

 Highlands is difficult to reconcile with this familiar exi^erience. 

 I have already partly indicated the evidence of persistent south- 

 eastward movement during the main period of nappe-formation. 

 As indicated in PL I, the Loch-Awe Nappe is interpreted as a 

 klippe, or outlier, resting on the Iltay Nappe. Naturally, one 

 might expect less evident distortion of the rocks of the Iltay 

 Nappe in Cowal than in Islay, but the reverse actually occurs. 

 In Islay many outcrojDs of flagstone are known with ripple-marks 

 still perfectly preserved ; in Cowal such original details are lost 

 sight of in the general deformation. As a tentative explanation, 

 I suggest that local conditions, including temperature, may have 

 been the determining factor in producing this anomaly. The 

 Cowal region may have been more heated than the Islay region, 

 and accordingly more inclined to react generously and diffusely to 

 mechanical stimulus. 



There remains but one other important source of information 

 that need be touched upon, and that is the facies of far- travelled 

 nappes. Igneous, as contrasted with sedimentary, facies helped 

 Hutton long ago to establish the subterranean origin of the lava- 

 flows of Scotland. Alpine, as contrasted with Helvetian, facies 

 helped Dr. Schardt in much more recent days to realize the 

 southern origin of the great invading nappes of his native moun- 

 tains. As in the Alps, so in the South-West Highlands, considera- 

 tions of facies are of great importance. They do not, indeed, tell 

 us from which direction the Loch-Awe Nappe travelled into its 

 present position ; but they do warn us against supposing this 

 nappe to have spread in mushroom fashion from a root beneath. 

 If the Loch-Awe Nappe originated as a mushroom, one would 

 expect it to reproduce in itself the Isla}'- facies ; but such is not 

 the case. 



