OF THE HIGHLANDS. 421 



From a consideration of these two sections it would seem that in the 

 eastern one across Perthshire we have the nearest approach to the normal 

 order of the rocks. In the interior of Highland Perthshire they are compara- 

 tively flat, but as the Highland frontier is reached the dip rapidly increases 

 to high angles, still, however, dipping beneath the rocks of the interior. Here 

 there is a syncline, of which the northern limb is comparatively flat and 

 composed of younger rocks, while the southern limb is exceedingly steep 

 ushering in the lower and older beds. This simplicity may, however, be more 

 apparent than real. One is at times inclined to suspect that the bedding has 

 been folded into a series of isoclines, and that the foliation-planes crossing 

 these parallel to the axes of the folds have made the structure appear more 

 simple than it really is, and the thickness of the beds greater than they 

 ought to be. 



On the western side of the great fault which passes through Glen Beich the 

 Loch Tay limestone zone seen on the summit of Meal Na Creige has been 

 carried downwards by it, and the structure of the shallow syncline becomes 

 more apparent, being well seen in Glen Ogle and the Kirkton Glen, 

 where the limestones and epidiorites are exposed near the bottoms of the 

 valleys and the overlying schists are seen on the higher grounds. This trough 

 stretches towards the shores of Loch Katrine and the head of Loch Lomond, 

 but in that direction the folding of the beds becomes more intense and 

 the southern limb steeper, until it becomes inverted and pushed over towards 

 the interior. The older rocks coming from beneath the syncline and seen 

 along the frontier Highlands are also placed at high angles, and towards the 

 shores of Loch Lomond they become reversed, dipping, also at high angles, to 

 the southeast. 



Traced into Cowal and along the shores of the Firth of Clyde the syncline 

 becomes more and more acute, being now actually in a recumbent position 

 with its axis heading towards the southeast at a low angle. The southern 

 limb, consisting of the two lower zones, becomes flatter, the beds dipping 

 southeast at 53. The rocks, which formed a gentle trough in Perthshire 

 with slightly undulating folds, become more violently contorted. But 

 still their relationship to the eastern section seems to be quite clear, and the 

 supposed anticline of the bedding described by the earlier geologists, and that 

 of the foliation by the officers of the Survey, appear to be entirely deceptive. 



Perhaps it may be somewhat misleading to use the term syncline as 

 descriptive of the structure of this region. Strictly speaking it appears to be 

 rather a series of isoclinal folds which traced from Loch Fyne across Cowal 

 to the Firth of Clyde gradually usher in still lower beds. This structure 

 will be better .understood by a reference to the sectional diagrams (page 420). 



Space does not permit of a detailed description of the minute structure 

 of these schists. An early, and probably the first, foliation of this region 

 took place along the lines of bedding, or parallel to the axes of the folds 

 in the bedding, as is still well seen in the more arenaceous rocks. That 

 this early foliation has been subjected to a series of later movements 

 admits of no doubt, especially in the highly contorted belt which runs 

 through Cowal, the structure of which has been minutely and carefully 

 described by the officers of the Survey. In Cowal there is evidence 

 that an early foliation has itself been folded and crossed by strain-slip, 

 which has again been folded and crossed by still later movements, the 

 process having been repeated oftener than once until all trace of the bedding 

 or early foliation has become entirely obliterated. In the garnetiferous 

 schist-zone and Upper Argillaceous zone of the central Highlands the 

 original clastic rocks seem to have become so completely mineralized that it 

 is almost hopeless to search for evidence of the original bedding, all their 

 divisional planes being clearly of secondary origin, so that it must remain an 

 open question as to the extent to which these secondary planes may be 



