1868.] AEGYLL ARGYLLSHIRE. 265 



a great synclinal trough. The pass of the Awe, which Mr. Geikie 

 quotes as an example of mere excavation, one of the most striking 

 bits of scenery in the Highlands, through which the waters of Loch 

 Awe find their way to the sea, is a rupture and chasm in the same 

 rocks, connected with the subterranean causes which upheaved the 

 great mass of Ben Cruachan to an elevation of 3600 feet. Glen 

 Fyne is a continuation of the same line of fault which constitutes 

 the sea-loch. The transverse valley of Loch Eck, connecting Loch 

 Pyne with the valley of the Clyde, which also Mr. Geikie assumes 

 to be a valley of erosion, lies across a steep anticlinal, and is due, in 

 my opinion, to the extreme tension to which the crystalline rocks 

 have been subjected along different lines of subsidence and upheaval. 

 Loch Long and Loch Goil are due to similar causes. Glen Croe 

 and Glen Kinglas lie in crumples of the strata, with every 

 mark which could tell to the eye and to the reason of breakage, 

 rupture, and dislocation. Many even of the smaller ravines which 

 furrow the sides of the mountains, are not channels cut, but cracks 

 occupied, by the torrents which now rush along their beds. Instead 

 of becoming broader and wider as they descend, they are often 

 chasms at the top of the mountains, and mere superficial channels 

 below. The little niches which water has succeeded in cutting, 

 during all the ages which have elapsed since the mountains became 

 mountains, are sometimes perfectly distinguishable from the rents 

 which subterranean force has opened to their course. 



I have thus stated the difference between my view and the theory 

 of Mr. Geikie as broadly as it can be stated, in order that we may 

 both be compelled to refer to those facts of detail upon which safe 

 conclusions can be based. 



I had the honour in 1853* of laying before this Society a de- 

 scription of the phenomena presented by the ridges which sepa- 

 rate the valley of Loch Awe from the valley of Loch Fyne. I 

 showed that the structure of these ridges is such as to indicate 

 conclusively that the slaty strata have fallen inwards, or subsided 

 towards the vaUey of Loch Awe, that when this movement took 

 place they were already in their present hardened, crystalline, and 

 metamorphic condition, and that, when so falling, great masses of 

 porphyrinic granite had risen along the planes of deposit, which 

 would be the lines of least resistance, and, lastly, that when these 

 granites so rose they were in a soft and viscid state. Let me 

 shortly recapitulate the facts which indicate these conclusions. 



In the first place it is a fact that all the slaty strata dip more 

 or less steeply towards the vaUey of Loch Awe. 



Their escarpments are everywhere presented to Loch Fyne, and 

 the slope side forms the south-east bank of Loch Awe. In the 

 second place, the summit-ridge is everywhere composed of these beds, 

 and there the dip is steepest. In the third place, the lower and in- 

 tervening ridges between this summit and Loch Fyne are generally 

 rounded bosses of porphyry, which the slaty strata underlie and overlie 

 conformably. In some few places the beds of slate or limestone are 

 * Quart. Journ. Geol. Sec. vol. ix, p. 3()0. 



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