362 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



varied and cliffy aspect ; partly due to the 

 escarpment side of the mica-slates, and 

 partly to the frequent alternations of 

 these with intrusive masses of a close- 

 grained porphyritic granite. 



It is the relative position which these 

 two rocks occupy with reference to each 

 other, and the manner in which they are 

 associated, that constitutes the great pe- • 

 culiarity of this district. 



We have seen that in the ridges be- 

 tween the Clyde and Loch Fyne, where 

 there is a great anticlinal effected from 

 some cause or another, there is no ap- 

 pearance of any intrusive rock ; and we 

 shall now find, that between Loch Fyne 

 and Loch x\we, where there is a perfect 

 conformity in the dip of the stratified 

 slates, there the intrusive rocks are ne- 

 vertheless developed in great force. 



The summit ridge of this district (see 

 fig. 1) is a ridge of mica-slate. It falls 

 rapidly into the basin of Loch Awe, the 

 dip of the strata being steeper along the 

 line of greatest elevation, which runs far 

 back from Loch Fyne, and much nearer 

 to Loch Awe. The intervening space 

 between this summit ridge and Loch Fyne 

 is occupied by a series of lower ridges, in 

 general diminishing in height as they 

 approach the Loch. The tops of these 

 ridges are granite ; but the tops only. 

 Both at their back and on their front, the 

 stratified rocks ascend generally to more 

 than half their height, as well as occupy 

 the whole of the intervening hollows. In 

 short, these granite tops may be said to 

 be intei'stratijied on a gigantic scale with 

 the mica-rslates ; the latter always pre- 

 senting the same dip and the same general 

 direction. At many spots the line of 

 junction is easily accessible ; and the ig- 

 neous and stratified rocks may be seen, 

 surface to surface, in undisturbing con- 

 tact with each other. 



The general character of this peculiar 

 association of the granite with the mica- 

 slates will be best understood by an ideal 

 section of the district (fig. 2). 



Before venturing upon any suggestion 





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