^^^' 55-] ^^ ^^^ REGION OF LOCH AWE. 491 



Mr. G. Barrow, has mapped in the Central Highlands rocks starting 

 from the condition of phyllites, through successive aureoles of fine 

 schist, staurolite-schist, and kyanite-schist ; in this case, however, 

 the zones of increasing metamorphism do not correspond with the 

 strike of the beds, but cross it obliquely. 



VI. Conclusions. 



The object of this paper has been to bring forward evidence that 

 a great series of comparatively unaltered rocks spread over a wide 

 area passes gradually into crystalline schists, and this fact is in 

 itself so important that it has not been considered necessary to 

 widen the scope of the paper by a more or less futile endeavour to 

 interpret the causes which have led to these results. To do so 

 would involve the advancing of theories which in the present state 

 of our knowledge could only be considered as matters of specula- 

 tion. A few words on the subject, however, may not be out of 

 place. We are dealing in the main with a type of metamorphism 

 which extends over large areas and, so far as we are aware, 

 removed from the neighbourhood of plutonic masses upon which it 

 might otherwise have been possible to look as the metamorphie 

 agency. When, however, we do approach the neighbourhood of large 

 plutonic masses, such as the Cruachan and Glen Fyne granites, we find 

 ourselves confronted with a type of metamorphism more intense 

 than that observed to the south-west of these granites ; but we see 

 that this metamorphism does not again diminish as we recede from 

 the granite-areas in a north-easterly direction. We do, however, find 

 in the neighbourhood of these plutonic rocks a type of metamorphism 

 which had evidently been produced by them ; but we are unable to 

 say definitely where the contact-type of metamorphism ends, and 

 the regional type begins. When on the ground, I had reason to 

 suspect that, in connexion with the intense progressive meta- 

 morphism that occurs in the area lying between the granite-masses 

 of Glen Eyne and Ben Cruachan, the intense regional type of 

 metamorphism was linked with the same phenomena as those that 

 afterwards resulted in the irruption of the granite-masses. But our 

 knowledge of the agencies of metamorphism must be considerably 

 enlarged before such speculations can lay claim to any value. 



I have had no opportunity of revisiting the northern portion 

 of the ground since 1893, when the materials' for this paper were 

 collected ; but my work on the upper part of Loch Awe, in so far 

 as it relates to the contact-metamorphism of the Cruachan granite, 

 has been considerably extended by Mr. Kynaston, who has dealt with 

 these phenomena at length in the Annual Reports by the Director- 

 General of the Geological Survey for 1897 & 1898. On reference 

 to these reports it will be noticed that, in addition to the large 

 amount of interesting material which he has collected bearing on these 

 contact-phenomena, some microscopic slides from the h or nf els-rocks 

 were found by Mr. Teall to contain the minerals cordierite and 



