﻿620 FOLDS IN THE SCHISTS OF THE SCOTTISH HIGHLANDS. [Nov. I9IO, 



The Secretary read the following extracts from a letter received 

 from Mr. C. T. Clough, who was unable to be present at the 

 Meeting : — 



' I think that special attention may be called to the similarity of the effects 

 produced on all the beds in the attenuated limbs of the slide-folds; the hard 

 massive quartzites, for instance, are not on the average any better preserved 

 than the Leven Schists. This seems contrary to what we should expect 

 a priori, and it is contrary also to what we find in some areas affected by the 

 post-Cambrian thrusts of the North- West Highlands. For instance, near Ord 

 in the Isle of Skye, just under the western limb of the folded Sgiath-bheinn 

 an Vird thrust the Fucoid Shales become thinner as the thrust is approached, 

 and are ultimately almost entirely squeezed away from between the Pipe-Rock 

 on the one side and the Serpulite Grit on the other. 



' It is interesting to consider what may be the relations in age between the 

 slides described by the Author and the Moine Thrust. The Moine Schists had 

 certainly been folded intensely, and were much in the same condition as they 

 are now, before the actual snap of the thrust took place. The slides of the Balla- 

 chulish district seem much more closely connected with the folding. This 

 difference suggests the question, whether, in the Moine Schists a little east of 

 the Moine district, slides of the Ballachulish type may not also occur. It is 

 certainly the case that the beds in the opposite limbs of some of the folds east of 

 the Moine Thrust show a marked want of correspondence. The differences have 

 hitherto generally been explained by the supposition that the folds concerned 

 were of unusually great depth, so that they brought into proximity beds which 

 originally were widely separated and were formed under different conditions 

 of sedimentation. It seems very possible, however, that the differences may, in 

 some cases, be due to the presence of slides accompanying the folds. If such 

 slides do occur not far east of the Moine Thrust, as is thus suggested, we may 

 be tolerably certain that they are somewhat older than it. 



1 In conclusion, I should like to express my high appreciation of the 

 perseverance and enthusiasm with which the Author has carried out these 

 investigations. I feel confident that his general conclusions may be accepted 

 as correct, and that they mark a great advance in the study of the tectonics of 

 the Scottish Highlands.' 



The Author thanked the Fellows for their reception of his paper. 

 He warned future workers against hasty correlations with the 

 sequence worked out in the Appin and Ballachulish district. The 

 Highlands of Scotland are probably divided into compartments 

 by structure-planes of great importance, and in each compartment 

 it will be necessary to determine the stratigraphical alphabet on 

 independent evidence. 



