Reports and Proceedings—Geological Society of London. 353 
2. ‘*Recumbent Folds in the Highland Schists.”' By Edward 
Battersby Bailey, B.A., F.G.S. 
A description is presented of the stratigraphy and structure of 
a considerable portion of the Inverness-shire and Argyllshire High- 
lands. The district considered les south-east of Loch Linnhe, and 
extends from the River Spean in the north to Loch Creran in the south. 
The following conclusions are arrived at :— 
(1) The schists of the district are disposed in a. succession of 
recumbent folds of enormous amplitude—proved in one case to be 
more than 12 miles in extent. 
(2) The limbs of these recumbent folds are frequently replaced by 
fold-faults, or ‘slips’, which have given freedom of development to 
the folds themselves. 
(3) The slipping referred to is not confined to the lower limbs of 
recumbent anticlines, and is therefore due to something more than 
mere overthrusting. It is a complex accommodation-phenomenon, of 
a type peculiar perhaps to the interior portions of folded mountain 
chains. In fact, the cores of some of the recumbent folds have been 
squeezed forward so that they have virtually reacted as intrusive 
masses. 
(4) In the growth of these structures many of the earlier formed 
cores and slips have suffered extensive secondary corrugation of 
isoclinal type. 
The Secretary read the following extracts from a letter received 
from Mr. C, T. Clough, who was unable to be present at the 
meeting :— 
‘‘T think that special attention may be called to the similarity of the effects 
produced on all the beds in the attenuated limbs of the slip-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 @ 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 slips 
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 slips of the Ballachulish 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, slips 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 slips accompanying the 
folds. If such slips 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. 
‘* 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.” 
1 Communicated by permission of the Director of H.M. Geological Survey. 
