TRANSACTIONS OF SECTION C. tapi 
It was shown that, though the sections vary indefinitely along this belt, there aie 
certain features characteristic of different stages of the movements which con- 
stitute well-marked types. 
In the strip that generally intervenes between the undisturbed area to the west 
and the powerful thrusts to the east, the geological structures may be arranged in 
two groups: 1. The strata are thrown into a series of inverted folds accompanied 
by reversed faults or thrusts, which dip in one general direction towards the 
E.S.E.; this type is well represented in the region of Eriboll and in the 
mountainous district south of Loch Maree. 2. Without incipient folding, the 
strata are repeated by a series of minor thrusts or reversed faults which lie at an 
oblique angle to the major thrust-planes, and dip in the direction from which the 
pressure came—that is, from the E.S.E. This type is admirably displayed in 
Glen Coul, in Glen Dhu, and on the hill slopes N.N.W. of Inchnadamph, in Suther- 
landshire. 
It sometimes happens, however, that the structures characteristic of this stage 
of the movements are buried underneath the materials driven westwards by the 
powerful thrusts ; but wherever denudation has laid bare the reduplication of the 
strata in advance of the great displacements, these structures are found. 
The features characteristic of the more powerful thrusts may also be arranged 
in two groups. In the first, masses of Lewisian gneiss, Torridon sandstone, and 
Cambrian rocks are made to override the underlying piled-up strata, and in some 
cases to overlap other thrusts to the west. Owing to the movements of the strata 
from east to west, and also to the friction along the plane of the thrust, the strata fold 
over and curve under the Lewisian gneiss, thus producing inversion of the beds. 
These features are exemplified in the Eriboll region, in Assynt, and in the Loch 
Maree district, by the Arnabol, Glen Coul, Ben More, and Kishorn Thrusts. The 
materials brought forward by these displacements can be referred to different 
types of Lewisian gneiss occurring to the west, and to the respective sub-divisions 
of the Torridonian and Cambrian systems. 
In the second group, which is represented solely by the Moine Thrust, the 
Eastern Schists, composed of quartz-schists, mica-schists, and muscoyite-biotite 
schists, with lenticular masses of acid and basic gneisses of Archzean type, are driven 
westwards, and in some cases overlap all major and minor thrusts till they rest 
directly on the comparatively undisturbed Cambrian strata, 
The planes of the major or powerful thrusts along which the materials have 
been driven are usually inclined to the E.S.E. at low angles, but in some cases 
they are folded, and, more rarely, are almost vertical. 
One of the distinctive features of the major thrust-planes is, that their outcrops 
resemble the boundary lines between unconformable formations, because (1) there 
is a complete discordance between the strata lying above and below the planes of 
disruption; (2) each successive thrust may be overlapped in turn by the higher one. 
By means of denudation, outliers of the materials lying above the thrust-planes are 
formed, of which excellent examples occur near Inchnadamph, in Assynt, and to the 
south of Loch Maree. 
iii. Contribution by J. J, H. Tratt, M.A., F.B.S, 
Effects of Earth Movements on Rocks, 
The effects of earth movements on rocks may be either local or regional. 
Local effects are confined to the immediate neighbourhood of dislocations ; 
regional effects are observable over areas that may be measured in tens, hundreds, 
or even thousands of square miles. 
Fault-breccias and mylonites may be cited as well-known examples of local 
effects, the former being especially characteristic of normal faults and the latter 
of thrust-planes. In the majority of cases fault-breccias and mylonites are formed 
at the expense of the adjacent rocks, but this is not always the case. Vein-stones 
have not infrequently been deposited in cracks and fissures along which movement 
has taken place, Some of the tin lodes of Cornwall, for example, give evidence of 
